Natural Dyes for Sustainable Textiles (The Textile Institute Book Series) [1 ed.] 0323852572, 9780323852579

Citation preview

Natural Dyes for Sustainable Textiles

The Textile Institute Book Series Incorporated by Royal Charter in 1925, The Textile Institute was established as the professional body for the textile industry to provide support to businesses, practitioners, and academics involved with textiles and to provide routes to professional qualifications through which Institute Members can demonstrate their professional competence. The Institute’s aim is to encourage learning, recognize achievement, reward excellence, and disseminate information about the textiles, clothing and footwear industries and the associated science, design and technology; it has a global reach with individual and corporate members in over 80 countries. The Textile Institute Book Series supersedes the former “Woodhead Publishing Series in Textiles” and represents a collaboration between The Textile Institute and Elsevier aimed at ensuring that Institute Members and the textile industry continue to have access to high caliber titles on textile science and technology. Books published in The Textile Institute Book Series are offered on the Elsevier website at: store.elsevier.com and are available to Textile Institute Members at a substantial discount. Textile Institute books still in print are also available directly from the Institute’s website at: www.textileinstitute.org To place an order, or if you are interested in writing a book for this series, please contact Matthew Deans, Senior Publisher: [email protected] Recently Published and Upcoming Titles in the Textile Institute Book Series: Handbook of Natural Fibres: Volume 1: Types, Properties and Factors Affecting Breeding and Cultivation, 2nd Edition, Ryszard Kozlowski Maria Mackiewicz-Talarczyk, 978-0-12-818398-4 Handbook of Natural Fibres: Volume 2: Processing and Applications, 2nd Edition, Ryszard Kozlowski Maria Mackiewicz-Talarczyk, 978-0-12-818782-1 Advances in Textile Biotechnology, Artur Cavaco-Paulo, 978-0-08-102632-8 Woven Textiles: Principles, Technologies and Applications, 2nd Edition, Kim Gandhi, 978-008-102497-3 Auxetic Textiles, Hong Hu, 978-0-08-102211-5 Carbon Nanotube Fibres and Yarns: Production, Properties and Applications in Smart Textiles, Menghe Miao, 978-0-08-102722-6 Sustainable Technologies for Fashion and Textiles, Rajkishore Nayak, 978-0-08-102867-4 Structure and Mechanics of Textile Fibre Assemblies, Peter Schwartz, 978-0-08-102619-9 Silk: Materials, Processes, and Applications, Narendra Reddy, 978-0-12-818495-0 Anthropometry, Apparel Sizing and Design, 2nd Edition, Norsaadah Zakaria, 978-0-08-102604-5 Engineering Textiles: Integrating the Design and Manufacture of Textile Products, 2nd Edition, Yehia Elmogahzy, 978-0-08-102488-1 New Trends in Natural Dyes for Textiles, Padma Vankar Dhara Shukla, 978-0-08-102686-1 Smart Textile Coatings and Laminates, 2nd Edition, William C. Smith, 978-0-08-102428-7 Advanced Textiles for Wound Care, 2nd Edition, S. Rajendran, 978-0-08-102192-7 Manikins for Textile Evaluation, Rajkishore Nayak Rajiv Padhye, 978-0-08-100909-3 Automation in Garment Manufacturing, Rajkishore Nayak and Rajiv Padhye, 978-0-08-101211-6 Sustainable Fibres and Textiles, Subramanian Senthilkannan Muthu, 978-0-08-102041-8 Sustainability in Denim, Subramanian Senthilkannan Muthu, 978-0-08-102043-2 Circular Economy in Textiles and Apparel, Subramanian Senthilkannan Muthu, 978-0-08102630-4 Nanofinishing of Textile Materials, Majid Montazer Tina Harifi, 978-0-08-101214-7 Nanotechnology in Textiles, Rajesh Mishra Jiri Militky, 978-0-08-102609-0 Inorganic and Composite Fibers, Boris Mahltig Yordan Kyosev, 978-0-08-102228-3 Smart Textiles for In Situ Monitoring of Composites, Vladan Koncar, 978-0-08-102308-2 Handbook of Properties of Textile and Technical Fibres, 2nd Edition, A. R. Bunsell, 978-0-08101272-7 Silk, 2nd Edition, K. Murugesh Babu, 978-0-08-102540-6

The Textile Institute Book Series

Natural Dyes for Sustainable Textiles

Padma Shree Vankar Dhara Shukla

Woodhead Publishing is an imprint of Elsevier 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, OX5 1GB, United Kingdom Copyright © 2024 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-323-85257-9 For information on all Woodhead Publishing publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Mathew Deans Acquisitions Editor: Sophie Harrison Editorial Project Manager: Tessa Kathryn Production Project Manager: Anitha Sivaraj Cover Designer: Christian Bilbow Typeset by TNQ Technologies

Contents

Preface

ix

1

Sustainability and its significance in textile wet processing 1.1 Introduction 1.2 Sustainable textile 1.3 Textiles wet processing 1.4 Sustainable textile 1.5 Textile wet processes and sustainability 1.6 Desizing 1.7 Scouring 1.8 Bleaching 1.9 Mercerization 1.10 Dyeing 1.11 Printing and final finishing 1.12 Textile wet process: eco-friendly/sustainable approach 1.13 Conclusion References

1 1 1 2 3 5 6 7 7 8 9 11 12 13 14

2

Role of natural dyes in making sustainable textiles 2.1 Introduction 2.2 Conclusions References

17 17 31 32

3

Using chemical management system in natural dyeing process to make it sustainable 3.1 Introduction 3.2 Dyeing process 3.3 Use of natural dyes and chemical management 3.4 Chemical management 3.5 Futuristic approaches for go-green 3.6 Conclusions References

37 37 38 39 45 48 49 50

vi

Contents

4

Room temperature natural dyeing for energy conservation 4.1 Introduction 4.2 Natural dyeing 4.3 Replacement of heat while dyeing 4.4 Examples of low temperature dyeing 4.5 Case study of low temperature dyeing 4.6 Futuristic approach 4.7 Conclusions References

55 55 55 57 59 59 63 64 65

5

Waterless natural dyeing to make it sustainable 5.1 Introduction 5.2 Promising solutions 5.3 Waterless dyeing 5.4 Supercritical fluid 5.5 Supercritical CO2 5.6 Advantages of using supercritical CO2 5.7 Disadvantages of using supercritical CO2 5.8 Supercritical fluid carbon dioxide dyeing 5.9 Waterless natural dyeing 5.10 Futuristic approach of waterless dyeing 5.11 Conclusions References

67 67 69 69 70 71 72 72 73 74 76 76 77

6

Use of newer technologies in natural dyeingdplasma and electron beam 6.1 Introduction 6.2 Plasma technology 6.3 Use of plasma technology in textile finishing 6.4 Case study one 6.5 Conclusions 6.6 Electron beam-mediated natural dyeing of synthetic fabrics 6.7 Conclusions References

81 81 81 82 84 96 97 99 99

7

Natural dyeing on polymeric material 7.1 Introduction 7.2 Advantages of polymeric versus natural fibers 7.3 Disadvantages of polymeric versus natural fibers 7.4 Pretreatments of polymeric textile before natural dyeing 7.5 Dyeing of polymeric textile 7.6 Materials 7.7 Analytical methods 7.8 Dyeing procedures 7.9 Natural dye/color extraction

103 103 104 104 105 105 110 110 110 110

Contents

7.10 7.11 7.12 7.13 7.14 7.15

vii

Surface modification methods of polyester Measurement of color strength and related parameters Determination of colorfastness properties Results and discussion Shades of dyed polyester Conclusions References

111 112 112 112 116 117 117

8

Sustainable processing of textiles 8.1 Introduction 8.2 Sustainability of natural dyes 8.3 Environmental consideration in natural dyeing 8.4 Economic impact through sustainable natural dyeing 8.5 Social importance 8.6 How can one make natural dyeing sustainable? 8.7 Water-less dyeing processes 8.8 Conclusion References Further reading

119 119 119 120 122 124 124 125 127 128 128

9

Effluent management from natural dyeing unit 9.1 Introduction 9.2 The environmental benefits and impacts of natural dyes 9.3 Ill effects of textile wastewater on the environment 9.4 Effluent treatments 9.5 Conclusion References

129 129 130 132 134 134 135

10

Sustainable measures taken in natural dyeing units 10.1 Introduction 10.2 Conclusions References

137 137 147 148

11

Traditional block printing for sustainability 11.1 Introduction 11.2 Traditional textile printing 11.3 Block printing 11.4 The block printing process 11.5 Techniques of block printing 11.6 Types of hand block prints 11.7 Bagru printing 11.8 Dabu printing 11.9 The traditional process of Bagru printing 11.10 Direct dye printing 11.11 Resist printing

151 151 151 152 152 153 153 154 155 155 156 158

viii

Contents

11.12 11.13 11.14 11.15 11.16 11.17 11.18

12

New era with “Bagru” print for modern consumers Washing Process chart of Bagru Printing Batik printing Screen printing Preservation of block printing Conclusion References

Sustainability in natural dye printing 12.1 Introduction 12.2 Textile dyeing and textile printing 12.3 Methods of textile printing 12.4 Traditional printing styles 12.5 Modern methods of textile printing 12.6 Types of modern textile printing methods 12.7 Digital printing on fabric 12.8 Dyes for textile printing 12.9 Textile printing with natural dyes 12.10 Natural dye ink formulations for textile printing 12.11 Screen printing modules with natural dyes 12.12 Conclusions References

Index

158 159 159 160 161 163 164 165 167 167 167 168 168 169 169 170 171 171 174 175 176 178 181

Preface

Natural dyes are dyes or colorants which are derived from animals, plants, or minerals. The majority of organic dye production is sourced from biological sourcesdsuch as trees, flowers, vegetables, and fungi. Before the creation of synthetic dyes, people had to use whatever was available to them in the natural world if they wanted to create dye for fabrics, textiles, or even ink. There is even evidence to suggest that the natural dyeing of textiles using plant dyes dates back as early as the Neolithic period. Natural dyes are biodegradable, nontoxic, and nonallergenic, making them generally better for the environment and for use around humans, as they do not have any health hazards which are found in many synthetic dyes. While natural dyes were established well before synthetic dyes, the human-created options have become much more widespread and are used in most of the clothing available till today. Recently, however, the world has acknowledged the harmful ecological impacts of synthetic dyes due to the toxic by-products they produce. In recent years, as consumers have become much more conscious of the need for environmental protection and a sustainable lifestyle, natural dyeing has seen resurgence. It has slowly regained its relevance among fashion designers, fabric producers and technologists, dyestuff suppliers and, of course, consumers. The use of natural dyes allows workers to avoid exposure to harsh chemicals and avoid the severe health implications that working with such toxins over long periods can cause. This allows textile production to once again become a healthy community trade, providing local people with ethical jobs. They can also produce beautifully vibrant colors when mixed correctly. The plants were used to produce colorant, and the rest of the plant was used by the local community in a variety of other ways: such as for medicinal qualities or for cooking and food scraps. Natural dyes can be used for textile processing, but the fastness and shading assessment of the colored materials often do not yield satisfactory results. To improve the fastness, brilliancy, and shading properties, metallic mordants can be applied. Metallic mordants are metal atoms that attach to the dye to improve the bonding between the dye and its substrate, thereby improving the colorfastness performance. Aluminum potassium sulfate, stannous chloride, ferrous sulfate, and copper sulfate are some of the most used mordants. Fabric or dyestuff suppliers should be cautious in the selection and use of these mordants, as certain metals or its salts are known for being hazardous to the environment and health.

x

Preface

Plants that are harvested for the extraction of plant dyes have a variety of other uses within the local community. This often means that natural dyeing creates zero waste, as the local community utilizes all parts of the plant after extracting dye. Natural dyes are prepared from numerous plant-based, mineral, and animal products, comprising vegetables, fruits, wood, bark, berries, lichen, roots, plants, grasses, nuts, and kernels as well as creatures, shellfish, and nonliving complexes.

Room temperature dyeing Many research groups are working on low temperature/room temperature for developing better and optimized dyeing process. The drive has been to reduce energy consumption and to make the natural dyeing process eco-friendly by reducing the temperature to 40 C. Low temperature dyeing with Camellia sinensis (tea leaves) extract has been carried out, mainly developed for the sake of energy conservation.

Waterless dyeing Another sustainable technique is waterless natural dyeing with carbon di oxide. When pressurized, CO2 becomes supercritical (SC-CO2), pressurizing and heating carbon dioxide to above 31.1 C, the temperature at which it becomes “super critical,” a phase between a liquid and a gas. The CO2 is then cleaned and 95% is recycled back into the machine to be reused. It saves water and chemicals. Because this approach is waterless, fabrics do not need to be dried, speeding up the dyeing process by 40% and cutting energy use by 60%.

Chemical management Extensive pollution of natural water resources by organic and inorganic pollutants has become an issue for many countries in recent years. Treatment of dye-containing wastewater, on the other hand, is a significant challenge because there is no specific and economically viable technique for adequately treating such a problem. The textile industry around the world is accountable for discharging 40,000e50,000 tons of dye in the water bodies. This has raised concerns and subsequently led to the adherence of strict rules and standards to protect the environment and practice sustainable working. Hence adopting eco-friendly methods and biodegradable substances for dyeing and finishing processes in textile and garment making can save resources of the nature and reduce chemical landfill in a big way.

Preface

xi

Natural dyeing on polyester Polyester fabric requires pretreatment process before dyeing with natural dyes. Among pretreatment process, majority of the work is carried out on mordant process. The natural dye along with mordant gives good fastness properties. Safflower, madder, onion skin, lac, turmeric, ratanjot, and eucalyptus have been successfully employed in polyester dyeing.

Sustainable natural dyeing Textile wet processing consumes lots of water, chemicals, color, and auxiliaries and generates high amount of effluent load and eco-standard of final product. Textile dyeing is the most polluting part of garment manufacturing, and it can be cleaned up the fastest and makes an immediate cut in carbon emissions. Increasing environmental consciousness throughout the globe has forced technologists and industrialists to adopt safer methods.

Innovating technologies: Use of newer technology Many safe newer technologies are being coming in foray of textile dye processing. As more consumers become aware of the harmful effects of current dyeing practices, new technologies make way for more cost-effective, resource-efficient, and nonpolluting sustainable dyeing alternatives. Innovation in dyeing technologies ranges from pretreatment of cotton, pressurized CO2 dye application, and more recently, the creation of natural pigments from microbes. Current dyeing innovations can help reduce water usage, replace wasteful practices with efficient and cost-effective ones, and minimize the impact on our ecosystems.

Plasma and electron beam Use of plasma and electron beam radiation is such clean green technology paving its way in textile natural dyeing. The plasma is an ionized gas with equal density of positive and negative charges which exist over an extremely wide range of temperature and pressure. Using plasma technology in textiles is an innovative solution for developing fabrics with stain repellant, hydrophobic, and moisture management properties. The foam technique utilizes foaming machines that fold air into concentrated chemical solution and then dilute it. The process ensures chemical penetration at optimum level without using large quantities of water. This is a productive, energy-saving, and nature-loving method.

xii

Preface

Block printing In the midst of a world where technology predominantly rules, a handmade and handwoven technique such as block print has a charm. Block printing is made using blocks made from rubber, wood, or linoleum. It requires the low consumption of resources and optimized use of natural dyes to embrace sustainability and authenticity. Acquiring a lesser carbon footprintdthere’s something absolutely beautiful about this slow fashion that must be adopted since block printing is a product of culture, tradition, and naturedthe demand for this technique is high on the rise.

Printing Natural dyes can be applied on the fibers not only with dyeing method but also with printing method. Textile printing is one of the most important and versatile methods among the methods used to design and colorize textile fabrics. Ancient men and women mixed the colorants such as coal or soil paint with oils and used them with their fingers in lines on various materials. Inkjet printing is a process where the dyes and pigments are applied directly to the fabric. This printing technique does not make use of large amount of water for treatment and power consumption. The major portion of water used for textile dyeing comes after dyeing, when fabrics, particularly cotton, have to be washed over and over again to remove unfixed dye. Instead, manufacturers can skip dyes and use pigments. Natural dyes have always been preferred for its soothing colors; it has been observed that the comscreen printing on cotton and silk fabrics using indigo, madder, and sappanwood has resulted in promising colors and also can be considered as the recommendable alternative to harmful synthetic dyes.

Textile units taking up new ways of dyeing There are various companies adopting newer technologies to make whole dyeing process and dyed product ecofriendly and without any carbon foot print. The textile industry being a manufacturing industry working under pressure, there is cutthroat competition. The innovative technologies still require a lot of optimization in terms of achieving low-cost production and commercial viability while meeting customer demands. Through various dyeing techniques and products, sustainable clothing brands are able to produce a variety of hues, designs, and color combinations. Sustainability consists of three aspects namely economic, environmental, and social. Sustainable use of natural dyes in textile industry can be achieved through low cost production of natural dyes while conserving biodiversity from biomass that is not damaging the environment.

Sustainability and its significance in textile wet processing 1.1

1

Introduction

Sustainability is a concept which reminds us of our responsibility to proceed in a manner which will help us to sustain life and will allow the next generations to live comfortably in an eco-friendly, clean, green, and healthy world. It is about recognizing social, environmental, and economic aspects to be dependent on each other. It must evaluate costs and benefits of decisions carefully including long-term costs and benefits to future generations. Resources are finite and hence any attempt toward sustainability should be flexible, safe, and doable. In this context, textile industry which is one of the world’s most polluting industries and sustainability issues in the textile industry have received great attention.

1.2

Sustainable textile

Sustainable textiles mean that all materials and process are safe for human and environment, and all the energy and material come from renewable or recycled sources, leading to the fact that at all stages in the product life cycle, it would eventually enhance social well-being. Sustainable textiles mean ways of planning and achieving more sustainable materials and technologies focusing to improve recycling in the industry. With geographically long and complex global production networks, as well as the dual pressure for cost and lead time, implementing sustainability in textile and apparel supply chains is challenging (Shen et al., 2014; Boström and Micheletti, 2016; Allwood et al., 2008). The process of turning raw materials into finished garments has significant negative environmental and social implications, including air and water pollution and exploitation of human resources, especially where production is outsourced to lower labor cost countries (Shen et al., 2012). Applying the 3 R’sd reduce, reuse, and recycle are to be aimed at achieving sustainability goals. Sustainability in textiles refers to the use of resources which are renewable. The definition of sustainable textiles involves that all materials and process inputs and outputs are safe for human and ecological health in all phases of the product life cycle. All energy, material, and process inputs come from renewable or recycled sources. All materials are capable of returning safely to either natural systems or industrial systems. All stages in the product life cycle actively support the reuse or recycling of these materials

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00005-0 Copyright © 2024 Elsevier Ltd. All rights reserved.

2

Natural Dyes for Sustainable Textiles

at the highest possible level of quality. All product life cycle stages enhance social well-being. In recent years, environmental benefit claims such as environmentally friendly, environmentally responsible, eco-safe, recycled, and green materials have often been used to describe and promote products which supposedly have minimal negative environmental impacts. Sustainability does not just mean ecologically sustainable, although that is often the part of sustainability focused on these days (Karthik and Gopalakrishnan, 2014). Sustainable development for textile manufacturing is a long-term strategy which includes economic, social, and environmental aspects. Its goals are very intensive wherein the society needs to become aware of a common responsibility. Textile manufacturers understand the need for environmental protection and thus look for integrated search for solutions and most importantly industry itself takes the responsibility for preventing pollution.

1.3

Textiles wet processing

Across the world and throughout history, textiles have been the base of some of the most lucrative economies and networks of exchange in the world. A lot of effort is put into our textiles or human-made fabrics. Textiles are important, and it’s not just because humans need them, but they are related to one of the major economical advances of history like the development of silk route. The impact of role as economic consumers of textiles is major, and consumer is becoming conscious about it. In accordance with that agenda, many people in the world are pushing for more sustainable textiles or ethically produced fabrics. Textile production is the result of long manufacturing and wet processing stages. These manufacturing stages involve yarn, fabric, and garments manufacturing and wet processing (Nawab, 2016). The textile wet processing industry is based on various preprocessing (pretreatment), processing (dyeing and printing), and postprocessing (finishing) stages that consume a significant amount of water, dyes, chemicals, and energy. All these treatments are crucial to ensure optimal performance and desired visual effects (Choudhury, 2006). Textile wet processing, which includes scouring, bleaching, coloration, and finishing in an aqueous medium, is of crucial importance for improving the performance and serviceability of textile materials. A massive amount of water, energy, and chemicals are required in the wet processing of textiles. However, there is an increasing demand from consumers for sustainable textile materials and apparel. A major challenge ahead for textile manufacturing is to improve textile wet processing by replacing harmful chemicals and reducing the consumption of water and energy, and therefore making a contribution toward sustainable textile materials (Shen and Smith, 2015). Main areas of concern in textile industry to attain sustainability aredthe use of renewable raw material, lesser use of water, lesser use of energy, and least emission or waste output. Textiles production processes such as sizing, scouring, bleaching, mercerizing, dyeing, printing, and finishing are characterized by a huge consumption of water, energy, and chemicals. The toxic effluent discharge generated in these processes mainly

Sustainability and its significance in textile wet processing

3

contains by-products, residual dyes, salts, acids and alkalis, auxiliary chemicals, and other solvents (Shahid-ul-Islam and Mohammad, 2014). An ideal sustainable textile wet processing product should have the following parameters: • • • • • • • • • • • • • • •

Should be equivalent to the product it replaces Performs as well as or better than the existing product Be available at a competitive or lower price Have a minimum environmental footprint for all the processes involved Be manufactured from renewable resources Use only ingredients that are safe to both humans and the environment No negative impact on water Greater use of sustainable raw materials Lower energy and water consumption Least pollution generation in production Lower impact in use Water, energy, chemicals in cleaning/laundering Design for easy disassembly/disposal/recycling Design for reduced consumption and longer life Disposable unsustainable products

These important points are solutions for producing sustainable apparel ready for consumers demanding viable alternatives in fabric. Textile industry has to search and initiate every step of wet processing with justifiable substitutes in order to make whole process green. In this perspective, fabric/cloth/ textile to be used in wet processing should be from sustainable raw resources. Thus the role of textile origin plays an important role in ecologically benign attire.

1.4

Sustainable textile

Textile fibers and fabrics are involved in long production and manufacturing processes before they are ready for making garments or apparel. The textile industry is shared between natural fibers such as wool, silk, linen, cotton, and hemp, and man-made ones, the most common of which are synthetic fibers (polyamide, acrylic) made from petrochemicals. Most of the clothes in wardrobes contain polyester, elastane, or Lycra. These cheap and easy-care fibers are becoming the textile industry’s miracle solution. However, their manufacture creates pollution and they are hard to recycle (with nylon taking 30e40 years to decompose). The textile and clothing industry is a diverse one, as much in the raw materials it uses as the techniques it employs. At each of the six stages typically required to make a garment, the negative impacts on the environment are as numerous as they are varied. Spinning, weaving, and industrial manufacture undermine air quality. Dyeing and printing consume vast amounts of water and chemicals, and release numerous volatile agents into the atmosphere that are particularly harmful to human health (Challa, 2014). Sustainable fabrics are often made from natural or recycled materials, aiming to reduce harm either through the production process, fiber properties, or overall

4

Natural Dyes for Sustainable Textiles

environmental impact. These fabrics can also contribute to waste reduction, water conservation, lowered emissions, and soil regenerationdthough, there isn’t one fabric that is entirely sustainable (Anonymous, 2022). Natural fibers are rapidly renewable, plant-based, and have a more potential for circularity. Fabric selection affects how to wash the garment and potentially recycle it (Ziyo, 2021). Sustainable fabrics and textiles are essentially produced with limited impact to the environment and community and can be categorized in the following ways. - Organic: A crop which is cultivated using organic agricultural principles such as biofertilizers and organic manures. The crop is cultivated without pesticides, chemicals, or synthetic fertilizers, for example: hemp, organic cotton, and organic ramie/jute (linen). Organic wool can be included here if the sheep have been raised on “organic” land and the finished yarn is produced and colored with organic pigments. - Eco-textiles: A textile product which is produced in a conscientious eco-friendly manner and processed under eco-friendly limits (defined by agencies like OEKOTEX, IFOAM, etc.). Natural fibers such as organic cotton, hemp, jute, and ramie are considered eco-textiles based on the process of cultivation. - Recycled and biodegradable: Natural and synthetic fibers and textiles which are biodegradable and/or can be broken down into pieces in order to produce more textiles or convert into fibers. People use fibers from two basic sources to make textiles: natural fibers from plant and animal sources, and synthetic fibers like rayon and nylon. The most common natural fiber in clothing is cotton, and many growers are working to produce organic cotton without pesticides or chemical fertilizers. Companies also blend cotton with other more ecologically friendly plant fibers. Apart from this some of the sustainable fibers are: • Bamboo Bamboo is a fast-growing, regenerative crop that does not require fertilization and is often considered as a sustainable garment fabric. Bamboo is incredibly absorbent, comfortable, and moisture-wicking, making it a favorite with sustainable brands. • Hemp Hemp is a specific type of cannabis plant. It’s fast-growing, doesn’t exhaust the soil, and doesn’t require pesticides. Hemp creates a durable fabric that’s nonirritating for skin and has many uses. It’s often used in place of cotton. • Linen Linen is made from flax, which can be grown without fertilizer and planted in areas where other crops cannot thrive. Flax can also be used in its entirety (seeds, oil, and crop), meaning there’s no waste. Linen is also biodegradable. • Modal Modal is another semisynthetic material made from wood pulp but mainly that of beech trees. The naturally occurring yet human-made fabric is generally more delicate and softer. • Organic cotton Organic cotton is produced without any toxic pesticides, synthetic fertilizers, or genetically modified seeds (GMOs). This usually implies a sustainably managed fabric production process, though it is not always a given without proper certifications. • Reclaimed (deadstock) Reclaimed fabric (often called deadstock) is leftover fabric from manufacturers. It can also mean vintage fabric or any unused material purchased secondhand.

Sustainability and its significance in textile wet processing

5

• Recycled polyester Recycled polyester is PET (the chemical used to create polyester) from plastic water bottles that have been broken down into fibers. The recycled fabric keeps plastic out of landfills and can be recycled again many times over. • Silk Silk comes from silkworms that subsist on a diet of only mulberry tree leaves, which are resistant to pollution and easy to grow. This plant’s characteristics make the production of silk a fairly low waste ordeal. But as silk requires animal labor, it’s essential to ensure it has been produced by ethical production methods. • Lyocell Lyocell, a type of rayon derived from cellulose fibers that come from tree pulp. It’s made with eucalyptus wood, sustainable practices, and responsible sourcing. • Wool Wool can be a sustainable fabric depending on how it’s produced. Wool is also compostable, incredibly insulating, and doesn’t shed plastic microfibers.

Each material has advantages and drawbacks. Manufacturers are making textiles by blending cotton and other fibers to find the most responsible and sustainable fabric. Synthetic fibers present different challenges. Some are made from petroleum-based substances, and not all of them can be recycled. Those can include polyester and some nylons, and companies are creating ways to sort and untangle the recyclable synthetic threads in textiles that also contain nonrecyclable fibers (Sustainable, Textiles et al., 2016).

1.5

Textile wet processes and sustainability

Textile wet processing normally includes pretreatment (or preparation), coloration (dyeing or printing), and finishing. It employs a huge amount of water, dyes, and chemicals, and other materials for processes such as dyeing, printing, and finishing. This industry is said to be a major cause of environmental pollution. To achieve sustainable production, many of the processes have been modified; the use of hazardous, carcinogenic dyes and chemicals has been banned. For better management, waste is classified based on its nature and how measures such as recycling are employed (Amutha, 2017). Cotton, the world’s most widely used fiber, is a substrate that requires a large amount of water for processing whether it’s bleaching, desizing, scouring, mercerizing, and dyeing, whereas other natural fibers generally don’t require these harsh processes. Almost all steps of textile wet processing required huge amount of water and consumption of energy to maintain high temperature. Over the last few decades, measures have been taken to reduce water and energy consumption substantially at each step of wet processing. The less use of water also reduces the consumption of chemicals which ultimately reduce effluent load and save cost of wastewater treatments. In new world, waterless treatment technologies are emerging as green alternatives to conventional wet processing of textiles (Gulzar et al., 2019). The main pollutants of wet processing are organic matters which come from the pretreatment process of pulp,

6

Natural Dyes for Sustainable Textiles

cotton gum, cellulose, hemicellulose, and alkali, as well as additives and dyes used in dyeing and printing processes. Pretreatment wastewater accounts for about 45% of the total, and dyeing/printing process wastewater accounts for about 50%e55%, while finishing process produces little waste water (Wang et al., 2011). The conventional threestep pretreatment process consists of desizing, scouring, and bleaching. Desizing of a gray fabric removes previously added size or starchy material which can be done by using water (rot steeping), acid, enzyme, oxidation chemicals, and alkali. Scouring uses alkali to remove oils, fats, and waxes to improve the absorbency, whereas bleaching uses oxidizing agents to improve the whiteness of the fabric. In a conventional process, scouring and bleaching are done once which results in underutilization of alkali and hydrogen peroxide (Harane and Adivarekar, 2017). Various pretreatment textile wet processes are the following.

1.6

Desizing

The first process of textile wet processing is desizing. It is one of the key processes for the pretreatment of cotton fabric wet processing. It is essential to remove the sizes coated on fabric prior to dyeing and printing. Warp yarns are coated with sizing agents prior to weaving in order to reduce their frictional properties, decrease yarn breakages on the loom, and improve weaving productivity by increasing weft insertion speeds. The sizing material present on warp yarns can act as a resist toward dyes and chemicals in textile wet processing. It must therefore be removed before any subsequent wet processing of the fabric. The sizing agents are macromolecular, film-forming, and fiberbonding substances, which can be divided into two main types: natural sizing agents which include native and degraded starch and starch derivatives, cellulose derivatives, and protein sizes; and synthetic sizes which include polyvinyl alcohols, polyacrylates, and styrene-maleic acid copolymers. Starch-based sizing agents are most commonly used for cotton yarns because of being economical and capable of giving satisfactory weaving performance. Other products are also used, either alone or in combination with starch sizes, when the higher cost can be offset by improved weaving efficiency. Some auxiliaries are also used in sizing for various functions and include softening agents, lubricating agents, wetting agents, moistening agents, size-degrading agents, and fungicides. The desizing procedure depends on the type of size. It is therefore necessary to know what type of size is on the fabric before desizing. Different methods of desizing are: • • • • • •

Enzymatic desizing Oxidative desizing Acid steeping Rot steeping (use of bacteria) Desizing with hot caustic soda treatment Hot washing with detergents

The most commonly used methods for cotton are enzymatic desizing and oxidative desizing. Acid steeping is a risky process and may result in the degradation of cotton

Sustainability and its significance in textile wet processing

7

cellulose while rot steeping, hot caustic soda treatment, and hot washing with detergents are less efficient for the removal of the starch sizes (Fibre2fashion.com Sep 2013). Cleaner production technologies, in which hazardous material is substituted with immobilized a amylase, an eco-friendly enzyme, are applied for desizing of cotton fabric in two different systems (conventional and ultrasonic bath procedures) and time (15 and 30 min). Immobilized enzyme brings about a significant increase in the starch-size removal along with a decrease in the retained strength values and can be use many times which enables to improve environment-friendly desizing processes for the textile industry (S¸ahinbas¸kan and Kahraman, 2011). This kind of sustainable procedure makes desizing an eco-friendly textile wet process.

1.7

Scouring

Cotton may contain between 4% and 12% by weight of impurities in the form of waxes, proteins, pectins, ash, and miscellaneous substances such as pigments, hemicelluloses, and reducing sugars. These impurities are removed from the fabric by scouring, since their hydrophobic nature negatively affects the enhancement of the fabric’s wettability and absorbency (Karapinar and Sariisik, 2004). Scouring is a cleaning process that removes impurities from fibers, yarns, or cloth through washing. Alkaline solutions are typically used for scouring; however, in some cases, solvent solutions may also be used. Scouring uses alkali, typically sodium hydroxide, to break down natural oils and surfactants and to emulsify and suspend remaining impurities in the scouring bath. The specific scouring procedures, chemicals, temperature, and time vary with the type of fiber, yarn, and cloth construction. The structure and composition of the outer layers of cotton fiber has been established on the basis of thorough literature study, which identifies wax and pectin removal to be the key steps for successful scouring process (Agrawal et al., 2007). An innovative approach addressing ecological problems associated with scouring of cotton-based textiles was developed with the use of b-cyclodextrin in the presence of a wetting agent. b-cyclodextrin is able to accommodate the wax in its cavity, complex with it, and dissolve it together with other cotton impurities by the aid of a wetting agent, thereby effecting their removal (Hashem et al., 2002).

1.8

Bleaching

Raw cotton contains natural-colored impurities which significantly impair the inherent white appearance of cotton cellulose. The process by which the natural color of a fiber can be removed and make the textile materials pure white and bright is termed as bleaching. Unless cotton is dyed deep or with dark shades, bleaching is required to remove the natural-colored impurities prior to dyeing and finishing for the preparation of cotton textiles (Wakelyn, 2006). Hydrogen peroxide is the most widely used

8

Natural Dyes for Sustainable Textiles

bleaching agent in textile industry (Zeronian and Inglesby, 1995). Rapid H2O2 bleaching is traditionally carried out under alkaline conditions (pH 10.5e12) at a temperature close to the boil, which results in high energy consumption and also gives rise to significant fiber damage. Additionally, it is essential to neutralize the bleach solution and rinse the fabric with copious amounts of water when the bleaching process is complete. Textile preparation of cotton typically includes scouring and bleaching at high temperature and high pH. Substantial amounts of wastewater are produced that must be treated prior to being released to receiving fresh water. Development and application of compounds that enhance the bleaching process is the demand of current scenario in recent textile wet process researches (Xu et al., 2011).

1.9

Mercerization

Mercerization is an old method of cellulose fiber modification, which is an alkaline treatment method for cellulose fibers. It is a chemical method that happens especially to cotton fabrics, in which raw fabrics are dipped in a caustic soda solution that increases their fiber strength and makes them shinier. The process was devised in 1844 by John Mercer of Great Harwood, Lancashire, England, who treated cotton fiber with sodium hydroxide. This treatment caused the fibers to swell; about 25% of hydrogen bonds are broken during the swelling process in the posttreatment (drying) (Dai and Fan, 2014). During mercerization, in a 22%e27% caustic soda solution, both mature and immature cotton fibers swell so that the secondary wall thickness is increased. The fiber surface appearance and the internal structure of the fiber are modified. This improves the uniformity of fabric appearance after dyeing, and there is an apparent increase in color depth after mercerization. Dead cotton fibers (i.e., those with little or no secondary wall) are, however, not improved after mercerization. Mercerization leads to a number of changes in fiber and fabric properties: • • • • • • • •

A more circular fiber cross-section Increased luster Increased tensile strength, a major factor for technical textile fabrics Increased apparent color depth after dyeing Improved dyeability of immature cotton (greater uniformity of appearance) Increased fiber moisture regain Increased water sorption Improved dimensional stability

After mercerization, the structure of native cotton fibers, cellulose I, is converted into cellulose II, which is the stable fiber form after drying. The sorptive capacity of mercerized cotton is greater when the fabric is mercerized without tension (slack mercerizing) to give stretch properties to the fabric (Holme, 2016). Caustic soda poses severe waste water hazard, so the process is in great need of sustainable alternate. The development of solvent-based processing techniques of textiles has gained much popularity in view of the water shortage in all parts of world. Two important steps of pretreatment, that is, mercerization of cotton and scouring of synthetic fibers, which consume lots of water and toxic chemicals have been examined by solvent treatment.

Sustainability and its significance in textile wet processing

9

Mercerizing can be change or converted into sustainable process by the use of ecofriendly solvents which can be recycled or reuse. Cotton fabric was mercerized using liquor ammonia (solvent) and compared with conventional caustic soda process. Ammonia is a powerful and rapid swelling agent for cellulosic fibers. The swelling reaction in liquid ammonia proceeds at considerably faster rate than in conventional caustic soda treatment. Further, the recycled ammonia has also comparatively faster rate of swelling than conventional process. Liquid ammonia treatment results in a smooth and more uniform fiber surface compared to caustic soda (Shah and Shah, 2013). Replacement of acetic acid by formic acid for the neutralization of fabric after scouring, mercerizing, and bleaching processes is effective, economical, and environment-friendly choice. The procedure also allows a sufficient level of neutralization in a short period of time, needs low volumes of water, and results in low levels of BOD (Biological Oxygen Demand) (Bradbury et al., 2000).

1.10

Dyeing

Dyeing and printing of fabrics are usually done after routine or basic finishes but prior to the application of other finishes. It is mainly done to give color to the fabric and thus improve the appearance of the fabric. Treatment of fiber or fabric with chemical pigments to impart color is called dyeing. The color arises from chromophore and auxochrome groups in the dyes (Szymczyk et al., 2007). In the dyeing process, water is used to transfer dyes and in the form of steam to heat the treatment baths. Dyeing textile involved immersing or dipping a fiber, yarn, or fabric in a color pigment to change its color. Mankind has been doing this for centuries and will continue to dye fabrics for many centuries to come. Color is known as a pigment and the way of keeping (fixing) the color is to use a mordant, a chemical that fixes the dye to help prevent loss of color when washing or wearing the product. This mordant/fixer of dye on to fabric is an important precursor of dyeing. This helps to amplify wash and other fastness of fabric after dyeing. In all of fabrics, cotton specially need pretreatment in the form of tannic acid treatment and mordanting to give beautiful shades with natural as well as synthetic dyes. Native silk and wool are easy to dye and sometimes can give rainbow of colors with very mild or no mordanting. Dyeing in ancient times has been started with natural sources, for example, flowers, roots, leaves, and sometimes special secretions of trees. At that point of time, dyeing was a distinctive art which was limited to special class of society. As the use and demand of dye increased, more and more of natural dye sources have been investigated and protocols of dyeing have been set. Natural sources have minimum or no waste generation in terms of water as well as other substances. The scenario completely changed when accidently a synthetic dye (mauve) has been invented in 1856 by W. H. Perkin. After this invention, synthetic dyes were produced and dyeing with them have been fully accepted worldwide. Natural dyes lost their magnificence due to incomplete or no documentation of extraction, lack of standard methods of applications, high dyeing costs, extensive labor involvement, and difficult maintenance of

10

Natural Dyes for Sustainable Textiles

dyed fabric. Whereas, synthetic dyes captured new horizons every day, due to ease of handling/dyeing, cheap cost, no or easy extraction process, fabulous fastness on dyed fabric, etc. Their presence became pervasive. In this extensive use of synthetic dye, people overlooked synthetic dye’s waste water and other pollution generating consequences until they started hampering our own health. Synthetic dyes generate huge volumes of waste water and generally they are not biodegradable. Researchers started looking for eco-friendly and greener options for dyeing industry and that’s the time when natural dyes regain their lost glory. Till the recent times, the use of natural dyes was restricted to special craftsman and dyers due to little acceptance and high cost involved. But now their eco-friendliness and being green have attributed to their recognition. Upsurge of natural dyes has also become possible due to many restrictions posed on the use of synthetic dyes by many nations. Natural dyes have always been greener and cleaner options in dyeing with aesthetic values, soothing earthen colors thus again becoming eye up of every garment dyed with them. Natural dyes have been used as colorants in food, leather, as well as textile since prehistoric times. These dyes are obtained from vegetable and animal matter with no or very little chemical processing. Environmentalists are always worried about the rampant use of synthetic dyes in textile industry as they cause water pollution and waste disposal problems. Natural dyes are biodegradable and do not cause any health hazards and hence they can be easily used without much environment concerns (Arora et al., 2017). The textile dyeing industry consumes large quantities of water and produces large volumes of wastewater from different steps in the dyeing and finishing processes. Wastewater from printing and dyeing units is often rich in color, containing residues of reactive dyes and chemicals, and requires proper treatment before being released into the environment. The toxic effects of dyestuffs and other organic compounds, as well as acidic and alkaline contaminants, from industrial establishments on the general public are widely accepted. Increasing public concern about environmental issues has led to the closure of several small-scale industries (Babu et al., 1995). The use of enzymes and biomordants also create eco-friendly dyeing process and doesn’t produce severe waste water after wet processing (Vankar et al., 2008) (Vankar, 2017). The flowers of Delonix bregia have been evaluated for the natural dyeing of silk using a biomordant and enzymes. This is an eco-friendly textile pretreatment that does not utilize metal mordanting. The silk fabric was treated with either an enzyme or biomordant. The resulting dyed fabric showed resistance to fading. In this process, enzymes used were protease, amylase, lipase, and diasterase and biomordant was Pyrus paschia (Vankar and Shanker, 2009). Mordants take an important place in natural dyeing. Currently, rare-earth metals, industrial organic wastes, or by-products are becoming increasingly popular as alter_ ¸ mal and Yıldırım, 2019). This approach native natural dye and mordant sources (Is can be a good start for making dyeing process environment friendly. Textile industry puts heavy strain on global resources as it utilizes huge amounts of energy, water, and hazardous chemicals. This situation has raised issues about the sustainability of textiles due to severe burden on environment. So, alternative approaches

Sustainability and its significance in textile wet processing

11

have become necessary to ensure the sustainability of textile wet processing. In recent years, green chemistry has emerged as an effective tool to make textile wet processing sustainable. Green chemistry has helped in the development of alternative green and biodegradable chemicals useable as wetting, washing, and finishing agents. Much more reactive and biodegradable dyes have been developed for effective dyeing processing to minimize the amount of unfixed dyes in wastewater. Ionic liquids have been developed as alternative medium to replace water consumption in wet processing, ensuring its sustainability. Further, a number of biomaterials have been developed for sustainable wet processing operations (Gulzar et al., 2019).

1.11

Printing and final finishing

Printing is a procedure of decorating textile fabrics by applying dyes, pigments, or other materials ultimately forming patterns. Fabrics are often printed with attractive colors and various patterns by utilizing variety of techniques as well as machine types. Textile printing process is the method carried after dyeing and prior to finishing in textile manufacturing process. Among all the techniques, the main methods of textile printing are block, screen, roller, and heat transfer printing. However, other methods, such as direct method, discharge, resist, and direct printing and others are also used commercially. Now a days digital printing has taken majority of printing space. Textile printing is the most important and versatile of the techniques used to add design, color, and specialty to textile fabrics. It can be thought of as the coloring technique that combines art, engineering, and dyeing technology to produce textile product images that had previously only existed in the imagination of the textile designer. Textile printing can realistically be considered localized dyeing. The world of textile printing is rapidly changing. Customers are demanding a greater variety of color and design. Responding to this demand is a necessity in today’s marketplace. Printers are forced to find new and innovative ways to provide printed samples while minimizing cost and waste. Digital printing technology allows customers to streamline the entire design, sampling, and production process. Future of textile printing will be digital. Today’s textile marketplace demands the benefits of digital printing, the textile industry has embraced this new technology, and most importantlyddigital printing machines have finally met the challenge of textile production printing (Tippett, 2002). Digital printing is considered as environmentally safe options, that’s why this technology has been encouraged. Finishing is the final step in the fabric manufacturing process, and it gives special functionalities to textiles. Finishing in textile processing can be understood to the practical and visual features of the fabric accomplished after all wet processing finishes. The final color and shape of fabric can be significantly differing from the raw fabric, in respect of texture, use, and performance. Traditionally, textile finishing is a final step to change the quality of fabric in terms of appearance, handle, and functionally through mechanical and chemical routes. Over the years, textile finishing has been modernized to the process by which textile

12

Natural Dyes for Sustainable Textiles

materials convert into technical textiles. Undoubtedly, the future trend in textile finishing is to develop multifunctional textiles, which are highly efficient, durable, cost effective, and manufactured in an environmentally sustainable manner. In this regard, nanofinishing will play a key role in the performance and properties of the finished products. Treatment methods with minimum use of chemicals requiring less capitalintensive machinery, few processing steps, and minimum effluent treatments are more preferred by fabric manufacturers. Besides, nanofinishing of textiles with no adverse effect on physical and mechanical properties of the fabrics will be more important (Montazer and Harifi, 2018). Given the increased market demand for environmental consideration, using “green” technologies, reducing carbon footprints, and employing sustainable practices, the textile industry continues to advance technologies toward this goal. Large internationally known brands and small boutique firms at both the manufacturing and retail levels are integrating sustainability as a core feature of their businesses. Raw materials in the supply chain, optimizing natural and renewable resources, energy and process inputs, transportation, and distribution are all aspects under consideration (Frumkin and Weiss, 2012). To improve the environmental impact of textile wet processing, enzyme-based biotechnology has found a broad range of applications within the textile industry, resulting in saving energy, reducing water consumption, and replacing harsh chemicals in the manufacturing of textile materials. Typical commercial applications of enzymes in textile processing include bioscouring in the cleaning process of natural fibers and fabrics, biostone-washing of denim jeans to create a worn effect, removal of residual hydrogen peroxide in the stage of bleach clean-up, and biopolishing of cellulosic fabrics to prevent pilling. The implementation of enzymes in textile wet processing has demonstrated the environmental benefits and made a massive contribution to the sustainability of textiles and apparel (Shen and Smith, 2015).

1.12

Textile wet process: eco-friendly/sustainable approach

Textile wet processing industry accounts for a huge proportion in the consumption and pollution of fresh water. Increasing consumer awareness on the environmental issues, tightening environmental legislations on the effluents generated by textile industry, and water scarcity in different areas of the world have compelled textile industry to review, restructure, and reduce its water consumption and the associated effluent hazards. Water conservation efforts in different segments of the textile industry can be waste water treatment and reuse, machine innovations, process innovations, chemical innovations, advanced water analysis, and water-saving tools (Hussain and Wahab, 2018). The contamination of resources and health problems arises normally in the conventional method of wet processing. So, the alternative methods are necessary to improve the sustainability of the textile wet processing. In the recent time, the new eco-friendly methods have been developed and are preferred mostly instead of conventional

Sustainability and its significance in textile wet processing

13

methods. Plasma, ultrasonic, laser, and biotechnology digital inkjet printing are the new innovated eco-friendly technologies, which provide more advantages to wet processing. In these methods, there are no any harmful chemical, wastewater, mechanical hazards to textiles, etc. (Kumar and Gunasundari, 2018). The total amount of water consumed depends on the type of fiber, the type of machinery used, and the type of finishing effect required in the final product. Due to the use of different chemicals, such as dyes, soda ash, caustic soda, salt, acid, formaldehyde-based resin, and chlorinated bleaching agent, in the textile processing house, a large amount of effluent is generated that has an adverse effect on the environment. In the past, for minimizing the toxicity of effluent and for reducing the consumption of water and chemicals (saving energy), different processes, namely, irradiation technology, low-liquor continuous processing, microwave-assisted processing, value addition using nanomaterial and biomaterial, foam finishing, digital printing, and others, have been developed (Samanta et al., 2019). Significant reductions in water use can be achieved by preventing unnecessary water consumption in textile processing mills. Implementation of in-plant control techniques should be employed for achieving significant reductions in water use, raw material and energy consumption, wastewater production, and, in some cases, even wastewater load. There are several new developments aimed at conserving water in the textile processing industries (Raja et al., 2019). To improve the environmental impact of textile wet processing, enzyme-based biotechnology has found a broad range of applications within the textile industry, resulting in saving energy, reducing water consumption, and replacing harsh chemicals in the manufacturing of textile materials. The implementation of enzymes in textile wet processing has demonstrated the environmental benefits and made a massive contribution to the sustainability of textiles and apparel (Shen and Smith, 2015). The concepts of reuse and recycle have been aptly defined as reuse means utilization of previously used wastewater for another process or purpose, whereas recycle can be defined as reuse of same wastewater one or more times for the same process or purpose. Reuse and recycle can be major technology in textile wet processing. Waste water reuse after remediation and/or its recycling after extracting harmful moieties in the same apparel industry can prove turning point and can be potential sustainable solution (USEPA, 2004). Various other mechanisms like nanofilters, membrane filers, use of other organic solvents for processes like scouring, bleaching, and mercerizing, and collection of volatile solvents after printing can be prospective sustainable practices which can be adapted to save the planet. One can look good in one’s textiles, but always want to feel good about them too. This is possible only with right attitude and moral consciousness to save our world. Thus the awareness about an impact on environment by clothing has indispensable and significant role.

1.13

Conclusion

This chapter gives an overview of the textile wet processing stages. In order to make textile processing sustainable, new processes have to be developed, as globally

14

Natural Dyes for Sustainable Textiles

sustainability is being talked about in order to restore the ecology of the planet, wet processing of textiles known to be the major polluting processes; hence, textile wet processing has to be modified to ecofriendly techniques at every stage.

References Agrawal, P.B., Nierstrasz, V.A., Klug-Santner, B.G., G€ ubitz, G.M., Lenting, H.B.M., Warmoeskerken, M.M.C.G., 2007. Wax removal for accelerated cotton scouring with alkaline pectinase. Biotechnology Journal 2 (3), 306e315. Anonymous, 2022. Sustainable-Clothing-Fabrics. Fashion. Allwood, J., Laursen, S.E., Russell, S., de Rodriguez, C.M., Bocken, N., 2008. An approach to scenario analysis of the sustainability of an industrial sector applied to clothing and textiles in the UK. Journal of Cleaner Production 16 (12), 1234e1246. Amutha, K., 2017. 12-Sustainable Chemical Management and Zero Discharges. In: Muthu, S.S. (Ed.), Sustainable Fibres and Textiles. Woodhead Publishing, pp. 347e366. Arora, J., Agarwal, P., Gupta, G., 2017. Rainbow of natural dyes on textiles using plants extracts: sustainable and eco-friendly processes. Green and Sustainable Chemistry 7 (01), 35. Babu, B.R., Parande, A., Raghu, S., Kumar, T.P., 1995. Textile Technology, vol 11. Technology, pp. 110e122. Boström, M., Micheletti, M., 2016. Introducing the sustainability challenge of textiles and clothing. Journal of Consumer Policy 39 (4), 367e375. Bradbury, M., Collishaw, P., Moorhouse, S., 2000. Controlled rinsing: a step change in reactive dye application technology. Colourage Annual 73 (5). Challa, L., 2014. Impact of Textiles and Clothing Industry on Environment: Approach towards Eco-Friendly Textiles. Retrieved from fibre2fashion. com. Choudhury, A.R., 2006. Textile Preparation and Dyeing. Science publishers. Dai, D., Fan, M., 2014. Wood fibres as reinforcements in natural fibre composites: structure, properties, processing and applications. In: Hodzic, A., Shanks, R. (Eds.), Natural Fibre Composites. Woodhead Publishing, pp. 3e65. Fibre2fashioncom, September 2013. Problems in Desizing Cotton Textile Materials. Frumkin, S., Weiss, M., 2012. 5-fabrics and new product development. In: Horne, L. (Ed.), New Product Development in Textiles. Woodhead Publishing, pp. 65e79. Gulzar, T., Farooq, T., Kiran, S., Ahmad, I., Hameed, A., 2019. 1-green chemistry in the wet processing of textiles. In: Shahid ul, I., Butola, B.S. (Eds.), The Impact and Prospects of Green Chemistry for Textile Technology. Woodhead Publishing, pp. 1e20. Harane, R.S., Adivarekar, R.V., 2017. Sustainable processes for pre-treatment of cotton fabric. Textiles and clothing sustainability 2 (1), 1e9. Hashem, M., El-Bisi, M., Hebeish, A., 2002. Innovative scouring for cotton-based textiles. Engineering in Life Sciences 2 (1), 23e28. Holme, I., 2016. Coloration of Technical Textiles. Handbook of Technical Textiles. In: Horrocks, A.R., Anand, S.C. (Eds.), second ed. Woodhead Publishing, pp. 231e284. Hussain, T., Wahab, A., 2018. A critical review of the current water conservation practices in textile wet processing. Journal of Cleaner Production 198, 806e819. € _ ¸ mal, O.E., Is Yıldırım, L., 2019. Metal mordants and biomordants. In: Shahid ul, I., Butola, B.S. (Eds.), The Impact and Prospects of Green Chemistry for Textile Technology. Woodhead Publishing, pp. 57e82.

