Green Nanoremediation: Sustainable Management of Environmental Pollution 3031305574, 9783031305573

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Fernanda Maria Policarpo Tonelli Arpita Roy H C Ananda Murthy   Editors

Green Nanoremediation Sustainable Management of Environmental Pollution

Green Nanoremediation

Fernanda Maria Policarpo Tonelli Arpita Roy  •  H. C. Ananda Murthy Editors

Green Nanoremediation Sustainable Management of Environmental Pollution

Editors Fernanda Maria Policarpo Tonelli Federal University of São João del-Rei Divinopolis, Brazil H. C. Ananda Murthy Adama Science and Technology University Adama, Ethiopia

Arpita Roy Department of Biotechnology Sharda University Greater Noida, India

ISBN 978-3-031-30557-3    ISBN 978-3-031-30558-0 (eBook) https://doi.org/10.1007/978-3-031-30558-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Industrial activities have long ignored the principles of sustainability, and consequently biological, organic, and inorganic contaminants have ended up polluting the environment and harming living beings. Once pollutants are present in ecosystems, it is necessary to remove them or convert them into less-harmful substances; however it is also necessary to stop them from being released into the water, soil, and air. Among the strategies developed to manage pollution are those developed by nanotechnology field that offers materials at the nanoscale (with unique characteristics that can be optimized for efficient nanoremediation) capable of eliminating or mitigating the damage that the pollutants from various chemical nature can do to ecosystems. These materials can be produced by applying, for example, the protocols of physical and chemical synthesis, but this processes are associated to a high cost, requiring expensive pieces of equipment or even the use of toxic chemicals that can even further raise the level of pollution. To surpass these limitations of nanoremediation, the principals of green chemistry can be applied to develop protocols for the green synthesis of nanomaterials. Among these green nanoremediators, the noncarbon-­based ones, especially silver and iron nanoparticles, deserve to be highlighted thanks to their high catalytic activity and adsorption capacity, which allow them to deal well with different environmental contaminants, especially when present in aqueous samples. This book is divided in four parts to display the seventeen chapters in a logical and didactic way, aiming to offer up-to-date, comprehensive views from authors from different countries on topics related to the sustainable management of environmental pollution by using green nanomaterials. The introductory chapter, written by authors from Ethiopia, addresses the important characteristics of nanomaterials that allow them to promote the remediation of environmental pollution. Part I focuses on generating ecofriendly nanoremediators, and its six chapters (contributions from authors from Ethiopia, India, and Sri Lanka) address themes such as the green synthesis of nanoremediators; the main strategies, advantages and disadvantages of green nanoremediation, highlighting the relevance of microbes as green raw materials in ecofriendly syntheses; fungi-based, v

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Preface

algae-­based, and plant-based syntheses of green nanoremediators; and innovations in the synthesis of metal nanoparticles to promote nanoremediation. In Part II, important green nanomaterials capable of managing environmental pollution receive due attention. Its four chapters, written by authors from Brazil, Egypt, India and South Africa, address topics such as green nanoremediation of water contamination, green noncarbon-­based nanoremediators, and green iron and green silver nanoparticles to promote the remediation of environmental pollution. Part III contains two chapters, contributions from Indian authors, focusing on linking green nanoremediation to other remediation strategies: phytoremediation and remediation performed by microorganisms. Part IV explores the safety aspects and includes an analysis of nanoremediation. Authors from Brazil, India, and Pakistan produced chapters to discuss the role of nanoinformatics in promoting the safety of nanomaterials, conventional strategies of environmental pollution remediation versus green nanoremediation, a cost–benefit analysis of the remediation performed by materials in nanoscale and strategies to evaluate the efficiency of nanoremediation. We are extremely grateful to all authors who contributed chapters to this project and to Springer for their generous cooperation in publishing this book. Divinopolis, Brazil Greater Noida, India Adama, Ethiopia

Fernanda Maria Policarpo Tonelli Arpita Roy H. C. Ananda Murthy

Contents

1 Important  Features of Nanomaterials for Environmental Remediation����������������������������������������������������������������������������������������������    1 Nigussie Alebachew, H. C. Ananda Murthy, Bedasa Abdisa, and Taye B. Demissie Part I Green Nanoremediation: Generating Eco-­friendly Nanoremediators 2 Green  Synthesis of Nanomaterials for Environmental Remediation����������������������������������������������������������������������������������������������   27 Kindnew Demssie Dejen, Fedlu Kedir Sabir, H. C. Ananda Murthy, Gezahegn Tadesse Ayanie, Minale Shegaw Shume, and Eneyew Tilahun Bekele 3 Strategic  Methods of Nanoremediation Through Nanomaterials Synthesized From Microbes: An Overview ������������������������������������������   67 J. Immanuel Suresh, P. Yogesh, and M. Andrew Pradeep 4 Fungal-Based  Synthesis to Generate Nanoparticles for Nanobioremediation��������������������������������������������������������������������������   83 N. G. Manjula, Tajunnisa, Vishalakshi Mamani, C. A. Meghana, and Shilpa Borehalli Mayegowda 5 Algae-Based  Synthesis to Generate Nanomaterials for Nanoremediation��������������������������������������������������������������������������������  109 Vijay Dubey, K. D. Parikh, Kun-Yi Andrew Lin, Rajeshwari Oza, Alejandro Perez Larios, and Suresh Ghotekar 6 Plant-Based  Synthesis of Nanomaterials for Nanoremediation����������  127 Vinidu Gamage, Gobika Thiripuranathar, Upul Nishshanka, Namal Priyantha, Siyath Gunawardene, and Sumedha Jayanetti 7 Innovations  in the Synthesis of Metal Nanoparticles for Nanoremediation��������������������������������������������������������������������������������  151 Gezahegn Tadesse, H. C. Ananda Murthy, Tegene Desalegn, and Eneyew Tilahun vii