Sustainability and its significance in textile wet processing

15

Karapinar, E., Sariisik, M.O., 2004. Scouring of cotton with cellulases, pectinases and proteases. Fibres and Textiles in Eastern Europe 12 (3), 79e82. Karthik, T., Gopalakrishnan, D., 2014. Environmental analysis of textile value chain: an overview. In: Roadmap to Sustainable Textiles and Clothing, pp. 153e188. Kumar, P.S., Gunasundari, E., 2018. Sustainable Wet ProcessingdAn Alternative Source for Detoxifying Supply Chain in Textiles. Detox Fashion. Springer, pp. 37e60. Montazer, M., Harifi, T., 2018. Introduction: Textile Finishing. Nanofinishing of Textile Materials. In: Montazer, M., Harifi, T. (Eds.). Woodhead Publishing, pp. 1e17. Nawab, Y., 2016. Textile Engineering. Walter de Gruyter GmbH, Germany. Raja, A.S.M., Arputharaj, A., Saxena, S., Patil, P.G., 2019. 9-water requirement and sustainability of textile processing industries. In: Muthu, S.S. (Ed.), Water in Textiles and Fashion. Woodhead Publishing, pp. 155e173. S¸ahinbas¸kan, B.Y., Kahraman, M.V., 2011. Desizing of untreated cotton fabric with the conventional and ultrasonic bath procedures by immobilized and native a-amylase. Starch Staerke 63 (3), 154e159. Samanta, K.K., Pandit, P., Samanta, P., Basak, S., 2019. Water consumption in textile processing and sustainable approaches for its conservation. In: Muthu, S.S. (Ed.), Water in Textiles and Fashion. Woodhead Publishing, pp. 41e59. Shah, S., Shah, J., 2013. A step towards environmental protection in textile wet processing. Research Journal of Recent Sciences 2, 35e37. Shahid-ul-Islam, Mohammad, F., 2014. Emerging green technologies and environment friendly products for sustainable textiles. In: Muthu, S.S. (Ed.), Roadmap to Sustainable Textiles and Clothing: Environmental and Social Aspects of Textiles and Clothing Supply Chain. Springer Singapore, Singapore, pp. 63e82. Shen, B., Wang, Y., Lo, C.K., Shum, M., 2012. The impact of ethical fashion on consumer purchase behavior. Journal of Fashion Marketing and Management: International Journal 16 (2), 234e245. https://doi.org/10.1108/13612021211222842. Shen, B., Zheng, J.-H., Chow, P.-S., Chow, K.-Y., 2014. Perception of fashion sustainability in online community. The Journal of the textile institute 105 (9), 971e979. Shen, J., Smith, E., 2015. 4 - enzymatic treatments for sustainable textile processing. In: Blackburn, R. (Ed.), Sustainable Apparel. Woodhead Publishing, pp. 119e133. Sustainable, 2016. I Textiles and Fashion. study.com/academy/lesson/sustainable-textiles-infashion.html, Study.com. Szymczyk, M., El-Shafei, A., Freeman, H.S., 2007. Design, synthesis, and characterization of new iron-complexed azo dyes. Dyes and Pigments 72 (1), 8e15. Tippett, B.G., 2002. The Evolution and Progression of Digital Textile Printing. http:// brookstippett.com/docs/Print2002-BGT.pdf. USEPA, 2004. Guidelines for Water Reuse. US Environmental Protection Agency. Vankar, P., 2017. Structure-mordant interaction, replacement by biomordants and enzymes. Natural Dyes for Textiles: Sources, Chemistry and Applications 89e102. Vankar, P.S., Shanker, R., 2009. Eco-friendly pretreatment of silk fabric for dyeing with Delonix regia extract. Coloration Technology 125 (3), 155e160. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S., 2008. Ecofriendly sonicator dyeing of cotton with Rubia cordifolia Linn. using biomordant. Dyes and Pigments 76 (1), 207e212. Wakelyn, P.J., 2006. Cotton Fiber Chemistry and Technology. CRC Press, Boca Raton. Wang, Z., Xue, M., Huang, K., Liu, Z., 2011. Textile dyeing wastewater treatment. In: Advances in Treating Textile Effluent, vol. 5, pp. 91e116.

16

Natural Dyes for Sustainable Textiles

Xu, C., Hinks, D., El-Shafei, A., Hauser, P., Li, M., Ankeny, M., Lee, K., 2011. Review of bleach activators for environmentally efficient bleaching of textiles. Journal of Fiber Bioengineering and Informatics 4 (3), 209e219. Zeronian, S., Inglesby, M., 1995. Bleaching of cellulose by hydrogen peroxide. Cellulose 2 (4), 265e272. Ziyo, C., 2021. Use Natural Fabric. https://theamente.com/blogs/create-your-own-way-ofsustainability-1-using-natural-fiber-fabrics.

Role of natural dyes in making sustainable textiles 2.1 2.1.1

2

Introduction Textile dyeing

Dyeing of fabric is as old as human civilization and is a technique which imparts beauty to the textile by applying various colors and their shades on to a fabric with predefined parameters for durable color fastness. It may be used to apply color to fiber stock, yarn, or fabric. Dyes can be used on vegetable, animal, or man-made fibers only if they have affinity to them. Generally, a dyeing process involves adsorption (transfer of dyes from the aqueous solution onto the fiber surface) and diffusion (dyes diffused into the fiber). The mechanism of textile substrates is said to have four stages as transport of the dye molecules from solution to the substrate surface, second is dye adsorption on the substrate surface, third is diffusion or penetration of the dye from the substrate surface to the interior of the fiber through its amorphous regions, and last is fixation of the dye onto and/or within the substrate via covalent bonds, hydrogen bonds, ion exchange or van der Waals forces, or through insolubilization of the predissolved dye inside the fiber (Ibrahim, 2011). In addition to direct absorption, dyeing may also involve the precipitation of dyes inside the fiber (vat dyes) or chemical reaction with the fiber (reactive dyes) (Shang, 2013). Dyeing is usually processed into textiles through a combination of water and the synthetic or natural dyes. The aim of successful dyeing is to “achieve the desired shade, at the right price, with sufficient levelness, whether dyeing loose fiber, yarn or piece goods, with sufficient color fastness to withstand both processing and consumer demands, but without adversely affecting the fiber quality.” Of these, an acceptable level of uniform dye uptake at all parts of the substrate may be the most important criterion (Anonymous, 2014). Dyeing is the aqueous application of color to the textile substrates, mainly using synthetic organic dyes and frequently at elevated temperatures and pressures in some of the steps (Moore and Ausley, 2004). It is important to point out that there is no dye which dyes all existing fibers and no fiber which can be dyed by all known dyes (Alc^antara and Daltin, 1996). Dyeing process involves the use of either synthetic dyes or natural dyes. Natural dyes are plant-based dyes, whereas synthetic dyes do not occur in nature, so they have been categorized as man-made dyes and derived from organic material like petroleum.

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00002-5 Copyright © 2024 Elsevier Ltd. All rights reserved.

18

2.1.2

Natural Dyes for Sustainable Textiles

Synthetic dyes

Synthetic dyes used today provide reproducible and consistent dyeing with broad shade ranges and light and wash fastness performance values between satisfactory and outstanding. Some of the synthetic dyes are water insoluble, whereas some of them are water soluble. They are applied on cotton, wool, silk rayon, polyester, nylon, acrylic, etc. The dyes are soluble organic compounds (Mahapatra, 2016), especially those classified as reactive, direct, basic, and acid dyes. Most of the synthetic dyes with a few exceptions are aromatic organic compounds which can be divided into groups like ionic (acidic) and cationic (basic) dyes. Synthetic textile dyes include acid dyes, used mainly for dyeing wool, silk, and nylon, and direct or substantive dyes, which have a strong affinity for cellulose fibers. Mordant dyes require the addition of chemical substances, such as salts to give them an affinity for the material being dyed. They are applied to cellulose fibers, wool, or silk after such materials have been treated with metal salts. Sulfur dyes, used to dye cellulose, are inexpensive, but produce colors lacking brilliance. Azoic dyes are insoluble pigments formed within the fiber by padding, first with a soluble coupling compound and then with a diazotized base. Vat dyes, insoluble in water, are converted into soluble colorless compounds by means of alkaline sodium hydrosulfite. These colorless compounds are absorbed by the cellulose, which are subsequently oxidized to an insoluble pigment. Such dyes are colorfast. Disperse dyes are suspensions of finely divided insoluble, organic pigments used to dye such hydrophobic fibers as polyesters, nylon, and cellulose acetates. Reactive dyes combine directly with the fiber, resulting in excellent colorfastness. The first range of reactive dyes for cellulose fibers were introduced in the mid1950, and from then a wide variety of these dyes are available now (Ladha, 2009). The industrial advantages for the use of synthetic dyes based on (i) being chemically stable over time, (ii) being inert to physical, chemical, and biological degradation, (iii) being able to give color to the fiber to be dyed through reproducible processes, maintaining the color intensity, and (iv) are low cost (Ardila-Leal et al., 2021). Although synthetic dyes have introduced a broad range of colorfastness and bright hues, they are often found in the environment as a result of their wide industrial use and their toxic character has become a reason of serious concern to the environment. Usage of synthetic dyestuffs has adverse impacts on all forms of life. Existence of naphthol, vat dyestuffs, nitrates, acetic acid, soaping chemicals, enzymatic substrates, chromium-based materials, and heavy metals as well as other dyeing auxiliaries makes the textile dyeing water effluent extremely toxic. Other hazardous chemicals include formaldehyde-based color fixing auxiliaries, chlorine-based stain removers, hydrocarbon-based softeners, and other nonbiodegradable dyeing auxiliaries. The colloidal material existing alongside commercial colorants and oily froth raises the turbidity resulting in bad appearance and unpleasant odor of water. Furthermore, such turbidity will block the diffusion of sunlight required for the process of photosynthesis which in turn is interfering with marine life. This effluent may also result in clogging the pores of the soil leading to loss of soil productivity (Khattab et al., 2020).

Role of natural dyes in making sustainable textiles

2.1.2.1

19

Ecological influences of synthetic dye usage

Synthetic dyes belonging to any category pollute mainly water bodies. An expected 200,000 tons of dyestuff is ousted into the waterbodies worldwide each year (Chequer et al., 2013), reason being their particle size ranging from 0.025 to 1.0 mm (easily dissolvable in water). It is estimated that over 10,000 different dyes and pigments are used industrially and over 7  105 tons of synthetic dyes are annually produced worldwide (Chequer et al., 2013; Gupta et al., 2013). In the textile industry, huge amounts of dyes are lost to effluents every year during the dyeing and finishing operations, due to the inefficiency of the dyeing process (Ogugbue and Sawidis, 2011). Unfortunately, most of these dyes escape conventional wastewater treatment processes and persist in the environment as a result of their high stability to light, temperature, water, detergents, chemicals, soap, and other parameters such as bleach and perspiration (Couto, 2009). Dye-based effluents can cause serious hazards to the water stream and environment due to their synthetic origin and complex molecular structures which decrease their ability to biodegrade. Most dyes are water soluble except disperse dyes and vat dyes among variety of synthetic dyes. Many dyes contain traces of metals such as copper, zinc, lead, chromium, and cobalt in their aqueous solution except vat and disperse dyes (Affat, 2021). In general, synthetic dyes are not biodegradable due to their chemical properties and structure, generating an adverse effect on the environment. Most synthetic dyes are used in the textile and tanning industries to dye a wide variety of products. Besides, other industries, such as the cosmetics industry, the paper industry, the food industry, the pharmaceutical industry, and service providers, use synthetic dyes (hospitals, universities, among others) (Tkaczyk et al., 2020). Though dyes are attractive in nature, their impact on environment depends on the type of substance used and removal and degradation of dye substances. The contaminated wastewater discharged out after dyeing process contains huge amount of chemical substances which has negative impact on environment. Dyes can be synthetic, which means they’re scientifically made with chemicals, or natural, meaning made with things found in nature. The water used for this process in textile manufacturing is immense, which has created the need to have other dry processing for dyes, but none of them are as effective as wet dyeing. The conventional uses of synthetic dyes have posed serious threat to global environment. This involves a huge amount of water for washing and dissolution media; consequently, it gets loaded with auxiliary chemicals and unfixed dyes as wastewater effluents. A major source of color release into the environment is associated with the incomplete exhaustion of dyes onto textile fiber from an aqueous dyeing process, and the need to reduce the amount of residual dye in textile effluent has become a major concern in recent years (Hassaan, 2016; Ananthashankar, 2012). Similarly, a number of chemicals used as washing and finishing agents pollute the water used during wet processing operations, but greater emphasis should be attributed to the large amount of nonbiodegradable organic compounds, especially synthetic textile dyes (Orts et al., 2018). This wastewater contaminates the ecosystem if discharged untreated. The environmental pollution is more noticeable during chemical processing operations of textiles, particularly dyeing. The toxic effluent of dyestuffs used during the dyeing process could severely damage the ground water and aquatic life.

20

Natural Dyes for Sustainable Textiles

Dyes cause harmful effects on the environment, even in low concentrations. There are various disadvantages in terms of pollution mainly in water, air, and soil as all these spheres are exposed to maximum in any industry’s functioning.

Air pollution by use of synthetic dyes Most processes performed in the wet processing industries produce gaseous emissions. The gaseous air has been identified as the second greatest pollution problem for dyeing and printing industries. Air pollution occurs by the emission of different types of gases such as CO2, NO2, SO2, etc. (Vallero, 2014). It also involves, for example, the release of particulate matter (PM) and dust, oxides of nitrogen and sulfur, and volatile organic compounds. Speculation concerning the amounts and types of air pollutants emitted from bleaching and dyeing operations has been widespread, but generally, air emission data from textile operations are not readily available. Air emissions include dust, oil mists, acid vapors, bad odors, and boiler exhausts. Cleaning and production changes result in sludge from tanks and spent process chemicals, which may contain toxic organics and metals. The condition further gets endangered by fumes developed by storage of chemicals and dyes used in processing area of the units. Evaporation of surface water due to increased atmospheric temperature (30e40 C) and evapotranspiration from soil and plants add to air pollution (Gupta et al., 2017). Again, air emission results from combustion of diesel from two major sources: point source boilers, ovens, and storage tanks, and diffusive source solvent based, wastewater treatment, warehouses, and spills. The contamination of air affects the surrounding area both directly and indirectly (Wang and Hao, 2012; Cole and Ellen, 2015). The main source of air pollution in dyeing and printing industries is also steam generation by coal and water. When the steam is generated, it produces carbon, carbon dioxide, carbon monoxide, and sulfur, which cause air pollution (Mia et al., 2019). Diesel engines and generators contribute to the problem by releasing PMs directly into the air and also emitting SO2 and NO2, which transform into secondary particulates in the atmosphere. PMs, PM2.5 and PM10, are generated during the incomplete combustion of diesel. Diesel exhaust is a group I carcinogen, which causes respiratory trouble. It contains several substances that are also listed individually as human carcinogens by the International Agency for Research on Cancer (Vallero, 2008). Increased levels of fine particles in the air as a result of anthropogenic particulate air pollution are consistently and independently related to the most adverse effects on human health.

Water pollution by the use of synthetic dyes The dyeing and printing industries use a huge amount of water in their manufacturing processes. The wastewater from the dyeing and printing industries is identified as the most polluted water considering the volume generated as well as the effluent composition (Nesaratnam, 2014). This wastewater is the main source of pollution problem in recent time, because most of the industries use conventional wastewater treatment plant. The dyes from different sources stay in the long time in the environment because of their high thermal and photo stability (Sakamoto et al., 2019). Color blocks light penetration which delays the photosynthetic activity and also has a tendency to chelate

Role of natural dyes in making sustainable textiles

21

metal ions which result in microtoxicity to fish and other organisms. The textile dyes significantly compromise the esthetic quality of water bodies, increase biochemical and chemical oxygen demand (BOD and COD), impair photosynthesis, inhibit plant growth, and enter the food chain. Low dissolved oxygen levels affect the entire aquatic biota life (Hassan and Carr, 2018). Textile dyeing also involves activities like dyeing, bleaching, and washing that use lots of water. Such processes produce salts, surfactants, which help dyes penetrate fabrics, and other surface-active agents, like detergent, that don’t decompose, so they endup in our water. It sometimes involves dangerous chemicals and substances like arsenic, lead, and mercury (Przybylek, 2018). Synthetic dyes which are used in textile dyeing are generally soluble organic compounds (Mahapatra, 2016), especially those classified as reactive, direct, basic, and acids. They exhibit high solubility in water, thus have the ability to impart color to a given substrate (Shamey and Zhao, 2014) because of the presence of chromophoric groups in its molecular structures. However, the property of fixing the color to the material is related to the auxotrophic groups, which are polar and can bind to polar groups of textile fibers (Wardman, 2017). In this respect, it is important to mention azo-type textile dyes which are significantly used in other industries as well, around 15%e50% of which, do not bind to the fabric, during the dyeing process, and are released into water stream (Rehman et al., 2018). Sometimes the process of applying dye on fabric is inefficient due to that; approximately 10%e15% of the dyes are released to the environment producing highly colored wastewater (Oguz Koroglu et al., 2019). This dye wastewater is considered to be one of the most harmful effluents, being carcinogenic to human and aquatic life. This is not only because dye produces harmful by-products but also is responsible for the eutrophication and nonesthetic pollution. Hazardous effects of dye on human life are dysfunction of central nervous system (CNS), kidney, reproductive system, brain, liver, etc. (Ghodke et al., 2018). Synthetic dye use puts environmental limitation because production of these dyes requires strong acids, alkalis, solvents, high temperatures, and heavy metal catalysts. In dyeing, it is known to use large quantities of water. Since production of these dyes needs very toxic and hazardous chemicals. They have not only resource-depleting impacts but the release of effluents or emissions have natural resource degrading impacts too (Usha and Nandhini, 2010).

Soil pollution by synthetic dyes Soil health plays an important role in the growth of plants and trees, maintaining the ecosystem with its natural fauna, flora, and indirectly sustains the environment to its natural conditions. Soil health is defined as the continued capacity of the soil to function as a vital living system, by recognizing that it contains biological elements that are key to ecosystem function within land use boundaries. These functions are able to sustain biological productivity of soil, maintain the quality of surrounding air and water environments, as well as promote plant, animal, and human health (Nathan, 2009). Soil pollution is caused by anthropogenic activities of man and due to rapid industrialization or due to other alteration the natural soil environment. Soil quality is also affected by past and present land use and nearness to pollution sources. Dyeing industry is one of the many industries which affect soil well-being badly. Liquid and solid wastes discharged from textile industries contain dyes, plastic, polyester, fibers, yarns, and other

22

Natural Dyes for Sustainable Textiles

hazardous materials. These polymeric compounds have been responsible for the pollution of local landfill habitats and agricultural fields, especially in developing countries. This soil pollution engenders plant growth inhibition by causing oxidative stress, lowering the protein content, photosynthesis, and CO2 assimilating rates (Vikrant et al., 2018). In the absence of stringent actions for soil pollution, dyeing industries generally/comfortably overlook this and lack of awareness also makes situation grim. The perception of soil as universal/omni-adsorbent and auto-remediating makes it more susceptible toward pollution negligence from industries in general. Textile industry puts heavy strain on global resources as it utilizes huge amounts of energy, water, and hazardous chemicals. This situation has raised issues about the sustainability of textiles due to severe burden on environment (Gulzar et al., 2019a,b). The presence of textile effluents has polluted the environment to great extent in last few decades, which has posed serious threats to soil fertility, crop production, and human health. So, alternative approaches have become necessary to ensure the sustainability of textile dyeing and subsequent finishing. Synthetic dyes exemplify a large group of colorful compounds that have detrimental effects on the environment, and in addition, some of them can pose risks to human health. The increasing complexity and difficulty in treating textile wastes has led to a constant search for new candidates that are economically effective and sustainably viable. This situation brings natural dyes in foray as they had already been used centuries ago successfully without harming environment and human health. Their use was enormous during time immortal, and they always have been respected for their esthetic and healing powers in human life.

2.1.3

Natural dyes

Any form of coloring moiety which was yielded through digestion, extraction, condensation, fermentation from plant, tree, flower, fruit, leaves, root, stem, bark, fungi, insects, and lichen, which can impart color on to fabric, fiber, leather, rock, paper, and human tissues is known as natural dye. The vista of natural dyes has increased many folds in recent years. In present scenario, natural dyes are the sole hope of human race to make the whole textile dyeing process sustainably viable for imminent generations. Life and light of the future textile dyeing process revolves around sustainably feasible natural dye components with technological enhancements to impart durable wash and light fastness on to dyed fabric. Natural dyes and colorants are still an essential part of the world’s ecological and cultural heritage; their selection and use to create permanent colors that were once common to all nationalities (Cardon, 2010). The advent of synthetic dyes caused rapid decline in the use of natural dyes, which were completely replaced by the former within a century. In present scenario, environmental consciousness of people about natural products, renewable nature of materials, less environmental damage, and sustainability of the natural products has revived the use of natural dyes in dyeing of textile materials. Natural dyes can be used for dyeing almost all types of natural fibers. Recent research shows that they can also be used to dye some synthetic fibers (Mansour and Yusuf, 2018). Apart from their application in textiles, natural dyes are also used in the coloration of food, medicines, handicraft

Role of natural dyes in making sustainable textiles

23

articles, and in leather processing. Many of the dye-yielding plants are used as medicines in various traditional medicinal therapies (Adeel et al., 2012; Yusuf et al., 2015, 2017). In spite of their mediocre fastness, many of natural dyes are antibacterial, antifungal, antioxidant, antileishmanial, and anticancer (Aggarwal et al., 2003; Mansour et al., 2013; Khan et al., 2012). Furthermore, they are more acceptable to environmentally conscious people around the world (Al-Sehaibani, 2000) and that’s why the attentions have been diverted to biodyes or natural dyes. Plants, animals, and microbes do produce cost-effective, nontoxic, and eco-friendly colorants applicable as dyes in textiles (Carvalho and Santos, 2015). In the last two decades, there has been a considerable increase in environmental awareness in response to uncontrolled greenhouse gas (GHG) emissions, ozone layer depletion, and pollution of water, air, and land. Therefore, natural dyes could provide a sustainable alternative to conventional dyes (Muthu and Gardetti, 2020). Fabric was earlier being dyed with natural dyes gave a limited and a dull range of colors. Besides, they showed low color fastness when exposed to washing and sunlight. As a result, they needed a mordant to form a dye complex to fix the fiber and dye together, thus making the dyers’ work tedious (Kant, 2012). Apart from this, natural dyes have their own strong advantages and some minor disadvantages. The advantages of natural dyes are: • • • • • • • •

Production of soft, lustrous earthy shades Production of rare colors Extraction from renewable sources Nonhazardous dye nature Biodegradability Ease of disposal Lack of environmental threats Reduced carbon emissions

The limitations of natural dyes are: • • • • • •

Lower reproducibility of colors/shades Less availability Low color yield Inadequate fixation Necessity for mordants (with the majority of natural dyes) Presence of heavy metals if synthetic mordants are used (Muthu and Gardetti, 2020)

2.1.3.1

Structure and type of natural dyes

Natural dyes are derived from natural resources; these are broadly classified as plant, animal, mineral, and microbial dyes. Natural dyes have different colors due to one basic chemical entity (chromophore) and auxochrome structure present in each of them. It is not necessary that dye is exclusively made from this chemical entity but can have other groups (auxochrome) as well to complete the compound. The unsaturated chromophore consists of atoms or groups of atoms, in which the organization of

24

Natural Dyes for Sustainable Textiles

alternate single and double bonds exist, thus letting the absorption of light energy. Most dyes all times comprise auxochrome groups, which are not responsible for color but are for intensity (tone) and affinity for the fiber, in addition to chromophores. Plantbased various dyes generally are polyphenols as chemical compounds. These phenolic compounds based on their various structural moieties can be categorized into groups such as quinones, flavonoids, tannins, lignanes, curcuminoids, coumarins, stilbenes, and their subgroups (Mansour, 2018). Major group of natural dyes based on their structural skeleton are different as: Indigoid dyes: This is perhaps the most important group of natural dyes. These colors are the oldest in human history to be used as fabric dye. The members include Indigo or Indigofera tinctoria and woad or Isatis tinctoria. Anthraquinone dyes: Some of the most important red dyes are based on the anthraquinone structure. They are obtained both from plants and insects. These dyes are characterized by good fastness to light. They form complexes with metal salts, and the resultant metal-complex dyes have good wash fastness. They exist in the form of hydroxyanthraquinones and usually have 1e3 hydroxyl groups. Alizarin and purpurin are two main anthraquinone-type colorants found in the root and tubers of Rubia tinctorum (common madder), Rubia peregrine (wild madder), and Rubia cordifolia (Indian madder). Carminic acid is another important hydroxyl-anthraquinone-based colorant, which is derived from cochineal and has been used to dye wool, silk, and cotton fabrics. Its brilliant red color with great light fastness could overcome many similar synthetic ones used in textiles (Alihosseini and Sun, 2011). Alpha-hydroxy-naphthoquinones: The most prominent members of this class of dyes are lawsone or henna, obtained from Lawsonia inermis and juglone, extracted from walnut (Juglans). This compound is well known for its cosmetic use to dye hair, nails, and skin, while it has been used to color textiles including leather, wool, and silk (Singh et al., 2015). Flavones: Most of the natural yellow colors are hydroxy and methoxy derivatives of flavones and isoflavones. Flavonoids provide the largest group of plant dyes ranging in colors from pale yellow (isoflavones) through deep yellow (chalcones, flavones, flavonols, and aurones), orange (aurones) to reds and blues (anthocyanins). Various plant sources of flavonoid dyes are Reseda luteola (weld), curcumin (Curcuma longa), palash or flame of the forest, etc. (Shriner, 1943). Dihydropyrans: Closely related to flavones in chemical structure are substituted dihydropyrans which include onion or Allium cepa. Anthocyananidins: Carajurin obtained from Bignonia chica. Carotenoids: In this group, the color is due to the presence of long conjugated double bond which give rise to yellow, orange, and red color. Bixa orellana, Crocus sativus, and Nyctanthes arbor-tristis are some of the example of this group containing dye plants (Niedzwiedzki et al., 2009). Tannins: Tannins are defined as water-soluble phenolic compounds and are obtained from the various parts of the plants such as fruit, pods, plant galls, leaves, bark, wood, and roots. Tannins play very important role in dyeing with natural dyes by improving the affinity of fibers toward different dyes. By mixing with different

Role of natural dyes in making sustainable textiles

25

natural dyes, it gives different shades like yellow, brown, gray, and black. Acacia catechu (cutch), Terminalia chebula (harda), Punica granatum (pomegranate), and Quercus infectoria (gallnut) are plant sources for tannins (Shabbir et al., 2017). Tannins are also used as biomordant to pretreat cotton (to increase their reactivity toward dye adherence) before mordanting. Apart from these chemical groups, Dihydropyran, Betalains, Quinonoids, and Pyridine groups can also be present as main structural compound in natural dyes. Bougainvillea flower is an example for betalain colorants as shown in Fig. 2.1.

2.1.3.2

Natural dyes and their intrinsic properties

The mystic and magical properties that were once inferred upon natural dyes by our ancestry, recognized by many indigenous people and acknowledged for centuries by mankind, all without any kind of scientific understanding as to why these properties existed could provide today’s society with more than nature’s colors. Certain natural dyes and colorants have been proven to possess medicinal healing qualities; these could be exploited to provide mankind for more than just color and initiate a return to wearing clothing dyed with natural coloration substances (dyes). Plant pigments such as anthocyanins and carotenoids have scientifically validated antioxidant and antiinflammatory benefits. The pomegranate (P. granatum) along with many other common natural dyes is also reported as potent antimicrobial agents owing to the presence of large amounts of tannin in their chemical structure. While several other sources of plant dyes are reported to exhibit both antibacterial, antifungal, antiviral, and antineoplastic activity (Gupta et al., 2004), and these contain the coloring pigments naphthoquinones such as lawsone from henna (Lawsonia inermis), juglone from walnut (Juglans regia), and lapachol from alkanet (Alkanna tinctoria) (Siva, 2007). Their intrinsic nature involves the following: •

Natural dyes generally give their best output on natural fabrics such as pure cotton, pure silk, and pure wool, especially they have very good affinity toward protein fibers.

Figure 2.1 Bougainvillea flower a source of natural dye.

26

• • • •

Natural Dyes for Sustainable Textiles

Natural dyes are energy savior as excessive heat disintegrates their molecular integrity and which sometimes affects their light and wash fastness. Natural dyes generally require some inorganic salts to act as mordants for good adherence, but new research has shown milder salts or other natural products (which can’t be used as dye) can act as biomordants. Sometimes enzymes can also act as biomordants. Natural dyes are also worker friendly as no harsh chemicals or excessive heat/energy are involved in whole dyeing process, so mild working conditions are best for dyeing industry workers. Although common basic principles of dyeing with natural dyes can be applied, but their high variability leads to the necessity of individual approach for each of them. It is necessary to optimize the dyeing conditions like time, temperature, liquor ratio, dosage and type of mordant preparation of plant material, and choice of suitable fibers (Krízova, 2015a,b).

These days, natural dyes have variety of applications. These are not only used in textile dyeing and functional finishing (antimicrobial, deodorizing, and ultraviolet [UV] protecting) but also food and cosmetic coloring, cosmetic healing additives, pH indicators, and in several other uses (Carvalho and Santos, 2015). The cosmetic industry now employs many natural dyes due to the fact they will cause fewer side effects than the employment of synthetic dyestuffs, but they can also provide extra properties such as UV protection, skin moisturizing, and antiaging (Chengaiah et al., 2010; Charlebois, 2007).

2.1.3.3

Sustainability of natural dyes

In recent years, green chemistry has emerged as an effective tool to make textile wet processing sustainable. Green chemistry has helped in the development of alternative green and biodegradable chemicals. In the past years, there is this inclination in the direction of the replacement of synthetic dye by natural ones, mainly due to the surge of consumer demand for natural products. Green chemistry has played its role to strengthen the idea of sustainable wet processing (Gulzar et al., 2019a,b). Much more reactive and biodegradable dyes have been developed for effective dyeing processing to minimize the amount of unfixed dyes in wastewater. Current interest into natural dyes and colorants in textile dyeing is growing within the Industrialized Nations in natural (green) products and sustainable ways of living (Cardon, 2010). This is a result of the meticulous environmental standards imposed by many countries in response to the toxic and allergic reactions associated with synthetic dyes. Natural dyes exhibit better biodegradability and are generally more compatible with the environment. Natural dyes based on their extraction are generally applied on natural fabrics. But before their application, textile/fabric needs to be treated with a metal moiety which grip up dye molecule and that’s how natural dye hold itself on to fiber specially cotton/cellulose. Cotton is an inactive material containing molecules of cellulose hard to hold dye. Earlier understanding of dyeing techniques and their applications was empirical and was not backed by scientific reasoning as they had developed essentially as a folk art. However, in recent times, the dyeing technique is interpreted on sound scientific principles, and the interaction between the dye and the dyed material is well understood

Role of natural dyes in making sustainable textiles

27

and the nature of bonding in certain dyes by looking at their structures and using metal ions for chelation is explained by various researchers (Vankar, 2000). Appropriate scientific techniques or procedures are being derived from scientific studies on dyeing methods, dyeing process variables, dyeing kinetics, and compatibility of selective natural dyes with minimal use of hazardous chemicals (Vankar et al., 2017a,b). Textile dyeing industry puts heavy strain on global resources as it utilizes huge amounts of energy, water, and hazardous chemicals. This situation has raised issues about the sustainability of textiles due to severe burden on environment (Gulzar et al., 2019a,b). Although in natural dyeing different aspects govern whole process as sometimes plants may have more than one color depending upon which part of the plant one uses. The shade of the color a plant produces will vary according to time of the year the plant is picked, how it was grown, soil conditions, etc. The minerals in the water used in a dye bath can also alter the color. Various natural dyes could present all the colors of the visible spectrum with different and enhanced hue with the use of some inorganic mild salts.

2.1.3.4

Natural dyes and sustainable technologies

The processes in wet textile dyeing can be converted into ecologically sustainable by the use of new improved technologically sound methods with lesser use of harmful/ harsh chemicals, energy, water, etc. For successful commercial use of natural dyes and making dyeing process ecologically sustainable, the appropriate and standardized dyeing techniques are in process to be adopted. Ionic liquids have been developed as alternative medium to replace water consumption in wet processing, ensuring its sustainability. Further, a number of biomaterials have been developed for sustainable dyeing processing operations, and an increased interest in sustainability appears to be a changing cultural landscape toward natural dyes (Cardon, 2010). Dyeing wastewater has a high coloration and a high content of electrolytes, so a combination of ultrafiltration and reverse osmosis technology can be used to treat it, saving reasonably good quantum of energy and treated water can be reused. The presence of metal species in dyeing wastewater can be significantly reduced by the use plant tannins as biomordant (A. catechu, Terminalia arjuna, and P. granatum) and enzymes (cellulases, amylases, trypsin, etc.) for all the fabrics. Fig. 2.2 shows an example of the role of enzyme in binding the colorant to the fabric. Commercial sonicator dyeing with Rubia showed that pretreatment with 2% biomordant, Eurya acuminata (local name, Nausankhee) shows very good fastness properties for dyed cotton (Vankar et al., 2008). The use of sonicator saves energy as no separate heating of dye bath is required and biomordant use can significantly reduce chemical usage. Two-step ultrasonic dyeing of cotton and silk fabrics with natural dyes, Terminalia arjuna, P. granatum, and Rheum emodi has been developed in which an enzyme (protease-amylase, diasterase, and lipase) is complexed with tannic acid first as a pretreatment. This was found to be comparable with one-step simultaneous dyeing and gave cotton and silk fabrics rapid dye adsorption kinetics and total higher dye adsorption (Vankar et al., 2007). The role of enzyme pretreatment is primarily for

28

Natural Dyes for Sustainable Textiles

Figure 2.2 Role of enzyme to bind the colorant molecule.

better absorbency, adherence, and dyeability of these dyes on cotton fabric, thereby completely replacing metal mordants with enzyme for adherence of natural dyes on cotton (Vankar and Shanker, 2008). All these researches pave the way for lesser usage of chemicals as well as less energy with natural dyes being harbinger of good dye adherence too. Energy management is a new game changer for any industry. It not only reduces production cost but also is a big leap toward eco-sustainability. Energy-saving mechanisms and new technologies should be welcomed in dyeing industry as the use of natural dyes can sometimes be very energy exhausting as from extraction to application natural dyes are heat-sensitive moieties. Heat consumption increases temperature for the same consistency in the dyeing process with respect to time. Some great heatsaving processes can be used in dyeing such as room temperature or low temperature dyeing (Vankar et al., 2017a,b) and lesser use of hot water for dye extraction and dyeing. New techniques such as supercritical fluid dyeing, microwave dyeing, etc., are good examples of energy-saving techniques which are compatible with natural dyes. These all innovations have given very good results and can be potential aspirant as heat/energy saviors in natural dyeing making whole processes economically and ecologically sustainable. Although energy and heat requirement of dyeing process can’t be fully eliminated but can be optimized by using proper technology, mechanics, vessel, process, auxiliaries, and even dye. Natural dyes can be good option in this regard as their constitution/structure will be fully adaptable to low processing heat. Another aspect of heat saving can result in less debilitated fabric, as the fabric when exposed to lower temperature during chemical processing will definitely go through with less abrasion and breakages of fibers within it compared to those exposed at conventional higher temperature. The fabric chemically processed and finished at lower temperature might have the same color, luster, and quality as compared to the one processed and finished at conventional higher temperatures (Md and Samanta, 2019). The alternatives for energy and chemical sustainability can be achieved by changing process

Role of natural dyes in making sustainable textiles

29

as continuous dyeing instead of jet treatments; optimization of existing processes and procedures of dye and mordant application; and the use of highly efficient washing and finishing technologies and reuse of clarified wastewater as process water again. Supercritical dyeing technique is an innovation to conserve the thermal energy as the fabric is in the dried state because at the end of process, CO2 is released in gaseous state. This is a new technique of using supercritical carbon dioxide as a dyeing medium. Dyeing is performed in a high pressure vessel called an autoclave. Carbon dioxide exists as a supercritical fluid at temperature at about 31 C and pressures above 72 bar. The anhydrous process offers number of ecological and economical advantages such as no preparation of processing water and low energy consumption for heating up liquor (Prince, 2008). The poor extraction of colorant from plants is one of the main hindrances of their use in modern textile because very little amount of natural coloring compounds can be extracted in water. Hence, extraction of coloring compounds is done by the rupturing of plant cell wall (Sivakumar et al., 2011). For the improvement of dye extraction and color fastness characterization, scientists have used different technologies such as suitable extraction media (Ali et al., 2009; Sinha et al., 2016) and radiation treatments (Cuoco et al., 2009; Ajmal et al., 2014). Another way of preventing synthetic products inclusive of synthetic dyes into textile manufacturing can be the adoption of eco-certification system which certifies and provides satisfaction to consumers of sustainable textile production in every realm of fabric processing whether dyeing or compatibility toward add-on like antifungal, antimicrobial, etc. All the processing divisions certified with such norms should strictly monitor the environment-friendly procedures, safeguard healthy and socially sound working conditions for all the staff, and take all the precautionary measure to prevent any calamity.

2.1.3.5

Need of natural dyes to minimize pollution

It is only since few decades ago that textile industries have turned to synthetic dyes, but they were so successful that natural dyes currently account only for about 1% of the total amount of dyes used worldwide (Gulrajani, 2001), and this is so even that the use of natural dyes has a strong tradition in many countries (e.g., India, Turkey, Mexico, Morocco, or countries of West Africa). Today, there is a whole spectrum of colors that can be obtained from a multitude of plants, insects, and fungi, and these have been used across the centuries to dye textiles, color artifacts, pattern and color skin, hair, and even color the food. The discovery and use of such natural colorants have contributed to the maintenance of a strong bond between humankind and nature, which with help could revive and enhance what was once integral to human society. Natural dyes and colorants are still an essential part of the world’s ecological and cultural heritage, their selection and use to create permanent colors that were once common to all nationalities (Fletcher, 2013). Unlike nonrenewable raw materials of synthetic dyes, natural dyes are mostly renewable and sustainable. Natural dye sources are agriculturally renewable sustainable vegetable-plant-based colorant sources, whereas main sources of synthetic dyes are limited (oil and coal), the production of synthetic dyes pollutes the water and the environment by toxic wastes in which

30

Natural Dyes for Sustainable Textiles

majority of water sources get polluted by wastewater from residual dyes used in coloring generally containing chemical moieties like sulpho, nitro, and azo groups of synthetic dyes. Apart from these, metal species like chromium, zinc, and lead make dyeing wastewater more deteriorating and when released without treatment immensely inhibit health of water body in terms of BOD and COD. This deterioration greatly affects health of water ecology comprising aquatic animals and plants and overall health of water body. The reason of limited use of natural dyes in textile industry to some extent is due to unparalleled color depth and quality of synthetic dyes. But this is anexcessive/ big price to pay for a fancy colored cloth of one’s choice. Thus there’s abundant prospective to develop and establish natural dyes as the “color of people.” That’s why sources of natural dyes are continually renewed in nature (Krízova, 2015a,b). So it might seem that natural dyes are not only environmentally friendly and health friendly but above all cost-friendly and consumer-friendly. In terms of sustainability, synthetic dyes are produced from nonrenewable resources; however, natural dyes are extracted from renewable sources. The ability to obtain the dye from renewable natural sources makes natural dyes an attractive dye class for more sustainable world.

2.1.3.6

Natural dyes and textile sustainability

In textile dyeing, the microwave and UV radiations are generally used for enhancing the dyeing ability of colorants and obtaining extract from the crude materials. It has been established that treatment of dyeing fabric and the crude plant material with UV radiations improves the quality of dye and color fastness (Bhatti et al., 2016). Radiation technology is also being used for the improvement of color extraction and surface modification of fabric in dyeing process (Sinha et al., 2012; Bhatti et al., 2012; Sinha et al., 2013; Ajmal et al., 2014). Bioactive textiles are new innovative textile products that are being developed to extend the existing boundaries of textile application. Future textiles will act as “repository” storing systems that are capable of continually releasing small doses of active substances from the fabric during wear which have a protective or therapeutic effect on the skin. This can be achieved through the creation of supermolecular host structures or other methods such as using aqueous solutions that are incorporated into nanocapsules, sol-gel layers, or storing active substances in water-absorbing polymers with network structures, fixed onto the fiber (Swerev, 2003). By employing these new technologies to natural dyes and their coloring chemical components, a possibility arises for enhancing the healing properties that these colors can provide. Metallic salts have been employed as mordants through history to help with dye fixation and improve dye fastness. Small ions like sliver, zinc, copper, and quaternary ammonium compounds can be linked to natural dyes compounds through selective choice of mordants for antibacterial activity (Wells, 2013). If such links could be made, it will greatly enhance the antibacterial function of the natural dye used to color the cloth. Dyes are also classified according to their end-use properties, most notably their fastness under a variety of end-use conditions, such as light, laundering, rubbing

Role of natural dyes in making sustainable textiles

31

(crocking), dry cleaning, etc. These properties, as customers’ requirements, are taken into account during dye selection. However, customers generally have little knowledge of the environmental consequences of their selections. For maximum pollution prevention, the dyer should encourage the customer to consider more environmentally friendly dyes. Often, a slight change in hue or brightness requirements allows the selection of different dyes and colorants that could potentially eliminate significant environmental problems (e.g., metals in wastewater) (Chavan, 2011). The most important pigments of natural dyes have been proven to have health giving qualities such as antimicrobial and antiinflammatory, like Anthracenes include several pigments found in the madder family such alizarin; munjistin and purpurin, emodin is found in Persian berries and polygonin from Japanese Knotweed. The insect dyes cochineal, kermes, and lac (laccaic acid) are also included in these (Maulik, 2011). Thus, the nontoxic, noncarcinogenic, biodegradable, and eco-friendly characteristics of naturally derived colorants made its own way to reach the hearts of conscious consumers for healthy lifestyle (Shahid, 2013). Antimicrobial textile as one of medical textiles act by protecting users from hygienic problems resulting from exposure to pathogenic or odor-generating microbes, where the growth of microorganisms results in the reduction of functionality by undesirable esthetic changes or rotting damage. New challenges as well as new opportunities in manufacturing of antimicrobial cellulosic textiles are the future concerns for textile and apparel industry. The major applications of antimicrobial textile could be ascribed according to consumer demands, represented in more comfort, easy care, health, and durable to laundering (Emam, 2019). There is considerable awareness among the consumers for environmental-friendly textiles. Stern environment protection regulations alsoled to change strategies by industries in this field.

2.2

Conclusions

World researchers are trying hard to establish/develop polyphenolic biomolecules present in and as natural dyes, to get high yields and the features like excellent fastness, sustainability, cost effectiveness, durability for all the available fabrics. It can be assumed that plant-based dyes have such composition that their noxious residuals are far less as compared to synthetic dyes. Second, their chemical nature is such that they are easily degradable in water and soil making it ecologically feasible. If natural colorants are used, the whole dyeing process can be optimized to greener one with lesser use of energy, plant-based mordants, eco-sustainable chemicals, and environment friendly technologies leading the path toward new horizons of commercial prosperity and environmental affluence. This could lead to rise and shine of textiles having been dyed with multifaceted natural dye components providing many qualities as antimicrobial, antifungal, antiperspiration and with all the other esthetic properties loved and appreciated by consumers. Certain natural dyes and colorants have been proven to possess medicinal healing qualities, and these could be exploited to provide mankind for more than just color and initiate wearing clothing dyed with natural dyes (Wells, 2013). Fabric so dyed will have improved quotient of sustainability and is health

32

Natural Dyes for Sustainable Textiles

friendly arty creation from contented industry to more satisfied customer having no guilt of distressing environment. Sustainable and multifunctional fabric can easily be adopted by people/person in any area of use whether military, sports, hospital, school, labor-intensive industry, and of course by consumer demanding natural products. The use of natural dyes also supports entire perception of pollution-free environment in synergy with industries abandoning harmful synthetic dyes and auxiliaries for ambience living in “Climate Smart” world and “Eco-Sensitive” consumers.

References Adeel, S., Bhatti, I.A., Kausar, A., Osman, E., 2012. Influence of UV radiations on the extraction and dyeing of cotton fabric with Curcuma longa L. Affat, S.S., 2021. Classifications, advantages, disadvantages, toxicity effects of natural and synthetic dyes: a review. University of Thi-Qar Journal of Science 8 (1), 130e135. Aggarwal, B.B., Kumar, A., Bharti, A.C., 2003. Anticancer potential of curcumin: preclinical and clinical studies. Anticancer Research 23 (1/A), 363e398. Ajmal, M., Adeel, S., Azeem, M., Zuber, M., Akhtar, N., Iqbal, N., 2014. Modulation of pomegranate peel colourant characteristics for textile dyeing using high energy radiations. Industrial Crops and Products 58, 188e193. Alc^antara, M., Daltin, D., 1996. A química do processamento têxtil. Química Nova 19 (3), 320e330. Ali, S., Hussain, T., Nawaz, R., 2009. Optimization of alkaline extraction of natural dye from Henna leaves and its dyeing on cotton by exhaust method. Journal of Cleaner Production 17 (1), 61e66. Alihosseini, F., Sun, G., 2011. Antibacterial Colorants for Textiles. Functional Textiles for Improved Performance, Protection and Health. Elsevier, pp. 376e403. Al-Sehaibani, H., 2000. Evaluation of extracts of henna leaves as environmentally friendly corrosion inhibitors for metals. Materialwissenschaft und Werkstofftechnik: Materials Science and Engineering Technology 31 (12), 1060e1063. Ananthashankar, R., 2012. Treatment of Textile Effluent Containing Reactive Red 120 Dye Using Advanced Oxidation. M.Sc., Dalhousie University. Anonymous, 2014. 1 - Introduction to dyeing and dyehouse automation. In: Shamey, R., Zhao, X. (Eds.), Modelling, Simulation and Control of the Dyeing Process. Woodhead Publishing, pp. 1e30. Ardila-Leal, L.D., Poutou-Pi~nales, R.A., Pedroza-Rodríguez, A.M., Quevedo-Hidalgo, B.E., 2021. A brief history of colour, the environmental impact of synthetic dyes and removal by using laccases. Molecules 26 (13), 3813. Bhatti, I.A., Adeel, S., Irshad, M., Abbas, M., 2012. Effect of mercerization and gamma irradiation on the dyeing behaviour of cotton using stilbene based direct dye. Radiation Physics and Chemistry 81 (7), 823e826. Bhatti, I.A., Adeel, S., Parveen, S., Zuber, M., 2016. Dyeing of UV irradiated cotton and polyester fabrics with multifunctional reactive and disperse dyes. Journal of Saudi Chemical Society 20 (2), 178e184. Cardon, D., 2010. Natural Dyes, Our Global Heritage of Colors. Carvalho, C., Santos, G., 2015. Global communities, biotechnology and sustainable designe natural/bio dyes in textiles. Procedia Manufacturing 3, 6557e6564.

Role of natural dyes in making sustainable textiles

33

Charlebois, D., 2007. Elderberry as a medicinal plant. In: Issues in New Crops and New Uses. ASHS Press, Alexandria, VA, pp. 284e292. Chavan, R.B., 2011. Environmentally friendly dyes. In: Clark, M. (Ed.), Handbook of Textile and Industrial Dyeing, vol. 1. Woodhead Publishing, pp. 515e561. Chengaiah, B., Rao, K.M., Kumar, K.M., Alagusundaram, M., Chetty, C.M., 2010. Medicinal importance of natural dyes-a review. International Journal of PharmTech Research 2 (1), 144e154. Chequer, F.D., De Oliveira, G.R., Ferraz, E.A., Cardoso, J.C., Zanoni, M.B., De Oliveira, D.P., 2013. Textile dyes: dyeing process and environmental impact. Eco-Friendly Textile Dyeing and Finishing 6 (6), 151e176. Cole, S., Ellen, E., 2015. New NASA Satellite Maps Show Human Fingerprint on Global Air Quality. National Aeronautical Space Administration NASA, Washington, DC, USA. Couto, S.R., 2009. Dye removal by immobilised fungi. Biotechnology Advances 27 (3), 227e235. Cuoco, G., Mathe, C., Archier, P., Chemat, F., Vieillescazes, C., 2009. A multivariate study of the performance of an ultrasound-assisted madder dyes extraction and characterization by liquid chromatography-photodiode array detection. Ultrasonics Sonochemistry 16 (1), 75e82. Emam, H.E., 2019. Antimicrobial cellulosic textiles based on organic compounds. 3 Biotech 9 (1), 29. Fletcher, K., 2013. Sustainable Fashion and Textiles: Design Journeys. Routledge. Ghodke, S.A., Sonawane, S.H., Bhanvase, B.A., Potoroko, I., 2018. Chapter 53 - Advanced engineered nanomaterials for the treatment of wastewater. In: Mustansar Hussain, C. (Ed.), Handbook of Nanomaterials for Industrial Applications. Elsevier, pp. 959e970. Gulrajani, M., 2001. Present status of natural dyes. Indian Journal of Fibre and Textile Research 26 (2), 191e201. Gulzar, T., Farooq, T., Kiran, S., Ahmad, I., Hameed, A., 2019a. Green Chemistry in the Wet Processing of Textiles. The Impact and Prospects of Green Chemistry for Textile Technology. Elsevier, pp. 1e20. Gulzar, T., Farooq, T., Kiran, S., Ahmad, I., Hameed, A., 2019b. The Impact and Prospects of Green Chemistry for Textile Technology. Elsevier. Gupta, D., Khare, S.K., Laha, A., 2004. Antimicrobial properties of natural dyes against Gramnegative bacteria. Coloration Technology 120 (4), 167e171. Gupta, V.K., Kumar, R., Nayak, A., Saleh, T.A., Barakat, M., 2013. Adsorptive removal of dyes from aqueous solution onto carbon nanotubes: a review. Advances in Colloid and Interface Science 193, 24e34. Gupta, B.G., Biswas, J.K., Agrawal, K.M., 2017. Air pollution from bleaching and dyeing industries creating severe health hazards in Maheshtala textile cluster, West Bengal, India. Air, Soil and Water Research 10, 1178622117720787. Hassaan, M., 2016. Advanced Oxidation Processes of Some Organic Pollutants in Fresh and Seawater. Ph.D., Port Said University. Hassan, M.M., Carr, C.M., 2018. A critical review on recent advancements of the removal of reactive dyes from dyehouse effluent by ion-exchange adsorbents. Chemosphere 209, 201e219. Ibrahim, N.A., 2011. 4 - Dyeing of textile fibre blends. In: Clark, M. (Ed.), Handbook of Textile and Industrial Dyeing, vol. 2. Woodhead Publishing, pp. 147e172. Kant, R., 2012. Textile dyeing industry an environmental hazard. Natural Science 4 (1), 22e26. Khan, S.A., Ahmad, A., Khan, M.I., Yusuf, M., Shahid, M., Manzoor, N., Mohammad, F., 2012. Antimicrobial activity of wool yarn dyed with Rheum emodi L. (Indian Rhubarb). Dyes and Pigments 95 (2), 206e214.

34

Natural Dyes for Sustainable Textiles

Khattab, T.A., Abdelrahman, M.S., Rehan, M., 2020. Textile dyeing industry: environmental impacts and remediation. Environmental Science and Pollution Research 27 (4), 3803e3818. Krízova, H., 2015a. Natural dyes: their past, present, future and sustainability. In: Recent Developments in Fibrous Material Science. Czech Republic. Kanina, pp. 59e71. Krízova, H., 2015b. Natural dyes: their past, present, future and sustainability. In: Recent Developments in Fibrous Material Science. Kosmas Publishing, Prague. Ladha, D.G., 2009. Dyeing. In: Dyes. Mahapatra, N., 2016. Textile Dyes. CRC Press, Woodhead Publishing Pvt Ltd, New Delhi. Mansour, R., 2018. Natural dyes and pigments: extraction and applications. Handbook of Renewable Materials for Coloration and Finishing 9, 75e102. Mansour, R., Yusuf, M., 2018. Natural dyes and pigments: extraction and applications. In: Handbook of Renewable Materials for Coloration and Finishing, pp. 75e102. Mansour, R., Haouas, N., Kahla-Nakbi, A.B., Hammami, S., Mighri, Z., Mhenni, F., Babba, H., 2013. The effect of Vitis vinifera L. leaves extract on Leishmania infantum. Iranian Journal of Pharmaceutical Research: IJPR 12 (3), 349. Maulik, S., 2011. Natural dyeean overview. In: Proceedings of the Vegetable Dye and its Application on Textiles National Workshop and Seminar. Md, A.H., Samanta, A., 2019. A cost minimization process of heat and energy consumption for direct dyeing of cotton fabric coloration with triethanolamine. Current Trends in Fashion Technology & Textile Engineering 5 (3), 75e78. Mia, R., Selim, M., Shamim, A., Chowdhury, M., Sultana, S., Armin, M., Hossain, M., Akter, R., Dey, S., Naznin, H., 2019. Review on various types of pollution problem in textile dyeing & printing industries of Bangladesh and recommendation for mitigation. Journal of Textile Engineering & Fashion Technology 5 (4), 220e226. Moore, S.B., Ausley, L.W., 2004. Systems thinking and green chemistry in the textile industry: concepts, technologies and benefits. Journal of Cleaner Production 12 (6), 585e601. Muthu, S.S., Gardetti, M.A., 2020. Sustainability in the Textile and Apparel Industries: Sourcing Synthetic and Novel Alternative Raw Materials. Springer Nature. Nathan, M., 2009. Soil testing for lead for garden and landscape soils. Missouri Environment and Garden 15 (4), 23e32. Nesaratnam, S.T., 2014. References. In: Nesaratnam, S.T. (Ed.), Water Pollution Control. Wiley online 284e296. Niedzwiedzki, D.M., Sandberg, D.J., Cong, H., Sandberg, M.N., Gibson, G.N., Birge, R.R., Frank, H.A., 2009. Ultrafast time-resolved absorption spectroscopy of geometric isomers of carotenoids. Chemical Physics 357 (1e3), 4e16. Ogugbue, C.J., Sawidis, T., 2011. Bioremediation and detoxification of synthetic wastewater containing triarylmethane dyes by Aeromonas hydrophila isolated from industrial effluent. Biotechnology Research International 2011. Oguz Koroglu, E., Civelek Yoruklu, H., Demir, A., Ozkaya, B., 2019. Chapter 3.9 - Scale-up and commercialization issues of the MFCs: challenges and implications. In: Mohan, S.V., Varjani, S., Pandey, A. (Eds.), Microbial Electrochemical Technology. Elsevier, pp. 565e583. Orts, F., Del Río, A., Molina, J., Bonastre, J., Cases, F., 2018. Electrochemical treatment of real textile wastewater: trichromy Procion HEXL. Journal of Electroanalytical Chemistry 808, 387e394. Prince, A., 2008. Energy Conservation in Textile Industries & Savings. Przybylek, S., 2018. Textile Production & The Environment: Impact & Issues. study.com/ academy/lesson/.

Role of natural dyes in making sustainable textiles

35

Rehman, K., Shahzad, T., Sahar, A., Hussain, S., Mahmood, F., Siddique, M.H., Siddique, M.A., Rashid, M.I., 2018. Effect of Reactive Black 5 azo dye on soil processes related to C and N cycling. PeerJ 6, e4802. Sakamoto, M., Ahmed, T., Begum, S., Huq, H., 2019. Water pollution and the textile industry in Bangladesh: flawed corporate practices or restrictive opportunities? Sustainability 11 (7), 1951. Shabbir, M., Islam, S.U., Bukhari, M.N., Rather, L.J., Khan, M.A., Mohammad, F., 2017. Application of Terminalia chebula natural dye on wool fiberdevaluation of color and fastness properties. Textiles and Clothing Sustainability 2 (1), 1e9. Shahid, M., 2013. Shahid-ul-Islam and F. Mohammad. Journal of Cleaner Production 53, 310e331. Shamey, R., Zhao, X., 2014. Modelling, Simulation and Control of the Dyeing Process. Elsevier. Shang, S.M., 2013. 13 - Process control in dyeing of textiles. In: Majumdar, A., Das, A., Alagirusamy, R., Kothari, V.K. (Eds.), Process Control in Textile Manufacturing. Woodhead Publishing, pp. 300e338. Shriner, R., 1943. The Chemistry of Natural Coloring Matters: The Constitution, Properties, and Biological Relations of the Important Natural Pigments (Mayer, Fritz; translated and revised by AH Cook). ACS Publications. Singh, D.K., Luqman, S., Mathur, A.K., 2015. Lawsonia inermis L.eA commercially important primaeval dying and medicinal plant with diverse pharmacological activity: a review. Industrial Crops and Products 65, 269e286. Sinha, K., Saha, P.D., Datta, S., 2012. Response surface optimization and artificial neural network modeling of microwave assisted natural dye extraction from pomegranate rind. Industrial Crops and Products 37 (1), 408e414. Sinha, K., Chowdhury, S., Saha, P.D., Datta, S., 2013. Modeling of microwave-assisted extraction of natural dye from seeds of Bixa orellana (Annatto) using response surface methodology (RSM) and artificial neural network (ANN). Industrial Crops and Products 41, 165e171. Sinha, K., Aikat, K., Das, P., Datta, S., 2016. Dyeing of modified cotton fiber with natural Terminalia arjuna dye: optimization of dyeing parameters using response surface methodology. Environmental Progress & Sustainable Energy 35 (3), 719e728. Siva, R., 2007. Status of natural dyes and dye-yielding plants in India. Current Science 916e925. Sivakumar, V., Vijaeeswarri, J., Anna, J.L., 2011. Effective natural dye extraction from different plant materials using ultrasound. Industrial Crops and Products 33 (1), 116e122. Swerev, M., 2003. What dermatologists should know about textiles. Textiles and the Skin 31, 1e23. Tkaczyk, A., Mitrowska, K., Posyniak, A., 2020. Synthetic organic dyes as contaminants of the aquatic environment and their implications for ecosystems: a review. Science of the Total Environment 717, 137222. Usha, M., Nandhini, M., 2010. An Overview about Usage of Dyes in Textile Industry. https:// www.fibre2fashion.com/industry-article/5291/an-overview-about-usage-of-dyes-intextile-industry. Vallero, D., 2008. Fundamentals of Air Pollution. US Environmental Protection Agency, Elsevier Academic Press, MA, US. Vallero, D., 2014. Fundamentals of Air Pollution. Academic press. Vankar, P.S., 2000. Chemistry of natural dyes. Resonance 5 (10), 73e80. Vankar, P.S., Shanker, R., 2008. Ecofriendly ultrasonic natural dyeing of cotton fabric with enzyme pretreatments. Desalination 230 (1e3), 62e69.

36

Natural Dyes for Sustainable Textiles

Vankar, P.S., Shanker, R., Verma, A., 2007. Enzymatic natural dyeing of cotton and silk fabrics without metal mordants. Journal of Cleaner Production 15 (15), 1441e1450. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S., 2008. Ecofriendly sonicator dyeing of cotton with Rubia cordifolia Linn. using biomordant. Dyes and Pigments 76 (1), 207e212. Vankar, P., Shukla, D., Wijayapala, S., 2017a. Low temperature optimized dyeing of cotton, wool and silk with extract of camellia sinensis (tea leaves). Journal of Textile Engineering & Fashion Technology 2 (1), 274e280. Vankar, P.S., Shukla, D., Wijayapala, S., Samanta, A.K., 2017b. Innovative silk dyeing using enzyme and Rubia cordifolia extract at room temperature. Pigment & Resin Technology 64 (4), 296e302. Vikrant, K., Giri, B.S., Raza, N., Roy, K., Kim, K.-H., Rai, B.N., Singh, R.S., 2018. Recent advancements in bioremediation of dye: current status and challenges. Bioresource Technology 253, 355e367. Wang, S., Hao, J., 2012. Air quality management in China: issues, challenges, and options. Journal of Environmental Sciences 24 (1), 2e13. Wardman, R.H., 2017. An Introduction to Textile Coloration: Principles and Practice. John Wiley & Sons. Wells, K., 2013. Colour, health and wellbeing: the hidden qualities and properties of natural dyes. Journal of the International Colour Association 11, 28e36. Yusuf, M., Shahid, M., Khan, M.I., Khan, S.A., Khan, M.A., Mohammad, F., 2015. Dyeing studies with henna and madder: a research on effect of tin (II) chloride mordant. Journal of Saudi Chemical Society 19 (1), 64e72. Yusuf, M., Shabbir, M., Mohammad, F., 2017. Natural colorants: historical, processing and sustainable prospects. Natural Products and Bioprospecting 7 (1), 123e145.

Using chemical management system in natural dyeing process to make it sustainable 3.1

3

Introduction

The global textile and clothing industry is bound to be huge, as it fulfills the second basic requirement of man. The consumption of textile products is very huge and is increasing day by day due to increase of population and also increase in sq. meter cloth consumption per person. Ultimately the overall impact the apparel industry has on our planet is quite large. It is said that textile is the second largest polluter (after paper industry) in the world. A general assessment says that pollutants released by the global textile industry are continuously doing unimaginable harm to the environment. The textile industry is water intensive and produces pollutants of different forms. The manufacturing operation also generates vapors during dyeing, printing, and curing of dye or color pigments. In textile industry, various types of fibers are used which leads to different process and various dyes and chemicals printing paste add to the load of pollution drastically. Major environmental issues in textile industry result from wet processing. Wet processes may be carried out on yarn or fabric, specifically for dyeing process, hundreds of dyes and auxiliaries are used. Processes that play a major role in the release of hazardous substances into the environment are the pretreatment, dyeing, and finishing of textiles. It can be assumed that only a small proportion of chemicals such as dyes, optical brighteners, and finishing chemicals remain on the textile substrate and rest get discharge into water. The textile industry is one of the most pollutants releasing industries of the world. Besides, 20% of all fresh water pollution is made by textile treatment and dyeing. Pollutants released by the global textile industry are continuously doing unimaginable harm to the environment. It is essential to have sharp focus on pollution and pollutants created by textile industry (Fiber2fashion, 2012). In total, a study by the Swedish Chemical Agency estimated that approximately 10% of the total amounts of over 2400 different chemicals that can be used in textiles have particularly hazardous properties. Thus to identify chemical use and content in the final garment has been recognized as crucial to meet customer and legal demands. To minimize the release of hazardous chemical substances into the environment (and to protect workers from exposure), an improved, systematic consideration of relevant chemical substances has to be achieved (Krupanek, 2021). For long-term improvement of chemicals handling and phase-out actions of hazardous chemicals, it is therefore

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00013-X Copyright © 2024 Elsevier Ltd. All rights reserved.

38

Natural Dyes for Sustainable Textiles

necessary to raise the awareness level for both suppliers and retailers (Anonymous, 2018). The United Nations (2015: 6.3) has specifically targeted improvements to “water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, having the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally” by 2030 (MacFeely, 2020).

3.2

Dyeing process

In general, dyeing can be described as a process in which a textile fiber absorbs the molecules of dye from its solution so that the dyed material retains the dye and resists the release of the dye back to the solution from which is has been absorbed. Dyeing processes which take place in water solutions of dyes are always distribution processes between two phases, that is, dye solution and solid substrate, and they are based on physicochemical interactions between the molecules of dye and the substrate (Grishanov, 2011). Textile materials can be dyed using batch, continuous, or semicontinuous processes. The kind of process used depends on many characteristics including type of material as such fiber, yarn, fabric, fabric construction, and garment, and also the generic type of fiber, size of dye lots, and quality requirements in the dyed fabric. Among these processes, the batch process is the most common method used to dye textile materials (Perkins, 1991). So there is a strong need for improved awareness, knowledge level and consensus, and the development of a chemical management course in a tool format with the specific aim of substituting chemicals of concern (Jönsson et al., 2021). Dyeing is generally carried out either by synthetic or natural dyes. Synthetic dyes have been chemically synthesized products exclusively which are originated in laboratory, whereas natural dyes are all available on our Earth in the form of plant, leaves, flowers, bark, etc. The synthetic textile dyes represent a large group of organic compounds that could have undesirable effects on the environment, and in addition, some of them can pose risks to humans. The increasing complexity and difficulty in treating textile wastes has led to a constant search for new methods that are effective and economically viable (Chequer et al., 2013). There are different types of synthetic dyes, namely reactive dyes, vat dyes, indigo dyes, direct dyes, naphthol dyes, acid dyes, basic dyes, sulfur dyes, disperse dyes, and natural dyes, which are an unsaturated organic compound that absorbs light and give color to the visible region (Rehman et al., 2020). The large quantities of dyes impart during the dyeing to the fabrics. A significant number of dyes are remaining unfixed in textile effluents that are toxic, carcinogenic, and mutagenic to all living things. These toxic dyes can remain in the environment for an extended period when released without appropriate treatment (Velusamy et al., 2021). One of the most difficult tasks confronted by the wastewater treatment plants of textile industries is the removal of the color of these compounds, mainly because dyes and pigments are designed to resist biodegradation, such that they remain in the environment for a long period of time (Hao et al., 2000). As synthetic dyes are artificial products, they generally involve liberal usage of chemicals in production and as auxiliaries to give brighter and long-lasting palette of shades by just one compound. The substantial use of chemicals in whole synthetic dyeing procedure

Using chemical management system in natural dyeing process to make it sustainable

39

and a newer approach toward cleaner-greener globe have added a new dimension of chemical management in not only dyeing but also in whole textile wet processing. As synthetic dyes are generally chemical compounds, they can only be replaced with another chemical. So the only available silver lining is natural dyes for greener replacement of synthetic colorants in dyeing process. The chemical usage is far low in whole natural dyeing process except in the form of minor auxiliaries as mordants and in some cases as finishing agents. To improve quality of natural dyeing, these little amounts of chemicals need to be replace/remove for better and green, ecologically safer dyeing options. The chemical management is thus requisite of time to make natural dyeing fully greener alternative for safe textile process for users/consumer as well as work force involve. The use of safer, milder, or ecologically safe chemical agents instead of harsh ones in natural dyeing can now pronounce as part of chemical management in textile processing. Newer ways and newer agents should be looked upon and researched on to make whole proposition of chemical management a success. The lesser usage of chemicals or their complete replacement will definitely make textile dyeing a homogenous process with vast applicability in changing human lives and ecological arenas. In this context, the use of natural dyes with minimum amount of eco-friendly chemicals (Sod. and calcium salts of carbonate, citric acid, etc.) or naturally available species containing metals/chemicals will prove game changer.

3.3

Use of natural dyes and chemical management

Natural dyestuffs of plant origins used as indigenous systems can be developed scientifically and can be substituted for the chemical dyes. These indigenous dyes can be produced in large scale and could be prepared commercially and economically. The practice of indigenous systems for preparing dyestuffs and the processes of dyeing has been developed using modern technological methods. A revived interest in the use of natural dyes in textile coloration has been growing, and there is pressing need for the availability of natural dye-yielding plants. These dyes are collected from nature and no need to apply manufacturing process to prepare them. These dyes are easily decomposed in nature after using them, and they do not pollute the environment while destroying them after end use (Alam et al., 2020). They don’t produce any undesired by-products, and at the same time, they help in regenerating the environment; therefore, natural dyes are the safe dyes (Chungkranget al., 2021). Natural dyeing commonly involved many steps as: • • •

Extraction Pretreatment/mordanting Color fixing

These steps generally contain chemicals for extracting, as mordanting agents and fixing agents. There are new ways which can be adopted for scaling down chemicals in these processes. Natural dyeing process generally uses dyes, salts, surfactants, urea, soda ash, metal mordants, and other auxiliaries. Several researchers are working on enzymatic treatment of cotton and wool fabric for improving softness and surface

40

Natural Dyes for Sustainable Textiles

appearance, for accelerating method of dyeing process, for one-bath method for enzymatic desizing-scouring of cotton fabrics, and for decolorization and detoxification of textile dyes aspects with different enzymes specifically designed for carrying out one function only at a time (Vankar and Shanker, 2008).

3.3.1

Extraction

Natural dyes are collected and then dried in order to make them size-fit for extraction. Sun/shade drying of natural materials significantly (40%e75%) reduces moisture, making them fit for extraction vessel and increase colorant yield. Sometimes extraction of natural dyes involves various solvents. So dye extracts in organic solvents pose risk of inhaling while working with them. Thus in creating extraction a green process, various approaches are being now tried. Extraction of green dyes can be carried out in several ways as percolation, acidebase processes, supercritical fluid (SCF) extraction, microwave-assisted extraction (MAE), and ultrasonication (Indraningsih, 2013). These are new and ecologically safer options to extract plant material to make dye powder or sometimes dye extract itself. These are also important ways to save chemicals use and leaching. Some of the important ways to manage chemicals in extraction process are:

3.3.1.1

Enzyme extraction

Diverse sorts of enzymes are generally utilized as a part of different phases of material handling for the alteration of chemical and physical surface properties or introducing functional groups on the surface of material strands (Duran and Duran, 2000; Araujo et al., 2008). As plant tissues include cellulose, starches, and pectins as binding substances, economically accessible enzymes such as cellulase, amylase, and pectinase have been utilized by a few specialists to release the surrounded material prompting to the extraction of colorant particles in reasonable terms. This procedure might be useful in the extraction of colorant from hard plant substances such as bark, roots, and so forth. In this enzymatic extraction method, liquor (2% conc.) of cellulase:pectinase (1: 2) was splashed on pomegranate skin (25g) for good immersing, then extracted after letting stay for overnight (Kasiri and Safapour, 2013). The dyed fabric revealed that enzymatic treatment brought about enhancement in colorant uptake in all cases and credited it to improve shrink-resistance properties of the treated filaments (Helmy, 2020). As plant tissues contain cellulose, starches, and pectins as binding materials, commercially available enzymes including cellulase, amylase, and pectinase have been used by some researchers to loosen the surrounding material leading to the extraction of dye molecules under milder conditions. This process may be beneficial in the extraction of dye from hard plant materials such as bark, roots, leaves etc. (Saxena and Raja, 2014).

3.3.1.2

Supercritical fluid extraction

SCF extraction is an advanced separation technique based on the enhanced solvating power of gases above their critical point. This is one of such major technologies that

Using chemical management system in natural dyeing process to make it sustainable

41

have emerged over the last two decades as the alternative to the traditional solvent extraction of natural products. It uses a clean, safe, inexpensive, nonflammable, nontoxic, environment-friendly, nonpolluting solvent, such as CO2. Supercritical fluid extraction technology is thus increasingly gaining importance over the conventional techniques for the extraction of natural products. CO2 is an ideal solvent in the food, dye, pharmaceutical, and cosmetic industries. This extracting technology is especially useful where colorant quantity in plant part is in low concentrations (Prabhu and Bhute, 2012). The extraction and purification of natural colorant from eucalyptus bark using SCF process has been studied (Vankar et al., 2007). Attempts have been made to standardize colorant derived from Arjun bark, babool bark, and pomegranate rind.

3.3.1.3

Aqueous extraction

This is the most used and old process of extraction of natural dyes. Little heat and water make wonders for natural dyes extraction. Only drawback is the use of large amount of water and then drying extract to concentrate dye or powder dye extract. In this extraction, plant parts are cut into small chunks and then soaked in water overnight/7e8 h so that water can be retained on cellular level and then boiled to yield maximum color. After heating, color is filtered and used for dyeing. As most of the dyeing operations are carried out in aqueous media, the extract obtained by this method can be easily applied to the textile materials. Disadvantages of this extraction method are long extraction time, large water requirement, use of high temperature, and low dye yield as only water-soluble dye components get extracted, whereas many dyes have low water solubility (Miah et al., 2016). The use of low temperature/room temperature dye extraction can solve drawback of high temperature extraction problem which is new area of research as natural dyes gave nice colors at room temperature.

3.3.1.4

Microwave-assisted extraction

MAE is a process of using microwave energy to heat solvents in contact with a sample in order to partition analytes from the sample matrix into the solvent. It is the process of using microwave energy to heat solvents in contact with a sample to partition analytes from the sample matrix into the solvent. MAE is an automated green extraction technique that offers many advantages such as the reduction of the extraction time and solvent consumption, the possibility of simultaneously extracting multiple samples, and drastically improving sample throughput (Llompartet al., 2019). MAE is a conventional technique for the extraction of active components from medicinal plants, using microwave energy to heat solvents containing samples, thereby partitioning analytes from a sample matrix into the solvent. The main advantage of MAE is its ability to rapidly heat the sample solvent mixture, resulting in its wide applicability for the rapid extraction of analytes, including thermally unstable substances (Kataoka, 2019). It is very useful technique because of low solvent consumption, short extraction time, and high extraction efficiency.

42

3.3.1.5

Natural Dyes for Sustainable Textiles

Ultrasound-assisted extraction

UAE has advantages of simplicity and is less time-consuming and uses less solvent than other methods, and it can be easily coupled with other extraction techniques. Since this technique can be performed under room temperature, this can prevent the oxidation and decomposition of target natural products. UAE has been widely applied in the isolation of different natural products (Louieet al., 2020). UAE is one of the most practical approaches to apply to algae for large-scale industrial production due to its fast extraction rate, simplicity, increased yield, high efficiency, low cost, and executing time (Yi et al., 2021). Ultrasound allows for process acceleration and attainment of the same or better results than existing techniques under less extreme conditions, that is, lower temperature and lower chemical concentrations. Textile wet processes assisted by ultrasound are of high interest for the textile industry for this reason (Vankar and Shanker, 2008). UAE uses acoustic waves in the kilohertz range that travel through the solvent producing cavitation bubbles. When the cavitation bubbles burst at the surface of the plant sample matrix, a shockwave-induced damage to plant cell wall enhances the mass transfer of phenolic/dye compounds across cellular membranes into solution. Filtration is used after extraction to separate the extract from the plant residue. The UAE extraction protocol is normally optimized with regard to solvent, temperature, and solvent to biomass ratio for the plant sample under investigation (Al Jitan et al., 2018). Ultrasound extraction has been considered a promising and innovative technique with many applications in the chemistry, pharmaceutical, cosmetic, and alimentary fields of the 21st century (Rostagno and Prado, 2013).

3.3.2

Pretreatment/mordanting

Pretreatment can be defined as preparing cloth/fabric before dyeing for maximum dye adherence. As some of the natural dyes elope after first or second washing, fabric needs to get some active sites for dye adherence. That’s why pretreatment is another necessary step of natural dyeing. As known cellulose/cotton is quite inert toward any type of dyeing, so it always required a pretreatment to adhere dye. For natural dyeing, cotton is sometimes treated with tannic acid as pretreatment before dyeing. Tannic acid oxidizes upper surface of cotton and creates some active sites to latch dye molecules, thus increases fastness to some extent. The major issues for natural dyed textiles are reproducibility of shade, nonavailability of well-defined standard procedure for application, and poor lasting performance of shade under water and light exposure. Natural dyes are also sometimes having poor affinity and substantively (Maulik and Bhowmik, 2006) for cellulosic fibers such as cotton and viscose. The absence of reactive groups in fibers and dyes does not allow for bond formation, so they need mordanting treatment to fix the dye on fiber surface. Protein fibers are having bond-forming groups in fiber structure, and the presence of carboxylic groups in natural dyes provides opportunity for bonding and gets bonded with fiber and shows good fastness properties. Natural dyes are having smaller molecular size, and they are not having conjugated linear structure (Samanta and Agarwal, 2009). Therefore, some natural dyes are having inferior exhaustion behavior. The presence of hydrogen bond and van der Waals force of

Using chemical management system in natural dyeing process to make it sustainable

43

attraction play important role in the fixation of natural dyes on the fiber. Natural dyes generally required a mordant to adhere fast on fabric. Mordants are in the form of a metal salt to create an affinity between the fiber and the pigment. These metals form a ternary complex on one side with the fiber and on the other side with the dye. Such a strong coordination tendency enhances the interaction between the fiber and the dye, resulting in high dye uptake (Mirjalili and Karimi, 2013). Figs. 3.1 and 3.2 show how the metal can coordinate with the colorant molecule. These mordants are inorganic salts of metal species like Cr, Al, Fe, Sn, etc. Chrome or mordant dyes and metal complex dyes are utilized for getting bright dark colors. Metal ion inclusion in a dye molecule exhibits a bathochromic shift producing deeper but duller shades, which provides excellent coloration. The mordanting step can take place in three ways. It can be carried out prior to dyeing which is premordanting, simultaneously with dyeing called meta-mordanting, and after the dyeing which is postmordanting. Different natural dyes show different adherence in all three types of mordanting, and different metals or plant materials can be used for these. The ejection of a massive volume of wastewater containing heavy metal ions such as Cr (VI), Pb (II), Cd (II), and Zn (II) and metal-containing dyes are an unavoidable consequence because the textile industry consumes large quantities of water, and all these chemicals cannot be combined entirely with fibers during the dyeing process. These high concentrations of metals/chemicals in effluents interfere with the natural water resources and cause severe toxicological implications on the environment with a dramatic impact on human health (Velusamy et al., 2021). These impacts of chemicals can be reduced by adopting safer alternatives as natural substitutes for metal mordants, fixers, etc. Studies on various plants show that their intrinsic compounds have both mordanting as well as dyeing capacity when used in different conditions. The dried fruits of Terminalia chebula constitute one of the most important vegetable tanning materials and have been used in India for a long time. This fruit pericarp thus can be used as a raw material for natural dyeing. Oak galls are good example biomordant as they are rich in tannin and are used for mordanting. They can also be used to get a brown color. Catechu or cutch obtained from the heartwood of Acacia catechu is used to dye cotton, wool, and silk to brown color directly. It is also rich in tannins and can be used to get black color with iron mordant (Saxena and Raja, 2014). Another biomordant Pyrus pashia containing copper as intrinsic metal was used in natural dyeing with Delonix regia. Many Pyrus and Prunus species have been reported to contain copper, such as Pyrus domestica L. which contains 0.33e34 ppm, Prunus serotina (black cherry stem)

Figure 3.1 A typical colorant molecule.

44

Natural Dyes for Sustainable Textiles

Figure 3.2 Metal chelation with the colorant.

which has 1.3e378 ppm, and Prunus persica L. (peach fruit) which has 0.3e30 ppm of copper, as well as Quercus phellos L., Liquidambar styraciflua L., Brassica oleracea L., Corylus avellana L., and Sassafras albidum (Vankar and Shanker, 2009). In another study, one more biomordant Eurya acuminate (Nausankhee, Turku) was used with Rubia cordifolia. Biomordant E. acuminata when used in conjunction with R. cordifolia was found to enhance the dye ability due to the aluminum content present in the leaves (Vankaret al., 2008). These biomordants had given good shades with their respective dyes, thus can be used instead of metal mordants.

3.3.3

Fixing dye on fabric (finishing)

Natural dyes are having poor exhaustion value due to subdued affinity for fiber materials, so to increase the exhaustion of dyes, common salt/Glauber’s salt are added in the dye bath (Samantaet al., 2020). Salt is necessary in three ways, firstly, to drive dye into textile during the dyeing process in textile. Secondly, the use of salt leads to maximum exhaustion of dye molecules during dyeing process in textiles. Thirdly, it is used as an electrolyte for migration, adsorption, and fixation of the dyestuff to the cellulose material. Salts plays an important role in natural dyeing by improving the affinity of the dyestuff toward the fiber and acceleration of the dyestuff’s association and lowering its solubility. Normally, Glauber’s salt or common salt is used for this purpose. The presence of chlorine ion in the common salt may cause corrosion of the equipment. Hence, Glauber’s salt (sodium sulfate decahydrate, Na2SO4.10H2O) is always preferred over common salt (Oelz, 2018).

3.3.3.1

Function of salt in the dyeing process

1. The salt in the reactive dyeing increases the affinity of the dye toward the cellulosic substrate. 2. Salt increases the exhaustion rate of dyes. 3. As natural dyes have a lower affinity, more inorganic salt is required in order to accelerate absorption.

While the amount of inorganic salt used varies according to the type of dyestuff used, recently developed high-fixation dyestuff’s with improved affinity allow the amount of inorganic salt to be reduced (Oelz, 2018).

Using chemical management system in natural dyeing process to make it sustainable

45

It can be presumed that some salt must leach into water after fixing. Although salt is not so harmful for water, still it hinders natural water body parameters and creates some sort of pollution. Thus it’s mandatory to replace this salt with some other biobase dye enhancer.

3.4

Chemical management

The textile finishing industry utilizes a broad range of chemical substances for its preparation, coloration, and the after-finishing processes. Many of these chemicals have different levels of health and physicochemical hazards. The risk of injury or ill health upon exposure at work depends on whether there are adequate safety measures in place. Sustainable chemistry in textile processing must have an assurance of safe human health and environment with the reduction of water consumption, chemical consumption, energy consumption, and air/water/soil pollution. Sustainable chemistry can play a vital role in sustainable development in textile processing avoiding hazardous chemicals. Chemical management can be defined as a procedure which tracks chemical products from procurement through to final disposal. Chemical management is necessary to ensure the health and safety of the stakeholders (Sakib, 2019). A good chemical management system can ensure sustainable chemistry in the textile processing industries. Synthetic dyes are dangerous to customers and very hazardous for workforces in the industry (Oda, 2012). The natural dyes colors are a source of engagement for the rustic subdivisions of poor countries. Apart from having a luster that artificial dyes can’t contest, some naturally colored textiles also have the control to heal (Pereira and Alves, 2012). As of now, ZDHC Foundation (Zero Discharge of Hazardous Chemicals) has a holistic solution to upgrade the running industry with a safer chemical which can ensure safe product as well as safe environment discharging zero hazardous chemicals (Islam, 2020). Under the Occupational Safety and Health Ordinance (Cap. 509), employers of a workplace are required to ensure safety and health of their employees in connection with the use, handling, storage, transport, and disposal of chemicals. This can be achieved through implementing a chemical safety program, which essentially comprises risk assessment of chemicals (Wu, 1999). Environmental problems with used dye baths are related to the wide variety of different chemicals/components added to the dye bath, often in relatively high concentrations. An important part of any sustainability strategy within the textiles and apparel industry is chemical management. Thus in the future, many of textile factories will face the requirement of using a significant part of all chemicals sustainably (Chequer et al., 2013). The objective of chemical management can be achieved by using natural dyes in textile dyeing throughout as now various methods for extraction, pretreatment/mordanting are available which led them to result in beautiful, earthy shades on fabric to be loved by environment-friendly customers too. The process of extraction and mordanting made out ecologically benign with the use of natural products itself, so there’s no point

46

Natural Dyes for Sustainable Textiles

of chemical use in these processes decreasing a substantial amount of chemicals leading to zero discharge of harmful chemicals in water bodies. In addition to this, the promotion of natural dyes supports the livelihood of indigenous groups and highlights cultural heritage through their woven textiles, and the practice of traditional dyeing serves as a platform for promoting folk tradition too (Labrador, 2013). In this way, natural dyeing facilitates indigenous people creating a socioeconomic balance in society.

3.4.1

Reduction of chemical consumption by use of different bioorigin products and techniques in natural dyeing

Synthetic dyestuffs have introduced a broad range of colorfastness and bright hues. Nonetheless, their toxic character has become a reason of serious concern to the environment. The usage of synthetic dyestuffs has adverse impacts on all forms of life. The existence of naphthol, vat dyestuffs, nitrates, acetic acid, soaping chemicals, enzymatic substrates, chromium-based materials, and heavy metals as well as other dyeing auxiliaries makes the textile dyeing water effluent extremely toxic. Other hazardous chemicals include formaldehyde-based color-fixing auxiliaries, chlorine-based stain removers, hydrocarbon-based softeners, and other nonbiodegradable dyeing auxiliaries. Therefore, it has been critical for innovations, environmentally friendly remediation technologies, and alternative ecosystems to be explored for textile dyeing industry. Synthetic dyes cause harmful effects on the environment, even in low concentrations. In addition, there are other highly toxic compounds in the discharge of colored wastewater that increase environmental problems (Khattabet al., 2020). In general, synthetic dyes are not biodegradable due to their chemical properties and structure, generating an adverse effect on the environment (Husain, 2006). Tannins from gall leaf from oak plant (i.e., oak galls containing gallic acid and tannic acid and helps in better dye fixation) from the Himalayan region were extracted and dyed onto cotton, woolen, and silk textiles with different mordants and obtained better color fast fabrics, which are skin friendly too (Mishra and Patni, 2011). The effect of various natural mordants (gallnut, pomegranate peel, Arjun bark, chlorophyll extract, and citric acid) and some commonly used metal mordants (ferrous sulfate, copper sulfate, stannous chloride, and sodium dichromate) on color and fastness properties of dyed wool samples was comparatively evaluated. It’s been found that synthetic fiber can also be dyed with natural dyes extracted by ultrasonication. Polyamide (nylon 6) fabric was successfully dyed by the extracted natural colorants with relatively high colorfastness properties. The ultrasound-assisted extraction (UAE) technique was employed for the extraction process of colorants from Hawthorn fruits. UAE technique was found to improve the extraction efficiency between 20% and 70% compared to the conventional extraction technique (Sadeghi-Kiakhaniet al., 2021). The extraction of natural dye from the roots of R. cordifolia by conventional extraction, as well as by using ultrasonic extraction, has been performed in this study. The extracted dye was used for dyeing leather and cotton fabric along with different mordants to obtain different shades (Vedaraman et al., 2017). The extractions of colorant using boiling method normally produce a small amount of yield. Low yield of natural

Using chemical management system in natural dyeing process to make it sustainable

47

dyes is one of the factors that limit the use of natural dyes in comparison with synthetic dyes. Hence, there is a growing demand for developing suitable extraction technique for more efficient and effective extraction of natural textile dyes. The utilization of ultrasonic cleaner was found to have significant improvement in the extraction of natural dyes compared to traditional boiling method (Rahman et al., 2013). According to the literature, plants such as Curcuma longa L.(Ghoreishianet al., 2013), Lawsonia inermis (Yusuf et al., 2012), and Rheum emodi L.(Khan et al., 2012), Catechu (Khan et al., 2011), Quercus infectoria Oliv (Shahid et al., 2012), Punica granatum peel (Ghahehet al., 2012), Saraca asoca, Albizia lebbeck (Baliarsingh et al., 2012), and so forth produce pigments which have widespread applications in textile dyeing industries and represent probable alternative to synthetic dyes and artificial antimicrobial agents. They are also useful in dyeing a polyamide synthetic fiber. Polyamides form an interesting polymer class with many applications, such as fibers, engineering plastics, films, and coatings. Major advantages of polyamide are high modulus and strength, stiffness, stretch, wrinkle, and abrasion resistances (Mirjalili and Karimi, 2013). It’s just not that natural dyes can’t be used on man-made fibers. The application of natural dyes such as turmeric, madder, catechu, Indian rhubarb, henna, and tea and pomegranate rind on man-made fiber nylon has been reported (Teli et al., 2010). Some studies have also been conducted on the application of Lac dyes on different fibers (Chairatet al., 2004). Advantages of natural dyes over synthetic are manifolds as they are eco-friendly, safe for body contact, and are harmonized (Brian, 1998). Many scientists have also suggested and reported the medicinal and antibacterial importance of natural dyes (Badri and Burkinshaw, 1993) (Alam et al., 2007). Yellow dye from rhizome of turmeric has been reported to be traditionally used in medicine as an antiinflammatory drug (Shah, 1997). Most of the natural dyes are proved to be nontoxic and eco-friendly. To enhance the shade palette of natural dyes, various fungi and other microbes are being researched to get fancy colors to the need of the customers. A study was conducted for natural dyeing with extracted and purified natural fungal pigment from Thermomyces sp. to apply on different textile fabrics to optimize and dyeing process parameters for silk, cotton, and woolen fabrics. This extracted pigment color obtained from Thermomyces sp. indicated good affinity toward silk fabrics than others, with good light fastness (rating 4), color fastness to washing (rating 4e5), and color fastness to rubbing (rating 3e4). This dye also has antimicrobial activity (Poorniammalet al., 2013). The stringent environmental standards imposed by many countries in a response to the toxic and allergic reactions associated with synthetic dyes are helping and letting compulsive use of natural dyes by dye houses. People/consumers are also demanding natural dyed fabric and ready to pay for it. Government of Germany was the first to take initiative to put ban on azo-dyes for manufacturing, dyeing, and importing textiles and other consumer goods dyed with these dyes from January 1, 1995 by the act of German Legislation (Consumer Goods Ordinance). The Netherlands followed a ban with effect from August 1, 1996 on similar lines. The European Union is likely to impose a ban on these toxic dyes shortly. India has also banned the use of specific azo-dyes, and under notification, sufficient “legal teeth” had been given for taking penal action against those who use these dyes (Kapoor and Pushpangadan, 2001). There are instances when people have

48

Natural Dyes for Sustainable Textiles

questioned impeccability and workability of natural dyes in terms of availability (huge/ massive amounts needed to replace synthetic dyes), applicability (in terms of synthetic fiber and all other kind of materials), performance (in terms of fastness and shades), and waste generation (huge amount of plant material after dyeing), but it must be taken in account that these limitations are manageable and our life and our environment is still important for all of human race. The things which should be making sense in this perspective are our responsibility toward Earth sustainability. Human race has to get over market-oriented/governed assumptions and start thinking about innovative and greener ways to bring change in everyday life and style in cloth they wear to bring ecological and economical sustainability. It was an old assumption that only Indigo (blue), Madder (red), Curcuma (yellow), and Lac (deep red) represent natural dye as a whole. Now the gamut of colors from natural dyes is available supporting age-old patterns and techniques like Ajrakh, Tie and Dye, and Bandhni making waves in present day fashion as a mark of style and fashion for young and old both genres. Natural dyeing also supports sustainability which means the use of environment-friendly auxiliaries along with economic growth. Almost all leading brands of the world should have taken the call of sustainability and act accordingly. If big brands will support natural dyes, smaller units will automatically follow them. Another aspect of decreasing chemical consumption in natural dyeing is to explore new indigenous plants like Pyrus and Eurya containing metal to replace metal mordants. In this endeavor, indigenous tribal people can greatly help. This step not only will reduce chemical consumption but will also support indigenous peoples supporting sustainability along with economic livelihood to such tribal societies and open new research.

3.5

Futuristic approaches for go-green

In a new development to reduce chemical and water usage, a new approach of dyeing was undertaken where eucalyptus (Eucalyptus camaldulensis) bark powder (without any further treatment/irradiation) using gamma ray irradiated natural colorant of dry powder of eucalyptus leaf extract, for producing natural-colored textiles of soothing brown color with improved color fastness by required pre- and/or postmordanting. Thus, when this fabric was therefore dyed in this case using gamma ray irradiated powder of eucalyptus dry leaf, it showed noticeable improved overall color fastness properties (Naz and Bhatti, 2011). Many natural dyes have intrinsic property of healing, antimicrobial, antiviral, antiitching, etc. These add-ons of green colors to fabric will not only increase their esthetic value but their commercial value too. Thus various future-friendly techniques have been paving way in textile dyeing with natural dyes as the coming of “Air Dyeing Technology.” Air dyeing technology is a dyeing process that uses air instead of water to dye garments, allowing companies to create garments with vivid designs and colors, without polluting the water and environment. This technology uses 95% less water, emits 84% less green house gases (GHGs), requires 87% less energy, and has no rules to washing and allows for new designs. Different sides of a single piece of fabric can be dyed in different colors or designs. Air-dyed fabrics can

Using chemical management system in natural dyeing process to make it sustainable

49

be washed at any temperature, with whites or colors, with or without bleach (Advanced Environmental Technologies, 2011). In another development, colors from a range of natural pigments can be sourced via very new DNA technology. In this procedure, microorganisms were engineered using DNA to convert agricultural by-products into dyes. When the microorganisms burst, they “fix” the color to the fabric, thus reducing the need for massive amounts of water. The organisms themselves can be grown, or fermented, once the DNA code for the necessary colorant has been implanted, and this natural reproduction is fast and efficient. Overall the whole process uses less water, produces less waste, and needs far less chemicals. A new way forward inspired by nature. This technology is called Colorfix. It replicates organisms carrying specific color DNA. Overall the whole process uses less water, produces less waste, and needs far less chemicals (BBCEarth, 2019). To further promote sustainable dyeing, the existing list of natural dyes could be appended with colorants sourced from waste materials from food and timber production (Adeel et al., 2020).

3.6

Conclusions

Over the centuries, humans have sought to brighten their appearance with clothing that reflects the vibrant natural colors seen in nature, and many colorants were originally sourced from the natural world around us. To identify chemical using steps in wet processing in general and dyeing in particular is crucial for reducing their use. As textile dyeing is a global phenomenon (most of the countries involve in this business), thus information distribution regarding chemical use reduction is also an important step from first user to last in the chain. For any change in any process, it is necessary to create an awareness, and the use of green alternatives instead of fully established chemical counterpart will definitely take some time. Initiation by small community toward it can bring up wave for both supplier and retailer and above all customer. Chemical management will start with development of ideas (sustainable) to be implemented, consensus toward substitution of chemicals, and above all knowledge base awareness to improvize. Targets to decrease chemicals should be set, and an early achievement of these targets should be done. Not only chemicals as entity but equipment modification along with technology can also play an important role in bringing greener alternatives into foray as natural dye sources extraction (using microwave, ultrasonication, etc., as green alternatives). Greener dyeing will definitely use renewable plant sources thereby preserving nonrenewable resources. The objective of using natural dyes and their green mordants, pretreatment agents, and other agents for finishing can support knowledge and consensus about chemical management and chemical concerns in the textile value chain. Therefore, the search of eco-sustainable methodologies to more effective dyes that can be fixed onto fiber with higher efficiency/fastness should be established. To achieve better implementation in practice, it is recommended to strengthen the interfaces and regulatory coherence between dyeing industry and regulation authorities too. The responsible management of chemicals as well as the reduction of hazardous substances should be included as a mandatory aspect in natural dyeing processing.

50

Natural Dyes for Sustainable Textiles

Proper chemical management can also lead to reduce wastage and can optimize the use of the resources which will be cost-effective for the industry while protecting the health of the employees, consumers, and environment. Enlightening individuals for using sustainable products is important; people should feel pride in using and promoting naturally dyed fabric. Natural dyes come from nature, and all the protocols of sustainability are about saving nature, so whatever sustainable standard may come, natural dyes will always pass. Positive attitude with strong determination to free environment from the clutches of synthetics are prerequisite to march forward in natural dye usage and making world with people wearing esthetically rich, pastel/earthy color dyed fashion clothes. This will appeal dyeing fraternity on saving the environment, serving society, and making the textile sector more sustainable.

References Adeel, S., Amin, N., Ahmad, T., Batool, F., Hassan, A., 2020. Sustainable isolation of natural dyes from plant wastes for textiles. Recycling from waste in fashion and textiles: A Sustainable and Circular Economic Approach 363e390. Advanced Environmental Technologies, 2011. Water Efficiency in Textile and Leather Industry Accepta-Leading Chemical Procurement. Statham house, Old Trafford, Manchester. Al Jitan, S., Alkhoori, S.A., Yousef, L.F., 2018. Chapter 13 - phenolic acids from plants: extraction and application to human health. In: Atta ur, R. (Ed.), Studies in Natural Products Chemistry, vol. 58. Elsevier, pp. 389e417. Alam, M., Rahman, M., Haque, M., 2007. Extraction of henna leaf dye and its dyeing effects on textile fibre. Bangladesh Journal of Scientific & Industrial Research 42 (2), 217e222. Alam, S., Islam, S., Akter, S., 2020. Reviewing the sustainability of natural dyes. Advance Research in Textile Engineering 5 (2), 1050. Anonymous, 2018. Chemical Management System e for Sustainability. Araujo, R., Casal, M., Cavaco-Paulo, A., 2008. Application of enzymes for textile fibres processing. Biocatalysis and Biotransformation 26 (5), 332e349. Badri, B., Burkinshaw, S., 1993. Dyeing of wool and nylon 6.6 with henna and lawsone. Dyes and Pigments 22 (1), 15e25. Baliarsingh, S., Panda, A.K., Jena, J., Das, T., Das, N.B., 2012. Exploring sustainable technique on natural dye extraction from native plants for textile: identification of colourants, colourimetric analysis of dyed yarns and their antimicrobial evaluation. Journal of Cleaner Production 37, 257e264. BBCEarth, 2019. Breathing Life into a Dyeing Art. Brian, G., 1998. Dyeing what comes naturally to the dye house. Society of Dyers and Colourists 114 (4), 240. Chairat, M., Rattanaphani, V., Bremner, J.B., Rattanaphani, S., Perkins, D.F., 2004. An absorption spectroscopic investigation of the interaction of lac dyes with metal ions. Dyes and Pigments 63 (2), 141e150. Chequer, F.D., De Oliveira, G.R., Ferraz, E.A., Cardoso, J.C., Zanoni, M.B., De Oliveira, D.P., 2013. Textile dyes: dyeing process and environmental impact. Eco-Friendly Textile Dyeing and Finishing 6 (6), 151e176. Chungkrang, L., Bhuyan, S., Phukan, A.R., 2021. Natural dyes: extraction and applications. International Journal of Current Microbiology and Applied Sciences 10 (1), 1669e1677.

Using chemical management system in natural dyeing process to make it sustainable

51

Duran, N., Duran, M., 2000. Enzyme applications in the textile industry. Review of Progress in Coloration and Related Topics 30 (1), 41e44. Fiber2fashion, 2012. Various Pollutants Released into Environment by Textile Industry. Industry-Article. Ghaheh, F.S., Nateri, A.S., Mortazavi, S.M., Abedi, D., Mokhtari, J., 2012. The effect of mordant salts on antibacterial activity of wool fabric dyed with pomegranate and walnut shell extracts. Coloration Technology 128 (6), 473e478. Ghoreishian, S.M., Maleknia, L., Mirzapour, H., Norouzi, M., 2013. Antibacterial properties and color fastness of silk fabric dyed with turmeric extract. Fibers and Polymers 14 (2), 201e207. Grishanov, S., 2011. Structure and properties of textile materials. In: Handbook of Textile and Industrial Dyeing. Elsevier, pp. 28e63. Hao, O.J., Kim, H., Chiang, P.-C., 2000. Decolorization of wastewater. Critical Reviews in Environmental Science and Technology 30 (4), 449e505. Helmy, H.M., 2020. Extraction approaches of natural dyes for textile coloration. Journal of Textiles, Coloration and Polymer Science 17 (2), 65e76. Husain, Q., 2006. Potential applications of the oxidoreductive enzymes in the decolorization and detoxification of textile and other synthetic dyes from polluted water: a review. Critical Reviews in Biotechnology 26 (4), 201e221. Indraningsih, A.W., 2013. Natural dyes from plants extract and its applications in Indonesian textile small medium scale enterprise. Eksergi 11 (1), 16e22. Islam, R., 2020. Sustainable chemistry in textile processing is the need of hour. Textile Today. In: https://www.textiletoday.com.bd/sustainable-chemistry-textile-processing-need-hour. Jönsson, C., Roos, S., Hildenbrand, J., 2021. Chemical management system in textiles. In: Chemical Management in Textiles and Fashion. Elsevier, pp. 1e18. Kapoor, V., Pushpangadan, P., December 2001. Use of natural dyes in preparation of HerbalGulals. In: Conventional Proceedings Natural Dyes. Department of Textile Technology, pp. 17e18. Kasiri, M.B., Safapour, S., 2013. Natural Dyes and Antimicrobials for Textiles. Green Materials for Energy, Products and Depollution. Springer, pp. 229e286. Kataoka, H., 2019. Pharmaceutical analysis | sample preparation. In: Worsfold, P., Poole, C., Townshend, A., Miro, M. (Eds.), Encyclopedia of Analytical Science, third ed. Academic Press, Oxford, pp. 231e255. Khan, M.I., Ahmad, A., Khan, S.A., Yusuf, M., Shahid, M., Manzoor, N., Mohammad, F., 2011. Assessment of antimicrobial activity of catechu and its dyed substrate. Journal of Cleaner Production 19 (12), 1385e1394. Khan, S.A., Ahmad, A., Khan, M.I., Yusuf, M., Shahid, M., Manzoor, N., Mohammad, F., 2012. Antimicrobial activity of wool yarn dyed with Rheum emodi L.(Indian Rhubarb). Dyes and Pigments 95 (2), 206e214. Khattab, T.A., Abdelrahman, M.S., Rehan, M., 2020. Textile dyeing industry: environmental impacts and remediation. Environmental Science and Pollution Research 27 (4), 3803e3818. Krupanek, J., 2021. Sectoral Guidance for Chemicals Management in the Textile Industry: HAZBREF-Project Activity 4.1 Report. Labrador, A.P., 2013. Hibla Ng Lahing Filipino. National Museum. Llompart, M., Garcia-Jares, C., Celeiro, M., Dagnac, T., 2019. Extraction | microwave-assisted extraction. In: Worsfold, P., Poole, C., Townshend, A., Mir o, M. (Eds.), Encyclopedia of Analytical Science, third ed. Academic Press, Oxford, pp. 67e77.

52

Natural Dyes for Sustainable Textiles

Louie, K.B., Kosina, S.M., Hu, Y., Otani, H., de Raad, M., Kuftin, A.N., Mouncey, N.J., Bowen, B.P., Northen, T.R., 2020. 6.12 - mass spectrometry for natural product discovery. In: Liu, H.-W., Begley, T.P. (Eds.), Comprehensive Natural Products III. Elsevier, Oxford, pp. 263e306. MacFeely, S., 2020. Measuring the sustainable development goal indicators: an unprecedented statistical challenge. Journal of Official Statistics 36 (2), 361e378. Maulik, S., Bhowmik, L., 2006. Studies on application of some vegetable dyes on cellulosic and lignocellulosic fibre. Man Made Textiles in India 49 (4), 142. Miah, M.R., Telegin, F.Y., Rahman, M.S., 2016. Eco-friendly dyeing of wool fabric using natural dye extracted from onion’s outer shell by using water and organic solvents. International Research Journal of Engineering and Technology (IRJET) 3 (9), 1e18. Mirjalili, M., Karimi, L., 2013. Extraction and characterization of natural dye from green walnut shells and its use in dyeing polyamide: focus on antibacterial properties. Journal of Chemistry 2013, 375352. Mishra, P., Patni, V., 2011. Extraction and application of dye extracted from eriophyid leaf galls of Quercus leucotrichophora-A Himalayan bluejack oak. African Journal of Biochemistry Research 5 (3), 90e94. Naz, S., Bhatti, I.A., 2011. Dyeing properties of cotton fabric using un-irradiated and gamma irradiated extracts of Eucalyptus camaldulensis bark powder. Indian Journal of Fibre and Textile Research 36 (2), 132e136. Oda, H., 2012. Improving light fastness of natural dye: photostabilisation of gardenia blue. Coloration Technology 128 (1), 68e73. Oelz, L.M., 2018. Salt as a Dye Enhancer for Textile: Textile Industry. Pereira, L., Alves, M., 2012. Dyesdenvironmental impact and remediation. In: Environmental Protection Strategies for Sustainable Development. Springer, pp. 111e162. Perkins, W.S., 1991. A review of textile dyeing processes. Textile Chemist and Colorist 23 (8). Poorniammal, R., Parthiban, M., Gunasekaran, S., Murugesan, R., Thilagavathi, G., 2013. Natural dye production from Thermomyces sp fungi for textile application. Indian Journal of Fibre and Textile Research 38 (3), 276e279. Prabhu, K., Bhute, A.S., 2012. Plant based natural dyes and mordants: a Review. Journal of Natural Product and Plant Resources 2 (6), 649e664. Rahman, N.A.A., Tumin, S.M., Tajuddin, R., 2013. Optimization of ultrasonic extraction method of natural dyes from Xylocarpus Moluccensis. International Journal of Bioscience, Biochemistry and Bioinformatics 3 (1), 53. Rehman, A., Usman, M., Bokhari, T.H., ul Haq, A., Saeed, M., Rahman, H.M.A.U., Siddiq, M., Rasheed, A., Nisa, M.U., 2020. The application of cationic-nonionic mixed micellar media for enhanced solubilization of Direct Brown 2 dye. Journal of Molecular Liquids 301, 112408. Rostagno, M.A., Prado, J.M., 2013. Natural product extraction: principles and applications. Royal Society of Chemistry. ISBN 978-1-84973-606-0. Sadeghi-Kiakhani, M., Tehrani-Bagha, A.R., Safapour, S., Eshaghloo-Galugahi, S., Etezad, S.M., 2021. Ultrasound-assisted extraction of natural dyes from Hawthorn fruits for dyeing polyamide fabric and study its fastness, antimicrobial, and antioxidant properties. Environment, Development and Sustainability 23 (6), 9163e9180. Sakib, S., 2019. Why is chemical management so essential? Textile Today. https://www. textiletoday.com.bd/chemical-management-essential/. Samanta, A.K., Agarwal, P., 2009. Application of natural dyes on textiles. Indian Journal of Fiber and Textile Research 34 (4), 384e399.

Using chemical management system in natural dyeing process to make it sustainable

53

Samanta, A.K., Awwad, N., Algarni, H.M., 2020. Chemistry and Technology of Natural and Synthetic Dyes and Pigments. BoDeBooks on Demand. Saxena, S., Raja, A., 2014. Natural Dyes: Sources, Chemistry, Application and Sustainability Issues. Roadmap to Sustainable Textiles and Clothing. Springer, pp. 37e80. Shah, N., 1997. Traditional uses of turmeric (Curcuma longa) in India. Journal of Medicinal and Aromatic Plant Sciences 19 (4), 948e954. Shahid, M., Ahmad, A., Yusuf, M., Khan, M.I., Khan, S.A., Manzoor, N., Mohammad, F., 2012. Dyeing, fastness and antimicrobial properties of woolen yarns dyed with gallnut (Quercus infectoria Oliv.) extract. Dyes and Pigments 95 (1), 53e61. Teli, M., Shah, R., Sabale, A., 2010. Dyeing of nylon with natural colourants. Colourage 57 (3), 96e101. Vankar, P.S., Shanker, R., 2008. Ecofriendly ultrasonic natural dyeing of cotton fabric with enzyme pretreatments. Desalination 230 (1e3), 62e69. Vankar, P.S., Shanker, R., 2009. Eco-friendly pretreatment of silk fabric for dyeing with Delonix regia extract. Coloration Technology 125 (3), 155e160. Vankar, P.S., Tiwari, V., Srivastava, J., 2007. Antioxidants from supercritical carbon dioxide fluid extracts (SCFE) of bark-peel of Eucalyptus globulus. EJEAF Chem 6 (11), 2550e2556. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S., 2008. Ecofriendly sonicator dyeing of cotton with Rubia cordifolia Linn. using biomordant. Dyes and Pigments 76 (1), 207e212. Vedaraman, N., Sandhya, K.V., Charukesh, N.R.B., Venkatakrishnan, B., Haribabu, K., Sridharan, M.R., Nagarajan, R., 2017. Ultrasonic extraction of natural dye from Rubia Cordifolia, optimisation using response surface methodology (RSM) and comparison with artificial neural network (ANN) model and its dyeing properties on different substrates. Chemical Engineering and Processing: Process Intensification 114, 46e54. Velusamy, S., Roy, A., Sundaram, S., Kumar Mallick, T., 2021. A review on heavy metal ions and containing dyes removal through graphene oxide-based adsorption strategies for textile wastewater treatment. The Chemical Record 21 (7), 1570e1610. Wu, W.-h. R., 1999. Safety Management: A New Challenge under the 1997 Occupational Safety and Health Ordinance, Chapter 509, Law of Hong Kong. Yi, Z., Su, Y., Brynjolfsson, S., Olafsdottir, K., Fu, W., 2021. Chapter 3 - bioactive polysaccharides and their derivatives from microalgae: biosynthesis, applications, and challenges. In: Atta ur, R. (Ed.), Studies in Natural Products Chemistry, vol. 71. Elsevier, pp. 67e85. Yusuf, M., Ahmad, A., Shahid, M., Khan, M.I., Khan, S.A., Manzoor, N., Mohammad, F., 2012. Assessment of colorimetric, antibacterial and antifungal properties of woollen yarn dyed with the extract of the leaves of henna (Lawsonia inermis). Journal of Cleaner Production 27, 42e50.

This page intentionally left blank

Room temperature natural dyeing for energy conservation 4.1

4

Introduction

Natural dyes are derived from plants and invertebrates. The majorities of natural dyes are vegetable dyes and obtained from plant parts such as roots, berries, bark, leaves, and wood. The most commonly used natural dyes are saffron, Indigo, Manjistha, Lac, etc. These natural dyes are always significant since antiquity, and each dye has been named according to their specific color. Natural dyes are often negatively charged. The positively charged dyes rarely exist. Natural dyes are thermo unstable and have poor chemical stability, which make the natural dyes unfit for dyeing at high temperature and pressure. The presence of hydrogen bond and Van der Waals force of attraction play important role in the fixation of natural dyes on the fiber (Gupta, 2019). Natural dyes are having wide application in the coloration of most of the natural fibers, for example, cotton, linen, wool and silk fiber, and to some extant for nylon and polyester synthetic fiber. Natural dyes have many advantages like nontoxicity, eco-friendliness, pleasing shade to eye, and having special aroma or freshness of shade (Dedhia, 1998; Chavan, 1999). They have always been looked upon as harbinger of change in dyeing procedures and sustainability. Somehow natural dyes have low affinity at room temperature for dye adherence, but their colorants get permanently damaged on high temperature. Indigo dyeing which is used since time immoral always been a low temperature dyeing as it is carried out in Vat.

4.2

Natural dyeing

Dyeing is a solid/liquid-phase process which proceeds through the migration of the dye molecules from the bath to the solid surface of the fiber. Once the dye molecules get into the fiber, a slow process, which is diffusion controlled, starts to take place along with swelling (enhancement of dye diffusion rate inside the fiber). Natural dyeing is one such process in which natural colorants seep in and give color to fiber. The natural dyes are loaded with an abundant amount of phytochemicals, which provide characteristic functional finishing to the textiles. These phytochemicals are generally heat sensitive, thus at lower temperatures, their dyeing as well as therapeutic properties are maximum. The demand of natural colorants for the dyeing of textile fibers has been increasing gradually in recent times due to a growing global ecological awareness as well as a greater emphasis on a cleaner and greener production process (Rahman Bhuiyan et al., 2018). The eco-friendly natural dyeing of textile at low temperature can be considered as a novel approach that needs to be extensively

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00001-3 Copyright © 2024 Elsevier Ltd. All rights reserved.

56

Natural Dyes for Sustainable Textiles

studied. The shades so produced supposed to have superior color stability and variable shades on fabric. This alternative ecological method for dyeing textile at temperatures below 70 C reduces energy expenses, dispenses with the need to invest in new equipment, and avoids the undesirable effects of nonbiodegradable methods and auxiliaries.

4.2.1

Natural dyeing protocols

The dyeing of textile substrates depends on dyeing parameters which are fiber structure, temperature, time and pH of the dye bath, and dye molecule characteristics. The fastness properties of dyes on textile substrates depend on bonding of dyes with fiber. Since natural dyes are lacking in the presence of active groups to make bonds with textile fibers, the fastness properties are not very good. The cellulosic fibers are difficult to dye with natural dyes as they have poor affinity and substantivity. The lack of bonding of natural dyes with cellulosic fiber requires mordanting treatment. Protein fibers have ionic groups and get bonded with natural dyes possessing ionic groups in dye structure (Gupta, 2019). In general, dyeing can be described as a process in which a textile fiber absorbs the molecules of dye from its solution so that the dyed material retains the dye and resists the release of the dye back to the solution from which is has been absorbed. Dyeing processes which take place in water solutions of dyes are always distribution processes between two phases, that is, dye solution and solid substrate, and they are based on physicochemical interactions between the molecules of dye and the substrate. These processes may be accompanied by chemical reactions between the dye molecules and the substrate (Grishanov, 2011). In the dyeing process, the fabric is given the desired color with defined requirements considering color fastness. The principle follows the subprocesses of application, fixation, rinsing, and washing, whereby different technologies are applied. The fabric is exposed to the appropriate dyestuff, whereby different auxiliaries are added according to the chosen technology. A high exhaustion degree is aimed at in order to reduce environmental impacts of the effluent (Tobler-Rohr, 2011). The preparation and pretreatment of yarns or fabrics also have significant effects on dyeing quality. For example, poor scouring and bleaching can lead to serious unevenness in dyeing, and the nonuniform winding of a yarn package can lead to color differences in package dyeing. As a result, sufficient and uniform preparation and pretreatment can make the dyeing quality more controllable and predictable. Therefore, process control in dyeing and printing is of significance in achieving high-quality products and increasing dyeing production efficiency (Shang, 2013). Low/room temperature dyeing also can give very good dyeing results if pretreatment of yarn done carefully. A study reports on low temperature dyeing of polyester fabrics of natural dye extracts from the barks of Ixonanthes icosandra Jack. The barks were extracted using boiling water and solvent (methanol) extraction methods. The dyeing process was conducted using exhaustion method at 85 C for 60 min (bin Ab Kadir et al., 2013). The boiling of dye in dyeing implies large energy consumption and environmental contamination. In order to improve the sustainability of the dyeing process, a

Room temperature natural dyeing for energy conservation

57

carrier-free and low-temperature dyeing procedure has to be developed. The drive has been to reduce energy consumption and to make the natural dyeing process ecofriendly by reducing the use of metal mordant. An innovative dyeing has been done at 40 C with the use of minimal amounts of metal mordant with tea extract, and it gave beautiful shades with good fastness (Vankar et al., 2017a,b). Dyeing of wool fabrics was carried out in the temperature range between 60 and 80 C using either mechanical or ultrasound agitation of the bath, and coupling the two methods to compare the results in terms of fastness tests to rubbing and domestic laundering yielded good values for samples dyed in ultrasound-assisted process even at the lower temperature. The results suggest the possibility, thanks to the use of ultrasound, to obtain a well-equalized dyeing on wool working at 60 C, a temperature process strongly lower than 98 C, currently used in industry, which damages the mechanical properties of the fibers (Ferrero and Periolatto, 2012). Eco-friendly and low-carbon emission productions for dyeing and printing productions are the important issues concerned in textile industry. All kinds of new dyeing and printing equipment, dyes and chemicals, and technologies related to the shortening process, lowering water and energy consumptions for increasing production efficiency and reducing carbon emission, need to be researched and worked on and launched on commercial scale (Shang, 2013).

4.3

Replacement of heat while dyeing

Irrespective of dyeing method introduced for a specific dyeefiber system, both dye and fiber must possess either suitable free volume inside with canals to diffuse and/ or reactive site to establish dyeefiber linkage which is essential to achieve desired shade with promising fastness. If required, fiber structure may be modified to make it efficient for the purpose. There are various parameters in dyeing which control the dyeing phenomenon and decides type of shade to be produced. Size of a dye molecule influences the dyeing pattern for a given fiber. In general, dyes of smaller size require lesser activation energy to diffuse easily, whereas dyes of bigger size cause poor diffusion and remain mostly on the surface of fiber resulting poor wash fastness. With a smaller dye, accessibility of the amorphous region will be a less important factor but, increase in size of dye plays more and more decisive role. Many dyes exist in aggregates with weaker bond among themselves. Being bigger in size, these aggregates have lesser accessibility of fiber pores. Heating of dye bath breaks down these aggregates, facilitating smooth entry of dye molecules into fiber structure. In order for the dyeing process to take place, the molecules of dye should penetrate into the fiber structure. For this (i) the concentration of the dye on fiber surface must be higher than inside the fiber; (ii) the polymer structure should have spaces large enough for the dye molecules to move into the fiber interior or, alternatively, the dye molecules should be sufficiently small for this to happen; and (iii) molecular chains of fiber polymer should have sufficient freedom of movement in order to facilitate the movement of dye molecules (Grishanov, 2011). Since the size of the dye molecule is proportional to its molecular weight, it is preferable to have dyes of low molecular weight in order to

58

Natural Dyes for Sustainable Textiles

increase the diffusion coefficient and thus to speed up the dyeing process. It is assumed that the pores in amorphous regions have a tendency to swell and significantly increase in size; they then are filled with water and provide a pathway for the dye molecules to move inside the fiber (Bae et al., 1997; Brady, 1992; Chen et al., 2001). Since the size of the dye molecule is proportional to its molecular weight, it is preferable to have dyes of low molecular weight in order to increase the diffusion coefficient and thus to speed up the dyeing process. Exhaustion in any dyeing process, whatever the chemical class of dye being used, heat must be supplied to the dye bath; energy is used in transferring dye molecules from the solution to the fiber as well as in swelling the fiber to render it more receptive. The technical term for this process is exhaustion. In this process, according to the transition-state theory, the diffusion takes place when a dye molecule gains an extra energy and passes from its equilibrium state to an activated (transition) state and then back to the equilibrium state but at a different location in the polymer structure (Evans and Polanyi, 1935; Eyring, 1935; Laidler and King, 1983; Winzor and Jackson, 2006). Thus, it can be understood that the increase in degree of crystallinity, which is defined as a percentage of crystalline part in a unit mass of a polymer, decreases the rate of diffusion; example is mainly cellulose (cotton) and many synthetic fibers. A good natural dyeing process must provide a satisfactory exhaustion of dye bath and an adequate penetration of dye into the fiber, with the practical advantages of good wet fastness and uniform coloration. The conventional methods for dyeing are based on long times at temperature of the bath close to the boiling point, in order to ensure good results of dye penetration and leveling. These conditions can damage the fibers, with bad effects on the characteristics of the finished material. The extent of the damage that can be caused to dyed fabric depends on pH and timeetemperature profile of the dyeing cycle. When the fabric is maintained at temperatures near 100 C in acid ambient for long times, the structure of the fiber is gradually damaged. Such damage can be minimized by reducing the operation time or, better yet, by reducing the dyeing temperature (Ferrero and Periolatto, 2012). The nature, size, and number of chemical groups present in a dye molecule influence dye uptake. Generally, polar groups improve solubility of dyes and penetrate into fiber structure more effectively. These groups also decide substantivity of dyes for different classes of fibers. The kinetics of dyeing is based on the concept that the rate-determining process in dyeing is the diffusion of the dye from the surface of the fiber into its interior. Then soluble dyes and dye-formers are absorbed in monomolecular form by the fiber, and this whole mechanism can be achieved at low temperature too. Another important aspect of replacing heat with the use of natural dyes is that dyes should have opposite electrical charge to that of fiber for efficient dye uptake. Chances of uneven shade formation may be reduced by applying retarding agents to control initial strike rate during dyeing. In contrast, if dye and fiber both possess identical electrical charge, electrolyte is to be added to promote exhaustion, for example, dyeing of cotton (Chakraborty, 2015). Thus to sum it up, natural dye should have positive charge, small molecule, and presence of polar group. These properties can lead to use lesser energy, and dyeing can be performed at low temperatures.

Room temperature natural dyeing for energy conservation

4.4

59

Examples of low temperature dyeing

There are examples which show that excessive high temperature doesn’t always help in high dye uptake as at temperature more than 70 C (Nonso et al., 2019). Dyeing characteristics in silk during natural dyeing using indigo plants and various dyeing conditions including the temperature of dyeing solution, dyeing period, the concentration and pH of dyeing solution, and mordants used are important. The dyeing solution was kept at 5 C and at room temperature and at 40 C. This work has shown enhanced coloring at even 40 C (Yun et al., 2005). In another study, eco-friendly natural dyeing by using enzyme replacing metal mordant and room temperature dyeing, which is a completely new concept was undertaken. Rubia dye from Sri Lanka has been used in conjunction with different enzymes to show that metal mordanting can be easily replaced by the use of eco-friendly and biodegradable enzymes. Good fastness properties and dye adherence have been also achieved in this study. The most attractive feature of this study is the low-temperature dyeing at 30e40 C. For any dyeing house, this process can be easily adapted on jigger, winch, or even in continuous padding machine (Vankar et al., 2017a, b). A simple, faster, and sustainable alternate process for vat dyeing at room temperature is established by using bacterial cell lysate that ensures superior performances concerning dye uptake, fastness properties, and levelness. In addition, the wastage of dye in dye bath is reduced significantly with muchsimplified application protocol (Patra et al., 2018).

4.5 4.5.1

Case study of low temperature dyeing Low temperature dyeing with tea leaves

An important case study with tea leaves was carried out at low temperature which has given good shades with better fastness. Camellia sinensis or tea is an evergreen plant. Tea leaves contain many compounds, such as polyphenols (catechins and flavonoids). Tea tannins called catechins include gallocatechin, epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (EGC), and epigallocatechin gallate (EGCG) have been considered as potential natural dye source. In this study, an optimized process in terms of usage of metal mordants, dyeing time, temperature, and dye extract for three natural fabrics with good color fastness properties and dye adherence with tea leaves (as dye) have been tried to develop. Before dyeing, cotton was treated with tannic acid. Tea leaves contain tannins, but the activation on cotton can only be done by specific tannin variety called tannic acid which solubilizes well in water and coats well on cotton for better dye adherence. Then cotton was treated with metal mordants solution (2% alum and ferrous sulfate, 1% each of stannous chloride, stannic chloride, copper sulfate, and potassium dichromate separately) and was kept on water bath at 40 C for one hour, whereas silk and wool have been only mordanted with metal salts and then dyeing with tea leaves powder extract was carried out for 3 h at temperature 40 C. Dyed fabrics were then dipped for 15 min in dye-fixing solution which consists of sodium chloride solution (2% w/v with respect to the fabric) and then rinsed thoroughly in tap

60

Natural Dyes for Sustainable Textiles

water and air dried. Tannic acid pretreatment, metal mordanting, and dyeing are all carried out at low temperature. Highlights of this process are low temperature dyeing (40 C), use of low metal mordant percentage, and dye effluents are less contaminated with metal salts, which is advantageous for industrial natural dyeing, being energy saving and eco-friendly. Thus the net enhancement of dye uptake due to metal mordanting has been found to be 64%e67% in cotton, 70%e75% in silk, and 67%e72% in wool with respect to control samples. The higher percentage of color strength in the case of silk and wool makes tea leaves best suited for these natural materials. However, when attempts were made with polyester and nylon fabric, the dyeing results were not good. Thus tea leaves powder is ideally suited for natural fibers which include bamboo fabric too (Satindar et al., 2012). It is proposed that under low solubility, large molecular size, the iron tannante complex that was formed occupied peripheral regions of the dyed fiber attributing good dye adherence (Burkinshaw and Kumar, 2008). This research provides beautiful and earthy shades of pastel brown which are generally not available among the known natural dye shade card (Fig. 4.1). Higher dye uptake with better levelness is achieved in each case of the newly proposed process as compared to the conventional dyeing method. Low temperature dyeing is an energy-saving process which ensures dye effluent load reduction and simplifies the existing process than the conventional one (Vankar et al., 2017a,b).

Mordant

Cotton

Silk

Wool

Control

Alum

Copper Sulphate Ferrous Sulphate Potassium dichromate Stannous Chloride Stannic Chloride

Figure 4.1 Shade card of low temperature dyeing on cotton, silk, and wool with tea.

Room temperature natural dyeing for energy conservation

4.5.2

61

Silk dyeing with Rubia cordifolia at low temperature

In a study, different enzymes (protease, amylase, xylanase, pectinase, and phytase) were used efficiently with Rubia dye by using simultaneous and two step processes. Both the processes were developed with an aim for the conservation of time and energy and for the ease of industrial use. The study serves two motives, first being eco-friendly natural dyeing by using enzyme replacing metal mordant and another is room temperature dyeing which is a completely new concept. The dyeing time was 3 h at a temperature of 30e40 C. For successful commercial use of natural dyes, innovative and standardized dyeing techniques need to be developed and adopted. An experiment was carried out where the enzyme treatment to the silk fabric was done by raising the temperature of the dye bath from 30 to 70 C for the purpose of denaturing the enzyme. Poor dyeability was observed in this case due to denaturing of the enzyme at high temperature. This process also has an advantage that room temperature dyeing saves a lot of energy which is very much desired in any industrial process. The enzymes are adsorbed by virtue of various ionic and nonionic forces of attraction on to the silk fabric through hydrogen bonding, dipoleedipole interactions, and electrostatic forces. As silk fibers mainly contain proteinaceous material, starches, and pectins as binding materials, enzymes like protease, amylase, and pectinase have been used to loosen the surrounding material leading to better dye uptake of dye molecules under milder conditions in fabric. The enzymeedye complex thus formed on the surface of the dyed silk fabric acts as a barrier for not letting the dye get washed off. Good fastness properties and dye adherence have been the other highlights of this study. Varied hues of brown color can be obtained from Rubia dyeing in this way (Fig. 4.2).

4.5.3

Hibiscus anthocyanin dyeing at low temperature

Anthocyanins are one of the most abundant natural dyes available. These are the vacuolar dye found in almost every part of higher plants and water-soluble strong color and have been used to color food since historical times. A new approach for natural dyeing with anthocyanin has been discussed along with a convenient method of extraction. Antioxidant activity of the anthocyanin extract seemed to have contributed to enhance the fastness properties of the dyed fabrics. They are harmless and water soluble, which makes them interesting for their use as natural water-soluble colorants. Another significant property of anthocyanins is their antioxidant activity. Despite the great potential of applications that anthocyanins represent for food, pharmaceutical, and cosmetic industries, their use has been limited because of their relative instability and low extraction percentages (Casta~ neda-Ovando et al., 2009). Their use in textile is negligible as they lack affinity for the fiber and cannot sustain washing. Nevertheless, anthocyanins are good food colorants, because in those applications, color fastness properties do not play such an important role as for the textile applications. The color of extracts from flowers having anthocyanins can be rich source for textile dyeing. Most natural dyeing is done with the use of mordants, a new technique for concentrating the anthocyanin extract by lyophilization. It is a technology used to freeze-dry products such as

62

Natural Dyes for Sustainable Textiles

Mordant

Silk

Control

Protease

Amylase

Xylanase

Pectinase

Phytase

Alum

Figure 4.2 Shade produced by Rubia on silk at low temperature dyeing.

biological/plant samples. It is a process that removes water from a substance. The cotton and silk were dyed with anthocyanin extract, keeping M:L ratio at 1:40 (although M:L ratio is on the higher side, it worked well in our case). Forty grams of anthocyanin extract was diluted in 1000 mL water for a piece of fabric weighing 10 g, keeping the fabric in dye bath for about 2 hours at 35 C. Beautiful shades of red purple were achieved with metal mordants proving that Hibiscus anthocyanins can be a potential colorant for not only food but for textile too (Vankar and Shukla, 2011). Low temperature in this dyeing plays a very important role as anthocyanin can’t withstand high temperature as it will get denatured and color on textile will eventually wash off despite the use of mordants. The use of metal mordants in conjunction with the anthocyanin extract of Hibiscus rosa sinensis was found to enhance the dye ability along with improved fastness properties of the dyed fabrics. The two-step dyeing process of cotton and silk fabrics with premordanting method at acidic value (pH 4) yielded

Room temperature natural dyeing for energy conservation

63

Figure 4.3 Shows the difference in colors from the same extract of Hibiscus red flower with alum (#0), stannous (#1) and stannic chlorides (#2), and copper sulfate(#4).

different color tones on silk and cotton, specially one with tin mordanted having very good wash and light fastness (Fig. 4.3). The developed shades on cotton and silk fabrics as shown in Fig. 4.4 will surely be liked by consumers in present global textile market.

4.6

Futuristic approach

Low temperature in natural dyeing can increase sustainability of dyeing process in multiples. Many research works are underway to make textile dyeing work a low

Mordant

Cotton

Silk

Control

Alum

Copper Sulphate

Potassium dichromate

Stannous Chloride

Figure 4.4 Shade card of anthocyanin dyeing on cotton and silk at low temperature dyeing.

64

Natural Dyes for Sustainable Textiles

heat consuming course. Various factors can be very advantageous while carrying out a low heat involving dyeing and will definitely be used vigorously in future. • • • • •

• • •

Use of extracted colorants for dyeing as anthocyanin dyeing. Dye extracted first and then concentrated dye to be used at low temperature. Fabric to be pretreated at warm condition like pure cotton as cationized cotton fabrics, as they absorb more natural dye. It can be very useful for wool and silk as both theses fibers are protein. Using modifiers to expand the color palette as an acid modifier by using lemon juice and an alkaline modifier by using iron water. Ultrasound-assisted dyeing is a promising technology that can accelerate heat and mass transfer. Lower temperature, shorter time, and higher efficiency compared to normal leaching method and thermal refluxing method are some of the proven merits of ultrasound dyeing (Kandasamy et al., 2021). Usage of chitosan as pretreatment agent for fabrics specially silk dyeing enhanced the natural dye uptake and the fastness properties, and it is reported to have wide applications including textile dyeing and printing (Fithriyah, 2013). Fancy color effects can be produced using the space dyeing technique with natural dyes extracts at low temperature. It is important to produce dye powders in smallest particle size to result in good solubilization and enhance penetration through fabric at even low/room temperature.

4.7

Conclusions

Indigo is the first thing come in mind when room temperature/temperature control dyeing is concerned. The use of natural dyes is getting pace with stringent laws and devotion of customer toward more sustainable clothing and fashion. This dyeing relies solely on environmental savvy practices and promotes people’s better life, better future, and healthy living today, tomorrow, and forever. The dyeing process can be simplified with a scientifically upgraded process that eliminates the traditional step of the boiling dye in dye bath. Dyeing process is also selected in such a way that it does not damage the fiber and at the same time results in optimum fastness and dye uptake during low temperature dyeing. Natural dyes are found to be best considering both the fastness of color and cost of dyeing, for textile dyeing considering their constitution. The ambient temperature processing technique is economic since it utilizes the minimum water and thermal energy. As the whole process is carried out at ambient condition, it is easy to control the processing conditions too. After development of a laboratory method, it could be transferred at industrial level, reducing both the energy consumption and fiber damage caused by the prolonged exposure to high temperature without the use of polluting auxiliary agents (metal mordants, harsh chemicals as finishing agents) as in natural dyeing. Dye extraction should be helped with microwave or another energy-involving technique before dyeing as the addition of microwave treatment has added value to the extraction of colorant under mild conditions. Thus low temperature dyeing can be next landmark step in dyeing industry involving natural dyes. Whole process will be aesthetically rich with considerable reduction in carbon footprint too.

Room temperature natural dyeing for energy conservation

65

References Bae, S.H., Motomura, H., Morita, Z., 1997. Diffusion/adsorption behaviour of reactive dyes in cellulose. Dyes and Pigments 34 (4), 321e340. bin Ab Kadir, M.I., Ahmad, W.Y.W., Ahmad, M.R., Misnon, M.I., Jabbar, H.A., 2013. Fastness properties and colorimetric characteristics of low temperature dyeing of natural dyes from the barks of Ixonanthes icosandra Jack on polyester fabric. In: 2013 IEEE Business Engineering and Industrial Applications Colloquium (BEIAC). IEEE. Brady, P., 1992. Diffusion of dyes in natural fibres. Review of Progress in Coloration and Related Topics 22 (1), 58e78. Burkinshaw, S., Kumar, N., 2008. A tannic acid/ferrous sulfate aftertreatment for dyed nylon 6, 6. Dyes and Pigments 79 (1), 48e53. Casta~neda-Ovando, A., de Lourdes Pacheco-Hernandez, M., Paez-Hernandez, M.E., Rodríguez, J.A., Galan-Vidal, C.A., 2009. Chemical studies of anthocyanins: A review. Food Chemistry 113 (4), 859e871. Chakraborty, J., 2015. Fundamentals and Practices in Colouration of Textiles. CRC Press. Chavan, R., 1999. Chemical Processing of Handloom Yarns and Fabric. Department of Textile Technology, IIT, Delhi, p. 6. Chen, B., Hui, C.W., McKay, G., 2001. Pore-surface diffusion modeling for dyes from effluent on pith. Langmuir 17 (3), 740e748. Dedhia, E., 1998. Natural dyes. Colourage 45 (3), 45e49. Evans, M.G., Polanyi, M., 1935. Some applications of the transition state method to the calculation of reaction velocities, especially in solution. Transactions of the Faraday Society 31, 875e894. Eyring, H., 1935. The activated complex in chemical reactions. The Journal of Chemical Physics 3 (2), 107e115. Ferrero, F., Periolatto, M., 2012. Ultrasound for low temperature dyeing of wool with acid dye. Ultrasonics Sonochemistry 19 (3), 601e606. Fithriyah, N.H., 2013. The application of chitosan for environmentally benign process of curcumin dyeing of silk fabrics. Journal of Basic and Applied Scientific Research 3 (1), 5e14. Grishanov, S., 2011. Structure and properties of textile materials. In: Handbook of Textile and Industrial Dyeing. Elsevier, pp. 28e63. Gupta, V.K., 2019. Fundamentals of natural dyes and its application on textile substrates. In: Chemistry and Technology of Natural and Synthetic Dyes and Pigments: 2019. Kandasamy, N., Kaliappan, K., Palanisamy, T., 2021. Upcycling sawdust into colorant: Ecofriendly natural dyeing of fabrics with ultrasound assisted dye extract of Pterocarpus indicus Willd. Industrial Crops and Products 171, 113969. Laidler, K.J., King, M.C., 1983. The development of transition-state theory. Journal of Physical Chemistry 87 (15), 2657e2664. Nonso, O.S., Genevieve, O., Chinedu, O., Onyinyechi, N., Kenneth, O.C., 2019. Effect of temperature and mordant on the dyeing of cotton using sodium hydroxide extract of Whitfieldia lateritia Dye. International Journal of Innovative Research in Science, Engineering and Technology 8 (6), 7301e7308. Patra, S., Patra, A., Ojha, P., Shekhawat, N., Khandual, A., 2018. Vat dyeing at room temperature. Cellulose 25 (9), 5349e5359. Rahman Bhuiyan, M.A., Ali, A., Islam, A., Hannan, M.A., Fijul Kabir, S.M., Islam, M.N., 2018. Coloration of polyester fibre with natural dye henna (Lawsonia inermis L.) without using mordant: a new approach towards a cleaner production. Fashion and Textiles 5 (1), 2.

66

Natural Dyes for Sustainable Textiles

Satindar, K., Chattopadhyay, D., Kaur, V., 2012. Dyeing of bamboo with tea as a natural dye. Research Journal of Engineering Sciences ISSN 2278, 9472. Shang, S., 2013. Process Control in Dyeing of Textiles. Process Control in Textile Manufacturing. Elsevier, pp. 300e338. Tobler-Rohr, M.I., 2011. Handbook of Sustainable Textile Production. Elsevier. Vankar, P.S., Shukla, D., 2011. Natural dyeing with anthocyanins from Hibiscus rosa sinensis flowers. Journal of Applied Polymer Science 122 (5), 3361e3368. https://doi.org/10.1002/ app.34415. Vankar, P., Shukla, D., Wijayapala, S., 2017a. Low temperature optimized dyeing of cotton, wool and silk with extract of camellia sinensis (tea leaves). Journal of Textile Engineering and Fashion Technology 2 (1), 274e280. Vankar, P.S., Shukla, D., Wijayapala, S., Samanta, A.K., 2017b. Innovative Silk Dyeing Using Enzyme and Rubia Cordifolia Extract at Room Temperature. Pigment and Resin Technology. Winzor, D.J., Jackson, C.M., 2006. Interpretation of the temperature dependence of equilibrium and rate constants. Journal of Molecular Recognition: An Interdisciplinary Journal 19 (5), 389e407. Yun, J.-G., Jang, H.-G., Heo, B.-G., Park, Y.-J., 2005. Effect of dyeing conditions on dyeing characteristics in silk during natural dyeing using the raw juice of indigo plants. Korean Journal of Polar Research 18 (3), 417e423.

Waterless natural dyeing to make it sustainable 5.1

5

Introduction

Coloration of textiles is the aqueous application of color, mostly with synthetic organic dyes, to fiber, yarn, or fabric in the form of dyeing and printing. It involves the utilization of auxiliaries/chemicals to the textile to obtain a uniform depth of coloration with color fastness properties suitable to the end use (Schlaeppi, 1998). Dyeing involves the application of dyestuffs (natural as well as synthetic) to textiles by various forms of continuous pad applications or exhaust dyeing in batch processing. It is well known that the textile industry is one of the largest consumers of water. Conventional textile dyeing uses huge amounts of fresh water and which then is disposed as waste water containing dyestuff chemicals. Water is used as a solvent in many pre-treatment and finishing processes in the textile industry, such as washing, scouring, bleaching, dyeing, and finishing (Miah et al., 2013). The dyeing medium is an inseparable part of textile dyeing. It is generally a liquid phase, maybe water, organic solvent, or an ionic solution. Among the various media, water is an excellent polar solvent and has been widely used for dyeing textiles for hundreds of years. According to statistics, an average of approximately 150 m3 of water is consumed for each ton of textiles processed (Lu et al., 2010). Moreover, approximately 3600 dyes and 8000 chemicals are used in the various bleaching, dyeing, and finishing processes of the textile industry at present (Kant, 2012). In addition, approximately 280,000 tons of textile dyes are discharged with industrial wastewater every year, which poses a direct threat to human health and aquatic life, and it causes water and soil pollution (Hussain and Wahab, 2018). Textile industry is a water-intensive industry that puts a high strain on the global water resource (Saxena et al., 2017). The increasing concern about the textile wet processing industry is its extremely high water consumption, huge wastewater discharge, and high pollution potential (De Moraes, Freire et al., 2000). The major culprit in this regard comprises the bleaching, dyeing, printing, and finishing segments of the textile industry, which use water as a primary medium to apply dyes and chemicals on the fabrics. In literature, different levels of water requirement have been reported to dye 1 Kg of textile material, depending upon the fiber type, dyestuff chemistry, and machinery used for dyeing. Traditional aqueous dyeing requires 100e180 L of water to dye 1 Kg of fibers (Petek and Glavi
c, 1996), Zheng et al. (2016).

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00008-6 Copyright © 2024 Elsevier Ltd. All rights reserved.

68

Natural Dyes for Sustainable Textiles

In a conventional dyeing and finishing mill, on average, about 150 m3 of water is consumed for every ton of textile processing. More than 80% of the industrial waste water is discharged by textile wet processing mills (Lu et al., 2010). Textile industry is the worst polluter of clean water after agriculture (Vandevivere et al., 1998). According to an estimate, around 280,000 tons of textile dyes are discharged as industrial effluent every year. Effluents from textile processing mills pose a direct threat to aquatic life too. Around 3600 different dyes and 8000 different chemicals are being used by textile industry today in various processes including bleaching, dyeing, printing, and finishing. Many of these chemicals pose a direct or indirect threat to human health and aquatic life and cause water and soil pollution. An average-sized textile mill with processing capacity of about 8000 kg of fabric per day consumes around 1.6 million liters of water every day. To produce enough finished fabric to cover a sofa, around 500 gallons of water is used on average (Kant, 2012). Thus, the textile industry has nowadays focused on alternative green technologies and eco-friendly chemical agents to minimize these problems. Water conservation efforts in different segments of the textile industry have been classified into five major categories. These include waste water treatment and reuse, machine innovations, process innovations, chemical innovations, advanced water analysis, and water saving tools. Waterless dyeing using supercritical carbon dioxide (SC-CO2) and the use of low liquor ratio machines in textile wet processing are two very promising approaches for water conservation. But waterless dyeing needs further working to dye natural fibers in a reliable way (Hussain and Wahab, 2018). Textile dyeing is carried out at high fabric to liquid ratio (1:10e20). This would consume a huge amount of water. Furthermore, huge volumes of effluents containing dye and dyeing auxiliaries are discharged from textile processing plants (Berradi et al., 2019). Dyeing process requires large amount of water for making solutions of different colors and for washing the colored fabric to remove excess solutions from it. On an average, textile industry uses 1.6 million liters of water for the production of 8000 kg of fabrics daily ; of this total consumption, 16% of it is used for dyeing purposes. Dyeing contributes to 15%e20% of total water wastage (Patil, 2020). This waste water also pollutes the water resources near to the mill. In other words, dyeing is the major cause of water usage and pollution in textile mills. In order to solve the problem of severe water pollution, numerous researches have been conducted over the last two decades to investigate the eco-friendly dyeing procedure for fibres, including solvent dyeing (Shukla and Mathur, 1997), foam dyeing (Yu et al., 2014), and other cleaner dyeing methods. Among them, SC-CO2 dyeing shows the potential of replacing the far more environmentally damaging aqueous dyeing procedure due to its low energy consumption, high uptake rate, recycling of dyes and carbon dioxide (CO2), as well as zero waste water emission (Zhang et al., 2015; Zheng et al., 2016). Moreover, CO2 is an attractive dyeing medium alternative for a wide variety of chemical solvents because of its low cost, wide availability, as well as environmentally friendly and chemically benign nature (Zhang et al., 2015; Zhang et al., 2016). Water recycling techniques are found quite successful in reducing the effluent discharge from the textile processing plant. However, these recycling techniques

Waterless natural dyeing to make it sustainable

69

have limited efficiency and they cannot provide any reduction in chemical consumption (Rott and Minke, 1999). Recently researchers have put much focus on the development of waterless procedures. Solvent dyeing (Gebert, 1971) and supercritical fluid (SCF) dyeing (Liu et al., 2018) are some examples of such procedures. Among them, SCF dyeing is found most successful, and it has gained wide attention, regime, and environmental protection. Due to the fresh water scarcity and to overcome pollution problems, a suitable dyeing method which uses less water had become a requirement. Keeping this in mind, several companies came up with different dyeing methods and technologies which use very less to negligible amount of water as compared to the normal dyeing processes (Patil, 2020).

5.2

Promising solutions

Water scarcity and increased environmental awareness are worldwide concerns, which are causing a sharp rise in prices for intake and disposal of water. New legislation will even endanger the continuity of textile industries in the near future. Each year as older products and processes are replaced by the technological diffusion of novel products and innovative processes. The elimination of process water and chemicals would be a real breakthrough. Although there have been efforts to reduce the water input such as altering conventional equipment, recycling water, and reusing wastewater. Water usage is still high in the textile industry. Nonaqueous systems of dyeing can reduce or completely eliminate the amount of water used. Reducing water use provides environmental benefits as well as cost savings. The application of ultrasonic waves, microwave dyeing, plasma technology, SC-CO2, and electrochemical dyeing of textiles are some of the revolutionary ways to advance the textile wet processing (Moore € and Ausley, 2004; Saravanan, 2006; Oner et al., 1995; Chena et al., 2011; Yi, 2012; Agrawal, 2015). As the demand of fresh water is increasing day by day for daily purposes, the above methods/techniques of dyeing can be something which can be relied on to save fresh water rather than wasting large amounts of it on conventional water dyeing. Also the washing process gets eliminated in waterless dyeing methods; hence, the water pollution due to disposal of waste water into fresh water resources is also prevented. The more these methods will be used, the more amount of water can be saved making textile dyeing more sustainable than ever.

5.3

Waterless dyeing

Conventional textile dyeing uses huge amounts of fresh water and which then is disposed as waste water containing dyestuff chemicals. Water is used as a solvent in many pretreatment and finishing processes in the textile industry, such as washing, scouring, bleaching dyeing, and finishing. So the experts are tried to develop a new technology to dye the textile material without using water (waterless dyeing

70

Natural Dyes for Sustainable Textiles

technology). In this regard, SC-CO2 dyeing technique is a promising alternative to conventional aqueous-based methods as it avoids the use of water, uses less energy, and fewer chemicals minimizing the waste generation which is important to improve the ecological footprint and reduced production cost. Elimination of the water process and chemicals will be a real and significant advance for the textile dyeing industry. This new process utilizes by-product CO2 for dyeing textile materials. It is a completely waterless dyeing process using recycled carbon dioxide on certain temperature and pressure. Waterless dyeing using dense CO2 as a solvent for dyes or pigments is a promising approach to save dyes and chemicals, avoid wastewater contamination, and make textile industry more flexible. Since the cost of dyes usually accounts for more than 20% of their total costs for chemicals, the loss of colors has a significant influence on production costs including treatment of wastewater and other expenses. During the last many years, the textile dyeing industry has been feeling the stress of liberalized economic pressure and thus desperately need low-cost preferences to run in a more sustainable mode. The waterless dyeing assisted by SC-CO2 thus can be great hope in achieving the goals of sustainability and cleaner dyeing process. The scarcity of water in the recent times has led to the development of new technologies, for textile chemical wet processing, based on minimum utilization of water. One such technology is based on the use of SC-CO2 for dyeing of synthetic and several natural fibers. Carbon dioxide has been investigated extensively as a nonflammable, environmentally benign, inexpensive solventdboth as a liquid and also in its supercritical state. In the 1980s, SC-CO2 was being hailed as a medium with solvent properties similar to those of n-alkanes and may be considered as a simple drop-in replacement for a wide variety of organic solvents. The concept of dyeing textiles with supercritical CO2 could be considered as green from the environmental as well as economic perspectives.

5.4

Supercritical fluid

Supercritical fluids are highly compressed gases which possess valuable properties of both a liquid and gas. Any gas above its critical temperature retains the free mobility of the gaseous state but with increasing pressure its density will increase toward that of a liquid. The properties, which are intermediate between gases and liquids, are controlled by pressure. Supercritical fluids do not condense or evaporate to form a liquid or a gas. The fluids are completely miscible with permanent gases, which leads to higher concentrations of dissolved gases than can be achieved in conventional solvents. Supercritical fluid refers to the phase of a substance with both temperature and pressure higher than the critical point (the point where liquid and gaseous phases of a substance become impossible to tell apart). This phase of a substance enjoys many advantages and can replace water in the dyeing process. Supercritical fluids have some amazing properties such as: •

Supercritical fluids feature a low viscosity

Waterless natural dyeing to make it sustainable

• •

71

Supercritical fluids are compressible Conductivity and capacity of heat of supercritical fluids can be adjusted

Hence, the density of the supercritical fluid can be manipulated by adjusting the pressure. The solubility of solutes is proportional to the density of the solvent. Thus, whenever the supercritical fluids act as solvents, their solvation power can easily be varied by adjusting the pressure. The process “rapid expansion of supercritical solutions” (RESSs) makes use of this circumstance (Braeuer, 2015). Supercritical fluids have large solvent power. Beams of small molecules such as adenine, caffeine, guanine, or vitamin K3 can be generated by seeding carbon dioxide (Tc ¼ 304 K, pc ¼ 73.8 bars). The solvent power can be adjusted between that of gas or liquid phase with only moderate changes in pressure. Moreover, carbon dioxide is compatible with ultrahigh vacuum conditions (Schermann, 2008). The supercritical fluid normally used is CO2, as the critical temperature and pressure are easier to achieve than that of other substances. Moreover, carbon dioxide is also nonflammable without residues, so it is suitable for industrial use. Supercritical fluids offer advantages in textile processing as they combine the valuable properties of both a gas and liquid. These fluids have solvating power or the ability to act as a solvent as well as a solute, making them desirable in the dyeing process in which disperse dyes are utilized. Carbon dioxide is the most investigated and used gas in the supercritical fluid dyeing process. It is naturally occurring, chemically inert, physiologically compatible, relatively inexpensive, and readily available for industrial consumption (Beckman, 2004).

5.5

Supercritical CO2

CO2 is naturally occurring, chemically inert, physiologically compatible, inexpensive, and readily available for industrial consumption. Depending on the pressure and temperature, CO2 appears in solid, liquid, gaseous, and supercritical states. The states of CO2 set its diversity of properties (Saus et al., 1993). The ability of CO2 to act as a solvent is poor or nonexistent in its gaseous state. The reason for this is its low density in the order of magnitude of 103 g/cm3. In its liquid and supercritical states, the solvent properties improve significantly. This makes liquid and especially SC-CO2 interesting for several extraction and impregnation processes (Letcher and Scott, 2012). Colorization of a material by dissolving a dye or pigment in CO2 and transporting it into the matrix of the material as an impregnation process is the focus of this work. Liquid CO2 can be converted to a supercritical fluid by increasing the temperature and pressure simultaneously. At the same pressure, the density of liquid CO2 and thus its dissolving power are higher compared with SC-CO2. However, the density of SCCO2 and its dissolving power can reach the order of magnitude of liquids by increasing the pressure. In comparison with the liquid state, the use of SC-CO2 usually offers a number of advantages. The viscosity of a supercritical fluid is in the range of gases. This has a decisive influence on the convective mass transport. Low viscosity

72

Natural Dyes for Sustainable Textiles

promotes intensive mass transport and ensures a constant dye concentration in the fluid phase, preventing it from being consumed locally. Furthermore, the diffusion coefficients of supercritical fluids are also in the range of gases, which promotes the introduction of dyes into porous and fine structures such as textiles or leather. The surface tension of CO2 is negligible in the supercritical state. This enables optimal wetting of surfaces. The simple separation of CO2 and the dissolved substance by lowering the pressure is also considered to be a major advantage (Brunner, 2004). The most significant advantage of supercritical CO2 extraction is after the extraction process there was no trace amount of solvent present in extracted compounds since the residual CO2 can be easily depressurized and vented. Supercritical CO2 attracts interest because of its high compressibility, nontoxic, nonflammable, and physiological compatibility (Sathasivam et al., 2022).

5.6 • • • • • • • • •

Water is not needed during coloration. Drying is not required due to gaseous characteristics of CO2. Save the environment by eliminating water pollution. There no risk of explosion of boiler and machine as the probability to use hard water. No probability to create stain on the surface of fabric of various salts of calcium (Ca) and magnesium (Mg) Dyeing occurs with high degree of levelness. CO2 easily recyclable in dying process as it is obtained from natural resources. CO2 is nontoxic. Short time required.

5.7 • • • • •

Advantages of using supercritical CO2

Disadvantages of using supercritical CO2

CO2 should take into the supercritical fluid state by maintaining the proper temperature and pressure. High pressure and temperature are needed. Highly skilled manpower is needed. Investment cost high. Complex dyeing process (Miah et al., 2013).

Dyeing with carbon dioxide delivers brilliant results in terms of dye levelness and shade development. The physical properties are also as good as the conventional dyeing methods. This kind of dyeing is done in equipment, where in the fabric is rolled and inserted in a high pressure vessel filled with carbon dioxide, and pressurized up to 250 bar. Removing excess dye is also done in the same vessel. The viscosity of dyes produced by this process is low. Waterless dyeing when compared to conventional dyeing forms consumes very less energy, disposes less waste, and completes the dyeing process in approximately two to three hours. This makes it an environment-friendly and

Waterless natural dyeing to make it sustainable

73

sustainable alternative. Carbon dioxide is readily available, is biodegradable, and does not release any form of volatile organic compounds. Moreover, it is nontoxic, nonflammable, and noncorrosive. These merits make it a very viable dyeing alternative. The biggest merit of using carbon dioxide is that it can be recovered, and reused again from the process of dyeing, making it a cost-effective option (Anonymous, 2013). It is well known that the textile industry is one of the largest consumers of water. But SC-CO2-assisted dyeing system is one such advanced technique which offers a water-free solution. The use of supercritical fluids as a solvent is in since many years. The advantages of the fluid are both economic, and SC-CO2 is an alternative dyeing technology that eliminates the use of water while achieving results comparable to current dyeing processes. This method of dyeing fibers replaces water from the dyeing process and also reduces the other effluents.

5.8

Supercritical fluid carbon dioxide dyeing

Colorization of a material by dissolving a dye or pigment in CO2 and transporting it into the matrix of the material as an impregnation process is the focus of waterless dyeing. The dyeing takes place in following steps: • • • •

Dye should soluble in supercritical fluid of CO2 Penetrate to the fibers (sorption) Adsorption of dye on fiber surface and Diffusion of dye molecules into the fiber molecules

To dye the textile material first of all the material is to be wrapped around a perforated stainless steel tube. After this it should be mounted inside the autoclave around the agitator. Dyestuff powder is placed at the bottom of the vessel, and the apparatus is preserved, cleaned with gaseous CO2, and preheated. When it reaches the working temperature 3100K, CO2 is isothermally compressed to the chosen working pressure under constant stirring. Pressure above 74 bar is maintained for a dyeing period of 50e70 min and therefore bath will be dropped. Afterward, the CO2 and excess dyes are separated and recycled. After this dyeing procedure, the residual dyes (unfixed dyes) are removed by rinsing with acetone if necessary. SC-CO2 dyeing is an anhydrous dyeing, and this process comprises the usage of less energy and chemicals when compared to conventional water dyeing processes leading to a potential of up to 50% lower operation costs. The advantages of SCCO2 dyeing method especially on synthetic fiber fabrics hearten leading textile companies to alter their dyeing method to this privileged waterless dyeing technology. SC-CO2 waterless dyeing is widely known and applied green method for sustainable and eco-friendly textile industry. However, not only the dyeing but also scouring, desizing, and different finishing applications take the advantage of SC-CO2 (Eren et al., 2017). To date, SC-CO2 can be readily employed as a dyeing medium in practice to completely avoid water consumption and wastewater discharge, which truly

74

Natural Dyes for Sustainable Textiles

embodies the concept of green chemistry and sustainable alternatives with numerous advantages over conventional aqueous coloration methodologies (Long et al., 2012; Banchero, 2013). However, there is still a challenge in the coloration of natural fibers by utilizing SCCO2 due to the unique properties of the supercritical fluid and the highly hydrophilic characteristics of the natural substrate (Long et al., 2012; Long et al., 2015; Van der Kraan et al., 2007; Zhang et al., 2017). The application of a special kind of dye, namely, disperse reactive dyes, can meet most of the demands of both the supercritical medium and natural substrates during coloration via SC-CO2. This method has attracted increasing attention in recent years not only due to its environmentally friendly advantages but also due to its facile and convenient implementation in practice (Zhang et al., 2017; Bach et al., 1998). Linking group between the chromophoric matrix and reactive group(s) also plays a crucial role in the coloration properties of dye uptake, adsorption, penetration, reactivity, fixation, and stability during application which is another important aspect taken care of during use of natural dyes with SCCO2 (Fan et al., 2019).

5.9

Waterless natural dyeing

Bio-based materials and new dyeing technologies have gained growing interest, as companies actively want to enhance their products sustainability and remove environmental and hazardous pollutants. This article describes for the first time waterless dyeing studies using SC-CO2 and a natural anthraquinone dye emodin for polylactide (PLA) and polyester (PET) fabric coloration. Under the pressure of sustainability and material efficiency, processes have been developed to decrease water and energy consumption. Bio-based materials and new dyeing technologies have gained increasing interest, as well as alternative methods to reduce water usage. For bio-based and degradable materials, bio-based dyes are an alternative to complement the figure of sustainability and circular economy (R€ais€anen et al., 2021). The SC-CO2 technique is already being used in apparel dry cleaning and has proved to be by far the best, most gentle, and the cleanest method to do so. There are various reasons as to why carbon dioxide is the best supercritical fluid for the dry-dyeing technique. It is a naturally occurring inexhaustible resource, physiologically compatible, and relatively inexpensive. As a green, safe, and environmentally friendly medium, SC-CO2 fluid, which was introduced at the first time in textile dyeing as an alternative to traditional water bath by E. Schollmeyer (Schmidt et al., 2003) and further developed by Knittel, has been worldwide investigated and tried for textile dyeing and other applications due to its essential advantages. Dyeing in SC-CO2 has been applied on synthetic fibers and especially on polyester fabrics. As the method has gained success on polyesters, the other fibers have begun to be applied too. Natural fibers, firstly cotton, than wool and silk fibers have been dyed in SC-CO2.

Waterless natural dyeing to make it sustainable

75

A novel red-hued disperse reactive dye involving an anthraquinonoid chromophoric matrix and a versatile bridge group was successfully used for dyeing. The preliminary applications in SC-CO2 further reveal that satisfactory uptake performance, color characteristics, leveling properties, fixation efficiency, and conventional color fastness were successfully achieved on both wool and silk substrates, followed by cotton fabric, by utilizing the synthesized anthraquinonoid disperse reactive dye. All the achieved results clearly prove that the novel disperse reactive dye was well designed and successfully synthesized and is also potentially useful and applicable in the coloration of natural substrates in the textile industry, particularly when employing SC-CO2 as a medium for sustainable and cleaner production (Fan et al., 2019). In a more recent study, curcumin natural dye was modified as ethyl, butyl, hexyl, and octyl curcumin to enhance the compounds solubility and dyeing ability in SCCO2 media (Liu et al., 2018). Dyed fabrics were natural fibers: cotton, silk, and wool. In addition, unmodified, natural curcumin from turmeric (Curcuma longa) as a disperse dye for polyester fabric in SC-CO2 dyeing without any additional chemicals or pretreatments of the fabric has been used (Abate et al., 2019; Abate et al., 2020). Dye concentration varied from 0.25% to 1% on the weight of the fiber (o.w.f.). Results showed that dye concentration increased color depth, which was revealed by the higher K/S values. The SC-CO2 dyeing technology is a green dyeing technology, and the usage of natural dye makes SC-CO2 dyeing technology safer and more environment-friendly. Nevertheless, after using natural dye in SC-CO2 dyeing, the color depth and fastness of dyed natural fabric are poor. In a study, alkyl and hydroxyalkyl groups were grafted onto alizarin, which is a natural dye, to elevate the color depths and fastness of alizarinderivative-dyed natural fabric. The results demonstrate that the color depths of alkylalizarin-dyed and hydroxyalkyl-alizarin-dyed natural fabrics were increased. This has to do with the increase in the solubility of alkyl alizarin and hydroxyl alkyl alizarin in SC-CO2 (Wu et al., 2019). The dry dyeing method, a pioneering work of a Dutch company in textile dyeing, does not make use of water at all. Carbon dioxide’s liquid-like densities proves to be beneficial for dissolving hydrophobic dyes and the gas-like densities have low viscosities and diffusion properties. Supercritical is a state where matter can be expanded into a liquid or heavily pressurized and converted to gas. When carbon dioxide is heated to over 31 C and pressurized to above 74 bar, the supercritical state is achieved. Carbon dioxide is readily available, is biodegradable, and does not release any form of volatile organic compounds. Moreover, it is nontoxic, nonflammable, and noncorrosive. These merits make it a very viable dyeing alternative. The biggest merit of using carbon dioxide is that it can be recovered and reused again from the process of dyeing, making it a cost-effective option. This method of waterless dyeing is also used for printing on garments. The waterbased dyeing techniques involve drying the garment, once it has been colored, while this new innovative technique eliminates this process altogether.

76

5.10

Natural Dyes for Sustainable Textiles

Futuristic approach of waterless dyeing

Ingenious technologies like use of SC-CO2 in fabric dyeing can bring a positive change in the dyeing processes of the textile industries. Such inventions will bring the textile and apparel companies and the users a step closer toward making the environment cleaner and greener. Needless to say, it will also solve the problem of water scarcity and value the ecological resources (fibre2fashion.com 2013). Currently, the SC-CO2 is limited to dyeing of synthetic and polyester fabrics with modified dispersed dyes. However, efforts are being made by the company and innovators to develop dyeing methods for cellulosics in the distant future. Carbon dioxide makes the polymer swell letting the disperse dyes to easily diffuse within the polymer, penetrating the pore and capillaries of the fibers. Circulation of the dye solutions using the aqua free dyeing method is easier and consumes less energy. The deep penetration leads to effective coloring of polymers. The residue produced is minimal and can be recycled. On an industrial level, acceptance data show that a Switzerland-based denim dyeing company created a new eco-friendly dye that uses 92% less water, 30% less energy, and saves up to 63% cotton waste and produces same coloring results when compared to conventional techniques. This state-of-the-art process hands over improved color fastness, better production of tones, and helps achieve deeper blues. Brands like Adidas and Nike have already considered using supercritical CO2 for dyeing clothes to meet the demands of consumers who are environment conscious. Since athletic and sportswear use polyester and single color, this process would be just perfect (fibre2fashion.com 2013). The waterless dyeing technology utilizes reclaimed CO2 as a dye medium. This technology does not uses water and harmful chemicals for dyeing. Closed loop process is used for the conversion of CO2 into supercritical state. The closed loop process is patented by Dutch company Dyecoo. In this process, CO2 is pressurized and converted into supercritical state which is a state which lies somewhere in between liquid and solid state. The main reason behind the conversion of CO2 into supercritical state is that it has high solvent power which allows dye to dissolve very easily. Two American enterprises namely ColorZen and AirDye have also patented waterless dyeing technique (Singh et al., 2019). Thus it can be assumed that coming era will foresee more of textile dyeing without water making global change in perspective of solvent-based dyeing technology. Industrialists will become aware as well as consumers will demand ecologically safe product manufactured/processed through ecologically benign technologies.

5.11

Conclusions

Supercritical fluids are characterized by a peculiar behavior due to their proximity to a critical point, displaying quite diverging values of several relevant properties. Theoretical approaches to describe critical phenomena are based on the key concepts of order

Waterless natural dyeing to make it sustainable

77

parameters, universal critical exponents, and universality classes, which are a manifestation of long-range correlations that dominate the system behavior near a critical point (Eren et al., 2017). SCFs have become of increasing significance in the past two decades for several reasons. However, it should be recognized that SCFs have been a subject of research for some time. SC-CO2 and supercritical water have been investigated extensively as media for application in solvent-free chemistry processes and, therefore, suggesting to some people, green chemistry. They have also been used in environmental remediation. SCFs offer opportunities to carry out novel chemistry and have been shown to be media for the study of organic, inorganic, and organometallic reactions (van Eldik and Hubbard, 2007). The unique combination of the physical properties of supercritical fluids has to be exploited and further researched to continue the development and establishment of high efficiency, compact plant to provide energy, and water-efficient dyeing processes. The use and potential applications of supercritical fluid carbon dioxide for a selected range of key and emerging industrial processes as a sustainable alternative to totally eliminate or greatly reduce the requirement of numerous conventional organic solvents and water (Ramsey et al., 2009). Water is a valuable resource for life because of its multifunctional properties. Thus, scarcity of water and augmented environmental awareness are worldwide concerns that result in a sharp escalation in prices for drinking and removal of wastewater. It is widely accepted that the textile sector is one of the highest water consumers. Thus there’s strong need of a viable technology which is sustainable among all its properties, and SC-CO2 seems a perfect candidate. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state, CO₂ has a very high solvent power, allowing the dyes to dissolve easily. Thanks to the high permeability, the dyes are transported easily and deeply into fibers, creating vibrant colors. The demand from customers is quickly increasing with the rapid development of supercritical coloration technology. This recent technological advancement has not only contributed toward pollution control but also enhanced the performance of natural and synthetic fibers by improving their physical and chemical properties. Another aspect of the use of advanced technology like SCCO2 dyeing in an efficient manner creates a good scope for this sector and makes textile processing very easy with higher efficiency, keeping sustainability intact with potential water savior in the field of dyeing whether natural or synthetic.

References Abate, M.T., Ferri, A., Guan, J., Chen, G., Nierstrasz, V., 2019. Colouration and bio-activation of polyester fabric with curcumin in supercritical CO2: Part I-Investigating colouration properties. The Journal of Supercritical Fluids 152, 104548. Abate, M.T., Zhou, Y., Guan, J., Chen, G., Ferri, A., Nierstrasz, V., 2020. Colouration and bioactivation of polyester fabric with curcumin in supercritical CO2: part IIeeffect of dye concentration on the colour and functional properties. The Journal of Supercritical Fluids 157, 104703.

78

Natural Dyes for Sustainable Textiles

Agrawal, B.J., 2015. Supercritical carbon-dioxide assisted dyeing of textiles: an environmental benign waterless dyeing process. International Journal of Innovative Research and Creative Technology 1 (2), 201e205. Anonymous, 2013. Waterless dyeing techniques. Dyes. Bach, E., Cleve, E., Schollmeyer, E., 1998. The dyeing of polyolefin fibers in supercritical carbon dioxide. Part II: the influence of dye structure on the dyeing of fabrics and on fastness properties. Journal of the Textile Institute 89 (4), 657e668. Banchero, M., 2013. Supercritical fluid dyeing of synthetic and natural textilesea review. Coloration Technology 129 (1), 2e17. Beckman, E.J., 2004. Supercritical and near-critical CO2 in green chemical synthesis and processing. The Journal of Supercritical Fluids 28 (2e3), 121e191. Berradi, M., Hsissou, R., Khudhair, M., Assouag, M., Cherkaoui, O., El Bachiri, A., El Harfi, A., 2019. Textile finishing dyes and their impact on aquatic environs. Heliyon 5 (11), e02711. Braeuer, A., 2015. Chapter 1-high pressure: fellow and opponent of spectroscopic techniques. In: Braeuer, A. (Ed.), Supercritical Fluid Science and Technology, vol. 7. Elsevier, pp. 1e40. Brunner, G.H., 2004. Supercritical Fluids as Solvents and Reaction Media. Elsevier. Chena, Y., Tanga, X., Chena, B., Qiua, G., 2011. Atmospheric pressure plasma vapor treatment of thermo-sensitive Poly (N-isopropylacrylamide) and its application to textile materials. Journal of Fiber Bioengineering and Informatics 4 (3), 285e290. De Moraes, S.G., Freire, R.S., Duran, N., 2000. Degradation and toxicity reduction of textile effluent by combined photocatalytic and ozonation processes. Chemosphere 40 (4), 369e373. Eren, H., Avinc, O., Eren, S., 2017. Supercritical carbon dioxide for textile applications and recent developments. In: IOP Conference Series: Materials Science and Engineering. IOP Publishing. Fan, Y., Zhang, Y.Q., Yan, K., Long, J.J., 2019. Synthesis of a novel disperse reactive dye involving a versatile bridge group for the sustainable coloration of natural fibers in supercritical carbon dioxide. Advanced Science 6 (1), 1801368. fibre2fashioncom, 2013. Waterless Dyeing Techniques. Gebert, K., 1971. The dyeing of polyester textile fabric in perchloroethylene by the exhaust process. Journal of the Society of Dyers and Colourists 87 (12), 509e513. Hussain, T., Wahab, A., 2018. A critical review of the current water conservation practices in textile wet processing. Journal of Cleaner Production 198, 806e819. Kant, R., 2012. Textile dyeing industry an environmental hazard. Natural Science 04. Letcher, T.M., Scott, J.L., 2012. Materials for a Sustainable Future. Royal Society of Chemistry. Liu, M., Zhao, H., Wu, J., Xiong, X., Zheng, L., 2018. Eco-friendly curcumin-based dyes for supercritical carbon dioxide natural fabric dyeing. Journal of Cleaner Production 197, 1262e1267. Long, J.-J., Cui, C.-L., Zhang, Y.-Q., Yuan, G.-H., 2015. Clean fixation of dye on cotton in supercritical carbon dioxide with a heterogeneous and phase transfer catalytic reaction. Dyes and Pigments 115, 88e95. Long, J.-J., Xiao, G.-D., Xu, H.-M., Wang, L., Cui, C.-L., Liu, J., Yang, M.-Y., Wang, K., Chen, C., Ren, Y.-M., 2012. Dyeing of cotton fabric with a reactive disperse dye in supercritical carbon dioxide. The Journal of Supercritical Fluids 69, 13e20. Lu, X., Liu, L., Liu, R., Chen, J., 2010. Textile wastewater reuse as an alternative water source for dyeing and finishing processes: a case study. Desalination 258 (1e3), 229e232. Miah, L., Ferdous, N., Azad, M.M., 2013. Textiles material dyeing with supercritical carbon dioxide (CO2) without using water. Chemistry and Materials Research 3 (5), 38e40.

Waterless natural dyeing to make it sustainable

79

Moore, S.B., Ausley, L.W., 2004. Systems thinking and green chemistry in the textile industry: concepts, technologies and benefits. Journal of Cleaner Production 12 (6), 585e601. € Oner, E., Bas¸er, I., Acar, K., 1995. Use of ultrasonic energy in reactive dyeing of cellulosic fabrics. Journal of the Society of Dyers and Colourists 111 (9), 279e281. Patil, A., 2020. Waterless Dyeing Techniques. Petek, J., Glavi
c, P., 1996. An integral approach to waste minimization in process industries. Resources, Conservation and Recycling 17 (3), 169e188. R€ais€anen, R., Montero, G.A., Freeman, H.S., 2021. A fungal-based anthraquinone emodin for polylactide and polyethylene terephthalate in supercritical carbon dioxide (SC-CO2) dyeing. Color Research and Application 46 (3), 674e680. Ramsey, E., Sun, Q., Zhang, Z., Zhang, C., Gou, W., 2009. Mini-Review: green sustainable processes using supercritical fluid carbon dioxide. Journal of Environmental Sciences 21 (6), 720e726. Rott, U., Minke, R., 1999. Overview of wastewater treatment and recycling in the textile processing industry. Water Science and Technology 40 (1), 137e144. Saravanan, D., 2006. Ultrasonics assisted textile processing: an update. Colourage 53 (4), 111e116. Sathasivam, R., Muthuraman, M.S., Park, S.U., 2022. Intensification of supercritical fluid in the extraction of flavonoids: a comprehensive review. Physiological and Molecular Plant Pathology 101815. Saus, W., Knittel, D., Schollmeyer, E., 1993. Dyeing of textiles in supercritical carbon dioxide. Textile Research Journal 63 (3), 135e142. Saxena, S., Raja, A.S.M., Arputharaj, A., 2017. Challenges in Sustainable Wet Processing of Textiles. Textiles and Clothing Sustainability. ISBN: 978-981-10-2184-8. Schermann, J.-P., 2008. 3-experimental methods. In: Schermann, J.-P. (Ed.), Spectroscopy and Modeling of Biomolecular Building Blocks. Elsevier, Amsterdam, pp. 129e207. Schlaeppi, F., 1998. Optimizing textile wet processes to reduce environmental impact. Textile Chemist and Colorist 30 (4), 19e26. Schmidt, A., Bach, E., Schollmeyer, E., 2003. The dyeing of natural fibres with reactive disperse dyes in supercritical carbon dioxide. Dyes and Pigments 56 (1), 27e35. Shukla, S., Mathur, M.R., 1997. Dyeing of solvent-pretreated polyesters. Journal of The Society of Dyers and Colourists 113 (5-6), 178e181. Singh, A., Jahan, S., Massey, S., 2019. Recent advances in chemical processing of natural and synthetic textiles. International Journal of Chemical Studies 7 (2), 659e663. Van der Kraan, M., Cid, M.F., Woerlee, G., Veugelers, W., Witkamp, G., 2007. Dyeing of natural and synthetic textiles in supercritical carbon dioxide with disperse reactive dyes. The Journal of Supercritical Fluids 40 (3), 470e476. van Eldik, R., Hubbard, C.D., 2007. 1.19 - Kinetics studies. In: Mingos, D.M.P., Crabtree, R.H. (Eds.), Comprehensive Organometallic Chemistry III. Elsevier, Oxford, pp. 509e539. Vandevivere, P.C., Bianchi, R., Verstraete, W., 1998. Treatment and reuse of wastewater from the textile wet-processing industry: review of emerging technologies. Journal of Chemical Technology and Biotechnology: International Research in Process, Environmental and Clean Technology 72 (4), 289e302. Wu, J., Zhao, H., Wang, M., Zhi, W., Xiong, X., Zheng, L., 2019. A novel natural dye derivative for natural fabric supercritical carbon dioxide dyeing technology. Fibers and Polymers 20 (11), 2376e2382. Yi, S., 2012. Cotton pad dyeing microwave fixation technology research. Journal of Dyes and Dyeing 49 (2), 23e26.

80

Natural Dyes for Sustainable Textiles

Yu, H., Wang, Y., Zhong, Y., Mao, Z., Tan, S., 2014. Foam properties and application in dyeing cotton fabrics with reactive dyes. Coloration Technology 130 (4), 266e272. Zhang, J., Zheng, L.-J., Zhao, Y.-P., Yan, J., Xiong, X.-Q., Du, B., 2015. Green dyeing of cotton fabrics by supercritical carbon dioxide. Thermal Science 19 (4), 1283e1286. Zhang, Y.-Q., Wei, X.-C., Long, J.-J., 2016. Ecofriendly synthesis and application of special disperse reactive dyes in waterless coloration of wool with supercritical carbon dioxide. Journal of Cleaner Production 133, 746e756. Zhang, Y.Q., Qi, L., Sun, J.P., Long, J.J., 2017. Synthesis of an anthraquinonoid disperse reactive dye based on a ligand-free Ullmann reaction. Coloration Technology 133 (4), 283e292. Zheng, H., Zhang, J., Yan, J., Zheng, L., 2016. An industrial scale multiple supercritical carbon dioxide apparatus and its eco-friendly dyeing production. Journal of CO2 Utilization 16, 272e281.

Use of newer technologies in natural dyeingdplasma and electron beam 6.1

6

Introduction

One of the largest necessities of mankind’s usage is clothing. It’s a huge industry involving many procedures from production to finish apparel. These procedures comprise many steps and lots of raw material producing wastewater and waste materials. Although apparel/clothing and fashion are known to be the most polluting industries, but the growing sense of social accountability and civic consciousness about the environment has enforced the textile manufacturers to produce more environmentally benign merchandises and dyeing is not distinct in this context. The use of natural dyes instead of synthetic dyes has paved the way for ecofriendly dyeing, still the enormous water usage makes the whole process not so justifiable. Thus there’s focus on the use of sustainable production techniques including natural dyes with textile surface modification for better dye uptake. Sustainable novel technologies for textile dyeing are needed that utilize enhanced dye uptake and improved performance characteristics of fabric. Such technology may reduce dye concentration in wastewater effluents from textile sector and ultimately become energy efficient and cost effective. A number of green processes have been explored due to ecological and economical awareness to deal with environmental issues in textile dyeing. Some problems such as low yield of dyeing and more than 50% dye lost in wastewater effluent, and some esthetic and environmental issues can be minimized by plasma treatment before, during dyeing, or finishing processes. Advantageously, this technology can operate at ambient conditions with lesser or no chemical auxiliaries are needed. Thus, this technology is attributed green textile technology (Naveed, 2018).

6.2

Plasma technology

Plasma is generally known as the “fourth state of matter,” after solid, liquid, and gaseous states. It consists of electrons, neutral species (i.e., molecules, radicals, and excited species), and ions. Plasma can be described as a quasineutral particle system in the form of gaseous or fluid-like mixtures of free electrons and ion, frequently containing neutral particles (atoms and molecules), activated and metastable species

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00012-8 Copyright © 2024 Elsevier Ltd. All rights reserved.

82

Natural Dyes for Sustainable Textiles

(NOx*), and free radicals like reactive oxygen species and reactive nitrogen species (Jaeger et al., 2014). Based on the thermal equilibrium between electron and other species, it is divided into thermal plasma (equilibrium) and nonthermal plasma (NTP)/cold plasma. In NTP, the gas temperature remains near room temperature, while the electrons’ temperature is extremely high, typically in the range of 1e10 eV (w10,000e100,000 K) (Loganathan and Assadi, 2021). Plasma is an ionized gas. It is generated when an electrical current is applied across a dielectric gas or fluid (an electrically nonconducting material). In plasma, a gas can be heated or an excess of free electrons is needed to displace electrons in the atoms and molecules of the bulk gas. Gas plasmas are ionized gases formed by liberating electrons from gas molecules and atoms using external energy sources such as lasers or high electrical voltages. Once ignited, and under the influence of an external energy source, electrons and other charged particles (e.g., ions) are accelerated to acquire considerable kinetic energy and, as a result, become capable of ionizing, exciting, and dissociating gas molecules and atoms to form highly reactive chemical species. Numerous examples of gas plasmas exist all around. They may be naturally occurring, such as flames, lightning, the auroras, and the sun, or artificially created, as in fluorescent lamps, welding arcs, and plasma television screens. A breakthrough occurred in the late 1980s when lowtemperature plasmas at atmospheric pressure, subsequently known as “cold atmospheric plasmas,” were first demonstrated. Reactive gases such as oxygen, nitrogen, air, or even water vapor usually are mixed in small quantities into the background noble gas to enable the production of reactive oxygen and nitrogen species. These innovations led to the start of a rapid development in cold atmospheric plasma science and technology (Kong and Shama, 2014). Gas plasma treatment of a biopolymer surface generates high energy reactive species that bond to the surface. Plasma treatment can be carried out in the presence of an inert or reactive gas, for example, air, argon, oxygen, or ammonia, with the formation of surface functional groups, such as eOH, eCHO, eCOOH, or eNH2. Plasma treatment has been used to alter the surface properties of polymers without affecting their bulk properties. Specific surface properties like hydrophobicity, chemical structure, and roughness can be altered to meet target requirements. Some major effects that have been observed in plasma treatment of polymer surfaces are the removal of organic contamination, micro- and nanoscale etching, cross-linking, and surface chemistry modifications. The main disadvantage of plasma treatment is that the induced surface modification is not permanent and diminishes with time due to surface rearrangement (Niaounakis, 2015).

6.3

Use of plasma technology in textile finishing

In textile processing, this technology can be explored in various areas like pretreatment, dyeing, and finishing through different methodology vis-a-vis glow-discharge method, corona discharge method, and dielectric barrier discharge method to add functionality and modification of surface properties of textile materials (Shah and Shah,

Use of newer technologies in natural dyeingdplasma and electron beam

83

2013). Plasma treatment is a dry and clean technique that operates at ambient temperature which is able to improve coloration and to develop characteristic functionalities on surface of textile fabric without altering the performance of bulk fiber. Furthermore, plasma treatment can couple with other natural treatment methods which further improve the performance of treated fabric. This results insignificant reduction of toxic chemicals and auxiliaries in effluent load which diminish energy usage and cost and environmental impact (Naveed, 2018). There has been swift research and commercialization of plasma technology to improve the surface properties of textile material without changing its bulk properties. Modification of surface by plasma treatment offers a lot of benefits and overcomes the drawback of the classical wet textile chemical processing. A major advantage of plasma surface treatment is the minimization of harmful by-products from the process. Plasma treatment of textiles saves large quantity of water, chemicals apart from electrical energy. This is made possible since the plasma process does not produce large volume of effluent or toxic by-products. Plasma technology is applicable to most of textile materials for surface treatment and is beneficial over the conventional process, since it does not alter the inherent properties of the textile materials. It is dry textile treatment processing without any expenses on effluent treatment. It is a green process and it is a simple process. This technology can generate more novel products to satisfy customer’s need and requirement (Shah and Shah, 2013). The plasma technology is considered to be very interesting future-oriented process owing to its environmental acceptability and wide range of applications. Plasma treatments have been used to induce both surface modifications and bulk property enhancements of textile materials, resulting in improvements to textile products ranging from conventional fabrics to advanced composites. These treatments have been shown to enhance dyeing rates of polymers, improve color fastness and wash resistance of fabrics, and change the surface energy of fibers and fabrics. Research has shown that improvements in toughness, tenacity, and shrink resistance can be achieved by subjecting various thermoplastic fibers to a plasma atmosphere. Recently, plasma treatments have been investigated for producing hydroscopicity in fibers, altered degradation rates of biomedical materials (such as sutures), and for the deposition of antiwear coatings (Malik and Parmar, 2007). Plasma treatment of textiles is a growing function of plasma technology. Plasma treatment of textiles is used to pretreat fibers to increase wettability which allows for solvent-free dyes to absorb and bond very strongly. These solvent/water-free natural dyes can give very nice shades to fabric. Also, plasma treatment of textiles is used to coat fabric with a specialized layer with varying characteristics. These surface coatings can have properties such as the ability to repel water or other liquids. This is known as a hydrophobic surface. They can also apply protective coatings to make textiles more durable. Plasma treatment has been shown to be effective in assisting the desizing of cotton, imparting improved hydrophilic characteristics to hydrophobic synthetic fibers such as polypropylene, antibacterial treatments based on the deposition of silver nanoparticles, and as ambient temperature sterilization of medical textiles. Some materials, such as untreated polypropylene, have poor adhesion to coatings and laminates, but with plasma treatment prior to coating, the adhesion strength is greatly

84

Natural Dyes for Sustainable Textiles

increased. Similar print adhesion improvements also can be achieved with materials that are subsequently ink-jet printed (Conway, 2016).

6.4 6.4.1

Case study one Plasma-mediated natural dyeing of polyester

In a study, the effect of plasma exposure on surface modification of synthetic fiberd polyester and its subsequent effects on its dyeing with different natural dyesdnamely, Rubia cordifolia, Turkey Red, Lac, Turmeric, and Catechu has been observed. The dye ability was further enhanced by the use of alum as mordant. This study also focuses on the betterment for cleaner pretreatment by avoiding chemicals to reduce wastewater and use of toxic chemicals for cleaner dyeing process. Good dye uptake and uniform coloration were attained with 1 and 2 min exposure of plasma pretreated polyester fabric with natural dyes except in the case of Catechu dye. Several researchers have conducted plasma-mediated polyester dyeing treated by using various gases: nitrogen, oxygen, air, carbon dioxide, and ammonia. It has been observed that plasma-treated polyester fabric showed a considerable change in surface structure and their wettability effect. Researchers have stated that the change on the surface structure of the polyester fibers was related to the treatment conditions and the type of gas used to generate the plasma. The best results of wetting were observed for oxygen and air plasma. A good correlation can be drawn between change on the surface structure of the fabric and its wettability (Purwar, 2016) (Leroux et al.,  2006) (Simor et al., 2003). Plasma pretreatment of textiles can be easily done by using atmospheric pressure. The holistic effect of plasma pretreatment depends on process parameters of plasma such as type of gas used, time of plasma exposure, and gas flow rate. By optimization of these parameters, the surface modification on the fabric can be enhanced and this can directly impact the wettability, create roughness on the fabric surface, and eventually increase the dyeability of polyester fabric. This enhances dye uptake and also shows improvement in the fastness properties of dyed fabrics. Due to the hydrophobic and highly crystalline nature of polyester, it does not take up natural colors easily. Some form of surface modification has been suggested such as specialized treatment with ozone or mordanting, or even plasma treatment for better dyeability with natural colorants. It has been shown that oxygen gas-mediated plasma can increase the surface roughness and wettability, thereby improving the hydrophilicity of polyester, causing better adsorption of natural and synthetic dyes. It has been shown that pretreatment with oxygen plasma and treatment with natural biomordant such as chitosan could improve the uptake and fastness properties of natural dye Caesalpinia sappan L (sappan wood) on polyester fabric (Park et al., 2008) (Agnhage et al., 2016) (Dave et al., 2014). The uptake of eco-alizarin (Indian madder) increased significantly, and the wash and light fastness improved (Dave et al., 2012). However, in the case of curcumin dye, no increase in color yield was observed by using air

Use of newer technologies in natural dyeingdplasma and electron beam

85

atmospheric plasma treatment of polyethylene terephthalate (PET) fabric (Kerkeni et al., 2012). Indian Maddar and pomegranate rind showed nearly 21% increase in color depth by using air plasma (Dave et al., 2013). Improved dyeability of polyester fabric was reported with natural dyes (madder and henna) and different types of synthetic dyes (Shahidi et al., 2015). A study has been carried out on polyester dyeing with natural dyes after treatment with plasma, as discussed.

6.4.2

Materials

100% polyester ready for dyeing (RFD) fabric (108 gm/m2) was locally purchased and used. In dyes, Turkey red dye (a brand name for Maddar dye) and R. cordifolia (madder) dyes were purchased from AMA Herbal laboratories private limited. Turmeric (Everest) powder was purchased from local market. Alum was purchased from Merck life science private limited.

6.4.3 6.4.3.1

Analytical methods Atmospheric pressure plasma treatment

A fully automated Grinp P-20 plasma chamber was used for plasma exposure of polyester fabric. It (flow rate of 5 L/min) was used as plasma gas. Other process parameters such as exposure times were 1 min and 2 min, distance between top and bottom electrodes was 0.5 mm, and power 2.5 kW was maintained during plasma treatment.

6.4.3.2

ATR-FTIR analysis

An ATR MIRacle Diamond crystal with FTIR spectrum-2 Perkin Elmer was used to scan the samples in the frequency range of 4000e400 cm1. The ATR-FTIR spectra were recorded at the resolution of 4 cm1.

6.4.3.3

SEM and EDAX analysis

The surface morphology of polyester fabric samples was recorded using advanced JEOL JSM IT 200 scanning electron microscopy (SEM) machine, magnification ranges from 10X to 3, 00,000X, and resolution of about 10 nm. Samples were coated with gold prior to SEM analysis. In addition, the elemental compositions of polyester samples were recorded by EDAX analysis.

6.4.3.4

Contact angle test

Easy drop Kruss GmbH Germany modal PS4000 was used to analyze the polyester fabrics. The measurements were made with distilled water as test liquid, and the drop volume was 5 mL. Five measurements were made for each sample, and the mean values were calculated. The temperature 25
C and 65% relative humidity were recorded during testing.

86

6.4.3.5

Natural Dyes for Sustainable Textiles

Vertical wicking

Vertical wicking was measured by the standard test method AATCC-197e2013. The sample size was (5 þ 20 þ 130) x 25 mm used to measure the vertical wicking height (mm) and the relative wicking rates (mm/min), after hanging vertically with the stand in a 100 mL of beaker and 30 mL of water in it, for the 30 min test period. Five tests of the warp and weft side of each sample were carried out, and the mean value was calculated.

6.4.3.6

Wash fastness of dyed polyester fabrics

The wash fastness of samples was evaluated by the standard test method, ISO: 105 C: 10. Launder-o-meter was used for washing the dyed samples at 60
C for 30 min.

6.4.3.7

Light fastness of dyed polyester fabrics

A solar box (model- SBX 3000- CRH) fadometer with xenon arc lamp was used for testing light fastness of the dyed samples, according to standard method IS-2454e85.

6.4.3.8

Dyeing procedure for the untreated and plasma-treated polyester fabric

In this study, two plasma exposure times (1 and 2 min) were selected to study the effect of the plasma exposure time on the dyeability of polyester fabric. Dye concentrations used were R. cordifolia and Turkey red 0.5%, turmeric 1.5%, and Lac 0.75%. Alum 0.5% was used as mordant. The polyester fabric was introduced into the dye bath at room temperature, and then the temperature of dye bath was raised at a rate of 2
C per minute to 130
C. At this temperature, the dyeing was continued for 45 min. After that, the temperature of the dyeing bath was rapidly reduced in approximately 15 min. The dyed fabrics were then rinsed under running water until the water was colorless (visual evaluation) and dried at room temperature. For each dye, a control sample (untreated with plasma) was also prepared. All the experiments were carried out in the HTHP Lab dyeing machine.

6.4.3.9

CIE lab values measurement of dyed polyester fabrics

CIE Lab values, color strength (K/S) at maximum, and integrated wavelength of the dyed fabric samples were measured by using premier color scan spectrophotometer. Color strength (K/S) measurement, the colors of the dyed and water-rinsed samples are expressed as their maximum K/S values. The reflectance (R) of the samples from 400 to 700 nm was measured by premier color scan machine, with D65 illuminant and 10 degrees standard observer. The color strength (K/S value) was then established according to KubelkaeMunk equation.

Use of newer technologies in natural dyeingdplasma and electron beam

6.4.4

87

Scanning electron microscopy

The samples were observed under SEM to study the effects of the dyeing process on the fiber surface. FESEM (JEOL JSM-7600F) was used for these tests. The condition of SEM was at U ¼ 5 kV and X (magnification) ¼ 2000. All the samples were coated with gold prior to observation by SEM.

6.4.5 6.4.5.1

Results and discussion Characterization of the untreated and plasma-treated polyester fabric effect of plasma exposure on the wicking effect and contact angle change

The wicking height of the samples before and after plasma exposure is presented in Fig. 6.1, and Table 6.1 shows the vertical wicking height of polyester fabric in warp direction. The contact angle test shows that untreated fabric having a contact angle of 88and plasma-treated fabric has contact angle of 0.

6.4.5.2

Effect of plasma treatment on the surface of polyester

The SEM images of the untreated and plasma-treated polyester fabric at 2000 times magnification are shown in Fig. 6.2, where untreated sample is 1 and plasma-treated sample is 2, respectively. The surface morphology of the untreated polyester and the plasma-treated fabrics shows clear surface etching for plasma-treated sample. The elemental composition of the polyester fabric before and after the plasma exposure was also determined (Table 6.2).

6.4.5.3

FTIR spectrum of untreated and plasma-treated samples

Plasma exposure showed very little effect in infrared spectra (Figs. 6.3 and 6.4). They reveal small changes. Treated polyester fabric showed lower transmittance values, so more energies absorbed by the chemical bonds and therefore lesser transmittance. Minor difference in the region 2800e3100 cm1 (CeH group) was present in the spectrum.

1

2

Figure 6.1 (1) Untreated polyester fabric, contact angle-88
. (2) 2 min plasma-treated polyester fabric, contact angle-0.

88

Natural Dyes for Sustainable Textiles

Figure 6.2 (a) Untreated polyester and (b) plasma-treated polyester (2-min).

Table 6.1 Vertical wicking rates of Polyester fabric. Vertical wicking rates (mm/min) Untreated polyester fabric

Treated polyester fabric

Warp

Weft

Warp

Weft

1.4

1.3

5.8

4.6

Table 6.2 EDAX analysis of the Untreated and Plasma-treated fabric. Sample id

Untreated polyester

Treated polyester

Element

CK

OK

CK

OK

Weight % Atomic % Error %

54.6 61.3 5.5

45.4 38.5 10.5

53.7 60.7 5.7

46.3 39.3 10.6

6.4.5.4

Effect of plasma on the dyeability of the polyester fabric

The wick height of the fabric showed improvement after 1 min of plasma treatment. The results of the capillary measurements of the polyester fabric showed improvement after plasma treatment. The SEM micrographs show a significant change in surface morphology after 2 min of plasma exposure. The study was chosen for 1 and 2 min exposures of the plasma treatment of the fabric prior to dyeing, although not much difference could be seen for the two exposure time, but dyed samples showed color uniformity (Fig. 6.5).

Use of newer technologies in natural dyeingdplasma and electron beam

Figure 6.3 FTIR of the untreated and plasma-treated polyester fabric.

Figure 6.4 IR spectrum of untreated and plasma-treated polyester fabric (2800e3200 cm1).

89

90

Natural Dyes for Sustainable Textiles

Figure 6.5 Procedure of natural dyeing on polyester fabric.

6.4.5.5

Effect of plasma treatment time on the color strength (K/S) spectra of the dyed polyester fabric

The color strength (K/S) of dyed samples was measured by premier color scan machine, after 1 and 2 min of plasma exposure over the range of 400e700 nm. Plasma-treated samples were evaluated for their K/S values and CIE Lab values (Tables 6.3e6.16) and color of the dyed swatches (Figs. 6.6e6.12). The use of plasma with alum mordanting in natural dyeing of polyester is the new feature in this research work. The results of 1 and 2 min are shown below for the chosen natural dyes.

Turkey red dyeing on polyester fabric 1 min plasma exposure

The increase in dE and K/S values shows that plasma þ alum have given the best results for Turkey red natural dye as shown in Table 6.3. The color depth is shown in Fig. 6.6. No difference was seen in wash fastness, but the light fastness of the plasma þ alum-dyed sample has improved from 3 to 3e4 as shown in Table 6.4. Table 6.3 CIE LAB values of Turkey red-dyed samples 1 min plasma. S. No

Name

K/S MAX

L*

a*

b*

C*

dE*

1 2 3

Control Alum Plasma D alum

11.739 12.142 12.639

69.774 62.624 62.99

12.472 19.084 18.846

58.628 64.209 66.582

59.94 66.985 69.198

— 9.11 10.688

Use of newer technologies in natural dyeingdplasma and electron beam

91

Table 6.4 Light and washing fastness values of Turkey red-dyed polyester fabric. S. No

Sample id

Light fastness

Washing fastness

1 2 3

Control Alum Alum D plasma

3 3 3e4

4e5 4e5 4e5

Table 6.5 CIE LAB values of lac-dyed samples 1 min plasma. S. No

Name

K/S MAX

L*

a*

b*

C*

dE*

1 2 3

Control Alum Plasma D alum

0.491 1.999 2.743

73.903 46.512 41.949

4.894 18.974 20.284

8.956 L6.071 L5.413

10.206 19.922 20.994

— 34.268 38.267

Table 6.6 Light and washing fastness values of lac-dyed polyester fabric. S. No

Sample id

Light fastness

Washing fastness

1 2 3

Control Alum Alum D plasma

3 3e4 3e4

4e5 4e5 4e5

Table 6.7 CIE LAB values of Turmeric-dyed samples 1 min plasma. S. No

Name

K/S Max

L*

a*

b*

C*

dE*

1 2 3

Control Alum Plasma D alum

10.617 11.446 13.468

77.04 78.081 80.612

L6.274 L2.209 L4.908

70.198 81.672 87.152

70.478 81.702 87.29

— 12.217 17.38

Lac dyeing on polyester fabric 1 min plasma exposure

The increase in dE and K/S values shows that plasma þ alum have given the best results for Lac natural dye as shown in Table 6.5. The color depth increased apparently as shown in Fig. 6.7. No difference was seen in wash fastness, but the light fastness of the plasma þ alum dyed sample has improved from 3 to 3e4 as shown in Table 6.6.

Turmeric dyeing on polyester fabric 1 min plasma exposure

The increase in dE and K/S values shows that plasma þ alum have given the best results for turmeric natural dye as shown in Table 6.7. The color depth increased

92

Natural Dyes for Sustainable Textiles

Table 6.8 Light and washing fastness values of Turmeric-dyed polyester fabric. S. No

Sample id

Light fastness

Washing fastness

1 2 3

Control Alum Alum D plasma

1 1 2

4e5 4e5 4e5

Table 6.9 CIE LAB values of catechu-dyed samples 1 min plasma.

S. No

Name

K/S Max

L*

a*

b*

C*

dE*

1 2 3

Control Alum Plasma D alum

2.469 2.148 1.783

56.483 60.104 53.018

12.164 10.904 9.638

18.204 19.957 19.937

21.894 22.742 22.144

— 4.216 7.217

Table 6.10 Light and washing fastness values of Catechu-dyed polyester fabric. S. No

Sample id

Light fastness

Washing fastness

1 2 3

Control Alum Alum D plasma

2 2 2e3

3e4 4 4e5

Table 6.11 CIE LAB values of Turmeric-dyed samples 2 min plasma. S. No

Name

K/S Max

L*

a*

b*

C*

dE*

1 2

Alum Plasma alum

11.357 12.996

78.057 78.64

0.037 L1.586

82.008 84.713

82.008 84.728

— 3.208

Table 6.12 Light and washing fastness values of Turmeric-dyed polyester fabric. S. No

Sample id

Light fastness

Washing fastness

1 2

Alum Plasma alum

1 2

4e5 4e5

apparently as shown in Fig. 6.8. No difference was seen in wash fastness, but the light fastness of the plasma þ alum dyed sample has improved from 1 to 2 as shown in Table 6.8.

Use of newer technologies in natural dyeingdplasma and electron beam

93

Table 6.13 CIE LAB values of Rubia cordifolia-dyed samples 2 min plasma. S No

Name

K/S Max

L*

a*

b*

C*

dE*

1 2

Alum Plasma alum

12.198 13.222

65.187 64.795

20.728 21.34

68.508 69.305

71.575 72.516

— 1.079

Table 6.14 Light and washing fastness values of Rubia cordifolia-dyed polyester fabric. S. No

Sample id

Light fastness

Wash fastness

1 2

Alum Plasma alum

5 5

4 4e5

Table 6.15 CIE LAB values of Catechu-dyed samples 2 min plasma. S No

Name

K/S Max

L*

a*

b*

C*

dE*

1 2

Alum Plasma alum

1.768 1.576

63.556 65.494

9.049 8.582

20.458 20.495

22.37 22.219

— 1.994

Table 6.16 Light and washing fastness values of Catechu-dyed polyester fabric. S. No

Sample id

Light fastness

Washing fastness

1 2

Alum Plasma alum

3 3e4

4 4e5

1

2

3

Figure 6.6 (1) Control, (2) alum mordanted, (3) plasma treated alum mordanted (1 min) for Turkey red dye.

Catechu dyeing on polyester fabric 1 min

The increase in dE and the K/S values showed a decrease, thus plasma þ alum have not given beneficial results for Catechu natural dye as shown in Table 6.9. The color depth decreased as shown in Fig. 6.9. Although it was observed that both wash fastness

94

Natural Dyes for Sustainable Textiles

1

2

3

Figure 6.7 (1) Control, (2) alum mordanted, (3) plasma treated alum mordanted (1 min) for lac dye.

1

2

3

Figure 6.8 (1) Control, (2) alum mordanted, (3) plasma treated alum mordanted (1 min) for turmeric dye.

1

2

3

Figure 6.9 (1) Control, (2) alum mordanted, (3) plasma treated alum mordanted (1 min) for Catechu.

and light fastness of the plasma þ alum dyed sample showed improvement as shown in Table 6.10.

Turmeric dyeing on polyester fabric 2 min plasma

The increase in dE and K/S values shows that plasma þ alum have given the best results for turmeric natural dye as shown in Table 6.11. The color depth increased apparently as shown in Fig. 6.10. No difference was seen in wash fastness, but the light fastness of the plasma þ alum dyed sample has improved from 1 to 2 as shown in Table 6.12. No significant improvement could be seen by increasing the exposure time.

Rubia cordifolia dyeing on polyester fabric 2 min

The slight increase in dE and K/S values shows that plasma þ alum have given the best results for R. cordifolia natural dye as shown in Table 6.13. The color depth

Use of newer technologies in natural dyeingdplasma and electron beam

95

2

1

Figure 6.10 (1) Control, (2) alum mordanted, (3) plasma treated alum mordanted (1 min) for turmeric.

has increased as shown in Fig. 6.11. No difference was seen in lightfastness; however, wash fastness of the plasma þ alum-dyed sample has improved from 4 to 4e5 as shown in Table 6.14.

Catechu dyeing on polyester fabric 2 min plasma

A slight decrease in K/S values shows that plasma þ alum has not given the desired results for Catechu natural dye as shown in Table 6.15. The color depth did not improve as shown in Fig. 6.12. The lightfastness improved from 3 to 3e4, and wash fastness of the plasma þ alum dyed sample has improved from 4 to 4e5 as shown in Table 6.16. So even by increasing the exposure time of plasma from 1 to 2 min, it did not improve the dye uptake, but it did improve the wash and light fastness of the dyed fabric. Discussion: Since the application of natural dyes on polyester fabric has been challenging in the field of textile dyeing and needed concerted efforts, we wanted to try a combination of plasma exposure as pretreatment followed by alum mordanting for natural dyeing of polyester. The use of alum in conjunction with natural dyes has been

1

2

Figure 6.11 (1) Alum mordanted, (2) plasma treated alum mordanted (1 min) for Rubia cordifolia.

1

2

Figure 6.12 (1) Alum mordanted, (2) Plasma treated alum mordanted (2 min) for Catechu 2 min plasma treatment.

96

Natural Dyes for Sustainable Textiles

reported in Vankar et al., 2008 and Haar et al., 2013. Exposure of plasma can be considered as a green and environmentally friendly approach for sustainable coloration of polyester fabric. It is envisaged that during the plasma exposure on polyester fabric for 1 and 2 min, the excited and energetic plasma species initiate several reactions on the polyester surface, and this causes surface etching. These energetically excited plasma species, when impacted on the fiber surface could degrade and etch the surface of the fabric, which subsequently improved the dyeability of the plasma exposed samples for Rubia, Turkey red, turmeric, and Lac; however, it did not improve for Catechu. An increase in the capillary capacity of the plasma-exposed samples could cause an increase in the dye uptake. The morphological changes of the plasma-exposed samples for 1 and 2 min s were different from the untreated sample. This was reflected in their differences in K/S values. By comparing the dyeing result with the wicking heights and SEM images of the plasma-treated samples, it can be said that the improvement in the dyeability of the plasma-exposed polyester fabric was partly due to the plasma treatment and partly due to alum used as mordants. The plasma exposure caused the physical and chemical surface modification of the material as well as caused an increase in the capillary capacity for increased mordant and dye penetration. When dyeing at the same dye concentration, the color of the plasma-exposed fabric was always found to be darker than that of the untreated fabric except in the case of Catechu dye. This could be due to the fact that Catechu dye has more of condensed tannins, which has larger dye aggregates as compared to Rubia, Turkey red, turmeric, and lac colorants. Thus, proper mordant and dye penetration could not be facilitated even after plasma exposure.

6.5

Conclusions

Modern apparel and technical textile material includes polyester as one of the major fabrics. However, its poor surface properties have limited its end-use versatility. In this study, the surface of a polyester fabric was modified by plasma exposure. The atmospheric pressure plasma treatment with a power of 2.5k W for a short time (for 1, 2 min) on polyester fabric could lead to significant surface modifications, such as: an increase in the fabric surface roughness and an increase in capillary capacity of the fibers. These surface modifications resulted in an increase in wicking heights, thereby affecting better mordant penetration and dye uptake. The use of plasma along with alum mordanting is the new feature in this research work. The improvement in dyeability of the plasma exposed fabric was not totally dependent on the plasma treatment time; however, significant increase in color depth could be observed for plasma-exposed samples for 2 min. These are quite favorable conditions for the application of plasma in the textile industry on an industrial scale. The color fastness properties of the dyed plasma-exposed fabric were excellent. The increase in dyeing efficiency in the initial stage could be due to the fact that plasma etches out the surface of the textile fibers, creating a coarser surface with roughness;

Use of newer technologies in natural dyeingdplasma and electron beam

97

the creation of a rougher surface makes the effective surface area larger, which improves interaction and diffusion of dye molecules. In polyester dyeing with natural dyes, plasma treatment has given fairly good shades, thus proving it can be very beneficial in future synthetic fiber dyeing with natural dyes. In the synthetic fibers, plasma causes etching of the fiber and the introduction of polar groups leading to improvement in dyeability. Plasma technologies are an innovative environmentally friendly class of processes for the surface modification of materials. This technology has shown to have the ability to improve numerous properties of textiles. For example, it can be used to enhance the hydrophilic/hydrophobic properties of fibers, promote good adhesion in coatings and laminates, confer antistatic properties on manufactured fibers, improve the dyeability or printability of textiles, and functionalize fiber surfaces for a wide variety of end uses. The effectiveness of the plasma treatments varies with the actual plasma used, however. The most commonly used plasma treatments are oxygen/helium or air/helium (Conway, 2016).

6.6

Electron beam-mediated natural dyeing of synthetic fabrics

Nowadays, the bulk and surface functionalization of synthetic fibers for various applications is considered as one of the best methods for modern textile finishing processes (Tomasino, 1992). Recently, electron beam technology has been used as a green replacement method for traditional textile wet processing, especially surface modification processes. Instead, radiation approaches featuring low consumption of energy, no additives, ease of operation, and fast treatment speed could significantly efficiently modify the surface of textiles and promote dye absorption, printing, fastness characteristics, coatings adhesion, and finishing agents adsorption (Zhang et al., 2014) (Sui et al., 2016) (Liu et al., 2015) (Xu et al., 2009). EB irradiation (EBI) is a dry, pollution-free, and cool technology that eliminates the need for solvents and reagents used in wet chemical procedures. It provides advantages such as speedy processing, high flow rate, consistency, and environmental and labor protection while manufacturing (Dietrich et al., 1996) (Liu et al., 2021) (Pang et al., 2005) (Ji et al., 2013) (Fei et al., 2020). Electron beam irradiation technology has gained attention as it is a promising economically and environmentally sustainable method which can replace the traditional wet chemical processing. It is a clean, solvent-free, timesaving, and ecologically benign with acceptable handling and operation properties. These types of surface modification are very useful for increasing the dyeability of polymeric textile fabrics. Surface modification of fabric can be easily done by electron beam radiation which can modify the surface of the fabric, producing functional groups. Common industrial electron beams from 0.1 to several mega electron volts have been used for various industrial processes, which can penetrate up to several millimeters in the case of polymeric materials. EB radiation is considered an energy carrier since the electron is

98

Natural Dyes for Sustainable Textiles

one of the components in the atom. The interaction of accelerated electrons with polymers is categorized into three phases: physical, physicochemical, and chemical. During the physical process, the accelerated (primary) electrons gradually transfer their energy to the polymer substrate, resulting in the formation of short-lived reactive species such as ions, and secondary electrons. Then during the physicochemical process, these species are transformed into polymer radicals. In the chemical phase, the polymer radicals start a wide range of chemical reactions in the polymer. The chemical alteration of polymers caused by these radicals affect the polymer surface and thus modifies for better dye adherence. The dyeing properties of hydrophobic polypropylene fibers using cationic dyes were investigated to improve dyeability by utilizing electron beam irradiation along with sulfonic acid incorporation. The best dyeing result was obtained when polypropylene fibers incorporated by sulfonic acid group after electron beam irradiation were dyed with cationic dyes at alkaline conditions and 30e75 kGy irradiation ranges. Exposing fibers to a stream of high-energy electrons is another method for surface modification. The dyeability of hydrophobic polypropylene fibers was enhanced by Kim and Bae using electron beam irradiation and sulfonic acid incorporation. The color strength of polypropylene fibers after irradiation was examined according to the dyeing conditions including the pH of the dye bath, absorbed doses, and the introduction of a functional group to the fiber substrate (Alberti et al., 2005) (Kim and Bae, 2009). Accelerated electrons generated by the EBI accelerator were applied to fix the pigment colors incorporated with these formulations to cotton and polyester fibers. The irradiated printed fibers by EBI obtained higher color strength and achieved durable fastness properties for roughness, rubbing washing, and perspiration of fabrics printed. The action of EBI on polymeric materials promotes essentially two processes: cross-linking, that is, the formation of chemical links between molecular chains, and or degradation/scission of polymer chains, in which the polymer structure is destroyed. Small chemical changes induced by radiation cause significant changes in the physical characteristics of the polymers. Although cross-linking and degradation may take place to some extent at the same time, one of them must predominate (Jung et al., 2014) (Chosdu et al., 1993) (Abou Elmaaty, Okubayashi et al., 2022). For surface modification of fabric, radiations can remove impurities and poor boundary layers on the surface of the fabric and change surface characterization and topography (Lee et al., 2019) (Han et al., 2007). EBI induces the hemolytic cleavage of CeC and CeH bonds on the surface of polymers. The dyeing properties of polypropylene, nylon 6, and polyester, which were pretreated using electron beam irradiation, were investigated. The effects of exposure doses (0e300 kGy) and different oxidation periods in the air on the synthetic fabrics and the optimum conditions were achieved at 300 kGy with 1 h oxidation time (Elmaaty et al., 2022). The dyeing showed good coloration behavior which could be commercially acceptable along with excellent color fastness.

Use of newer technologies in natural dyeingdplasma and electron beam

6.7

99

Conclusions

Natural dyes can result in chemical bonding with the polyester fiber through the different chemical moieties. Their diffusion into the fiber can be challenging. The dye uptake of different dyes is different when the same type of plasma-treated fabrics is used. It can be assumed that the fiberedye pair should be such that the fiber and the dye are compatible with each other for improving the dye uptake. This is due to the different types of interrelating groups on the dye molecule that have affinity to the sites on the fiber and plasma treatment help in this. Plasma process is a safe, clean, simple, and multifunctional procedure, which follows stringent economic and ecological norms and regulations as formulated by governments and industry. The main advantages of plasma treatments are a reduced treatment time and the absence of water in the process/method. Standard protocols of plasma treatment should be adopted and used for prospective usages. Thus there’s a great potential for significant improvements in the properties of textiles by plasma-enhanced modifications. The improvement of dyeability is exceedingly encouraging and can be attributed to the surface itching/ coursing and the functional groups incorporation in the surface topography during the treatment. A potential method which can produce uniform plasma in simple operation and undertake good surface modification of textile material can be excellent technological advancement for safer, cleaner textile industry. Electron beam irradiation promotes fundamentally two processes in polymeric materials: cross-linking, which is the development of chemical linkages between molecular chains, and degradation/scission, which is the destruction of the polymer structure; both capable of replacing a chemical treatment for polymer modification. Moreover, in terms of cost and time, the electron beam is more efficient than the conventional methods and almost other radiation methods. Furthermore, EBI can be used with other treatment methods, such as biological treatment, to achieve better results. As a result, EBI is better suited for application prospects in the industrial domain.

References Abou Elmaaty, T., Okubayashi, S., Elsisi, H., Abouelenin, S., 2022. Electron beam irradiation treatment of textiles materials: a review. Journal of Polymer Research 29 (4), 1e19. Agnhage, T., Perwuelz, A., Behary, N., 2016. Eco-innovative coloration and surface modification of woven polyester fabric using bio-based materials and plasma technology. Industrial Crops and Products 86, 334e341. Alberti, A., Bertini, S., Gastaldi, G., Iannaccone, N., Macciantelli, D., Torri, G., Vismara, E., 2005. Electron beam irradiated textile cellulose fibres.: ESR studies and derivatisation with glycidyl methacrylate (GMA). European Polymer Journal 41 (8), 1787e1797. Chosdu, R., Hilmy, N., Erlinda, T., Abbas, B., 1993. Radiation and chemical pretreatment of cellulosic waste. Radiation Physics and Chemistry 42 (4e6), 695e698. Conway, R., 2016. 7 - technical textile finishing. In: Horrocks, A.R., Anand, S.C. (Eds.), Handbook of Technical Textiles, second ed. Woodhead Publishing, pp. 189e210.

100

Natural Dyes for Sustainable Textiles

Dave, H., Ledwani, L., Chandwani, N., Desai, B., Nema, S., 2014. Surface activation of polyester fabric using ammonia dielectric barrier discharge and improvement in colour depth. Dave, H., Ledwani, L., Chandwani, N., Kikani, P., Desai, B., Chowdhuri, M., Nema, S., 2012. Use of dielectric barrier discharge in air for surface modification of polyester substrate to confer durable wettability and enhance dye uptake with natural dye eco-alizarin. Composite Interfaces 19 (3e4), 219e229. Dave, H., Ledwani, L., Chandwani, N., Kikani, P., Desai, B., Nema, S., 2013. Surface modification of polyester fabric by non-thermal plasma treatment and its effect on coloration using natural dye. Journal of Polymer Materials 30 (3), 14. Dietrich, J., Hirt, P., Herlinger, H., 1996. Electron-beam-induced cyclisation to obtain C-fibre precursors from polyacrylonitrile homopolymers. European Polymer Journal 32 (5), 617e623. Elmaaty, T.A., Abouelenin, S., Elsisi, H., Okubayashi, S., 2022. Eco-friendly approach for dyeing synthetic fabrics with natural dyes using electron beam irradiation. Fibers and Polymers 23 (3), 759e767. Fei, X., Jia, W., Wang, J., Chen, T., Ling, Y., 2020. Study on enzymatic hydrolysis efficiency and physicochemical properties of cellulose and lignocellulose after pretreatment with electron beam irradiation. International Journal of Biological Macromolecules 145, 733e739. Haar, S., Schrader, E., Gatewood, B.M., 2013. Comparison of aluminum mordants on the colorfastness of natural dyes on cotton. Clothing and Textiles Research Journal 31 (2), 97e108. Han, Y.H., Han, S.O., Cho, D., Kim, H.-I., 2007. Kenaf/polypropylene biocomposites: effects of electron beam irradiation and alkali treatment on kenaf natural fibers. Composite Interfaces 14 (5e6), 559e578. Jaeger, H., Knorr, D., Meneses, N., Reineke, K., Schlueter, O., 2014. Food safety: shelf life extension technologies. In: Van Alfen, N.K. (Ed.), Encyclopedia of Agriculture and Food Systems. Academic Press, Oxford, pp. 289e303. Ji, S.G., Hwang, J.H., Cho, D., Kim, H.-J., 2013. Influence of electron beam treatment of jute on the thermal properties of random and two-directional jute/poly (lactic acid) green composites. Journal of Adhesion Science and Technology 27 (12), 1359e1373. Jung, J.-Y., Park, M.-S., Kim, M.I., Lee, Y.-S., 2014. Novel reforming of pyrolized fuel oil by electron beam radiation for pitch production. Carbon letters 15 (4), 262e267. Kerkeni, A., Behary, N., Perwuelz, A., Gupta, D., 2012. Dyeing of woven polyester fabric with curcumin: effect of dye concentrations and surface pre-activation using air atmospheric plasma and ultraviolet excimer treatment. Coloration Technology 128 (3), 223e229. Kim, H., Bae, J.-S., 2009. Modification of polypropylene fibers by electron beam irradiation. I. Evaluation of dyeing properties using cationic dyes. Fibers and Polymers 10 (3), 320e324. Kong, M.G., Shama, G., 2014. Cold atmospheric gas plasmas. In: Batt, C.A., Tortorello, M.L. (Eds.), Encyclopedia of Food Microbiology, second ed. Academic Press, Oxford, pp. 493e496. Lee, J., Le Boulicaut, N., Kwon, O.H., Park, W.H., Cho, D., 2019. Electron beam irradiation effect on the mechanical and thermal properties of 2-D silk fibroin fabric/poly (lactic acid) biocomposites. Journal of Industrial and Engineering Chemistry 71, 150e159. Leroux, F., Perwuelz, A., Campagne, C., Behary, N., 2006. Atmospheric air-plasma treatments of polyester textile structures. Journal of Adhesion Science and Technology 20 (9), 939e957.

Use of newer technologies in natural dyeingdplasma and electron beam

101

Liu, L., Wu, F., Yao, H., Shi, J., Chen, L., Xu, Z., Deng, H., 2015. Investigation of surface properties of pristine and g-irradiated PAN-based carbon fibers: effects of fiber instinct structure and radiation medium. Applied Surface Science 337, 241e248. Liu, Y., Zhou, L., Ding, F., Li, S., Li, R., Li, Z., Huang, D., Ren, X., 2021. Flame-retardant cotton fabrics modified with phosphoramidate derivative via electron beam irradiation process. Journal of Industrial Textiles 51 (3), 396e408. Loganathan, S., Assadi, A.A., 2021. Chapter 15 - nanomaterials for photocatalytic and cold plasma-catalytic hydrogenation of CO2 to CO, CH4, and CH3OH. In: Nguyen Tri, P., Wu, H., Nguyen, T.A., Barnabé, S., Bénard, P. (Eds.), Nanomaterials for CO2 Capture, Storage, Conversion and Utilization. Elsevier, pp. 353e373. Malik, T., Parmar, S., 2007. Use of plasma technology in textiles. Industry article. https://www. fibre2fashion.com/industry-article/1798/use-of-plasma-technology-in-textiles. Naveed, M., 2018. Plasma treatment as green technology for dyeing of textile fabrics. Trends in Textile Engineering and Fashion Technology 2 (2), 1e6. Niaounakis, M., 2015. Chapter 8 - surface treatment. In: Niaounakis, M. (Ed.), Biopolymers: Processing and Products. William Andrew Publishing, Oxford, pp. 303e326. Pang, Y., Cho, D., Han, S.O., Park, W.H., 2005. Interfacial shear strength and thermal properties of electron beam-treated henequen fibers reinforced unsaturated polyester composites. Macromolecular Research 13 (5), 453e459. Park, Y., Koo, K., Kim, S., Choe, J., 2008. Improving the colorfastness of poly (ethylene terephthalate) fabrics with the natural dye of Caesalpinia sappan L. Wood extract and the effect of chitosan and low-temperature plasma. Journal of Applied Polymer Science 109 (1), 160e166. Purwar, S., 2016. Application of natural dye on synthetic fabrics: a review. International Journal of Home Science 2 (2), 283e287. Shah, J., Shah, S., 2013. Innovative plasma technology in textile processing: a step towards green environment. Research Journal of Engineering Sciences 2278, 9472. Shahidi, S., Ghoranneviss, M., Wiener, J., 2015. Improving synthetic and natural dyeability of polyester fabrics by dielectric barrier discharge. Journal of Plastic Film and Sheeting 31 (3), 286e308.   ak, M., Imahori, Y., Stefe  cka, M., Kando, M., 2003. Atmospheric-pressure Simor, M., Cern plasma treatment of polyester nonwoven fabrics for electroless plating. Surface and Coatings Technology 172 (1), 1e6. Sui, X., Xu, Z., Hu, C., Chen, L., Liu, L., Kuang, L., Ma, M., Zhao, L., Li, J., Deng, H., 2016. Microstructure evolution in g-irradiated carbon fibers revealed by a hierarchical model and Raman spectra from fiber section. Composites Science and Technology 130, 46e52. Tomasino, C., 1992. Chemistry and Technology of Fabric Preparation and Finishing. North Carolina State University North Carolina. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S., 2008. Ecofriendly sonicator dyeing of cotton with Rubia cordifolia Linn. using biomordant. Dyes and Pigments 76 (1), 207e212. Xu, Z., Liu, L., Huang, Y., Sun, Y., Wu, X., Li, J., 2009. Graphitization of polyacrylonitrile carbon fibers and graphite irradiated by g rays. Materials Letters 63 (21), 1814e1816. Zhang, S., Wang, W., Wang, H., Qi, W., Yue, L., Ye, Q., 2014. Synthesis and characterisation of starch grafted superabsorbent via 10 MeV electron-beam irradiation. Carbohydrate Polymers 101, 798e803.

This page intentionally left blank

Natural dyeing on polymeric material 7.1

7

Introduction

Polymeric materials play an integral role in modern society. Engineering polymers are often used as a replacement for wood and metals. Examples include polyamides, often called nylons, polyesters (saturated and unsaturated), aromatic polycarbonates, polyoxymethylenes, polyacrylates, polyphenylene oxide, and styrene copolymersd styrene/acrylonitrile and acrylonitrile/butadiene/styrene (Candlin, 2008). Polymers can be of two typesdnatural and synthetic. Synthetic ones are composed of petroleum oil and are man-made by scientists and engineers. Examples include teflon, epoxy, polyethylene, and polyester. Natural ones are extracted from nature that includes natural rubber, starch, proteins, and cellulose. In the textile industry, mainly nylon and polyester polymers are used. Both these polymers are used in the production of clothes. Polymeric textiles are converted into a vast number of consumer products including garments, carpets, towels, bags, table cloth, blankets, and beds. Applications for technical or industrial textiles are very diverse and include products such as filters, industrial geotextiles, upholstery, conveyer belts, heavy-duty tires, seat covers, seat belts, air bags, parachutes, fishing nets, optical fibers, packing textiles, insulation and roofing materials, ribbons, and tapes. Polymeric textiles are also used in composite materials as reinforcements such as fiberglass and carbon fiber-reinforced plastics. Textile fiber polymers used in clothes provide an understanding of how the fibers behave and how they are dyed. Moreover, their strength, colorfast properties, and shrinking ability can also be determined. Generic fibers used to make clothes include silk, cashmere, ramie, wool, linen, cotton, polyester, nylon, rayon, olefin, and acetate. Cotton, rayon, ramie, and linen are made up of cellulose, and wool and cashmere are made up of alpha keratin (News, 2022). The two most important fibers used in the textile industry are cotton and polyester. Cotton dominated the textile market until the end of the last century, whereas today, most textile products are made of synthetic fibers (63%). The three most important synthetic fibers are polyester (55%), nylon (5%), and acrylic (2%) (Exchange, 2016). Besides cotton and polyester, many other synthetic polymers are spun into fibers. The majority of these are high-performance fibers that are used for very demanding applications such as bulletproof vests, heat resistant garments, highperformance sporting goods, heavy-lifting lines, tow cables, etc. (Ahmed and MacCarthy, 2021).

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00011-6 Copyright © 2024 Elsevier Ltd. All rights reserved.

104

Natural Dyes for Sustainable Textiles

The ability to shape polymeric materials into fibers has revolutionized the textile industry. Synthetic fibers not only offered a solution to some of the shortcomings of natural fibers but also made it possible to design textile fabrics for use in new, and high-performance, applications (Ouederni, 2020). The use of synthetic fibers in the last two decades has increased enormously which demanded the production of these fibers to surpass the production of natural fibers. There are several advantages of these fibers such as low cost, high strength, stiffness, elasticity, wrinkle, and abrasion resistances, and they are also very convenient to process along with easy recycling. Their disadvantages are reduced wearing comfort, build-up of electrostatic charge, and low dyeability. Due to their hydrophobic nature, there is poor workability. In order to make their surfaces hydrophilic, various physical, chemical, and bulk modification methods have been employed (Gashti et al., 2011). Polymers in the textile industry refer to any class of natural or synthetic substance which is made up of very large molecules which are multiple of several chemical units called monomers. Monomers have the ability to combine with similar looking molecules, and this process is called polymerization. Silk sarees use bright polyester which is cheap and durable. The polymers in textile are not a new thing. Since the inception of nylon in the year 1930, it captured a large portion of industrial yarn and fabrics such as wall ropes, belts, tyre cords, and then in household use such as sarees, swimming costumes, etc. Gradually polyester arrived in 1970 and conquered the world of textile for its own several positive properties. Today it is gradually by passing natural fibers like cotton, jute, etc., because of their limitations in growing and are unable to fulfill such huge requirements in the world of textile (Basu, 2012).

7.2

Advantages of polymeric versus natural fibers

In polymeric fibers, the life of the finished product is longer and the fabric strength is higher. In natural fiber, it is lesser as compared to polymers. The outlook of polymers is better as compared to natural fibers. Polymers have a better scope in elaborate styles and designs such as semi-dull, micro, super bright, easy dye, biocomponents, and cationic dyes. If you use natural fibers, there is less variety available. The cost of fabric manufacturing in polymers is less as compared to natural fibers. Moreover, polymers have high operational advantages as natural fibers need humidification, high speed, and better preparation. Wet process of fabric is tough in natural fibers. Even the daily maintenance of natural fiber is high as it requires more washing and ironing.

7.3

Disadvantages of polymeric versus natural fibers

Initial cost of raw material is higher in polymers and less in natural fibers. During extreme weather conditions, natural fiber is more comfortable to wear as compared to polymeric fabric. They have less moisture-absorbing property as compared to natural fibers (News, 2022).

Natural dyeing on polymeric material

7.4

105

Pretreatments of polymeric textile before natural dyeing

Color cannot be fixed on the fiber if it has no affinity to the fibers. Pretreatment of textile creates this affinity between the color and fiber. Man-made fibers like polyester, nylon, and acrylic retain mainly added impurities. Pretreatment is the most crucial technique in the polymeric textile process. It is the removal of added or natural impurities present in textile fibers to improve the absorbency of color/dye. Achieving good dyeing results and improving the overall efficiency of the dyeing process are possible only when the fabric coming onto the dyeing machine is prepared well before dyeing. As synthetic fibers have relatively high level of orientation and crystallinity posing resistance toward dyeing, thus some kind of surface modification is required for the enhancement of dye receptiveness. Modification of the fabric is one of the best routes to improve the affinity between dye and fabric. To improve their dyeability, many physical methods (corona discharge, plasma, laser, electron beam, ultraviolet [UV], and ozone) and chemical methods (enzymatic modification, use of supercritical carbon dioxide, and solegel technology) and various bulk modification methods have been proposed/used (Textor et al., 2003; Farouk et al., 2010). Polymeric fabric is generally hydrophobic in nature and quickly dry. The lack of polarity and the very crystalline structure resist the entry of water molecules into the polymer system. So, before dyeing the polyester fiber, it should be pretreated. Generally it can be treated with plasma, ozone, mordant, alkalis, or heating before dyeing (Purwar, 2016). Recent methodologies use environmentally benign method for polymeric surface modification for improved dyeing and consequently achieve good wash fastness. To increase hydrophilicity of synthetic fiber, polyester is preferably dry heat set for structural stabilization, while nylon is steam set. Acrylic, on the other hand is not sized as the main use is in knitting; mild scouring, chlorite bleaching, and stabilization by autoclaving at 105
C with steam to develop bulkiness completes pretreatment (Chakraborty, 2010). By all these many applications, a hydrophobic polymeric textile is transformed into hydrophilic one with suitable treatment. Enhanced dyeing can be accomplished by improving wettability of polymeric fabric (Deshmukh and Bhat, 2011).

7.5

Dyeing of polymeric textile

Dyeing is a process of thorough coloration of textiles, and its success lies on type and extent of pretreatment imparted to develop good absorbency and whiteness. Other factors, viz. pH, form of textile, type of fiber, formulation of dyeing recipe, preparation of dye solution, liquor ratio, selection of machinery, etc., too play a crucial role in the process to develop leveled shades with least effort and cost (Chakraborty, 2010). Natural fibers such as wool, cotton, and silk (and later nylon and synthetic) were well understood, and they had good dye attraction, owing to multiple fiber functionalities such as eNH2, eCOOH, and eOH. The highly crystalline structure and a lack of polarity make polyester fiber hydrophobic in nature (El-Nagar et al., 2006) that in turn resists any entry of water molecules into the polymer system and also imparts a limited swelling in water. Consequently, the hydrophobicity of polyester fiber restricts the

106

Natural Dyes for Sustainable Textiles

diffusion of dye molecules into the fiber interior during dyeing (Peters and Ingamells, 1973) that also makes the dyeing process exceedingly difficult. The only way to dye polyester is to first force the dye into the fiber and then rely on van der Waals forces to hold the dye in place. Classical cationic and anionic dyes for wool and silk or direct dyes for cotton all had water-solubilizing groups such as eNR3 þ and eSO3 groups. Such dyes have little or no affinity for the hydrophobic PET (McIntyre, 2005), whereas disperse dyes were found useful for dyeing polymeric fabric. The main mechanism of dyeing is to swell the fiber so that the dye molecule gets enough space to stay inside the fiber. In hydrophilic fibers such as cotton, this swelling is done by wetting. However, when polyester fiber is dyed, it is not able to swell on wetting due to the compact structure, being a hydrophobic fiber (Blacker and Patterson, 1969). Its moisture regain percentage is 0.04%, so it is highly hydrophobic. Thus, it needs a special arrangement. Swelling is done by applying chemicals or heat. The chemical swells the fiber is called carrier. Heating of the dye liquor swells the fiber to open up and assists the dye to penetrate the fiber polymer system. Thus, the dye molecule takes its place in the amorphous regions of the fiber. Once taking place within the fiber polymer system, the dye molecules are held by hydrogen bonds and van Der Waals’ force. When the system is taken off, the molecular areas shrunk and dye molecules are entrapped inside the polymer (Uddin et al., 2002). The classical chemical modifications of synthetic polymers are done by using alkaline or acidic agents. Alkaline scouring renders synthetic fibers more hydrophilic, they also lead changes the surface morphology of the polymer. This was followed by surface modification by using chitosan prior to dyeing with natural dyes (Silva and Cavaco-Paulo, 2008). An eco-friendly method for dyeing synthetic fabrics with natural dyes using UV/ozone pretreatment to activate fiber and improve dyeability of polyester and nylon has been discussed. Fabrics are pretreated with UV/ozone for different periods of time ranged from 5 min to 120 min. Dyeability of the treated samples was investigated in terms of their color strength expressed as K/s in addition to fastness to washing and light. This research showed the increment of the affinity of the studied synthetic fabrics toward curcumin and saffron natural dyes using eco-friendly technique (Elnagaret al., 2014). The rate of uptake of dyes into PET fibers has received considerable attention, and detailed accounts are available (Yang et al., 2017). In essence, the diffusion behavior of dyes within PET and other types of fiber is almost ideal and analysis of dyeing rates have been undertaken using equations that relate to both finite and infinite dye baths. Such virtual ideal diffusion behavior has been attributed to a low degree of dyeefiber interaction that enables the ready movement of dye molecules through the substrate (Ren et al., 2012). The effect of a low-temperature plasma and/or chitosan pretreatment as a mordant on the dyeing of poly(ethylene terephthalate) fabrics with an aqueous extract of Caesalpinia sappan L. wood, which showed a remarkably high coloring property in a natural dyeing system, was investigated. Dyeing with the C. sappan L. extract led to fair-to-good fastness properties in conventional natural dyeing. The results clearly show that the pretreatment with chitosan and/or plasma is better than a metal mordant in terms of the dye uptake and reduction in the dyeing time that the proposed pretreatment coloration reaction could be carried out without the need for repetitive dye steps, and that it prevents the excessive use of dye chemicals, thereby resulting in a more ecofriendly process (Park et al., 2008). Purified curcumin was applied on polyester, and

Natural dyeing on polymeric material

107

various shades of yellow were obtained like brown orange, black orange, etc., with different dyeing parameter of pH value, temperature, and time. Before applying of exhaust dyeing method, polyester fabric was premordanted by aluminum potassium sulfate, copper sulfate, and tartaric acid (Hasan et al., 2014). In the absence of any physical interaction, dyes are only mechanically retained. This may be due to insolubilization of the dye inside the fiber or may be due to self-association into possibly quite large molecular aggregates following their entry into the fiber. PET has no functional groups to give affinity for usual dyestuffs (Ketema and Worku, 2020). A work on polymeric textile has been carried out with Ratanjot (Arnebia nobilis) where Ratanjot extract behaves as disperse dyes and affinity for hydrophobic filament such as nylon and polyester (Bairagi and Gulrajania, 2005). Natural dyes, namely, indigo carmine, cochineal carmine, curcumin, and annatto, were encapsulated in silica by a solegel method and applied in the dyeing of different textile fibers by exhaustion. The silica-structured dyes showed better affinities with the polymeric fibers such as polyester, PET, etc., in dyeing with cochineal carmine, while cotton showed better affinities with the encapsulated curcumin and annatto dyes (dos Santos et al., 2018). During the last few decades, the use of synthetic dyes is gradually decreasing due to an increased environmental awareness and harmful effects because of either toxicity or their nonbiodegradable nature. Natural dyes have also better biodegradability and generally have higher compatibility with the environment. They are nontoxic, nonallergic to skin, noncarcinogenic, easily available, and renewable (Kundal et al., 2016). Madder and weld natural dyes were applied on polyester fiber after plasma sputtering treatment. Madder (Rubia tinctorum) root produces red dye, whereas Reseda luteola or weld produces bright yellow dye. In dyeing process, the plasma sputtered samples were dyed with madder by using exhausted method. It was observed plasma-treated fabric dyed with madder showed chemical bond with polyester fabric and improved fastness property as compare to unexposed plasma fabric (Motaghi and Shahidi, 2012). In the recent years, there has been a resurgence of natural dyes. Natural dyes are eco-friendly and exhibit better biodegradability and have better compatibility with the environment (Samanta and Konar, 2011). In general, natural dyes apply on polymeric fabric using exhaust dyeing method.

7.5.1

Case study

A study has been carried out to improve the hydrophilicity of synthetic fabrics through alkaline pretreatment followed by chitosan treatment which imparted deep coloring effect of the synthetic fabrics when dyed with natural dyes. The highlight of this work is relatively low temperature natural dyeing of polyester fabric with surface modification by chitosan. Finally natural dyeing of polyester with four natural dyesdRubia, onion skin extract, jackfruit bark sawdust, and tea dust as shown in Figs. 7.1e7.4 in the order of onion skin, jackfruit sawdust, Rubia, and tea dust. The main colorant molecules are shown in Fig. 7.5aec as quercetin present in onion skin, catechin present in tea dust, and morin present in jackfruit bark sawdust, Fig. 7.6a and b as tellimagradin II and theaflavin present in Tea dust along with Fig. 7.7a and b munjisthin and purpurin present in Rubia dye.

108

Figure 7.1 Onion skin.

Figure 7.2 Jackfruit bark sawdust.

Figure 7.3 Rubia root and stem.

Natural Dyes for Sustainable Textiles

Natural dyeing on polymeric material

109

Figure 7.4 Waste tea dust.

Figure 7.5 (a) Quercetin (from onion), (b) Catechin (tea dust), and (c) Morin (jackfruit bark).

Figure 7.6 (a) Tellimagrandin II (tea dust) and (b) Theaflavin (tea dust). Figure 7.7 (a) Munjistin (Rubia) and (b) Purpurin (Rubia).

110

7.6

Natural Dyes for Sustainable Textiles

Materials

100% scoured and bleached plain weave polyester (109 g/m2) fabric was used purchased locally. Tea dust waste, onion skin, and jackfruit bark sawdust were collected from the local market, and Rubia dye was purchased from the AMA Herbals, Lucknow. Chitosan and sodium hydroxide were purchased from Pragati Instruments, Kanpur.

7.7

Analytical methods

Alkaline pretreatment: The polyester samples are to be firstly treated with aqueous solution of NaOH (12%) at L.R 1:50 at 60
C for 90 min.

7.8

Dyeing procedures

(A) Mordanting: The polyester was premordanted by treating in a bath containing chitosan keeping material to liquor ratio 1:15 at 60
C for 60 min followed by rinsing with cold water and air drying.

7.9

Natural dye/color extraction

7.9.1 7.9.1.1

Onion skin Extraction of onion skin (Allium cepa)

Dark onion skin was extracted by conventional solvent extraction (CSE). From 10 g sample of dried onion skin, the highest yield of each method could be achieved at 20 min of process time under 55e60
C for CSE with 50: 50% ethanol: water. Process of extraction: The distilled water and ethanol of 50:50 ratio are taken, 10 g of the onion skin in weight was poured into container, and the extract was heated to 70e75
C for 60 min. Then, the soluble pigment from the skins was collected. The onion skins and ethanol were mixed in the ratio of 50:50, and the extraction was done for an hour, being stirred thoroughly. Then, the extracted liquid was collected. Extraction can be done in ethanol directly also using Soxhlet.

7.9.2

Rubia

Ethanol extraction: Dried and ground Rubia/madder root (10 g) was immersed in ethanol (300 cm3) and heated under reflux with stirring for 3 h. Solids were removed by filtration, and the filtrate was evaporated to dryness first on a rotary evaporator and then on the high vacuum system. This resulted in a reddish orange powder approximately (1.50 g).

Natural dyeing on polymeric material

111

Water extraction: Dried and ground Rubia/madder root (0.75 g) was immersed in water (100 cm3) and heated under reflux with stirring for 3 h. Acetone:water extraction: The powder of air-dried roots of Rubia cordifolia macerated three times in acetone:water (1:1) for 48 hrs at room temperature. The combined decanted solvent will be distilled by simple distillation to remove acetone. A reddish brown-colored solid separated after the removal of acetone taken forward for further dyeing for darker red shades.

7.9.3

Jackfruit bark sawdust

Ethanol extraction: Dried and ground jackfruit bark sawdust (10 g) was immersed in ethanol (300 cm3) and heated under reflux with stirring for 3 h. Solids were removed by filtration, and the filtrate was evaporated to dryness first on a rotary evaporator and then on the high vacuum system. This resulted in a reddish orange powder approximately (1.20 g).

7.9.4

Tea dust

Water extraction: Dried and ground tea dust powder (100 g) was immersed in water (500 cm3) and heated with stirring for 1 h. Solids were removed by filtration, and the filtrate was evaporated to dryness first on a rotary evaporator and then on the high vacuum system. This resulted in a reddish orange powder approximately (30 g).

7.10

Surface modification methods of polyester

7.10.1 Alkali treatment The polyester samples firstly treated with aqueous solution of NaOH (12%) at L.R 1:50 at 60
C for 90 min. Terephthalate dianion or ethylene glycol by “un-zippering” (i.e., the progressive reaction of the chain with hydroxide ion, beginning at a free end group) occurs at locations that may be solvated, and hence can be expected to have rates that are faster than the rates of chain cleavage.

7.10.2 Cationization using chitosan The alkali pretreated polyester fabrics were then cationized with chitosan (15%) o.w.f. at L.R. 1:50, at 30e90
C for 30e90 min. pH 5.5. Natural dyeing of pretreated polyester: The pretreated polyester fabric was dyed in a solution that contains the respective natural dye with different concentrations (1%e5%), at 30e100
C, for 30e90 min. at L.R 1:20 using exhaust dyeing method. The pretreated fabric was specifically dyed with 5% Rubia, 10% jackfruit bark extract, and 20% onion skin extract solution at 60
C for 90 min. L.R 1:30 having pH ranges from 4e6 (acidic) by adding mild acid such as acetic acid. The dyeing is carried out for 1e1.5 h.

112

Natural Dyes for Sustainable Textiles

After dyeing, the dyed fabric samples are washed in a bath with 1 g/L of nonionic soaping agent (mild soap solution) at 60
C temperature for 10 min as well as rinsed with cold water and then dried in a dryer.

7.11

Measurement of color strength and related parameters

The color yield value of naturally dyed polyester fabric samples was analyzed by using color measurement spectrophotometer (premier color scan). The depth of color of the dyed fabric was determined by analyzing the K/S value of a given dyed sample by KubelkaeMunk equation: K = S ¼ ð1  RÞ2 =2R where R is the reflectance percentage; K is the absorption coefficient; and S is the scattering coefficient of dyes. This value was derived from the attenuation ratio of light due to absorption and scattering, which was found based on reflectance. CIELABdColorimetric properties of the dyed fabrics such as lightness (L*), redness-greenness (a*), yellowness-blueness (b*), chroma (c*), and hue (ho ) were evaluated according to AATCC test method 173e2006 in illuminant D65, large area view, and CIE 10
standard observer. Each sample was folded twice to give an opaque view, and color reflectance was measured four times at different parts of the fabric surface.

7.12

Determination of colorfastness properties

The colorfastness property of dyed fabric samples against washing was conducted according to ISO 105-C06 by launder-o-meter. The change and staining (with multifiber fabric) of color due to washing were assessed by comparing the undyed fabric with the dyed polyester fabric samples with respect to the ratings of color change and colorstaining gray scales. The colorfastness property of dyed fabric samples against light fastness was conducted according to ISO 105-B02 by fadometer fitted with xenon arc lamp.

7.13

Results and discussion

The dyeing performance was investigated in terms of depth of shade measurement by K/S values, analysis of colorimetric properties of color by CIELab values, and assessment of color fastness properties of naturally dyed polyester fabric samples (Tables 7.1e7.4). Two concentrations 10% and 20% were taken for each of the

Natural dyeing on polymeric material

Table 7.1 CIELAB color values. Natural dyes

Dye concentration

Temperature 8C

K/S

L

a

b

DE

Madder (Rubia)

10%

90 120 90 120 90 120 90 120

8.500 23.146 23.633 39.077 6.017 10.906 5.417 11.276

92.462 93.192 93.191 93.554 93.292 93.088 93.201 93.069

6.335 6.842 6.932 7.204 0.445 1.142 0.543 1.207

6.311 8.432 8.416 9.316 8.087 7.246 7.471 7.191

7.382 9.062 9.122 9.958 5.506 4.785 4.906 4.747

20% Onion skin

10% 20%

113

114

Table 7.2 CIELAB color values. Dye concentration

Temperature 8C

K/S

L

a

b

DE

Jackfruit bark saw dust

10%

90 120 90 120 90 120 90 120

5.504 4.755 4.681 7.443 4.597 5.138 5.341 8.296

92.604 92.436 92.480 92.627 92.560 92.335 92.299 92.211

0.919 1.555 1.508 1.188 0.907 1.143 1.083 1.229

6.159 5.670 5.794 5.822 5.997 5.306 5.167 4.939

3.593 3.374 3.465 3.384 3.429 2.846 2.691 2.553

20% Tea waste

10% 20%

Natural Dyes for Sustainable Textiles

Natural dyes

Natural dyeing on polymeric material

115

Table 7.3 Light and wash fastness values. Natural dyes

Dye concentration

Temperature 8C

Light fastness (ISO 105 B-02)

Wash fastness (ISO 105 C-06)

Madder (Rubia)

10%

90 120 90 120 90 120 90 120

3e4 3e4 3e4 4 3 3e4 3 4

3e4 4 4 4 3e4 4 3e4 4

20% Onion skin

10% 20%

Table 7.4 LIGHT and wash fastness values. Natural dyes

Dye concentration

Temperature 8C

Light fastness (ISO 105 B-02)

Wash fastness (ISO 105 C-06)

Jackfruit bark saw dust

10% 20%

Tea waste

10%

90 120 90 120 90 120 90 120

3 3e4 3 3e4 3e4 3e4 3e4 4

3e4 4 3e4 4 4 4 4 4

20%

dyes, and the dyeing was carried out at two different temperatures 90 and 120
C. In Rubia dye, 20% concentration at 120
C gave the best K/S value and DE value. However, in the case of onion skin, jackfruit bark sawdust, and tea dust, there was only marginal increase in K/S value between 10% and 20% concentrations even at 120
C temperature. While considering the light and wash fastness, best results were obtained for 20% concentration and 120
C for all the four dyes. Thus polyester dyeing with chitosan pretreatment with Rubia dye is far better suited than tea dust, jackfruit bark sawdust, and onion skin. The mechanism of surface activation of the polyester surface has been shown in Fig. 7.8. After the alkaline hydrolysis of the polyester, chitosan binds to the hydroxyl and carboxyl group readily, thereby offering better chelation sites for the natural colorant (Shukla and Vankar, 2018). The amount of dye absorption by polyester fiber which was surface modified by alkaline hydrolysis followed by chitosan treatment and the resulting depth of shade were found to increase with increasing dyeing temperature. In case of colorfastness properties, all dyed substrates demonstrated improvement in the light and wash fastness. Overall the fastness is well within the acceptable limits for industrial application.

Figure 7.8 Process of surface activation of polyester fiber by alkaline hydrolysis and chitosan.

7.14

Shades of dyed polyester

A variety of orange color was obtained with the Rubia dye on polyester, shades of camel brown with onion skin, shades, shades of light brown with jackfruit bark sawdust, and shades of brown with tea dust as shown in Table 7.5. Table 7.5 Shades of dyed Polyester swatches.

Natural dyeing on polymeric material

7.15

117

Conclusions

The textile industry is one of the oldest and most widespread industries and played a vital role in economic development of many Asian and Europian countries. The ability to shape polymeric materials into fibers has revolutionized the textile industry. Synthetic fibers not only offered a solution to some of the shortcomings of natural fibers but also made it possible to design textile fabrics for use in new, and high performance, applications. The results of above case study explained that treatment of alkaline scoured polyester with chitosan increased the cationic sites in the fiber polymer which resulted higher absorption of natural dye at relatively low temperatures. The concentration of chitosan in fabric showed a noticeable effect on dyeability. The fastness properties of the chitosan-treated fabrics also displayed better ratings than the untreated fabric. Hence the treatment of the polyester with chitosan for improved adherence of natural dyes provides a significant scope for commercialization of eco-friendly dyeing of polyester. The following study proved that surface modification of polymeric materials increase dye adherence onto them. The use of natural dyes makes the whole dyeing process a cleaner greener experience paving way for widespread use of natural dyes in dyeing of polymeric material. In this context, when polymeric textile almost acquiring a big portion of apparel and domestic cloth industry, the successful use of natural dyes creates a big boon for this industry to become a safer and eco-mark industry.

References Ahmed, W.A., MacCarthy, B.L., 2021. Blockchain-enabled supply chain traceability in the textile and apparel supply chain: a case study of the fiber producer, Lenzing. Sustainability 13 (19), 10496. Bairagi, N., Gulrajania, M., 2005. Studies on dyeing with shikonin extracted from Ratanjot by supercritical carbon dioxide. Indian Journal of Fibre and Textile Research 30 (2), 196e199. Basu, B., 2012. Polymers-in-Textiles. Industry Article. Blacker, J., Patterson, D., 1969. Molecular mechanisms of disperse dyeing of polyester and nylon fibers. Journal of the Society of Dyers and Colourists 85 (12), 598e605. Candlin, J.P., 2008. Chapter 3 polymeric materials: composition, uses and applications. J. M. Chalmers and R. J. Meier Comprehensive Analytical Chemistry 53, 65e119. Elsevier. Chakraborty, J.N., 2010. 1 - Introduction to Dyeing of Textiles. Fundamentals and Practices in Coloration of Textiles. J. N. Chakraborty. Woodhead Publishing India, pp. 1e10. Deshmukh, R., Bhat, N., 2011. Pretreatments of Textiles Prior to Dyeing: Plasma Processing. Textile Dyeing, pp. 33e56. dos Santos, C., Brum, L.F.W., de Fatima Vasconcelos, R., Velho, S.K., dos Santos, J.H.Z., 2018. Color and fastness of natural dyes encapsulated by a sol-gel process for dyeing natural and synthetic fibers. Journal of Sol-Gel Science and Technology 86 (2), 351e364. El-Nagar, K., Saudy, M., Eatah, A., Masoud, M., 2006. DC pseudo plasma discharge treatment of polyester textile surface for disperse dyeing. Journal of the Textile Institute 97 (2), 111e117.

118

Natural Dyes for Sustainable Textiles

Elnagar, K., Abou Elmaaty, T., Raouf, S., 2014. Dyeing of polyester and polyamide synthetic fabrics with natural dyes using ecofriendly technique. Journal of Textiles 2014, 363079. Exchange, T., 2016. Preferred Fiber Market Report 2016. Lamesa (SAD). Textile Exchange: Dostupno. Farouk, A., Textor, T., Schollmeyer, E., Tarbuk, A., Grancaric, A.M., 2010. Sol-gel-derived inorganic-organic hybrid polymers filled with zno nanoparticles as an ultraviolet protection finish for textiles. Autex Research Journal 10 (2), 58e63. Gashti, M.P., Willoughby, J., Agrawal, P., 2011. Surface and Bulk Modification of Synthetic Textiles to Improve Dyeability (chapter). Hasan, M.M., Hossain, M.B., Azim, A., Ghosh, N., Reza, M.S., 2014. Application of purified curcumin as natural dye on cotton and polyester. International Journal of Engineering & Technology 14 (5), 17e23. Ketema, A., Worku, A., 2020. Review on intermolecular forces between dyes used for polyester dyeing and polyester fiber. Journal of Chemistry 2020. Kundal, J., Singh, S.V., Purohit, M., 2016. Extraction of natural dye from Ficus cunia and dyeing of polyester cotton and wool fabric using different mordants, with evaluation of color fastness properties. Natural Products Chemistry & Research 4 (3), 1e6. McIntyre, J.E., 2005. Synthetic Fibers: Nylon, Polyester, Acrylic, Polyolefin. Taylor and Francis US. Motaghi, Z., Shahidi, S., 2012. Development of Polyester-Wool fabrics dye ability using Plasma Sputtering. In: RMUTP International Conference, vol. 2012. Textiles and Fashion. News, F.I., 2022. Polymers-Everything-You-Need-To-Know. fashinza.com. Ouederni, M., 2020. Chapter 10 - Polymers in Textiles. Polymer Science and Innovative Applications. M. A. A. AlMaadeed, D. Ponnamma and M. A. Carignano. Elsevier, pp. 331e363. Park, Y., Koo, K., Kim, S., Choe, J., 2008. Improving the colorfastness of poly (ethylene terephthalate) fabrics with the natural dye of Caesalpinia sappan L. Wood extract and the effect of chitosan and low-temperature plasma. Journal of Applied Polymer Science 109 (1), 160e166. Peters, R.H., Ingamells, W., 1973. Theoretical aspects of the role of fiber structure in dyeing. Journal of the Society of Dyers and Colourists 89 (11), 397e405. Purwar, S., 2016. Application of natural dye on synthetic fabrics: a review. International Journal of Home Science 2 (2), 283e287. Ren, Z., Qin, C., Tang, R.C., Chen, G., 2012. Study on the dyeing properties of hemicyanine dyes. II. Cationic dyeable polyester. Coloration Technology 128 (2), 147e152. Samanta, A.K., Konar, A., 2011. Dyeing of textiles with natural dyes. Natural Dyes 3 (30e56). Shukla, D., Vankar, P.S., 2018. Curcuma dye with modified treatment using chitosan for superior fastness. Fibers and Polymers 19 (9), 1913e1920. Silva, C., Cavaco-Paulo, A., 2008. Biotransformations in synthetic fibers. Biocatalysis and Biotransformation 26 (5), 350e356. Textor, T., Bahners, T., Schollmyer, E., 2003. Modern approaches for intelligent surface modification. Journal of Industrial Textiles 32 (4), 279e289. Uddin, M.Z., Watanabe, M., Shirai, H., Hirai, T., 2002. Dyeing conventional and microfiber polyester with disperse dyes. Textile Research Journal 72 (1), 77. Yang, D.-F., Kong, X.-J., Gao, D., Cui, H.-S., Huang, T.-T., Lin, J.-X., 2017. Dyeing of cotton fabric with reactive disperse dye contain acyl fluoride group in supercritical carbon dioxide. Dyes and Pigments 139, 566e574.

Sustainable processing of textiles 8.1

8

Introduction

Textile industry is known for using toxic and hazardous chemicals, particularly synthetic dyes during the wet processing. The wastewater that is generated needs to be controlled in an eco-friendly manner in order to save the environment. The danger posed by the use of synthetic dyes has compelled the stakeholders to consider natural dyes as substitutes for fabric coloration. Both in dyeing and printing of textiles, the consumption of synthetic dyes and pigments is very large. The wastewater generated from these two sources produces effluent with very high BOD (biological oxygen demand), COD (chemical oxygen demand), TSS (total suspended solids), and pH. This directly affects the biodegradation of the effluent and become environmental pollutant. Thus, there is a need to look for alternative, safe, eco-friendly, and biodegradable colorant source. Natural dyes most appropriately fulfill the demand.

8.2

Sustainability of natural dyes

Sustainability is a complex multidimensional concept of environment, human health, economy, and social impact. Sustainability comprises “the needs of present generation without compromising the ability of future generation.” After the first invention of synthetic dyes “Mouve” the use of natural dyes become a thing of past, only about 1% of total natural dyes are used by traditional dyers, enthusiasts, and hobby groups are the main users of natural dyes who at the cottage level. Some small industries are also using natural dyes, and there are a number of companies who are manufacturing and selling natural dyes both as finely ground plant material as well as purified extracts. Natural dyes are obtained from mostly plant sources, and higher uses of natural dye would lead to planting of more dye-bearing plant which leads to higher carbon fixation in the form of biomass synthesis by plants (Saxena and Raja, 2014). Since they are derived from natural sources, they are biodegradable and renewable. Although the demand for natural dyes is growing very fast, but the characteristics of the colors produced by natural dyes cannot match with the quality of synthetic dyes in two aspectsdcolor palette and cost of production. These challenges need to be overcome in order to popularize larger use of natural dyes. A lot of research is going on all over the world to overcome these challenges.

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00007-4 Copyright © 2024 Elsevier Ltd. All rights reserved.

120

Natural Dyes for Sustainable Textiles

1. Color palette can be modified by using eco-friendly mordants and auxiliaries. The use of nonhazardous mordants such as alum and ferrous sulfate can enhance better dye uptake. The use of biomordants such as chitosan and enzymes (Chairat et al., 2011; Vankar et al., 2007, 2008, 2009; Vankar and Shanker, 2008) have been shown to help in natural dyeing process. Some of the metal accumulator plants like Eurya acuminata and Pyrus pashia have been found to be useful when coextracted with the natural dye-yielding plant. 2. Cost of production can be reduced by the following means: a) By using cheap sources such as directly using agricultural waste, forest waste, waste generated from food and beverage industries, temple waste, and other renewable sources. b) Efficient and fast extraction of the colorant. By developing cheaper and less energyintensive processes for extraction of the colorant from natural sources. c) By practicing modern dyeing processes for better dye uptake and color adherence such as sonicator dyeing (Vankar et al., 2017) and low temperature dyeing (Vankar, Shanker). d) By using biotechnological processes.

For making a sustainable textile process, three aspects have to be kept in mindd they are environmental, economical, and social aspects. Careful selection of natural dyes, their appropriate usage, choice of safe mordants, and above all a sensible chemical management system (CMS). In order to attain sustainability by the use of natural dyes in the textile industry, proper connectivity between the social, environment, and economic must be established. This can be done by upgradation of technology, increasing the productivity, and ensuring constant supply of raw materials. Sustainability cannot be achieved merely by taking only the economic or the environmental aspects. Social obligations are equally important to make a process sustainable. Environmental consideration would further depend on the 3R* principle of reduce, reuse, and recycle. This is where the CMS plays a major role, thereby reducing the pollution load in the environment. How feasible is it to follow the 3R principle in natural dyeing process. If we can replace or reduce the use of metal mordant from 4% to 10% of alum to 0.4% of rare earth (RE) salts, the pollution load due to metal ions will be certainly reduced.

8.3 8.3.1

Environmental consideration in natural dyeing Eupatorium dyeing using rare earth salt as mordant and PA auxiliary

An example of the same can be seen in Table 8.1 where cotton dyeing has been carried out using Eupatorium natural dye. By using 4% alum, the K/S values obtained was 13.75, while with RE salt (yttrium chloride) used in 0.4%, K/S enhanced to 31.49 further more when an eco-friendly auxiliary PA was used as pretreatment, the K/S value drastically enhanced to 54.90 (alum) and 72.79 (yttrium chloride), and the DE value too changed from 11.40 (alum) to 20.39 (yttrium chloride), and with the use of PA, it further changed from 28.47 to 33.49. This confirms two factsd10% lesser amount of RE has shown better result and use of PA has further adsorbed the dye molecules, so lesser load in effluent. This is an example of reduce.

Sustainable processing of textiles

121

Table 8.1 CIELab value of Eupatorium dyed cotton.

S.No

Name

Std 1 2 3

Control Alum PAaþalum Yttrium chloride PAa þ Y C

4 a

K/S INT

La

a

b

C

H

DEa

7.62 13.75 54.90 31.49

75.20 74.52 57.56 57.97

0.85 0.64 7.08 1.21

23.16 33.84 41.09 24.76

23.17 33.85 41.69 24.79

92.14 91.19 80.18 87.16

— 11.40 28.47 20.39

72.79

45.14

4.46

23.93

24.34

79.39

33.49

PA is the auxiliary, used as pretreatment before mordanting.

The best part of the natural dyeing is that the dye bath can be reused by dozing appropriate quantity of natural dye and reused. Table 8.2 shows the effect of the mordants (alum and yttrium chloride) and auxiliary on light and wash fastness properties of Eupatorium dyed cotton swatches. Light fastness that could be achieved by alum þ PA could be achieved by yttrium chloride, while PA pretreatment in the case of latter makes it even better. The result shown in Tables 8.1 and 8.2 clearly indicates that the auxiliary pretreated cotton has shown significantly increased exhaustion of the dye. This is because of cellulose chains having strong ionic attractions between the natural dye Eupatorium and pretreated cotton fabric, and the dye is adsorbed on fiber surface. The kinetics of conventional dyeing has mainly four stages: dye diffusion in bath, adsorption, diffusion into the fabric, and chemical reaction. Due to significant improved affinity for the dye and increased dye concentration on the fabric surface, the auxiliary pretreated cotton has an increased concentration gradient for diffusion of the dye into the fabric. The increase in concentration gradient is accelerating the dye diffusion. Between the two mordantsdalum and yttrium chloridedthe oxophilicity of Yþ3 is far better than Alþ3 owing to the hard Lewis acid character and large ionic radius. REþ3 ions prefer to bond with hard Lewis base donors, such as F, O, and N, and to have high coordination numbers. Colorants present in the leaves of Eupatorium adenophorum are mainly flavonoids such as Apigenin, Rhamnetin, Luteolin, Quercetin, Kaempferol, Tamarixetin, and

Table 8.2 Fastness properties of Eupatorium dyed cotton fabrics. S.No

Name

Washing fastness

Light fastness

Std 1 2 3 4

Control Alum PA*þalum Yttrium chloride PA* þ Y C

3e4 3e4 4e5 4 5

3 3 5 5 5e6

122

Natural Dyes for Sustainable Textiles

Dihydrokaempferid. Structurally they are best suited for metal mordanting as shown in Fig. 8.1 given below. Eupatorium leaves extract also has Eupafolin which can offer dual chelation site to the rare earth metal (REþ3) as shown in Fig. 8.2. The stronger chelation of the metal salt with the colorant results in better dye uptake and dye adherence. Thus the effluent has lesser load of metal salts. This is an eco-friendly dyeing process ideally suited for commercial bulk dyeing process houses. By using biodegradable natural resource as natural dye and by conserving the biodiversity, one can aim at sustainable natural dyeing unit. We have a vast biodiversity in India; at different altitude, different dye-yielding plants are available, and by proper tapping of the natural sources, it is possible and feasible to derive at sustainable solution in textile industry. Any sustainable system is governed by three verticalsdenvironmental considerations, economic impact, and social importance (Fig. 8.3).

8.4

Economic impact through sustainable natural dyeing

Economic impact through sustainable natural dyeing refers to value addition to the dyed fabric by natural dyeing, consumer’s choice, and requirement and eventually that impacts the economic growth of the natural dye manufacturers. The demand of natural dyed fabric will surely reflect in the economic growth of the textile industry.

Figure 8.1 Flavonoid components of Eupatorium.

Sustainable processing of textiles

Figure 8.2 Dual chelation site of Eupafolin present in Eupatorium.

Figure 8.3 Sustainability and its three major components.

123

124

Natural Dyes for Sustainable Textiles

More and more natural dye manufacturers are now coming up with newer dyes derived from natural sources.

8.5

Social importance

Natural dyes are cheap because they are easily available in plenty and decompose easily in nature. These dyes are easily decomposed in nature after using, and they do not pollute the environment while destroying them after end use. These dyes are collected from natural resources, and there are no elaborate manufacturing processes involved in their preparation. Textiles, both natural and synthetic, when dyed with natural dyes provide excellent feel. They have nontoxic and nonallergenic characteristics, thus do not harm to the tender skin of infants. Some of the natural dyes have wonderful capabilities to protect our skin from ultraviolet radiation. Shades created by natural dyes are shooting to humane eye, comfortable, and soft feel. Dyers working with natural dyes do not face any health hazards. At the same time, consumer’s health safety is also assured by using natural dyes.

8.6

How can one make natural dyeing sustainable?

In order to meet the global requirements of the fashion industry, use of good dye receptive textile material, high fixing dye molecules from the natural dye source, efficient chelating mordant, low MLR dyeing machine for better exhaustion of the colorant, as far as possible to design eco-friendly dyeing method along with well-planned supply chain, management can make a sustainable textile dyeing industry. Meticulous management and proper understanding about the eco-friendly approaches starting from the materials selection to supply of the finished garments to the market are required. In the sustainability of the dyeing industries for the smooth supply of fashion garments, the factors discussed below play a major role. There has been a drive that researchers and academicians are incessantly working on technologies which are sustainable and at the same time can reduce the pollution load in the textile industry, because conventional dyeing consumes large quantities of chemicals, energy, and water. Textile fibers, both manmade and natural, have several impurities, and removal of these impurities by chemical treatment or noninvasive techniques is a challenging task for scientists. To be able to develop a suitable technology which would be overall energy-efficient, cost-effective, and sustainable dyeing process is definitely not an easy task. Translation of a sustainable technology from laboratory to commercial set up depends on many factors such as their economy, ease of operation, and technological know-how about the dyeing. Development of natural dyes for green textile products by adapting sustainable technologies can lead to revival of natural resources, which is the basic need of future generations.

Sustainable processing of textiles

8.7 8.7.1

125

Water-less dyeing processes Nebulization technology for dyeing

The micronebulization system is a novel finishing system for garments like jackets, dresses, jeans, t-shirts, and shirts. There are several possibilities for finishing the garments such as softening, dyeing, and functional effects. The technology is very simple. The nebulization process converts air in nanobubbles, which transport along with water the other functional product’s mixture, creating a homogeneous atmosphere. Nanobubbles surface get into the fibers, contacting them with the finishing products. This equipment can be connected to a conventional washing machine/dryer. The diameter of nanobubbles is smaller than 200 nm which gives larger contact surface to the nanobubbles. Advantages of nebulization technology are savings, not only in terms of chemicals, energy, and water used, as well as lesser load of wastewater produced (Shukla and Vankar, 2018).

8.7.2

Smart foam technology

Smart foam is the new technology that makes water saving easy as blowing bubbles. Through an innovative patented technology, smart foam has the goal of revolutionizing garment finishing. The system is designed to minimize natural resource consumption, particularly water and dyes, making sustainable garment production easy and accessible. To treat garments in any kind of exhaust dyeing machine, smart foam introduces foam as a new carrier of dyes and dyeing auxiliaries. It can be used to create a variety of finishes starting from traditional finishes to unique and specialized finishes. Smart foam greatly reduces the consumption of water and energy. Compared to traditional dyeing processes, the application of chemicals through smart foam allows savings of up to 80% of water. All the treatments are performed at room temperature, therefore reducing the energy required. When combined with Garmon certified chemicals, they are known to give excellent results (https://re-fream.eu/portfolio/micronebulization-technology%E2%80%8B/) (Fig. 8.4). When the smart foam machine was used for natural dyeing of jacket using this technology, the following result was obtained (Fig. 8.5): Compared to nebulization systems, smart foam is up to three times faster to load chemicals in the washing machine, and it doesn’t require a sealed equipment, allowing technicians to interrupt finishing treatments and check garments with safety and ease. Any type of washing machinedfrom the traditional to the advanceddcan be utilized with the smart foam equipment and process.

8.7.3

Spray dyeing

A newly developed sustainable spray dyeing system has been developed by Lin et al. (2021) (https://www.garmonchemicals.com/en) for cotton fabric in the presence of

126

Figure 8.4 Smart foam machine supplied by Garmon.

Figure 8.5 Garment dyed through smart foam technology.

Natural Dyes for Sustainable Textiles

Sustainable processing of textiles

127

Figure 8.6 Mechanism of spray dyeing.

reactive dyes, which has the potential to minimize the textile dyeing industries environmental impact in terms of water consumption and save significant energy. The results suggest that fresh dye solution can be mixed with an alkali solution before spray dyeing to avoid the reactive dye hydrolysis phenomenon. After that, drying at 60e100 C, wet fixation treating for 1e6 min, and combined treatments (wet fixation þ drying) were sequentially investigated and then dye fixation percentages were around 63%e65%, 52%e70%, and above 80%, respectively. The results will encourage carrying out additional experiments with a new system in the presence of other kinds of dyes such as direct dye, acid dye, base dye, and so on to improve dye fixation rate onto cotton fabric using this spray dyeing technology. Moreover, the developed dyeing process may reduce chemicals and water consumption in textile industries (Fig. 8.6).

8.8

Conclusion

For attaining sustainability in the field of dyeing, use of natural dyes in the textile industry can provide the answer through low-cost sourcing, efficient extraction, and sensible chemical management of natural colorants and mordants. This would certainly bring down the cost of production of natural dyes along with conserving the biodiversity. It can provide value addition to the waste biomass and its utilization before final composting. This will not damage the environment. Metal mordants can be replaced by biomordants and auxiliaries. Some of the water-less dyeing methods such as nebulization dyeing, smart foam dyeing, and spray dyeing have been described which may directly or indirectly influence the wastewater management, thus making the dyeing process sustainable.

128

Natural Dyes for Sustainable Textiles

References Chairat, M., Darumas, U., Bremner, J.B., Bangrak, P., 2011. Coloration Technology 127 (5), 346e353. https://re-fream.eu/portfolio/micro-nebulization-technology%E2%80%8B/. https://www.garmonchemicals.com/en. Lin, L., Zhu, W., Zhang, C., Hossain, Md, Oli, Z., Pervez, M.N., Sarker, S., Hoque, M., Ikram, U., Cai, Y., Naddeo, V., 2021. Combination of wet fixation and drying treatments to improve dye fixation onto spray-dyed cotton fabric. Scientific Reports 11, 15403. Saxena, S., Raja, M.S., 2014. Roadmap to Sustainable Textiles and Clothing, vols. 37e80. Springer, Singapore. Shukla, D., Vankar, P.S., 2018. Curcuma dye with modified treatment using chitosan for superior fastness. Fibers and Polymers 19, 1913e1920. Vankar, P.S., Shanker, R., 2008. Ecofriendly ultrasonic natural dyeing of cotton fabric with enzyme pretreatments. Desalination 230 (1e3), 62e69. Vankar, P.S., Shanker, R., Verma, A., 2007. Enzymatic natural dyeing of cotton and silk fabrics without metal mordants. Journal of Cleaner Production 15 (15), 1441e1450. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S.C., 2008. Ecofriendly sonicator dyeing of cotton with Rubia cordifolia Linn. using biomordant. Dyes and Pigments 76 (1), 207e212. Vankar, P.S., Tiwari, V., Singh, L.W., Potsangbam, L., 2009. Sonicator dyeing of cotton fabric and chemical characterization of the colorant from Melastoma malabathricum. Pigment and Resin Technology 38 (1), 38e42. Vankar, P.S., Shukla, D., Wijayapala, S., Samanta, A.K., 2017. Innovative silk dyeing using enzyme and Rubia cordifolia extract at room temperature. Pigment and Resin Technology 46 (4), 296e302.

Further reading Vankar, P.S., Shanker, R., June 2009. Eco-Friendly Pretreatment of Silk Fabric For Dyeing With Delonix Regia Extract, 125, pp. 155e160, 3.

Effluent management from natural dyeing unit 9.1

9

Introduction

Management of the effluent generated from the textile processing is one of the most technologically challenging issues in textile industries. Globally the textile mills and their wastewater have grown in proportion due to the increasing demand of textile products, causing a major pollution problem. Most of the chemicals used in the textile wet-processing like synthetic dyes and auxiliary chemicals which are hazardous to the environment and human health. The only solution to this global environmental problem can be solved by the use of natural dyes replacing synthetic dyes and hazardous processing chemicals which cause water pollution in the discharged untreated effluent, by safer analogs. Due to the rise in industrial production of textiles originating from natural or manmade synthetic fabric, there has been a big demand of water for processing these textiles. Conventional water treatment plants find it a very challenging job to properly manage the wastewater generated by textile industries causing serious environmental challenges. The untreated dye-containing wastewater when discharged into water bodies has detrimental impact on aquatic ecosystem. Due to the heavy load of nonbiodegradable metals and aromatic dyes, the aquatic organisms and fish species get killed. Dyeing is a technique for the coloration of the fabric. Dyeing can be done at any stage yarn, or even sometimes finished products like garments and apparel. If synthetic dyes are replaced by natural dyes, they would also provide colored textiles. The dyeing process is more or less similar, that is, the interaction of a dye with fiber, as well as the migration of dye into the internal section of the fiber. During the dyeing process, not all of the dye is bonded to the fiber, and some dye remains in the dye bath, which is discharged with effluents. Therefore, the dyes should fix to the fabric well so that the effluents have least amount of unfixed dye which would not be harmful to the environment. To ensure these properties, the substances that give color to the fiber requirement show high affinity, uniform color, resistance to fading, and be economically feasible.

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00009-8 Copyright © 2024 Elsevier Ltd. All rights reserved.

130

Natural Dyes for Sustainable Textiles

9.2 9.2.1

The environmental benefits and impacts of natural dyes Biodegradable, nontoxic, and hypoallergenic

Some of the key environmental benefits of natural dyes include: •

•

•

They are fully biodegradable, which means that they will eventually degrade naturally without releasing any hazardous toxins into the effluent and the dye bath solution can be easily used for horticulture watering without having any adverse effect on the soil or environment. As these natural dyes are extracted from plants, they are safe and nontoxic. Natural dyes are made fully from sources such as plants and insects, which make them nontoxic to those who are exposed, and they do not release any harmful by-products into the environment like the synthetic dyes. Natural dyes are usually hypoallergenic, which means they are less likely to cause any allergic reactions when skin is exposed to them. This is ideally suited for infants and old people, particularly for those with sensitive skin conditions.

9.2.2 •

• • • •

The environmental benefits and impacts of metal mordants

Metal mordants are required for natural dyeing process as they act as bridging head between the fabric and the colorant molecules. Some of the conventional metal mordants used in natural dyeing are alum, ferrous sulfate, stannic chloride, stannous chloride, and rarely copper sulfate and potassium dichromate (Vankar et al., 2009). Tannic acid, oxalic acid, and citric acid are other mordants sometimes used in natural dyeing (Oktav Bulut et al., 2014). Most natural dyes are able to form metal complexes (Bhattacharya and Shah, 2000) and thereby produce different shades (hues). Conventional metal mordants can be replaced by biomordants and enzymes (Shanker et al., 2007; Shanker and Vankar, 2008; Shukla et al., 2017; Vankar et al., 2008). Conventional metal mordants can be replaced by rare earth (RE) metal salts (Gangwar and Vankar, 2021a,b, 2022).

Based on the quantities of metal mordant, its adverse effect could be assessed. Conventional metal mordants are usually used in 4%e10% (OWF), but biomordants and enzymes are required in lesser quantities 0.5%e1.0%(OWF). Even RE metal mordant salts are required in 0.4% (OWF). The same effectivity can be seen in lesser percentage as shown in the following table. Alum-mordanted and RE-mordanted results of natural dyeing with Rheum emodi dye have been discussed.

9.2.3

How do natural dyes fit into the future of sustainable fabric production?

The statistics recorded in 2019 of carbon emissions and waste water generation show that the fashion industry has been shown to be responsible for 10% of annual global

Effluent management from natural dyeing unit

131

carbon emissions, and around 20% of wastewater comes alone from fabric dyeing and treatment. These are shocking values; therefore, it is extremely important to address the problems in order to make sustainable fabric production. Apart from having significant eco-benefits such as protecting the environment, the use of natural dye also helps to support communities and local industries of each region, providing safe jobs for local workers and offering them a healthy option to gain economic growth. It is well established fact that the textile industry cannot completely switchover to the use of natural dye. However, smooth transition to move toward more sustainable methods of fabric production is required in today’s time in order to be able to slowly and deliberately adapt these production methods. From the consumer’s perspective, they also have to accept that clothing that is naturally dyed may not be exactly like synthetically dyed, but they can still be earthy, beautiful, and bold. The use of natural dye plays a major role in the sustainable fabric production process. All textiles companies which are into textile processing involving dyeing should seriously consider switching to natural dyeing methods for the benefit of their workers and the planet. The demand from consumer can drive the brands to invest in developing naturally dyed fabric/garments. This is the most appropriate way toward sustainable fabric production. Natural dyes however have poor dyeability as compared to their synthetic analogs, and thus they need auxiliaries such as metal mordants. Minimizing the use of metal salts can take care of the sustainability. Our effort in this direction has been by to lower the concentrations of metal salts in order to avoid their excess in dye effluents.

9.2.4 9.2.4.1

How to reduce the ill effects of metal mordants? Toxic index study for rare earth salt mordants

We were also interested to find out the traces of RE salts on the fabric as well as on effluents.

9.2.5 • •

Total digestion method analyzed by MethodeDIN EN 1671-I is 313.9 mg/kg. Perspiration method analyzed by MethodeDIN EN 16711-II is 0.558 mg/kg.

9.2.6 • •

Cotton-dyed fabric treated by cerium salt (when we used 1% mordant solution)

Now we are using only 0.4% mordant solution of rare earth salts

Total cerium content in the used mordant solution is 1.09 mg/kg. Total yttrium content in the used mordant solution is 0.78 mg/kg.

132

Natural Dyes for Sustainable Textiles

We can definitely use RE metal mordants safely during natural dyeing of fabrics. This makes natural dyeing sustainable and safe for both human beings and environment. The use of biomordants or enzymes in natural dyeing is another alternative, wherein biomordants are used in less than 1% and enzymes are used in 0.5% OWF.

9.3

Ill effects of textile wastewater on the environment

As we all know that the processing houses of the textile mills discharge a huge amount of the effluent which contains hazardous and dangerous substances that harm the environment. Textile effluents often show toxic effects on aquatic plants and animals. When such hazardous effluents are released into the air, water, or on land, they cause higher health risks. The problem caused by the dyeing process is still bigger, as the volumes of effluents are very high. These effluents are complex combinations of various substances such as synthetic dyes and heavy metals, and if these effluents are not effectively treated, they can pollute the nearby water bodies severely. Textile wastewaters generated from different stages of textile processing comprise huge amounts of toxins that are significantly harmful to the environment if released without suitable treatment.

9.3.1

Sources and causes of textile effluent

The total distribution of the textile effluent comes from dyeing, printing, and finishing stages of the textile effluents, and it has been found that 45% of effluent is produced in preparatory, 33% in dyeing, and 22% in finishing processes. Water pollution occurs due to the dyeing and printing effluents. The increasing demand for dyed products with synthetic dyes has caused the production of huge quantities of wastewater. The synthetic dyes do not degrade and stay longer time in the environment due to their high thermal and photostability. Currently, the water consumption for a dyeing process varies from 30 to 150 L/kg of cloth, depending on the type of dye and substrate. Washing of the dyed fabric also contributes to the water pollution problem, and about 17%e20% of water pollution comes from the textile dyeing process. It is reported that after treating one ton of cotton fabric, the effluent has 200e600 ppm BOD, 1000e600 ppm of total solids, and 30e50 ppm of suspended solids contained in a volume of 50e160 m3 (Moustafa, 2008). Thus if synthetic dye is replaced by natural dyes, it can bring down these values tremendously. Methods for better color exhaustion, safe dye auxiliaries, and natural dyes can make the natural dyeing process very sustainable. These can be checked by measuring the amount of dye in the dye bath at the start and finish of natural dyeing. This can be used to calculate the dye fixation. If the chemical bonding between fiber and natural dye molecule is good, then there will be less discharge of unfixed dyes. By means of process optimization, one can reduce color loads in the effluents. Proper choice of the natural dye having chelating groups, appropriately suited mordant, and use of safe auxiliaries can make all the difference and benefitting wet

Effluent management from natural dyeing unit

133

Figure 9.1 Curcumin coordinated by RE salts.

textile processing making it sustainable. The natural biodegradability of natural dyes is an advantage. New technologies have been developed for the past few decades to reduce the effluent load, energy, processing cost, and manpower as well as increase the process efficiency and reproducibility, which play an important role in its sustainability (Ammayappan et al., 2016). Due to the oxophilicity of RE metals, the turmeric dye molecule curcumin is well coordinated with the RE metal salt as shown below in Fig. 9.1.

9.3.2

Chemical parameters measurements of wastewater of prime importance

Effluent management of dye house can only be managed through efficient reduction in biochemical oxygen demand (BOD), chemical oxygen demand (COD), control over dissolved oxygen (DO), pH, and alkalinity. Since natural dyes are biodegradable, it is possible to manage these parameters easily.

9.3.2.1

Biochemical oxygen demand

BOD is a parameter that reflects the quantity of oxygen required to biochemically oxidize organic materials in water. Once biodegradable organic matter like natural dyes and natural auxiliaries are released into water, microorganisms feed on the wastes, breaking into simpler substances. This decomposition further produces stable end products (CO2, SO4, PO4, and NO3) and draws down the DO content of water. Formic acid has been often used as an efficient, inexpensive, and eco-friendly reagent which is capable of neutralization and achieving a low BOD with a small amount of water.

134

Natural Dyes for Sustainable Textiles

9.3.2.2

Chemical oxygen demand

COD is the amount of oxygen required to oxidize organic materials contained in a water sample with a powerful chemical oxidizing agent.

9.3.2.3

Dissolved oxygen

The amount of oxygen present in water in the dissolved state is referred to as dissolved oxygen. If the amount of DO reduces below 4e5 mg/L, then forms of life that can survive begin to reduce. Thus, DO is a water quality component that proper concentration is essential not only to keep the living organisms but also to sustain species reproduction, vigor, and the development of populations. Aquatic life cannot survive in the absence of sufficient oxygen. This effluent discharge standard showed that effluent must contain 4.5e6.0 mg/L of DO before discharge into a surface water body. As per discharge standard, the minimum DO must be 4.50 mg/L.

9.3.2.4

pH and alkalinity

Alkalinity neutralize acids caused by this alkalinity. The presence of calcium, magnesium, sodium, potassium, carbonates, and bicarbonates, and it is the capacity of water to neutralize acids caused by the. The acidity and alkalinity of water are measured by pH. If wastewater is alkaline and has a pH greater than 7, it needs to be neutralized before it can be released.

9.4

Effluent treatments

Effluent treatment of the natural dyeing units do need the same series of water treatment processes which includes mixing and treatment of all the wet-processing units. Whether the effluent is generated from natural dye unit or synthetic dye units, they need to be treated before discharge (Kim, 2013). Therefore, the textile industry needs a “paradigm shift” from wastewater treatment to resource optimization. For the sake of economic and environmental benefits, recycle and reuse in textile manufacturing (Elimelech and Phillip, 2011) should be practiced.

9.5

Conclusion

Textile effluent treatment generated from natural dye unit contains less toxic compounds that have good biodegradability. Natural dyes replacing synthetic dyes, harsh detergents being replaced by nonionic detergents, ecofriendly auxiliaries in place of hazardous ones, mordants being replaced by biomordants, RE salts or enzymes which are used to improve the textile process are either used in minimal quantities or replaced by safer agents. The textile manufacturing industry thus became eco-friendly in its overall textile processing. There has been a great drive to work on waterless technologies by textile industry experts to reduce water consumption in the industry.

Effluent management from natural dyeing unit

135

Chan et al. (2002) studied the performance of waste-extracted natural dyes and mordants with respect to the environment, and they have been able to verify that when compared to the traditional mordants containing heavy metals, the former are safer. It was found out by them that the COD/BOD5 ratio of these waste-extracted natural dyes was approximately 2, which is considered as the most desirable ratio for effluent treatment. Moreover, the absence of restricted heavy metals in natural mordants enhances their application in dyeing process. The results of BOD5 shown by Chan et al. that the traditional mordants containing heavy metal did not affect the performance of bacteria during the degradation of the organic matters in the biochemical process. As well as they found out that the organic matters originated from natural dyes are the dominant factor to determine the BOD5 values. From environmental point of view, the COD/BOD5 ratio of most of the dyeing processes using natural dyes in conjunction with natural mordants is near 2, implying that the natural dye effluent is highly environmentally biodegradable and treatable. Although eggshell contains a lot of calcium, its presence in the dye effluent does not impose adverse effect on the environment. On the contrary, the amount of copper, iron, and chromium detached from the premordanted fabric does exceed the ceiling of acceptable limit required by world standards. In conclusion, the use of waste-extracted natural mordant to replace harmful traditional mordants is feasible and can offer a partial answer to ecological environment that demands attention and exploration.

References Ammayappan, L., Jose, S., Arputha Raj, A., 2016. Sustainable production processes in textile dyeing. In: Muthu, S., Gardetti, M. (Eds.), Green Fashion. Environmental Footprints and Eco-Design of Products and Processes. Springer, Singapore. Bhattacharya, S.D., Shah, A.K., 2000. Metal Ion Effect on Dyeing of Wool Fabric With Catechu, 116, pp. 10e12, 1. Chan, P.M., Yuen, C.W.M., Yeung, K.W., 2002. The effect of Natural dye effluent on the environment. RJTA 6 (1), 57e62. Elimelech, M., Phillip, W.A., 2011. The future of seawater desalination: energy, technology, and the environment. Science 333 (6043), 712e717. Gangwar, A., Vankar, P.S., 2021. Surface modified Rare earth mordanted cotton, dyed with Eupatorium extract. BTRA Scan (3), 7e11. VolL. Gangwar, A., Vankar, P.S., 2021. Improved Fastnesses through modified Turmeric dyeing using Rare earth salts as mordants. BTRA Scan (4), 6e9. VolL. Gangwar, A., Vankar, P.S., 2022. Better dyeability in Natural dyeing of Silk using Rare earth (RE) salts as mordant. BTRA Scan (2), 4e9. VolLI. Kim, J.K., 2013. Using Systematic Design Methods to Minimise Water Use in Process Industries. In: Handbook of Process Integration (PI). Moustafa, S., 2008. Environmental impacts of textile industries. In: Process Analysis of Textile Manufacturing. UNESCO-IHE, Delft. Oktav Bulut, M., Baydar, H., Akar, E., 2014. Ecofriendly natural dyeing of woollen yarn using mordants with enzymatic pretreatments. The Journal of The Textile Institute 105 (5), 559e568.

136

Natural Dyes for Sustainable Textiles

Shanker, R., Vankar, P.S., 2008. Enhancement of dye uptake by enzymes in natural dyeing. Desalination 230, 62e69. Shanker, R., Verma, A., Vankar, P.S., 2007. Enzymatic natural dyeing of cotton and silk fabrics without metal mordants. Journal of Cleaner Production 15 (15), 1441e1450. Shukla, D., Wijayapala, S., Vankar, P.S., 2017. Innovative Silk dyeing with Rubiacordifolia extract using enzymes. Pigment & Resin Technology 46 (4), 296e302. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S.C., 2008. Sonicator dyeing of cotton with Rubiacordifolia Linn. using biomordants. Dyes and Pigments 76 (1), 207e212. Vankar, P.S., Shankar, R., Wijayapala, S., 2009. Utilization of temple waste flower-tagetus erecta for dyeing of cotton, wool, and silk on industrial scale. Journal of Textile Apparel technology and Management 6 (1), 1e15.

Sustainable measures taken in natural dyeing units 10.1

10

Introduction

The textile industry is the second most polluting industry in the world. Synthetic dyes contribute to a major part of this pollution, with nearly 20% of global water pollution being linked to the textile dyeing processes (Morlet et al., 2017). The main contributors to this problem are the use of nonbiodegradable petroleum-based colorants to dye textiles, the use of toxic agents to fix colorants on the textiles, and the release of large proportions of these colorants and fixation agents into the surrounding ecosystem. In the wake of strict environmental regulations, industries are now looking into greener ways to color clothes. One such potential alternative is natural dyes. These are sustainable and cover the area of green chemistry. Natural dyes never pollute like synthetic dyes as they are obtained from the renewable resources. Some natural dyes have very good color fastness properties. Synthetic dyes incline to remain quite steady to general oxidation and reduction processes as per their scheming and so are very tough to remove from the wastage of textile industries which is the main reason for their discontinuation. On contrary, natural dyes are biodegradable without the application of any oxidant or reductant agents. If the synthetic dyes are degraded as byproducts, those are directly or indirectly confirmed to be health risks. But, it is tentative that the natural dyes totally degrade under natural conditions in a healthier way (Alam et al., 2020). Although viable alternative to synthetic colorants are natural colors extracted from biodegradable plant sources, however, toxic fixation agents still need to be used with these colorants (Mogilireddy, 2018). The effluent generated by using synthetic dyes causes environmental problems, and it is categorized as hazardous wastes as the degradability of most of the synthetic dyes is poor. In contrast, the use of natural dyes is reported to produce fewer pollutants and degrades easily. However, natural dyes need mordants for improving the quality of the dyeing process; some of them are heavy metals which may release hazardous pollutants. Altogether, textile and fashion industries are now in search of alternative coloring methods and new techniques. A “bio-based dyeing” has been developed with more benefits such as safe, eco-friendly, durable, and also cost-effective with natural dyes (Gudulkar, 2021). In order to claim that the use of natural dyes promotes the sustainable textile industry, it is challenging but not impossible to find alternative sources of mordant-like materials that are environmental-friendly. Textile dyeing mills are striving hard at all levels to conserve natural resources and energy. Owing to the demands of global consumers, research is being carried out to establish new eco-friendly technology. Problems related to toxicity and other health hazards have resulted in the replacement of chemical processing by more eco-

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00010-4 Copyright © 2024 Elsevier Ltd. All rights reserved.

138

Natural Dyes for Sustainable Textiles

friendly physical methods (Denton and Daniels, 2002). Plasma, biotechnology, ultrasonic treatment, supercritical carbon dioxide, and laser technologies, for example, are technologies which are gaining ground because they offer many advantages against wet techniques with fewer or no harmful chemicals in wet processes or waste water. As the textile industries are the backbone of human civilization, all efforts are made to improve its sustainability. The use of eco-friendly textile materials, dye and chemicals, adaptation of new, improved processes with strict process controls, and waterless dyeing are some of the ways by which sustainability can be improved. Sustainable textiles should be environmentally friendly and should satisfy the rational conditions to respect social and environmental quality by pollution prevention or through installation of pollution-control technologies (Choudhury, 2015). It has been reported that biomordants (Bulut et al., 2014; Vankar et al., 2007; Vankar and Shanker, 2008; Vankar et al., 2017, 2008), enzymes (Vankar and Shanker, 2008; Vankar et al., 2017), and tannins (Hossain et al., 2018) could replace metal mordant for dyeing process using natural dyes. The use of natural dyes in the textile industry based on economic, environmental, and social aspects apart from sustainable dyeing processes can be used on commercial scale. Sustainable textiles should be environmentally friendly and should satisfy the rational conditions to respect social and environmental quality by pollution prevention or through the installation of pollution-control technologies. Sustainability of textile processing can be improved by several ways such as: 1. Substitution of unsustainable textile materials and chemicals by greener organic and biodegradable materials. 2. Elimination or minimization of the use of toxic chemicals in production and packing. 3. Minimization of the use of water and chemicals and recycling them. 4. Minimization of consumption of energy and fuel in production and transport. 5. Minimization of waste and easy waste disposal. 6. Maintaining environmental management systems strictly (Choudhury, 2022).

Traditional dyeing and finishing methods can influence the environment in an adverse manner. That is the reason why there is a necessity for sustainable approaches in current times. Some of the sustainable approaches like: plasma technology, nanotechnology, and ultraviolet (UV) technology are implemented in the textile industry for the betterment of our environment. As a result, sustainable dyeing and finishing processes in the textile industry have earned a lot of attention, for the emerging concept of sustainability. Sustainable dyeing process in textile industry: The natural dyeing has to fulfill the following features in order to be sustainable process: 1. Good exhaustion of the colorant from the dye bathdvarious dyeing techniques have been adapted for natural dyeingdexhaust dyeing, soft flow dyeing, foam dyeing, waterless dyeing, plasma dyeing, and spray dyeing are a few methods being currently used. 2. Minimal use of metal mordant and other processing auxiliaries. 3. Easy method of dye effluent treatment. 4. Recycling the wastewater for reuse.

Sustainable measures taken in natural dyeing units

139

10.1.1 Exhaust dyeing Exhaust dyeing process is also termed as batch or direct or coordinate dyeing. Direct dyeing involves the direct application of dye to fabric without the help of any fixing agents. This process is called exhaust because the dye molecules slowly get transferred from a comparatively large volume dye bath to the substrate or material that is to be dyed. The exhaust dyeing process is used for staple fiber dyeing. Yarn and fabric could also be dyed by exhaust dyeing method. Dye solution or dye bath is produced by dissolving the dyestuff according to required liquor ratio. Then textile material is immersed in to the dye first solution. Initially the surface of the fiber is dyed when dyes contact with the fiber, then the dyes entered in the core of fiber. Proper temperature and time are maintained for diffusion and penetration of dyes molecule in the fibers core. The traditional exhaust dyeing with madder dye is shown in Fig. 10.1. Several steps are involved in exhaust dyeing as first stage (dissolving and dispersion of the dye), followed by adsorption, during adsorption, diffusion takes place, and finally migration of the dye into the fabric (Gudulkar, 2021).

10.1.2 Continuous soft flow dyeing Continuous soft flow dyeing process typically consists of the dye application, dye fixation with heat or chemicals, and finally washing. Various sequential operations are used for the continuous dyeing of fabric. An initial padding stage is common to all sequences. The model of continuous soft flow machine is shown in Fig. 10.2. It involves immersion of the fabric in the dye liquor contained in a tank of set volume. A liquor ratio as low as 1:20 may be used; in general, low-substantivity dyes are used in continuous dyeing process. The vigorous agitation of fabric and dye formulation in the cloth increases the dyeing rate and uniformity (Fig. 10.3). 1. In soft flow dyeing machines, the fabric is transported by a stream of dye liquor. 2. These machines use a jet having lower velocity that used on conventional jet dyeing machines.

Figure 10.1 Exhaust dyeing by traditional method using madder.

140

Natural Dyes for Sustainable Textiles

Figure 10.2 Model of continuous soft flow dyeing machine.

Figure 10.3 Catechu dyeing on continuous soft flow.

A soft flow dyeing machine is suitable for dyeing a wide range of knitted and woven constructions of fabric in rope form. This machine is very useful for the dyeing of lightweight woven fabrics and pile fabrics like terry towels.

Sustainable measures taken in natural dyeing units

141

Advantages of soft flow dyeing machine: 1 2 3 4 5

The soft flow dyeing machine minimizes liquor usage. The soft flow dyeing machine avoids fabric distortion, pilling, and creasing. Improved rinse efficiency results. Tensionless fabric movement helps to improve warp-wise fabric shrinkage after washing. Low dye chemical cost results in soft flow dyeing due to low material liquor ratio.

10.1.3 Foam dyeing Foam dyeing is an attractive alternative to traditional dyeing methods due to the potential environmental benefits and supply chain savings. The main dyeing element in this process is foam, using air instead of water to carry the chemistry or dye onto the fabric. Foam is the key factor in foam dyeing process. Foam is a dispersion of a gas in a liquid. Here water is used as liquid phase, and the gas usually as air. A wet processing which uses air in the form of dispersion foam is also referred as foam finishing. By foaming the concentrated treating liquor, its volume is considerably increased, thereby minimizing the problem of uniform distribution over the fabric. The foam is attaching onto the fabric to ensure that there is no excess liquor which must be removed and recycled. Foams are formed using foaming agents, and usually foam is obtained from aqueous solution which is then spread on the textile material. These foaming agents must produce foam immediately, should be unaffected by temperature, should be quickly wetting, and the foam should be able to stabilize itself (Sivaramakrishnan, 2015). Foam may be of dispersion foam or condensation foam. Dispersion foam is mixing of gas with the liquid, while condensation foam is producing gas within the liquid physically or chemically. In continuous foam processing, chemicals or dyes are formulated with a foaming agent in a more concentrated dispersion. The formulation is mechanically foamed, increasing its volume 5e20 times. The resultant foam is applied as a coating on the fabric, and the coated fabric is passed through squeeze rolls which collapses the foam and distributes the chemicals uniformly through the fabric. The fabric then enters the drying oven as before, but the water to be evaporated is 65% less as compared to the conventionally dyed fabric. Through a combination of higher line speeds and lower dryer temperatures, energy consumption can be reduced anywhere between 40% and 70% (Sivaramakrishnan, 2015). A classic example of foam dyeing by Annato natural dye has been shown in fig. 4.

10.1.3.1 The continuous methods of foam dyeing have the following steps: a. A good system for foam generation. b. Uniform way for foam application on to the substrate. c. Even foam distribution along with diffusion of the dye liquid into the substrate, by the foam collapse active substance are released. d. Fixation of the active substance.

142

Natural Dyes for Sustainable Textiles

Figure 10.4 Foam-dyed garment using natural dye Annato.

10.1.3.2 Advantages of foam dyeing 1. 2. 3. 4. 5.

Fixation of dye into fiber seems to improve. Diffusion of dye into fiber is likely to get enhanced. Stability of the dyed fiber is better. Better outcome in short time duration of application. It is an energy-saving process with lesser waste generation (Fig. 10.4).

10.1.4

Spray dyeing technology

Textile wet processing industry is one of the highest water-consuming industries. More than 20% of today’s industrial pollution is the result of the textile coloring treatment, which is accompanied by more than 70e80 toxic chemicals. To reduce these water contaminations, a new technology called “spray dyeing” has been introduced. This method is a kind of waterless for dyeing; instead, it employs air to enter into fibers. In this method, the fabric is first heated and then the dye is injected directly into the fibers in the form of gas. The outcome of this technology is more beneficial than any other conventional dyeing methods. The color after spray dyeing process results in rich look and shows good durability in terms of washing.

10.1.4.1 Advantages of spray dyeing ⁃ The spray dyeing uses 90%e95% less water and 80%e85% less energy than conventional fabric dyeing processes. ⁃ Rarely only 1%e2% of spray-dyed fabrics are damaged during this process. ⁃ It gives maximum color durability. ⁃ No posttreatment or finishing is required in this process.

The spray dye process radically reduces the environmental pollution arising for colored effluents. By being a unique method of color application on fabric, it is best suited for regions that lack the water resources. As the traditional processes require good amount energy to heat the water and to dry the dyed fabric, spray dye technology

Sustainable measures taken in natural dyeing units

143

Figure 10.5 Denim jacket dyed by Indigo through spray dyeing method.

also significantly reduces the energy requirements. It is expected that as spray dye technology matures, more additional benefits by the direct application of dye without the intermediacy of a donor fixative can be envisaged. Spray dye is a new technology for improving the process of coloration of textiles. It is a clear response to an increasing awareness of the environmental impacts associated with traditional dyeing process prevalent currently. An example of spray dyeing is the use of Indigo to dyefinished clothing (denim jacket (Fig. 10.5)).

10.1.4.2 Modification in use of metal mordants Natural dyes are used alone for textile dyeing, but the fastness and shading assessment of the colored materials often do not yield acceptable results. To improve the fastness, brilliancy, and shading properties, metallic mordants are being used. Metallic mordants are inorganic salts of metal atoms that attach to the dye to improve the bonding between the dye and the fabric used, thereby improving the colorfastness performance. Aluminum potassium sulfate, stannous chloride, ferrous sulfate, and copper sulfate are some of the most used mordants. Their presence creates wastewater having ample amount of used metal species; thus, they can be possible threat to sustainability. Their use has been dejected throughout the textile world. Metal mordants are currently being replaced by biomordants, enzymes, and organic acids like tannic acid and citric acid. The use of biomordants can significantly reduce the metal load of the dye effluent (Vankar et al., 2008). Eurya acuminate and Pyrus pashia are two metalaccumulating plants having aluminum and copper, respectively; these plants when coextracted by dye-yielding plant can give sufficient metal ion species to do effective mordanting (Vankar et al., 2008; Kumari et al., 2020). The use of rare earth salts like cerous sulphate, lanthanum chloride, and yttrium chloride in just 0.4% owf has proven to be the most innovative technology in metal mordanting method (Gangwar and Vankar, 2021a,b, 2022). This is due to the stable

144

Natural Dyes for Sustainable Textiles

Figure 10.6 Metal chelation sites for cis and trans conformers of Indigo.

coordination bonds between the RE salt, natural dye, and fabric. On the other hand, it is ascribed to the interaction of the multiple complexes formed by rare earth ions (Ce, La, and Y) and natural dyes which enable the dyed fabrics to resist color fading. The rare earth metal chelation has been shown with Indigo dye in Fig. 10.6. The high coordination capability of the rare earth metal has been the cause of better dye uptake. Different natural dyes have been demonstrated to show better dyeing results with RE salt as compared to conventional mordants. Even the quantity of rare earth mordant required to get desired results is 1/10th quantity of the conventional mordants, thereby directing toward lesser effluent load. Thus the use of rare earth mordant has good prospects in the natural dyeing of these fabrics. Dyeing of cotton and silk fabrics was carried out with 15 natural dyesdnamely Indigo, Maddar, Rheum, Punica, Lac, Leafy green, Henna, Turmeric, Yeliona, Myrobalan, Red Sandal, Walnut, Eupatorium, Turmeric, and Catechu using all the three RE salts mainly to check the dye compatibility with the RE salt and also to demonstrate the improvement in dye uptake by the use of the one RE salt. Each of the natural dye showed unique reactivity toward a particular RE salt (Table 10.1).

10.1.4.3 Ease of dye effluent treatment As natural dyes are biodegradable, the dye effluent can be easily used for irrigation and horticulture purposes as their chemical composition do not necessarily hamper the soil chemistry. To reduce the impact of textile process pollution, practices like sustainable dyeing, the use of new and less polluting technologies, effective treatment of effluent, and recycling waste processes need to be adapted. Many new technologies have been developed for easy and efficient dye effluent treatment. Sustainable biotreatment of textile dye effluent water by using earthworms through vermifiltration has been developed (Kannadasan et al., 2021).

Sustainable measures taken in natural dyeing units

145

Table 10.1 Natural dye compatibility with different RE salts. SlNo

Natural dyes

Compatible RESalt

1 2 3 4 5 6 7 8 9 10 11 12 13

Madder (Rubia) Eupatorium Rheum emodi Punica Myrobalan Dry walnut Turmeric Red sandal Catechu Leafy green Lac (nimbus) Henna Yeliona

YCl₃ YCl₃ Ce₂(SO₄)₃ YCl₃ YCl₃ YCl₃ LaCl₃ YCl₃ YCl₃ YCl₃ Y₂O₃ YCl₃ LaCl₃

Recycling and reuse: One advantage with natural dyes is that the dye bath can be reused after balancing the dye content in the dye bath. Also, sometimes redyeing is recommended, as in the case of natural dyeing with indigo, redyeing was carried out to get darker shades (Fig. 10.7).

Figure 10.7 Redyeing with Indigo for getting darker shades.

146

Natural Dyes for Sustainable Textiles

In a study, the utilization of waste black tea leaf (BT)-based tannin brown natural colorant for silk dyeing using microwave treatment has been carried out. Dye (tannin) has been isolated in various media before and after microwave treatment up to 6 min and applied at various conditions. It is inferred that waste black tea leaves (BTs) in an aqueous medium have an excellent potential to serve as a source of natural tannin brown dye for the coloration of surface-modified silk fabrics under the influence of cost, energy, and time-effective microwave treatment. Additionally, the utilization of a low amount of sustainable chemical and biomordants has valorized the dyeing of silk by developing soothing and sustainable shades with good fastness properties (Hayat et al., 2022). Another study of natural dyeing technique for the mordanting and dyeing of polyester fabric with natural henna dye using the advanced technology of microwaves. For providing a complete “green” and eco-friendly dyeing process, lemon was used as a natural biomordant with microwaves and results were compared with conventional mordanting method followed by the natural henna dyeing of polyester fabric with microwave. Microwave technique clearly reduced the mordanting and dyeing time upto 60%e65% with improved fixation and color characteristics (Arain et al., 2021). Bio-based dyes for textile dyeing have been widely studied on account of their environmentally friendly approach, but in order to be considered as an ecofriendly dyeing concept, additional parameters need to be considered. The purpose of this study was to improve a textile (polyester) dyeing process with madder dye (Rubia tinctorum L.), from an eco-sustainable point of view determining the environmental impacts associated with the dyeing process, at research lab scale. The identified hotspots were: the solvent and energy use for madder dye extraction and the liquor:fabric ratio in the dyeing phase. The reduced impacts from both hotspots were needed in order to perform the best in all impact categories studied. Indeed, decreased solvent and energy consumption by ultrasound-assisted dye extraction reduced the global warming potential, photochemical ozone creation potential, and air acidification, while minimized water consumption in the after-wash of the dyed fabric was a promising option for improvement in water depletion and eutrophication (Agnhage et al., 2017). Some natural dyes have very good color fastness properties. Several plants used in the dyeing process are documented, together with their taxonomic characteristics; local names; how the dyes are produced and fabric dyed; the colors obtained; in addition to how various patterns are designed. Sustainable utilization of this important renewable natural resource is needed. In addition, the methods used to obtain these dyes and to dye fabric, together with the techniques used to produce various patterns on fabric need to be documented (MacFoy, 2004).

10.1.4.4 Natural dyeing innovations Current dyeing innovations can help reduce water usage, replace wasteful practices with efficient and cost-effective ones, and attempt to completely transform the way in which the dyes have been used that give clothing the beautiful colors admired by everyone.New sustainable advancements that enhance the dye ability are ultrasound, ozone, plasma, UV, gamma illumination, laser, microwave, particle implantation, air-dye, and other waterless technologies (Gudulkar, 2021). These innovations can

Sustainable measures taken in natural dyeing units

147

very well be adapted with natural dyes as processes involve avoids excess dyes with harsh chemicals and no wastewater is created in them. Waterless technology in which liquid carbon dioxide is used seems to be best suited technology for natural dyes as due to its high permeability, the dyes are transported easily and deeply into fibers, creating vibrant colors on to fabric. CO2 is abundantly available and can even be captured from industrial processes in a cluster. After dyeing, most of the CO2 is recovered and can be reused. This technology eliminates water use in dyeing and prevents water pollution. Other technologies like plasma, microwave, and air drying are also paving their way in the local natural dye units. New technologies make way for more cost-effective, resource-efficient, and sustainable natural dyeing alternatives and auxiliaries. Innovation in dyeing technologies ranges from pretreatment of cotton, pressurized CO2 dye application, and even creating natural pigments from microbes. There are not the only companies blazing a trail in this most fascinating of areas, but they are certainly two to watch, as their processes continue to be developed and refined. The first company is Switzerland-based Archroma; the second is England-based Colorifix. Both companies make the use of natural hues but in very different ways. Archroma has created a limited palette of dyes derived from nonedible agricultural and herbal waste, capable of replacing petrol-based raw materials, while Colorifix uses microorganisms to grow color based on natural DNA codes including from plants, animals, and insects that can be applied to textiles without added chemicals. Both innovations open up a myriad of possibilities for forward-thinking dye houses that could potentially build elements of more natural dyeing into their existing operations (Filarowski, 2022). Another aspect of sustainability is theme “Vocal for Local,” in which locally grown dyes should be popularized and used. Major brands should endorse color palette of locally grown dyes, thus encouraging native dyes grower. Locally grown dyes provide a local market and sustainable income for local people in the region. Buying clothing that has been dyed with local dyes through local supply chains contributes to a healthy eco-system and helps to sustain local jobs, in turn providing economic stability for an entire community. This allows them economic stability without having to move far away to look for work or be exposed to unethical and unsafe working conditions through factory work such as used in the mainstream textile industry.

10.2

Conclusions

Recently, awareness about eco-friendliness in apparel textiles has become one of the important issues. Increasing cognizance globally about organic sustainable products has caused transformed concern of consumers toward the usage of textiles dyed with eco-friendly natural dyes. The precise choice of mordants and natural dyes having most appropriate coordination and high exhaustion of the dye could be facilitated. If the dye effluent has less amount of dye in the used dye bath, very rigorous treatment is not required which eventually is cost effective too. Rare earth salts as mordants which are used in 0.4% as compared to the conventional metal mordant which are

148

Natural Dyes for Sustainable Textiles

used in 4%e10%; this can be a very safe and sustainable dyeing technique. Some of the sustainable approaches like: plasma technology, nanotechnology, and UV technology are implemented in the textile industry for the improvement of environment. As a result, sustainable dyeing and finishing processes in the textile industry have received a lot of consideration. Governments should encourage industrialist to adopt latest technologies and the use of latest equipment like water-saving and chemical-saving equipment. There should be schemes where businesses can get some tax benefits or subsidies on purchase of such equipment. Intensive research with established R&D labs should be promoted for easy solutions that can easily be embraced by domestic units. Natural dyes are attractive in nature, and their production can really benefit local communities who work with textiles, helping to preserve the native environment as well as the health of their community and workers and create stable jobs for indigenous people. People have started to recognize the benefits of using plant dyes once again: leading to a novel golden age for natural dyes with natural constituents and the progressing concept of sustainability. As the existing palette is limited, agricultural waste can be processed to use as a replacement of synthetic dyes. They will definitely be versatile and bring soothing earthy shades into limelight which will definitely be liked by consumer. This will certainly increase the limited palette of natural dye as sometime complained by industrialists.

References Agnhage, T., Perwuelz, A., Behary, N., 2017. Towards sustainable Rubia tinctorum L. dyeing of woven fabric: how life cycle assessment can contribute. Journal of Cleaner Production 141, 1221e1230. Alam, S., Islam, S., Akter, S., 2020. Reviewing the sustainability of natural dyes. Advance Research in Textile Engineering 5 (2), 1050. Arain, R.A., Ahmad, F., Khatri, Z., Peerzada, M.H., 2021. Microwave assisted henna organic dyeing of polyester fabric: a green, economical and energy proficient substitute. Natural Product Research 35 (2), 327e330. Bulut, M.O., Baydar, H., Akar, E., 2014. Ecofriendly natural dyeing of woollen yarn using mordants with enzymatic pretreatments. The Journal of The Textile Institute 105 (5), 559e568. Choudhury, A.K.R., 2022. Sustainability in Textile Processing. Choudhury, R., 2015. Development of eco-labels for sustainable textiles. In: Roadmap to Sustainable Textile and Clothing: Regulatory Aspects and Sustainability Standards of Textiles and the Clothing Supply Chain, pp. 137e174. Denton, M.J., Daniels, P.N., 2002. Textile Terms and Definitions. Textile Institute. Filarowski, A., 2022. Innovation for Sustainable Dyeing. Gangwar, A., Vankar, P.S., 2021a. Improved fastnesses through modified Turmeric dyeing using rare earth salts as mordants. BTRA Scan 50 (4). Gangwar, A., Vankar, P.S., 2021b. Surface modified, rare earth mordanted cotton, dyed with Eupatorium extract. BTRA Scan 50 (3). Gangwar, A., Vankar, P.S., 2022. Better dyeability in natural dyeing of silk using rare earth (RE) salts as mordant. BTRA Scan 51 (3).

Sustainable measures taken in natural dyeing units

149

Gudulkar, P.S., 2021. Sustainable Dyeing Methods in Textile Industry. Hayat, T., Adeel, S., Batool, F., Amin, N., Ahmad, T., Ozomay, M., 2022. Waste black tea leaves (Camelia sinensis) as a sustainable source of tannin natural colorant for bio-treated silk dyeing. Environmental Science and Pollution Research 29 (16), 24035e24048. Hossain, A., Samanta, A., Bhaumik, N., Vankar, P., Shukla, D., 2018. Non-toxic coloration of cotton fabric using non-toxic colorant and nontoxic crosslinker. Journal of Textile Science & Engineering 8 (5), 374. Kannadasan, N., Balasubramanian, B., Palanisamy, T., Shanmugam, S., Pushparaj, K., AlDhabi, N.A., Arasu, M.V., Narayanan, M., 2021. Sustainable biotreatment of textile dye effluent water by using earthworms through vermifiltration. Journal of King Saud University Science 33 (8), 101615. Kumari, M., Gahlot, M., Rani, A., 2020. Extraction of natural dye from the leaves of Wild Himalayan pear (Pyruspashia) and optimization of the dyeing parameters using BoxBehnken Design (RSM). Journal of Applied and Natural Science 12 (4), 497e503. MacFoy, C., 2004. Ethonobotany and sustainable utilization of natural dye plants in Sierra Leone. Economic Botany 58 (1), S66eS76. Mogilireddy, V., 2018. Sustainable Dyeing Innovations: Greener Ways to Color Textiles. Morlet, A., Opsomer, R., Herrmann, S., Balmond, L., Gillet, C., Fuchs, L., 2017. A New Textiles Economy: Redesigning Fashion’s Future. Ellen MacArthur Foundation. Sivaramakrishnan, C.N., 2015. Foam Dyeing and Finishing: A Step towards Sustainable Processing of Textiles (industry-article). Vankar, P.S., Shanker, R., 2008. Ecofriendly ultrasonic natural dyeing of cotton fabric with enzyme pretreatments. Desalination 230 (1e3), 62e69. Vankar, P.S., Shanker, R., Mahanta, D., Tiwari, S., 2008. Ecofriendly sonicator dyeing of cotton with Rubia cordifolia Linn. using biomordant. Dyes and Pigments 76 (1), 207e212. Vankar, P.S., Shanker, R., Verma, A., 2007. Enzymatic natural dyeing of cotton and silk fabrics without metal mordants. Journal of Cleaner Production 15 (15), 1441e1450. Vankar, P.S., Shukla, D., Wijayapala, S., Samanta, A.K., 2017. Innovative Silk Dyeing Using Enzyme and Rubia Cordifolia Extract at Room Temperature. Pigment and Resin Technology.

This page intentionally left blank

Traditional block printing for sustainability 11.1

11

Introduction

Textile printing is one of the most important and versatile methods among the methods used to design and colorize textile fabrics. Ancient men and women mixed the colorants such as coal or soil with oils and used them with their fingers in lines on various materials. The staining of the plant extracts and fabrics has provided different approaches. The patterns can be produced by the wax applications to provide resistant dye liquor, or the surrounding areas provide a tightly attached and reserved area. The word print is referred to a process that uses pressure to impart colorant to the material. And there is no doubt that the first textile printing was occurred by the blocks with embossed printing surfaces, then these blocks were inked and printed on the fabric. Some of the first blocks were made of clay or terracotta, while others were made of carved wood (Yıldırım et al., 2020). Printing textiles can be a cheaper way of incorporating different colors and designs than weaving or knitting the patterns into the fabric. Once a fabric has been prepared, there are a variety of printing techniques and methods that can be used to achieve the desired results. There should be a combination of technical information, design considerations, and business aspects, all of which must be taken into account when selecting designs, colors, and printing techniques for textiles (Ujiie, 2015).

11.2

Traditional textile printing

The term printing signifies the production by various means of colored patterns or designs on textile material rather than woven, embroidered, or painted designs. It’s probably the cheapest method of ornamenting textile materials and is very popular because of its beautiful effect. The fabric is printed with one or more vibrant colors, in particular, sharply defined patterns, instead the whole cloth is uniformly covered with one color by exhaust process by direct, discharge, and resist methods. Nowadays, textile printing uses specific methods, techniques, and machines (Screen printing, digital ink-jet printing, or the usage of thermal transfer processes or transfer printing). Time, productivity, flexibility, and creativity are unique features of contemporary methods in textile printing (Hada and Meena, 2022).

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00003-7 Copyright © 2024 Elsevier Ltd. All rights reserved.

152

11.3

Natural Dyes for Sustainable Textiles

Block printing

Block printing refers to the printing technique of pressing and stamping fabric with carved wooden blocks filled with color. “Hand block printing” is other term that refers to block printing. It is a method of printing on a fabric with the help of carved wooden pieces dipped in a dye. Among the traditional crafts of India which have stood similar with the evolution over time is the art of hand block printing. The age of old art in India conveys its expression in different forms and different regions such as Kalamkari from Andhra Pradesh, Ajrakh from Gujarat, Bagru, Daboo, Sanganeri from Rajasthan, and so on. Each form of these arts has achieved perfection by skilled artisans and comprises distinct patterns and palettes. The art of block printing has encouraged various craftsmen to develop such art under the rule of Mughals and created a number of motifs that are still used. The rhythmic print of patterns and the grace of dyes add charm to the weaving story of block prints (Fabriclore, 2022). The block printing process goes beyond pressing blocks onto fabric. There are so many steps involved, from carving each wooden block to preparing fabric, mixing dyes, and applying final touches. Each block printing technique requires artistry, skill, and patience. It is the sum of these tasks that produces gorgeous block-printed fabrics. Block printing is a confluence of human culture, tradition, and nature. It responsibly delivers environmentfriendly textile art that answers the need of the hour for sustainable fashion (Cluny, 2021). Every aspect of this process involves sustainable practices. Block printing requires the low consumption of resources and optimized use of natural dyes to embrace sustainability and authenticity and thus resulting in a lesser carbon footprint.

11.4

The block printing process

It is the earliest, simplest, and slowest of all methods of textile printing. Block printing by hand is a slow process. It is, however, capable of yielding highly artistic results, some of which are unobtainable by any other method. The process is long and tedious, and has following simple steps: 1. Prewashing the fabric The fabric is first soaked in water for 24e48 h to remove some of the starchiness of the fibers and then laid out to dry in the Sun, which also acts as natural bleach. 2. Carving the blocks The design to be printed is first drawn on paper and then transferred to a block of wood. The design itself is usually a traditional Indian motif. The wooden block needs to be perfectly smooth and may be sourced from a variety of trees, such as mango wood or teak. It is maintained 2e3 inches thick to prevent warping. It is oiled in order to soften and hold color, and smoothed before the design is carved into it. 3. Dyeing the fabric The fabric is dyed its base color. Then it is spread flat on a surface and affixed firmly with pins to prevent any movement of the fabric that could result in smudges. 4. Printing The artisan mixes four to five basic, natural colors and creates many dyes. The carved block is then dipped into the dye and pressed firmly on the fabric. Since it requires a firm

Traditional block printing for sustainability

153

pressing, the stamp is either hit by hand or a hammer. This process requires the steadiest hands and is repeated over and over until the design covers the fabric. If more than one color has to be used, the artisan will allow each color to dry before applying the nextdeach with a new stamp. This is an extremely labor-intensive procedure, requiring a lot of time and precision to ensure the pattern that emerges is uniform. 5. Final washing and drying of the fabric Once the color has set, the fabric is washed thoroughly in the river and sun-dried. Sundrying is sustainable, minimizing energy consumption, and thereby leaving a much smaller carbon footprint when compared to other manufacturing processes. 6. Quality check A final quality check is carried out after which the fabric is cut and sewn into garments (Cluny, 2021).

11.5

Techniques of block printing

There are only three widely used techniques of block printing in India: • • •

Direct printing, Resist printing, and Discharge printing

Direct printing sees the fabric bleached first, then dyed, and finally printed using carved blocks (first the outline blocks, and then to blocks to fill in color). The most common style of printing textile fabric is direct printing. The dye is directly applied onto white fabric or colored fabric. The printed portion is significantly darker than the dyed background. The direct style of printing is used in block printing, screen printing, or roller printing methods. Resist printing requires some areas of the fabric to be protected from the dye, which are shielded with the use of clay and resin. The dyed fabric is then washed, but the dye spreads through the protected areas, causing a rippled effect. Resist printing involves the application of wax, mud, or some other substance, which becomes a pattern after the fabric is dipped in dye and the resist material is washed away. After dying, the material attached to the fabric to resist the dye is removed. The seepage of dye into the edged of the resist areas creates a tonal effect. The tonal effect thus produced is subtle and soft. Next, further use of blocks adds desired designs. The last technique of discharge printing, on the other hand, sees the use of chemicals to remove portions from dyed fabric which are then filled in with different colors (Gandhi, 2019). In discharge printing, the artisan removes color from a piece of fabric, creating a lightened effect to create and reveal a pattern. Basically, all these printing process are for bringing together a design idea and one or more colorants with a substrate (usually a cloth) using a method for applying the colorants with precision in any pattern or motifs.

11.6

Types of hand block prints

With a printing tradition dating back to ages, India is host to a wide variety of textile arts and the handicrafts sector in India has been one worth mentioning. Different

154

Natural Dyes for Sustainable Textiles

regions boast of different textures, styles, and techniques, and each has a different method along with a unique output. Each has a distinct style which is easily recognizable when worn. The entire concept of printing has undergone a complete revolution, and currently, the industry is blooming and following are different kinds of block printing techniques in India that deserve to be preserved, promoted, and appreciated (Saree.com, 2021). It is good to know that almost all of these printing techniques generally use natural colors and other natural/green auxiliaries (mud, clay, resin, etc.) making whole printing process ecologically sustainable. 1. Bagh This is an indigenous printing technique from the state of Madhya Pradesh. It essentially refers to a technique of block printing by hand where the colors used are absolutely natural. 2. Kalamkari Distinct kinds of cotton hand-printed or block-printed material; kalamkari originates in the state of Andhra Pradesh. 3. Ajrakh A particular kind of block printing from the western states in India where they display designs made using block printing by stamps. 4. Bagru Being popular Jaipur in Rajasthan, the printing technique is laborious but produces exquisite results. 5. Daboo Dabu or daboo originates in Rajasthan and is a beautiful mud-resist hand block printing technique. It survived the test of time with some difficulty and is a time-consuming printing technique involving many phases and a great amount of labor. 6. Sanganeri Sanganeri, a kind of block printing that originated in Rajasthan, adorns home decor materials as well as apparel (Saree.com, 2021).

Hand block printing has been recognized as a craft through generations in different clusters in the country. Each cluster follows its distinctive style and methods, and uses locally available natural materials and motifs of some specialty. Two most important block printing art are “Bagru” and “Dabu” which are centuries-old traditional art of hand block printing still alive. Bagru is famous for its Syahi-Begar prints and Dabu prints. The former are designs in a combination of black and yellow ochre or cream. The latter are prints in which portions are hidden from the dye by applying a resist paste.

11.7

Bagru printing

Bagru printing is said to have started around 450 years ago. It is an ancient art. The villager of Chippa, a traditional community used this art for printing fabrics by hand. These traditional people came from different districts of Rajasthan such as Alwar, Madhopur, Jhunjhuna, and permanently settled at Bagru. These people were well-known for their distinctively unique design using different natural colorants. The base color of Bagru print is off-white, and the colors used were from natural

Traditional block printing for sustainability

155

resources. They had their own way of preparation of the colorant. The main natural colors are prepared in typical manner. The Chippas have their own block typical designs. Traditionally the cloth is prepared in certain mannerdtheir unique collections of the block are considered to be the actual wealth of Chhipa’s that they have collected over a period of time. The fabric is then soaked in fuller’s earth and then dipped into turmeric water to get a tone of yellow color. The cloth to be printed is soaked in the solution of clay and other chemicals to make the fabric soften and then dried before used for printing. Neat stamping is foremost to get the appealing prints. Then the dyed fabric is stamped with the beautiful designs known as blocks. The base color of the fabric is usually the dull shades such as white, cream, and beige and natural colors. After printing, the cloth is left for drying in the Sun for a final touch-up. Bagru printing is a traditional hand block printing method. The printing is done using natural dyes. The colors are achieved through mixtures of flowers, tree barks, roots, and clay. Though the industry has flourished over the years, there is a great imbalance between the popularity of industry and the state of artisans. The introduction of synthetic dyes has also created more problems for the artisans creating a disparity among the craftsmen leading to more commodification and disengagement among the artisans (Meitei and Ahemad, 2022).

11.8

Dabu printing

Essentially a hand block printing technique, dabu has been revitalized over the years, making it as relevant to the world today as it was during the ancient times thanks to its fine-drawn allure and the intricate modus operandi of its production. With its roots in the 675 AD, dabu printing is believed to have first made its way to Rajasthan in India from China. The name of the technique is said to have been derived from either the Gujarati word “dabu” or the Hindi word “dabaana”, both of which connote “to press.” “Dabu or Daboo” is block-printed mud-resisted traditional textiles in dark earthy tones of stunning designs and conventional patterns on natural fabrics in which carved wooden way on wooden/metal blocks are stamped using mud-resist print techniques. Dabu printing is a long-standing tradition, usually passed down through a lineage, and the practicing families are mostly concentrated in one region as Akola in Rajasthan (Foundation, 2021). It is different from Ajarakh prints in terms of lime replaced by black clay (Mud). Dabu is a precious wooden block of printed fabric that ought to be protected. Hand block printing for fabric has been around for centuries and transforms each piece into a unique one.

11.9

The traditional process of Bagru printing

Bagru block printing process makes use of natural dyes and eco-friendly materials to produce beautiful, sustainable products that last for generations. These designs are

156

Natural Dyes for Sustainable Textiles

printed by hand onto cotton cloth using natural dyes. This process is slow and requires great attention to detail as opposed to modern, industrial printing methods that produce high volumes at a much faster rate. This traditional technique relies on natural dyes and is predominantly done on indigo or blue base fabric. Its trademark design is an amalgamation of geometric patterns and animal/bird motifs. The motifs are comparatively larger as well as bolder. Historically, water was scarcely available in this region due to which resist printing was preferred. This brought out a reddish tinge in the Bagru block prints. The traditional process of preparing Bagru print is quite easy and it looks like the practice and working of printing with natural dyes or elements which contains a critical series of steps as follows: (a) initial preparation of raw cloth by removing different types of dirt, oil, and starch present as impurities. This is done by washing the cotton fabric by a mixture of soda ash, sesame oil, and cow dung. After washing, the cotton cloth is treated with myrobalan (Harda). The treated fabric is dried in the Sun. The purpose of harda treatment of cotton fabric is to hold the metal on fabric by reaction with tannin present in harda. This metal ion is then subsequently available for reaction with the coloring component/s of the vegetable dyes applied subsequently by dyeing or printing techniques. (b) Making of dyes or natural colors: The dyestuffs are mixed in a printing tray which has fixed size 25 cms/35 cms. First a bamboo frame known as Tati is put inside the tray. On top of that, a layer of Kamali is placed, which is a woolen cloth. The dye solution is prepared by mixing the color into the Binder and is then poured into the tray, where it gets soaked by the woolen cloth. After these preparations, printing of the fabric starts. Nowadays the village community made a new initiative to reuse the used water for recycling or charging inside the ground. There are mainly two types of printing used in Bagru: direct dye printing and resisting printing. In both of the procedures, firstly the blocks are soaked with refined oil or mustard oil overnight and then washed. Printing is done on wooden table, the size of which depends on the length of to be printed (18 foot approx.). These tables have a layer of ply on which there are 20 layers of tart and a sheet of cloth on which comes the final fabric.

11.10

Direct dye printing

In the very first process, the dye solutions need to be poured in the tray. The printer presses the block into the dye tray and then onto the cloth until the pattern is complete. For every imprint, the block is pressed into the tray to get a fresh smear of paste. The outline pattern is done in blocks for the background and highlights in different colors. Once each pattern is complete, the cloth is ready for the dye. The cloth is dyed in a dyed solution if white base is not required (Figs. 11.1 and 11.2). The outline pattern is done in blocks for the background and highlights in different colors. This printing is by using another darker dye. In the first process, the dye solutions are poured in the tray. The printing process begins with raw, gray cotton cloth which is either hand-woven or mill-made. The cloth is treated with several different

Traditional block printing for sustainability

157

Figure 11.1 Direct dye printing samples.

Figure 11.2 Direct dye printing samples.

auxiliaries (for example: bleaching) to make it softer and more absorbent. The swelling of fibers and opening the pores in order to absorb the printing paste uniformly ensures that the dyes will be colorfast and bright. After this, the fabric is given a primary creamish-yellow color (pila karma) by applying harda (myrobalan) solution. This solution is invariably a solution of harda powder in water without any addition of oil. The cloth is then dried in the Sun and is ready to start printing. Once the cloth has been printed, it is dried in the Sun and finally ready for dyeing. The cloth is dyed either in a hot dye bath in a copper vessel or a cool dye vat dug in the ground. For the hot dye, the copper vessel or Tamda is filled with various combinations of a red dye traditionally made from madder root mixed with Dabudiya flowers, and other vegetable and mineral dyestuffs and fixations. Indigo dyeing: The cool sunken vat, called Math, is reserved for Indigo dyeing which imparts shades of blue. The vat is dug about 2 m deep into the ground and is filled with indigo, lime, molasses, and water. The dyer may dip the cloth several times for a deeper shade of blue or dry it for further Dabu printing to retain light blue and then later redye it.

158

Natural Dyes for Sustainable Textiles

Figure 11.3 Resist printing with Indigo.

11.11

Resist printing

A different type of printing technique of resist style is called “DABU” printing, which is primarily dependent on resist mechanism. The printing is carried out with specially prepared “Dabu” paste, then a thick black mud paste is applied on the cloth, and then finally the fabric is dyed. Each family follows its own recipe to create a distinctive Dabu print (Fig. 11.3).

11.12

New era with “Bagru” print for modern consumers

Customers are increasingly aware of their responsibility toward the environment and society, now days. That’s why slow and sustainable fashion is on the rise, with an increasing demand for natural fabrics, traditional printing techniques using natural or vegetable dyes, and timeless designs. Block print is a confluence of human culture, tradition, and nature. It responsibly delivers environment-friendly textile art that answers the need of the hour for sustainable fashion (Cluny, 2021), with the demand of new consumers befitting their modern lifestyle, culture, habits, etc. The village Chippas has also modified the Bagru print designs with different kinds of garments meant for men and women including household tapestry. Bagru can be print in any type of clothing. Basically, cotton fabric is being used for Bagru print. Different motifs have been developed apart from the traditional ones (Fig. 11.4). All the motifs are first carved on wooden blocks which are made by craftsmen called Kharaudi. They specialize exclusively in the skill of hand-carving the designs on the blocks and do not use the electric machinery. They work with their traditional tools which include a ruler, compass, saw, and wooden maller. Wooden blocks of teak wood are used for printing the design which is soaked in oil overnight and then washed before putting it to use. Each design usually requires a set of several different blocks, including an outline (rekh), a background (gad), and filler (datta). Hand block printing

Traditional block printing for sustainability

159

Figure 11.4 Different modern motifs of Bagru.

is a complex and labor-intensive craft that involves a variety of skills at different stages: carving the block (usually done by craftsmen), preparing the cloth, mixing the dyestuffs, and finally the printing, dyeing, and washing steps, which may be repeated several times to obtain a final color and design. Traditional main patterns carved on the blocks are: (1) Patashi with its tiny floral designs of buds, leaves, and stems. (2) Jhad with its intertwining tendrils and distinctive border lines. (3) Hathidthe elephant design and many more.

Different types of motifs used in Bagru printing are Aath Kaliya, Chopard, and Kamal.

11.13

Washing

Once the printing and dyeing are complete, the cloth is again hand-washed and sundried. This completes the whole process of block printing. It is a labor-intensive process that requires a lot of skillfulness, time, and tolerance power of artisan.

11.14

Process chart of Bagru Printing

Raw fabricdCow dung, soda ash, sesame oil treatment for scouring, preparation of solution of three ingredients in water, and then the raw cloth is kept for two days in that solution. After washing in sufficient floating water and constant sun bleach in open sunlight, the impurities are removed and the cloth is ready for the next step. This process is called Sun Bleach-cum Scouring process. Myrobalan treatmentdthe scoured cloth is dyed in myrobalan solution and dried in open sun. Concentrated thick

160

Natural Dyes for Sustainable Textiles

paste of three ingredientsdalum, red soil called Geru, and natural gum is prepared in water and printed with traditional wooden block. Printed cloth is beaten on stone by dipping in water twice or thrice to ensure that there is no gum in the printed portion of the cloth. This process is called degumming process. Degummed cloth is dyed with madder, Dabudiya Flowers, and other natural auxiliaries in the hot solution of these ingredients still the required red shade comes, and finally postmordanting with alum gives the desired shade.

11.15

Batik printing

It is another example of resist printing using wax as the resist material unlike mud as used in Bagru printing. Traditional printers used natural colorants which could be more than two to three colors keeping the base color as white. The colors are used in the increasing order of their intensities protecting the previous color by wax application on the desired spots and finally the fabric is washed in boiling water and soap to remove the wax and the unreacted dye. A sample of batik is shown in Fig. 11.5. Another method of dyeing and printing is tie and dye, where the motifs are created by tying the fabric and then immersing in dye solution. Fig. 11.6 shows a tie and dye technique applied on silk fabric. Batik is a technique of wax-resist dyeing applied to whole cloth or cloth made using this technique. Batik is made either by drawing dots and lines of the resist with a spouted tool called a canting or by printing the resist with a copper stamp called a cap. The applied wax resists dyes and therefore allows the artisan to color selectively by soaking the cloth in one color, removing the wax with boiling water, and repeating if multiple colors are desired. A tradition of making batik is found in various countries, including Indonesia, Singapore, Malaysia, India, Bangladesh, Sri Lanka, and Nigeria.

Figure 11.5 Batik printing sample.

Traditional block printing for sustainability

161

Figure 11.6 Tie and dye.

Besides this, the other motifs used are floral, spiral, geometrical, and figures like fishes are used for batik printing and tie and dye. A batik creation involves three basic stepsdwaxing, dyeing, and scraping or removing. In the first step, wax is used to create designs on certain predefined areas on the fabric. After this, the fabric is dyed and the wax is removed by scraping, or by boiling the cloth so that the wax peels off. Today, there is no one single community involved in the production of batik clothes. While the techniques used have evolved over time and the screen printing method is used to create beautiful designs, there are still many clusters where batik is still a manual painstaking craft which results in unconventional and lovely patterns (Roy et al., 2014). Typical batik printing method was suggested in which dye solution was prepared by adding appropriate quantity of inorganic salts or mordants (5e10 gm/L) to the aqueous solution of natural colorants and kept for 30 min at room temperature in order to complete the reaction to form colored lake. This was followed by the impregnation of waxcoated cotton fabrics at room temperature for 5e10 min, dried and steamed at 102 C for 30 min in a cottage steamer. In another method, cracks were created on the dyed fabric. In this case, the application of aqueous solution of natural colorants in the presence of inorganic salts or mordants was done following a pad-dry technique. For the above purpose, the impregnation of the cotton fabric in solution containing Allium cepa and aluminum sulfate was performed at nearly 100% wet pick up in a miniature lab model two bowl padding mangle. The impregnated fabric was dried and subsequently coated with paraffin wax. This wax-coated fabric was then crushed for creating crack effects and again immersed in another solution containing Terminalia chebula and ferrous sulfate for 5e10 min, followed by drying and steaming (Mauliket al., 2014).

11.16

Screen printing

It is another printing method used for printing cotton and silk by using traditionally designed screens. Figs. 11.7 and 11.8 show screen printing on silk and cotton fabrics.

162

Natural Dyes for Sustainable Textiles

Figure 11.7 Screen printing of silk using natural dyes.

Figure 11.8 Screen printing of cotton using natural dyes.

Screen printing using natural dyes in India has helped in creating bridge between conventional printing techniques and mass production of textiles in an efficient way. It has been shown that the screen printing on cotton and silk fabrics using indigo, madder, and sappanwood has resulted in promising colors and also can be considered as the recommendable alternative to harmful synthetic dyes. Screen printing using natural dyes in India has helped in creating bridge between conventional printing techniques and mass production of textiles in an efficient way (Samantaet al., 2020). Natural dyes such as madder, sappanwood, and indigo are used under optimized temperature, pH, and duration for extraction. The cotton and silk substrates are prepared for screen printing by scouring the fabrics. Screens were developed based on the patterns obtained by conventional shibori dyeing techniques. During printing process, madder, sappanwood, and indigo dye extracts were used to

Traditional block printing for sustainability

163

provide color (Kavyashree, 2020). More often it is assumed that color will change depending on printing methods and the substrate used. But in natural dyes, this expectation is somewhat high, and especially in printing processes, the effect of mordant type is of great importance for the shade of the color as printing is totally a different approach compared with dyeing of textiles. As a sustainable approach toward screen printing, mordants and binding agents used were natural. 20% alum is used with madder and sappanwood extraction as a meta-mordanting agent. Tamarind kernel powder is used as a thickening agent for madder and sappanwood. Cornstarch is used as a thickening agent for indigo. The trials were undertaken to screen print silk fabric with Butea monosperma flower dye extract using natural thickening against, that is, cassia seed gum and mango kernel gum with two mordants. Copper sulfate and ferrous sulfate were selected for the experiments. The screen-printed samples were studied for color fastness properties and CIE Lab values. Screen-printed silk samples with both the mordants exhibited very good to excellent fastness rating for light, washing, rubbing, and perspirations. The results revealed that silk fabric can successfully screen printed with natural dye and natural thickening agents (Babel and Gupta, 2016). Printing ink was prepared with different dye concentrations and used it to print by flat screen printing technique on two papers made of Japanese knotweed stem and on two commercial papers as well as on cotton and polyester fabrics. The color of the prints was evaluated spectrophotometrically, and the fastness of the printing inks on different printing materials was analyzed. The research results confirmed the usefulness of the natural dye derived from the Japanese knotweed rhizome for printing, especially on papers whose prints showed very good rub resistance, its application for printing on textiles was observed to be limited due to its lower fastness to wet treatments such as washing, wet rubbing, and wet ironing. The natural dye is resistant to fading under the influence of light, but its color becomes darker (Klancnik, 2021).

11.17

Preservation of block printing

Traditional block prints possess artistic and decorative with purity and richness of color is still very demandable and used by many consumers and fashion brands. Traditional craft reflects the cultural, socioeconomic, historical behavior of the society. So it has to be conserved with two propositions: the preservation from misuse and commercialization and modification of craft by the contemporary environment. All the block printing art forms like Dabu and Bagru are the treasured block-printed textiles that need to be preserved. So drawing out the entire process would be enormously useful and, more significantly, provide a path for the preservation for complete illustration and write up about motifs, tool, techniques, colors, and history (Muthu, 2017). The conservation needed precise documentation of the craftwork, its chronology, procedure, motifs, vibrant colors, and by-products (Hada and Meena, 2022). This is a product created by hand, using a technique that focuses on precision, skill, and time. The painstaking effort that goes into each stage of the block printing process is fully deserving of

164

Natural Dyes for Sustainable Textiles

our recognition and appreciation. Also, the fact that it is eco-friendly, through its use of natural dyes and low consumption of resources, is another very important reason to support this traditional art form. While the technique has evolved over the centuries, its original method remains intact, lending authenticity to every hand block-printed product. The human touch is very apparent, with its fascinating imperfections that cannot be replicated by machines. Hand block printing requires skill and plenty of practice in order to create uniform and clear block printing patterns. The tiny variations in the block printing, its vibrant and meaningful motifs, and the handmade technique of Indian block print fabric are what give it such a unique charm. They need to be preserved as these printing art forms have beautiful exquisite patterns that reflect the skill, tremendous patience, and perfection of the artisans involved, and fabrics created with so much passion spark a sense of joy and pride while using/wearing it.

11.18

Conclusion

Textile traditions of India are vast and complex cultural, historical, and political domain. All the traditional printing methods use mostly natural dyes and natural auxiliaries, thereby making the printing process sustainable. Although there was a time when printers switched to synthetic colorants due to high demand of the printed fabric, but again they have returned to the use of natural colorants in the wake of the environmental concern. Environmental impact assessments of the effluents generated from traditional printing show that chemical oxygen demand (COD) of 0e200 mg/L and total suspended solid (TSS) of 25e250 mg/L indicated that the wastewater generated is safe to discharge to the environment without treatment. Bagru block printing is a product that is created with skill and care. As with any artisan-produced textile, hand block print fabrics are all the rage and for good reason. They also happen to contain a special quality that is really one of a kind. The hand printing on authentic fabric is intricate and beautiful. The human touch can’t be replicated by a machine, and there are always these little details that make the fabric and its designing interesting. Most ancient textile printing art forms like Dabu and Bagru are eco-friendly. Every aspect of its process involves sustainable practices that are respectful to the planet as sustainability is the development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Thus, each block-printed fabric is nothing less than a piece of art that speaks of its uniqueness and also carries a message of sustainable fashion. Hand printing is an environmentally friendly artwork because the prints are laid out with plants, animals, and heritage elements. The natural colors are also very vivid and show off the beauty of nature. Lastly, the experience of hand block printing that goes into every stage of creating a fabric is worth gratitude as its a procedure of ecological sustainability and integrity in which plants, nature, and people are closely knitted and involved. The art forms like Bagru and Dabu printing connect old generations to new ones and adapt to new demands and create new arrays/patterns, thus creating plethora of designs and keep antiquity into them. These environment-friendly printing art is

Traditional block printing for sustainability

165

indeed the need of the hour. Apart from that, the esthetics, eco-friendliness, and versatility are major properties that make these printing protocols to be embraced as they always convey lessons of sustainability in every piece of fabric.

References Babel, S., Gupta, R., 2016. Screen printing on silk fabric using natural dye and natural thickening agent. Journal of Textile Science & Engineering 6 (230), 2. Cluny, J., 2021. Block print: the art of sustainable fabric design. Fabriclore, B.O., 2022. Making of dabu directly from the land of artisans. Dabu Print. Foundation, I., 2021. Dabu Print. Save-the-weave. Gandhi, S., 2019. Exploring the Indian block print’s rich cultural history. Hada, J.S., Meena, C.R., 2022. Dabu, the sustainable resist printed fabric of Rajasthan. Sustainable Approaches in Textiles and Fashion: Manufacturing Processes and Chemicals 69. Kavyashree, M., 2020. Printing of textiles using natural dyes: a global sustainable approach. In: Chemistry and Technology of Natural and Synthetic Dyes and Pigments. IntechOpen. Klancnik, M., 2021. Screen printing with natural dye extract from Japanese knotweed rhizome. Fibers and Polymers 22 (9), 2498e2506. Maulik, S.R., Bhowmik, L., Agarwal, K., 2014. Batik on handloom cotton fabric with natural dye. Indian Journal of Traditional Knowledge 13 (4), 788e794. Meitei, O.B., Ahemad, T., 2022. Communication and challenges of capacity development: a case study of Bagru hand block printing. Textile 20 (3), 311e321. Muthu, S.S., 2017. Sustainable Fibres and Textiles. Woodhead Publishing. Roy, M.S., Lina, B., Khusbu, A., 2014. Batik on handloom cotton textile with natural dye. Indian Journal of Traditional Knowledge 13 (4), 788e794. Samanta, A.K., Awwad, N., Algarni, H.M., 2020. Chemistry and Technology of Natural and Synthetic Dyes and Pigments. BoDeBooks on Demand. Saree.com. 2021. 10-printing-and-dyeing-techniques-from-india. Printing Crafts. Ujiie, H., 2015. Chapter 20 - Fabric finishing: printing textiles. In: Sinclair, R. (Ed.), Textiles and Fashion. Woodhead Publishing, pp. 507e529. Yıldırım, F.F., Yavas, A., Avinc, O., 2020. Printing with sustainable natural dyes and pigments. In: Muthu, S.S., Gardetti, M.A. (Eds.), Sustainability in the Textile and Apparel Industries : Production Process Sustainability. Springer International Publishing, Cham, pp. 1e35.

This page intentionally left blank

Sustainability in natural dye printing 12.1

12

Introduction

Textile printing is a process where a specific pattern or design is created by applying color to the fabric, or printing is also the process of decorating a fabric by applying different colors, patterns, or designs (Tabassum, 2022). The word “printing” is derived from the Latin word meaning “pressing” and implies the application of “pressure.” Textile printing is the process of applying color to the fabric in definite patterns or designs. It is a part of wet textile processing. Textile printing is related to dyeing, whereas in dyeing, the whole fabric is uniformly covered with one color. In printing, one or more colors are applied to the fabric in certain parts only and in sharply defined patterns. Printing is therefore called as localized dyeing. In printing, the dyes and pigments are applied locally or discontinuously (Kiron, 2011). Printing, unlike dyeing, can use many colors to add a pattern on to a piece of woven fabric. Inspiration for these printed designs come from the world around us, with many iconic prints as popular today as they were in the last century. Printing designs onto fabric has been around for thousands of years, and the printing methods have changed over the time. Different printing methods can be applied to transfer the dyestuff and chemicals to the surface of the fabric. There is evidence of fabric prints dating as far back as the fourth century BC. The first common method of textile printing originated in China, where examples of woodblock printing from 220 AD have been discovered. Both block printing and screen printing slowly became popular throughout Asia, India, and then Europe. During this time, little changed in the printing process as it traveled around the globe. During the 18th century, the popularity of Calico printing spread rapidly, with new print works opening in different parts of Europe. During the industrial revolution, these methods became mechanized, and cylinder or roller printing was developed. In the 1960s, a rotary machine based on screen printing was invented that was quicker than the traditional flat bed method. And today things are even fasterdwith digital textile printing, using rapid ink-jets that not only make the process quicker but also far easier to produce one-off designs (Patra, 2014).

12.2

Textile dyeing and textile printing

Dyeing is the uniform coloring of the whole surface of the substrate. Textile dyeing can take place in any textile manufacturing stage. Printing is applying color only to the target areas, thus introducing various colors, patterns, and designs to the textile

Natural Dyes for Sustainable Textiles. https://doi.org/10.1016/B978-0-323-85257-9.00006-2 Copyright © 2024 Elsevier Ltd. All rights reserved.

168

Natural Dyes for Sustainable Textiles

fabrics. It is also called localized dyeing. The importance of the dyeing and printing process is to enhance the look of the fabric (Pidiliteindustrialproducts.com, 2022).

12.3

Methods of textile printing

Different methods are used to produce an impression on fabrics. Method of printing depends on the demand of the user and the quantity to be printed. It also depends on the type of material and the end use of the printed product.

12.4

Traditional printing styles

Each country has a different style and method of printing which is an identity of that region. These printing styles are broadly as following: I. Direct style of printing: The most common style of printing textile fabric is direct printing. The dye is directly applied onto white fabric or colored fabric. The printed portion is significantly darker than the dyed background. The direct style of printing is used in block printing, screen printing, or roller printing methods. In this style, printing is done with pastel or white-colored background by any method. II. Discharge style of printing: Discharge printing in textile is also known as extract printing. It is based on the chemical destruction of the original dye in the printed area. The discharging agents used can be oxidizing or reducing agents, acids, alkalis, and various salts. For discharge printing, the ground of the substrate should be dischargeable. If no color is added to the discharge print paste, the result is a white discharge. Discharge is only carried out by reduction. In white discharge style, the print is created by removing the color from the dyed material. When the color is removed and the print is created by the color, that style is known as color discharge style. III. Resist style of printing: In this, the color-resistant material is used for the printing. First, the color-resistant material is applied on the fabric, then the fabric is dyed, and then the color-resistant material is removed and the material which is not dyed is filled with different colors or in the resist style of printing style, RFD fabric is first printed with resist paste which prohibits the penetration of the dye into the fabric. The fabric is then dyed and subsequently, the resist paste is removed leaving the desired pattern (Pidiliteindustrialproducts.com, 2022). Mud and wax are being used as color-resistant materials. The printing style in which mud is used is known as Dabu style and that in which wax is being used is known as Batik style. Liquid wax is applied on the fabric with pen, brush, or block on the images (fibre2fashion, 2007).

Each and every region has some special styles and they use the material which is locally available. The craftsmen use a blend of locally available and traditional material, and when they do not have traditional material, they borrow it from other regions. Each region has its different style of patterns, designs, color combination, motifs, and arrangement and presentation. Sometimes, some similarities are also found because of

Sustainability in natural dye printing

169

the nearness of the regions. Some other specific printing styles which basically use above-said printing methods are the following: •

• • •

•

Block printing: This technique was originally developed by China but eventually became great art form of India and famous all over the world for their beautiful motifs and colors. First of all, the original wooden block is developed and then with the help of ink, the duplicate is produced by the craftsmen. Highly skilled people are needed for this. Hand printing: Hand printing is one of the traditional techniques of tie-and-dye, and it is used for decorative values of textiles. Tie-and-dye: This technique includes tying of both wrap and weft threads. Normally, bright colors are used in this. Kalamkari: Kalamkari work is done with kalam, from which it derived its name. “Kalam” means pen and “Kari” means work. Thus, the work done with pen is called Kalamkari. It is a very ancient work of India. Batik: Batik is a dyeing process in which first, color-resistant material is applied on the fabric and then the fabric is dyed. After dyeing, the color-resistant substance is removed. So the fabric attains its original color at those places (fibre2fashion, 2007).

12.5

Modern methods of textile printing

The modern textile-printing techniques are also called wet printing techniques that consist of flat-bed screen, rotary screen, and engraved copper roller. This is because each technique applies a print paste, which is a thickened dye mixture, to the fabric in the printing process. For wet printing processes, once the fabric has been prepared and delivered to the printing plant, the basic steps in the printing process are as follows: 1. 2. 3. 4. 5.

Preparation of the print paste. Printing the fabric. Drying the printed fabric. Fixation of the printed dye or pigment. After washing (Miles, 1994).

12.6

Types of modern textile printing methods

There are five main methods of printing a fabric, these being the block, roller, screen, heat transfer, and ink-jet methods.

170

12.6.1

Natural Dyes for Sustainable Textiles

Block printing

Block printing is the oldest method of printing that still exists; this printing technique product has been in much demand since the last decade specially in India. Color is applied evenly to the wooden block with different designs and the pattern is stamped on the fabric.

12.6.2

Roller printing

It is the most economical and fastest printing. This technique is used whenever long runs of fabric are to be printed with the same design. Engraved printing rollers used one for each color, press against the fabric and the central cylinder. The printed fabric passes from the main cylinder and through a drying and steaming chamber to fix the color.

12.6.3

Screen printing

It is like a photographic process. In this method, the design is applied by passing print paste through a silk or nylon screen on fabric. The screen of a single design is reused for a single color. Screen printing may be a hand operation or an automatic machine process.

12.6.4

Heat transfer printing

Papers with printing patterns are applied to the fabric and then passed together through a type of hot calendar, and the pattern is transferred from one to the other. This type of printing is very popular for polyester fabrics, especially. The heat transfer method differs from the others in that it involves the transfer of color from the design printed on paper through the vapor phase into the fibers of the fabric, while in the other methods, the dye or pigment is applied to the fabric surface through a print paste medium.

12.7

Digital printing on fabric

Digital printing is a modern age technology with improvements in machines and ink. Compared with traditional screen printing, digital ink-jet printing was seen as breakthrough technology showing various features and advantages such as noncontact printing, no printing screen, excellent image quality, artistic design, flexible output, low electrolyte use, etc. (El-Sayed et al., 2022). Digital printing is a growing and noncontact method that deposits tiny droplets onto the specific location of the substrate. It transfers colored ink drops on the fabric substrate using special electrical signals to get unlimited color combinations. In the case of digital printing on textiles, the most used technology is ink-jet. It is a technology in which ink is sprayed through the nozzles onto the substrate. The ink-jet printing process however is a comparatively recent innovation and is referred to as a “nonimpact” method, because the print paste is fired

Sustainability in natural dye printing

171

on to the textile from a jet which is not actually in contact with the fabric. It is further divided as: Continuous ink-jet (CIJ): In this, a small portion of the continuous flow of ink drop is directed onto the fabric in line with the image signal, and the balance unprinted droplets are returned for reuse. Drop on demand (DOD): In this, drops of ink are only generated if only the image signal information demands. This is further divided into (a) thermal, (b) piezo, and (c) electrostatic ink-jet (Pidiliteindustrialproducts.com, 2022).

12.8

Dyes for textile printing

Dyes and inks need to be highly suited to the fabric they are being applied to, not just for the look of the garment, the vibrancy, the detail but also the water fastness, resistance to abrasion, light, and detergents. Dyes are fiber specific; therefore, dyes are chosen for printing based on the fibers, which compose the textile fabric. Textile printing has become specialized science, and a thorough research is going on to develop printing method and dyes, particularly natural ones to be used in digital printing. In the 1990s, textile digital printing emerged as a prototyping tool for printing small batches of fabric for advertising materials such as flags and banners mostly. Recent decades have seen the growing popularity of preparing water-based ink-jet inks for textile printing. At present, about 5%e7% of all textiles’ printed material is digitally printed. Conventional textile printing is predicted to grow at a rate of 2% per year, whereas digital textile printing is presently growing at a rate of 13% and is expected to reach a 20% growth rate in coming years (Savvidis et al., 2014). Natural dyes have long been used in globally to dye and print textile articles. Dye sources included vegetable, animal, and mineral extracts. Thus, even though the availability of natural dyes has been known for centuries, synthetic dyes are so popular mainly because they are simple to produce in large quantities, can be manufactured at a reasonable price, can provide a variety of colors, and can produce dyeings of high color fastness to meet today’s requirements.

12.9

Textile printing with natural dyes

Natural “green” dyes can be considered as an alternative to synthetic dyes if they can be produced at a comparable price and exhibit similar fastness characteristics to the synthetic dyes. The use of natural dyes came back to the agenda due to an increased ecological and sustainable awareness (El-Sayed et al., 2022). Unlike nonrenewable raw materials of synthetic dyes, natural dyes are mostly renewable and sustainable, so make printing a clean and green process; natural dyes are new hot players of the ecologically safe printing. Natural dyes from various plant sources, such as alkanet, rhubarb, manjistha, turmeric, marigold, chrysanthemum seed, locust bean seed, madder, buckthorn, walnut bark, red poppy, Butea monosperma flower, golden

172

Natural Dyes for Sustainable Textiles

dock, cutch, pomegranate peel, nutshell, orange tree leaves, dyer’s chamomile, and annatto (Hebeish et al., 2015; Rungruangkitkrai and Mongkholrattanasit, 2012; Devi and Karuppan, 2015; Rekaby et al., 2009; Salem et al., 2013; Chattopadhyay et al., 2018; Osman, 2014; Teli et al., 2013; Pratoomtong, 2015; Abd-El-Thalouth, 2011; _ I_ et al., 2013; Babel and Gupta, 2016; Savvidis Babel and Gupta, 2016; BahtIyar et al., 2014; Bahtiyari et al., 2017; Savvidis et al., 2013; Ragheb et al., 2017), have already been investigated for textile printing. Some traditional natural dyes used in ancient Indian textile printing were: Red color is obtained from Manjistha (Rubia cordifolia) bark, roots. Brown is obtained from Kachhakatha (Acacia catechu) from its extract, from Acroth (Juglans regia) bark, from Babul (Acacia arabica) seed. Yellow orange from Lal Chandan (Adenanthera pavonina) bark. Beige from Fuel wood (Dipterocarpus turbinatus) saw dust. Mustard form Marigold (Tagels erecta) petals. Golden from Henna (Lawsonia inermis) leaves (fibre2fashion, 2007). The most traditional method for preparing the dye for printing consists of dissolving natural dye extract in powder form in water and then increasing the consistency of the solution with a binder, generally a kind of natural gum (guar gum mostly). At this point, the more guar gum is used, the thicker the dye will be. Thus, printing with natural dyes is definitely possible. By mordanting the fabric first, and then preparing the dye using natural dye extract, beautiful, unique results can be obtained by using a variety of printing techniques. Screen printing on cotton fabric using Cochineal natural dye in the presence of stannous chloride as the mordant has been investigated. It has been found that 6% Cochineal pigment in dye recipe prepared in water worked very well, where the fabric was soaked in the heated stannous chloride mordant for an hour and cured at 160
C for 3 min. This produced the best screen print on 100% cotton fabric in terms of appearance and color wash fastness (Dasgupta and Ghosh, 2018). The development of chitosan as a thickener for direct printing of natural dye on cotton fabric better than sodium alginate has been studied. The results exhibited that chitosan affected the fabric properties by increasing fabric yellowness and stiffness. Direct printing on cotton fabric with 3% natural chestnut at varying chitosan concentrations showed that the optimum chitosan concentration for the printing was at 3%w/ v, being equivalent to the viscosity of 17,800 mPa. The 3%w/v chitosan imparted the best color yield, print outline sharpness, and a minimal dye bleeding on the unprinted area of the fabric. The use of chitosan concentration higher than 3%w/v led to poor print properties on the fabric (Choomchit et al., 2013). Three different natural dye sources (rose flower, teak leaf, and tamarind seed husk) extracted in aqueous medium were applied on 100% cotton knit fabric with three different thickeners prepared from the powder of guar gum, mango seed, and tamarind seed. The printed samples exhibited excellent wash fastness with grading 4e5 for all printed samples, light fastness 7 for tamarind seed husk and tamarind seed, rose flower and tamarind seed printed fabrics and rubbing fastness 4e5 for all printed fabrics. Dye-fiber bond formation was confirmed by FTIR, which revealed phenomena of strong covalent bond between

Sustainability in natural dye printing

173

dye and fiber molecules. Other essential features, determination of K/S value, CIE lab values, and durability of printing paste demonstrated successful application of natural dyes and thickeners for printing cotton fabric. Environmental impact assessments, chemical oxygen demand (COD) of 0e158 mg/L, and total suspended solid (TSS) of 1e55 mg/L indicated that the wastewater generated was safe to discharge to the environment without treatment (Mondal et al., 2022; Kavyashree, 2020). Digital printing with natural ink-jet inks is of great importance, as it not only allows the production of high added-value ecofriendly textile articles but also can be used in the packaging, food, and cosmetics industries for the production of novel ecofriendly materials. Ink-jet printing is one of the fastest growing imaging technologies, showing benefits over the conventional printing methods of roller and flat-bed screen printing and offering unique advantages such as simplicity, lower production costs, reduced effluent waste, and lower water and energy consumption, together with unlimited design combinations, which makes it possible to produce innovative designs. During recent decades, there has been a growing interest in the preparation of water-based inkjet inks for digital textile printing using synthetic dyes. Ink-jet printing with natural pigments is a novel process offering all of the above advantages together with unparalleled ecological characteristics. In properly printed fabrics, the color is bonded with the fiber so as to resist washing and friction. Ink-jet printing with natural pigments is a novel process offering advantages like clarity, sharpness plus the possibility of small, production with the use of a number of natural dyes replacing synthetic dyes. This may pave the way for the development of innovative, ecofriendly, water-based, digital inkjet inks applied to textiles using digital printing techniques. The suitability of printing natural fabrics (wool, silk, cotton, and flax) with two natural dyes (alkanet and rhubarb) using pigment-printing technique has been investigated. The effect of different factors, that is, dye concentration, nature of thickening agent, type of fixation, concentration, and type of mordant, has been studied. The printed goods were evaluated by measuring the K/S value and the overall fastness properties. Results show that the highest K/S value was obtained by using Meypro gum as a thickener. The K/S increases rapidly as the concentration of the natural dye powder in the printing paste increases from 10 to 40 g/kg printing paste. The effect of mordants on color development was also studied, and alkanet dye was chosen as an example for this investigation. The best results were obtained by using mordant at a concentration of 20 g/kg printing paste. Different color yields could be obtained by using different mordants, and all of color fastness results were ranging between very well and excellent (Rekaby et al., 2009). To solve ecological and toxicological issues related to some synthetic dyestuffs, the potential application of a new thickening agent from wild taro corms and natural indigo dye in the screen printing process of woven cotton and knitted fabrics was investigated. For this purpose, effects of the dye, thickening agent, thiourea dioxide, and sodium hydroxide concentrations were varied and investigated with respect to the color yield, fastness, and physical properties. Results revealed that the printing paste comprising the thickening agent prepared from the modified starch of wild taro corms can be applied for the printing of cotton fabric using natural indigo dye. The colorfastness to washing, water, and perspiration of the printed samples was found to be good to

174

Natural Dyes for Sustainable Textiles

very good, whereas the colorfastness to light and rubbing was mostly at good and fair, respectively. The printed fabric also had increased tensile strength, tear strength, bursting strength, and stiffness compared to the original fabric (Mongkholrattanasit et al., 2022). Ecofriendly chemical processing of jute fabric followed by printing with natural dyes using natural thickeners produces printed jute fabric that may be used for variety of diversified and value-added applications. Natural dyes were extracted from seeds of annatto, roots of manjistha, and bark of ratna jot by aqueous extraction method. Four natural thickeners like guar gum, gum arabic, sodium alginate, and gum indulka were used for printing. The evaluation of these printed fabrics reveals that very good wash and rubbing fast printed jute fabric can be produced from natural dyes and natural thickener guar gum by substantive screen printing method and can be used as decorative, furnishing, and apparel textiles (Chattopadhyay and Pan, 2019).

12.10

Natural dye ink formulations for textile printing

The natural dye ink-jet inks were prepared by using a water/dipropylene glycol monomethyl ether 80/20 system resulted in lower dye solubility and in a significant lmax shift of the dye. This system gave better dye solubility, and no significant shift in lmax of the dye was observed, so this was the system used for the preparation of all natural ink-jet dye inks. The mixture of ingredients was stirred for 30 min using a homogenizer at 18000 rpm (Kosolia et al., 2011). Another recipe for the screen printing inks, the printing paste for pigment printing was prepared with ingredients 150 g of a self-crosslinking acrylic binder Binder SECONC, 18 g of acrylic thickener Clear MCS, and up to 1000 g of demineralized water. The violet dye was added in six different concentrations: 0.5, 1, 2, 3, 4, and 5 g per 100 g of the prepared printing paste with pH 7.43. The violet inks from light to dark shades were obtained. To prepare an alkaline printing paste, 1 g of Na2CO3 was added to 100 g of the prepared printing paste, thus raising the pH value to 8.99. To this alkaline paste, 3 g of the violet dye was then added and a bluish-green printing ink was obtained. To prepare an acidic printing paste, 2 mL of CH3COOH 60% was added to 100 g of the originally prepared paste to obtain a pH of 5.38, and then 3 g of a violet dye was mixed into the paste and a lighter violet printing ink was obtained (Klancnik, 2021). The printing inks so prepared were applied to the substrates using the semiautomatic screen printing machine with the flat printing screen made of polyester fabric with 77 threads/cm and a thread diameter of 55 mm with three strokes of a squeegee. The prints were dried at room temperature overnight and then cured at 150
C for 5 min (Klancnik, 2021).

Sustainability in natural dye printing

12.11

175

Screen printing modules with natural dyes

A study has been carried out with different natural dyes along with natural mordant as recipe for screen printing, and very nice color palette along with good fastness was obtained. In the first experiment, dye extraction was carried out at acidic and neutral medium for madder and myrobalan at the temperature of 70
C for 60 min, dye extracts were cooled to room temperature, and then 7.5 g of alum is added as metamordanting agent for both madder extracts. Additionally, 15 g of myrobalan was added to madder dye extract solution as mordanting agent. Then the extracted solution of madder was steeped for 12 h, which was later stirred and filtered. This madder darkened with Myrobalan was used for screen printing, and motifs were very vibrant and buoyant (Figs. 12.1 and 12.2). Figs. 12.3 and 12.4 show the screen printing using natural dyes myrobalan and gall nut (Quercus infectoria) impregnated by ferrous mordant to get black coloration prints. The screen printing with Rheum emodi and alum as mordant was carried out, and it has created beautiful theme with very distinguish background (Fig. 12.5). The range of Figure 12.1 Screen printing using myrobalan þ mordant natural dye ink.

Figure 12.2 Screen printing using maddar and myrobalan natural dye ink.

176

Natural Dyes for Sustainable Textiles

Figure 12.3 Screen printing using myrobalan þ mordant natural dye ink.

Figure 12.4 Screen printing using gall nut þ mordant natural dye ink.

design and choice of natural dye along with appropriate mordant can give a plethora of textile printing options. There is an enormous scope of textile printing using natural dyes; only fact is to create and establish new sources of natural dyes along with new procedures to act parallel with new trends in apparel fashion, thereby paving way for natural dye applications in textile printing foray globally and commencing new era in global market for textiles printed with natural dyes.

12.12

Conclusions

Natural dyes are very good option for printing in general and screen printing in particular. To improve the colorfastness of natural dyes, appropriate mordants play a very

Sustainability in natural dye printing

177

Figure 12.5 Screen printing using Rheum emodi þ mordant natural dye ink.

significant role. Screen parameters have been optimized in the printing process, which provided good print quality with acceptable resolution of the print figures. A wash down study was conducted after printing, which showed an approximate 8%e10% loss in color strength as measured using K/S values of the printed samples. These were very promising result for several natural dyes, and the ease of making the printing ink with natural dyes make it a very adaptable process. Dye adherence and dye uptake during printing process would depend on the most appropriate selection of mordant, which would directly impact the wash fastness of the printed material. Ancient textile printing techniques are using natural dyes, and they have created global niche for them and now its high time for natural dyes to be used as potential printing candidate along with natural printing auxiliaries like mordants, binders, and fixers. Digital printing is the method that best suits this demanddit is economical, fast, and has a low ecological impact and stands up to the consumer driver of mass customization. So the importance of printing is essential to take the fashion industry to a much higher peak. Apart from this, it is hoped that the field of textile printing will be further expanded in the future if various types of designs can be catered to the customers by utilizing creative ideas like using natural dyes as printing dye. Digital textile ink-jet printing has major benefits such as high quality and scalable processing. It’s important to be versatile enough to meet the demands of new age customer who believes in sustainability and ready to pay for this. There’s strong need to be “vocal for local” theme as world today become closer and technology transfer helps to achieve what is invented in a nook of universe. New technologies and new developments in existing methods promise to continue the expansion of the capabilities of textile printing well into the future.

178

Natural Dyes for Sustainable Textiles

Natural dye printing technology can help small cluster of society to get benefited, thereby emphasizing on maximizing efficiency and flexibility along with ecosustainability.

References Abd-El-Thalouth, J., 2011. Synthesis and application of eco-friendly natural-printing paste for textile coloration. The Journal of American Science 7 (9), 632e640. Babel, S., Gupta, R., 2016. Screen printing on silk fabric using natural dye and natural thickening agent. Journal of Textile Science & Engineering 6 (230), 2. _ I, _ M., Benli, H., Yavas, A., 2013. Printing of wool and cotton fabrics with natural dyes. BahtIyar Asian Journal of Chemistry 25 (6). _ H., Yavas¸, A., Candan, A., 2017. Use of different natural dye sources Bahtiyari, M.I., BENLI, for printing of cotton fabrics. Textile and Apparel 27 (3), 259e265. Chattopadhyay, S.N., Pan, N.C., 2019. Ecofriendly printing of jute fabric with natural dyes and thickener. Journal of Natural Fibers 16 (8), 1077e1088. Chattopadhyay, S., Pan, N., Khan, A., 2018. Printing of jute fabric with natural dyes extracted from manjistha, annatto and ratanjot. Indian Journal of Fibre and Textile Research 43 (3), 352e356. Choomchit, J., Suesat, J., Porntip, S.B., 2013. Chitosan as a thickener for direct printing of natural dye on cotton fabric. In: Advanced Materials Research, 610. Trans Tech Publications. Dasgupta, S., Ghosh, S., 2018. Evaluation of screen printing using cochineal natural dye. Trends in Textile Engineering & Fashion Technology 2. Devi, S., Karuppan, P., 2015. Reddish brown pigments from Alternaria alternata for textile dyeing and printing. Indian Journal of Fibre and Textile Research 40, 315e319. El-Sayed, E., Othman, H., Hassabo, A.G., 2022. A short observation on the printing cotton fabric using some technique. Journal of Textiles, Coloration and Polymer Science 19 (1), 17e24. fibre2fashion, 2007. Textile-Printing-in-India-Traditional-Approach. Industry article. Hebeish, A., Shahin, A., Rekaby, M., Ragheb, A., 2015. New environment-friendly approach for textile printing using natural dye loaded chitosan nanoparticles. Egyptian Journal of Chemistry 58 (6), 659e670. Kavyashree, M., 2020. Printing of textiles using natural dyes: a global sustainable approach. In: Chemistry and Technology of Natural and Synthetic Dyes and Pigments. IntechOpen. Kiron, M.I., 2011. Different Types of Printing Techniques on Fabric. Textile-printing-methods. Klancnik, M., 2021. Printing with natural dye extracted from impatiens glandulifera royle. Coatings 11 (4), 445. Kosolia, C.T., Tsatsaroni, E.G., Nikolaidis, N.F., 2011. Disperse ink-jet inks: properties and application to polyester fibre. Coloration Technology 127 (6), 357e364. Miles, L.W., 1994. Traditional methods. Textile Printing 1. Mondal, B.V., Kabir, S.F., Ali, A., Hannan, M.A., 2022. Sustainable natural printing of cotton fabric without metal-based mordant. Journal of Natural Fibers 19 (17), 15327e15342. Mongkholrattanasit, R., Klaichoi, C., Rungruangkitkrai, N., Vuthiganond, N., Nakpathom, M., 2022. Eco-printing on cotton fabric with natural indigo dye using wild taro corms as a new thickening agent. Journal of Natural Fibers 19 (13), 5435e5450.

Sustainability in natural dye printing

179

Osman, H., 2014. Eco-friendly printing of textile substrates with rhubarb natural dye nanoparticles. World Applied Sciences Journal 29 (5), 592e599. Patra, R., 2014. Grand designs: fabric printing through the ages. History of Science. Pidiliteindustrialproducts.com, 2022. Fabric-printing-methods. Pratoomtong, T., 2015. The property of screen ink from natural mordant, colorant, and additive for art. IJBSS 6, 68e76. Ragheb, A.A., Tawfik, S., Thalouth, J.I.A.E., Mosaad, M.M., 2017. Development of printing natural fabrics with curcuma natural dye via nanotechnology. International Journal of Pharmaceutical Sciences and Research 8, 611e620. Rekaby, M., Salem, A.A., Nassar, S.H., 2009. Eco-friendly printing of natural fabrics using natural dyes from alkanet and rhubarb. The Journal of The Textile Institute 100 (6), 486e495. Rungruangkitkrai, N., Mongkholrattanasit, R., 2012. Eco-friendly of textiles dyeing and printing with natural dyes. In: RMUTP International Conference: Textiles and Fashion. Salem, A.A., Shahin, M.F., El Sayad, H.S., El Halwagy, A.A., 2013. Transfer printing of polyester fabrics with natural dyes. Research Journal of Textile and Apparel 17 (3), 61e67. Savvidis, G., Zarkogianni, M., Karanikas, E., Lazaridis, N., Nikolaidis, N., Tsatsaroni, E., 2013. Digital and conventional printing and dyeing with the natural dye annatto: optimisation and standardisation processes to meet future demands. Coloration Technology 129 (1), 55e63. Savvidis, G., Karanikas, E., Nikolaidis, N., Eleftheriadis, I., Tsatsaroni, E., 2014. Ink-jet printing of cotton with natural dyes. Coloration Technology 130 (3), 200e204. Tabassum, N., 2022. Textile printing and its importance in fashion industry. Printing, Textile Industry. Teli, M., Sheikh, J., Shastrakar, P., 2013. Exploratory investigation of chitosan as mordant for eco-friendly antibacterial printing of cotton with natural dyes. Journal of Textiles 2013. https://doi.org/10.1155/2013/320510.

This page intentionally left blank

Index ‘Note: Page numbers followed by “f ” indicate figures and “t” indicate tables.’ A Air dyeing technology, 48e49 Air pollution, synthetic dyes, 20 Ajrakh, hand block printing, 154 Alkali treatment, polyester, 111 Alkyl-alizarin-dyed natural fabrics, 75 Alpha-hydroxy-naphthoquinones, 24 Anthocyananidins, 24 Anthocyanins, 61e63 Anthracenes, 31 Anthraquinone dyes, 24 Antimicrobial textile, 31 Aqueous extraction, 41 Archroma, 147 B Bagh, hand block printing, 154 Bagru block printing process, 154e156 modern motifs, 158, 159f process chart, 159e160 traditional main patterns, 159 Bamboo, 4 Batik printing method, 160e161, 169 Bioactive textiles, 30 Bio-based dyeing, 137 Biochemical oxygen demand (BOD), 133 Biodegradable textiles, 4e5 Biomordant, 43e44 Black tea leaf (BT), 146 Bleaching, 7e8 Block printing process, 169e170 Bagru printing, 154e156 batik printing method, 160e161 block carving, 152 Dabu printing, 155 direct printing, 153, 156e157 discharge printing, 153 final washing and drying, 153 hand block printing, 152e154

preservation, 163e164 prewashing, 152 printing, 152e153 quality check, 153 resist printing, 153, 158 screen printing, 161e163 washing, 159 C Carminic acid, 24 Carotenoids, 24 Cationization, polyester, 111e112 Chemical management, 120 dye fixing, 44e45 extraction aqueous extraction, 41 enzyme extraction, 40 green dyes, 40 microwave-assisted extraction (MAE), 41 supercritical fluid extraction, 40e41 ultrasound-assisted extraction (UAE), 42 indigenous dyes, 39 objective, 45e46 pretreatment/mordanting cellulose/cotton, 42e43 colorant molecule, 43f metal chelation, 44f mordants, 42e44 synthetic dyes, 45e46 Chemical oxygen demand (COD), 134 Chitosan, 172e173 Cochineal pigment, 172 Cold atmospheric plasmas, 82 Continuous ink-jet (CIJ), 171 Continuous soft flow dyeing process, 139e141 Conventional metal mordants, 130

182

D Daboo, hand block printing, 154 Dabu printing, 155 Desizing, 6e7 Digital printing, 170e171, 173 Dihydropyrans, 24 Direct printing, 168 Discharge printing, 153, 168 Dispersion foam, 141 Dissolved oxygen, 134 Drop on demand (DOD), 171 Dyeing innovations, 146e147 Dyeing medium, 67 Dyeing process, 9e11 characteristics, 38e39 chemical management. See Chemical management dye solution and solid substrate, 38e39 natural dyes, 22e31 synthetic dyes, 18e22, 38e39 textile substrates, 17 E Eco-textiles, 4 Effluent management, 144e146 chemical parameter measurements, 129 biochemical oxygen demand (BOD), 133 chemical oxygen demand (COD), 134 dissolved oxygen, 134 pH and alkalinity, 134 dyeing process, 129 textile effluent curcumin, 133, 133f dye fixation, 132 water pollution, 132 wet-processing units, 134 Electron beam-mediated natural dyeing cross-linking and degradation, 98 electron beam irradiation (EBI), 97 electrons-polymers interaction, 97e98 hemolytic cleavage, 98 hydrophobic polypropylene fibers, 98 radiation approach, 97 surface modification, 97e98 Evironmental benefits and impacts metal mordants, 130 biomordants, 131e132 cerium salt, 131 toxic index study, 131

Index

natural dyes, 130 sustainable fabric production process, 130e131 Environmental consideration, natural dyeing economic impact, 122e124 Eupatorium dyeing, rare earth salt auxiliary pretreated cotton, 121 CIELab value, 121t colorants, 121e122 Eupafolin, 123f fastness properties, 121t flavonoid components, 122f K/S value, 120 social importance, 124 Exhaust dyeing process, 139, 139f F Flavones, 24 Foam dyeing advantages, 142 continuous methods, 141 dispersion foam, 141 foam finishing, 141 foaming agents, 141 G Gas plasmas, 82 Generic fibers, 103 Glauber’s salt, 44 Green process, 81 Guar gum, 172 H Hand block printing, 152e154 Hand printing process, 169 Heat transfer printing, 170 Hemp, 4 Hibiscus anthocyanin dyeing, 61e63 Hydroxyalkyl-alizarin-dyed natural fabrics, 75 I Indian textile printing, 171e172 Indigoid dyes, 24 Ink-jet printing process, 170e171, 173 K Kalamkari, hand block printing, 154, 169

Index

L Linen, 4 Low/room temperature dyeing, 56 dyeing characteristics, 59 eco-friendly natural dyeing, 59 hibiscus anthocyanin dyeing, 61e63 Rubia cordifolia, 61 tea leaves, 59e60 Lyocell, 5 M Mercerization, 8e9 Metal mordants, 46e48, 130 biomordants, 143 metal chelation sites, 144f rare earth metal, 144 rare earth salts, 143e144, 145t Micronebulization system, 125 Microwave-assisted extraction (MAE), 41 Modal, 4 N Natural dye ink formulations, 174e175 Natural dyeing process bioorigin products and techniques, 46e48 cellulosic fibers, 56 dye and substrate, 56 ecological method, 55e56 exhaustion, 58 heat replacement, 57e58 kinetics, 58 phytochemicals, 55e56 sustainable, 124 water-less dyeing process, 125e127 wool fabrics, 57 yarn package, 56 Natural dyes, 10, 55 advantages, 23 applications, 22e23 color palette, 120 energy management, 28e29 environmental awareness, 23 intrinsic properties, 25e26 limitations, 23 pollution minimization, 29e30 production cost, 120 structure and type, 23e25 supercritical dyeing technique, 29 sustainability, 26e27, 119e120

183

sustainable technologies, 27e29 and textile sustainability, 30e31 ultrasonic dyeing, 27e28 Nebulization technology, 125 Nonaqueous systems, 69 Nonbiodegradable petroleum-based colorants, 137 O Organic cotton, 4 P Pigment-printing technique, 173 Pigments, 25e26 Plasma technology ambient temperature, 82e83 bulk property enhancements, 83 disadvantage, 82 gas plasmas, 82 hydrophobic surface, 83e84 nonthermal plasma, 81e82 polyester dyeing atmospheric pressure plasma treatment, 85 ATR-FTIR analysis, 85 Catechu dyeing, 93e96 CIE lab values measurement, 86, 90te92t color strength (K/S), 90e96 contact angle test, 85, 87 dyeability, 88 EDAX analysis, 85, 88t FTIR spectrum, 87 gases, 84 Lac dyeing, 91 light fastness, 86, 91te93t materials, 85 ozone/mordanting, 84e85 pretreatment, 84 procedure, 86 Rubia cordifolia dyeing, 94e95 scanning electron microscopy (SEM), 85, 87 Turkey red dyeing, 90 turmeric dyeing, 91e92, 94 vertical wicking, 86 wash fastness, 86, 91te93t wicking effect, 87 reactive gases, 82

184

Plasma technology (Continued) solvent/water-free natural dyes, 83e84 surface properties, 82 surface treatment, 83 thermal equilibrium, 81e82 Pollutants, 37 Polyamide, 46e48 Polymeric material CIELAB-colorimetric properties, 112 CIELAB color values, 113te114t colorfastness properties, 112 cotton and polyester, 103 dyed polyester shades, 116 dyeing process alkaline scouring, 106 analytical methods, 110 chitosan pretreatment, 106e107 diffusion behavior, 106 hydrophobic, 105e106 jackfruit bark sawdust, 108f, 111 natural dyes, 107 onion skin, 108f, 110 procedures, 110 Ratanjot extract, 106e107 Rubia root and stem, 108f, 110e111 swelling, 106 synthetic dyes, 107 tellimagrandin II, 109f theaflavin, 109f UV/ozone pretreatment, 106 waste tea dust, 109f light and wash fastness values, 115t natural, 103 versus natural fibers, 104 pretreatments, 105 surface activation, 115 surface modification, 111e112 synthetic, 103 synthetic fibers, 104 R Rapid expansion of supercritical solutions (RESSs), 71 Reactive dyes, 18 Reactive gases, 82 Reclaimed fabric, 4 Recycled polyester, 5 Recycled textiles, 4e5 Resist printing, 153, 158, 168

Index

Roller printing, 170 Rubia cordifolia, 61 S Sanganeri, hand block printing, 154 Scouring process, 7 Screen printing, 170 cotton, 162f inks, 163 modules, 175e176 natural dyes, 162e163 silk, 162f, 163 Silk, 5 Smart foam technology, 125, 126f Spray dyeing system, 125e127, 142e147 advantages, 142e143 color after, 142 Denim jacket dye, 142e143, 143f Soft flow dyeing process, 139e141 Soil pollution, synthetic dyes, 21e22 Supercritical carbon dioxide advantages, 72 closed loop process, 76 disadvantages, 72e73 dyeing, 73e74 liquid CO2, 71e72 Supercritical dyeing technique, 29 Supercritical fluid, 70e71 Supercritical fluid extraction, 40e41 Sustainable chemistry, 45 Sustainable dyeing process continuous soft flow dyeing process, 139e141 dye effluent treatment, 144e146 exhaust dyeing process, 139 foam dyeing, 141e142 metal mordants, 143e144 spray dyeing technology, 142e147 Sustainable fibers, 4e5 Sustainable textiles, 1e2 Synthetic dyes, 9e10, 38e39, 137 acid dyes, 18 azoic dyes, 18 ecological influences air pollution, 20 dye-based effluents, 19 soil pollution, 21e22 water pollution, 20e21 water used, 19

Index

hazardous chemicals, 18 industrial advantages, 18 mordant dyes, 18 reactive dyes, 18 sulfur dyes, 18 vat dyes, 18 T Tannins, 24e25, 46e48 Tellimagrandin II, 109f Textile industry, 67e68, 119 Textiles wet process bleaching, 7e8 desizing, 6e7 dyeing, 9e11 environmental impact, 13 in-plant control techniques, 13 mercerization, 8e9 printing and final finishing, 11e12 product parameters, 3 scouring, 7 Theaflavin, 109f Tie-and-dye technique, 169 Traditional natural dyes, 171e172 Traditional textile printing, 151

185

U Ultrasound-assisted extraction (UAE), 42, 46e48 W Water conservation efforts, 68 Waterless dyeing CO2 solvent, 70 natural dyeing, 74e75 bio-based dyes, 74 curcumin natural dye, 75 dry-dyeing technique, 74e75 red-hued disperse reactive dye, 75 nebulization technology, 125 Smart foam technology, 125 spray dyeing, 125e127 supercritical CO2, 71e72 supercritical fluid, 70e71 Water-based ink-jet inks, 173 Water pollution, 69 synthetic dyes, 20e21 Water recycling techniques, 68e69 Water scarcity, 69 Wet process, 37 Wool, 5 Word print, 151

This page intentionally left blank