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Part II Important Green Nanomaterials in the Management of Environmental Pollution 8 Main  Green Nanomaterials for Water Remediation����������������������������  175 Ahmed Ali Ali Romeh 9 Green  Noncarbon-Based Nanomaterials for Environmental Remediation����������������������������������������������������������������������������������������������  211 Adedapo O. Adeola, Odunayo T. Ore, Demilade T. Adedipe, and Philiswa N. Nomngongo 10 Green  Iron Nanoparticles for Nanoremediation ����������������������������������  231 Christopher Santos Silva, Vinicius Marx Silva Delgado, Vitória de Oliveira Lourenço, Flávia Cristina Policarpo Tonelli, Larissa Cristiane Souza Prote, Celso Judson Tadeu Batista Ferreira, Danilo Roberto Carvalho Ferreira, Antônio Pereira Ribeiro Arantes, Bryan da Paixão, Eduardo Thomaz, and Fernanda Maria Policarpo Tonelli 11 Green  Silver Nanoparticles for Nanoremediation��������������������������������  253 Kajalben Patel, Yogita Abhale, Rajeshwari Oza, Kun-Yi Andrew Lin, Alejandro Perez Larios, and Suresh Ghotekar Part III Conjugating Nanoremediation to Other Remediation Strategies 12 Green-Based  Nanomaterials and Plants in Nano-Phytoremediation Strategies����������������������������������������������������  277 Bargavi Purushothaman and Saranya Kannan 13 Main  Interaction of Green Nanomaterials and Microorganisms on Nanoremediation Protocols����������������������������������������������������������������  289 Devaraja Gayathri and Rajanna Soundarya Part IV Safety Aspects and Analysis of Nanoremediation 14 Supporting  Nanotechnology Safety Through Nanoinformatics����������  313 Sesuraj Balasamy, Surya Sekaran, and Rajalakshmanan Eswaramoorthy 15 Conventional  Strategies of Bioremediation Versus Green Nanoremediation��������������������������������������������������������������������������������������  333 Mehreen Shah and Sirajuddin Ahmed 16 Using  Nanoremediation Strategies: Cost–Benefit Analysis������������������  357 Gustavo Alves Puiatti 17 Strategies  to Evaluate Nanoremediation Efficiency������������������������������  375 Sheeza Rafaqat, Umair Riaz, Faiza Hassan, Abid Hussain, Tanveer-ul-Haq, Ghulam Murtaza, and Qamar-uz-Zaman

About the Editors

Fernanda  Maria  Policarpo  Tonelli PhD, currently working as an Assistant Professor with specialization in Biochemistry/Molecular Biology/Biotechnology, she teaches topics related to these themes to graduate students. Dr. Tonelli has edited and/or authored 7 books, has reviewed various articles/book proposals, has authored 14 scientific articles and more than 30 book chapters from international publishers. From research projects developed by Dr. Tonelli 10 patent applications were produced, 3 of them already analyzed and approved. She has presented and participated in numerous national and international conferences and has also had the opportunity to contribute to the organization of various scientific events. Dr. Tonelli has also dedicated herself to promoting science and technology cofunding through a nongovernmental organization (NGO) and has joined a scientific publication group composed of only women. She has had her efforts as a researcher recognized by various awards (including “For Women in Science Brazil,” from L’Oreal/UNESCO/ABC, and Under 30 Brazil, from Forbes) and certificates of merit.

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About the Editors

Arpita Roy currently working as an Assistant Professor with specialization in “Plant Biotechnology, Nanobiotechnology, Environmental Biotechnology and Microbiology”. She has been teaching graduates/post graduates Biotechnology. She has taught topics related to Plant Biotechnology, Microbiology, Bioprocess Engineering and Solid Waste Management. She has authored more than 25 scientific articles and 14 book chapters from international publishers. She has presented and participated in numerous State, National and International conferences, seminars, workshops and symposium. She received the Commendable Research Award for excellence in research in 2019 and 2020, from DTU. She has served as an editorial board member and a reviewer of reputed international journals. H. C. Ananda Murthy PhD, has been a sincere, committed and dedicated faculty member at various prestigious universities in India, Tanzania, and Ethiopia for the past 24 years. He is currently working as an associate professor at the Department of Applied Chemistry, Adama Science and Technology University, Adama, Ethiopia, East Africa. He completed his BSc (1995) and MSc (1997) in chemistry at Bangalore University, India. He obtained his MPhil (2006) from Bharathidasan University, India; then he was awarded a PhD (2012) for his work on composite materials from Visvesvaraya Technological University, Belgaum, India. Prof. Ananda has authored a number of books, compendia, and book chapters, published more than 90 research articles in the journals of international repute and presented many papers at national and international conferences. He has been a guest editor of the Journal of Nanomaterials and the Journal of Renewable Materials. He is also a review editor of the Frontiers in Catalysis journal and an editorial board member of the Annals of Applied Science journal. He has four patents to his credit. He has delivered many invited talks at various platforms. He has taught various chemistry courses to UG, PG, and PhD students at various universities and has supervised MSc and PhD students. He is currently guiding seven MSc and nine PhD students (one awarded). His research interests include mainly the synthesis and application of composite

About the Editors

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materials and nanomaterials. He has successfully completed projects sanctioned by Adama Science and Technology University, Ethiopia, and the National Innovation Foundation of India (NIFI). He is currently associated with research projects related to the green synthesis of metal and metal oxide nanoparticles/nanocomposites for multifunctional applications.

Chapter 1

Important Features of Nanomaterials for Environmental Remediation Nigussie Alebachew, H. C. Ananda Murthy, Bedasa Abdisa, and Taye B. Demissie

1.1 Introduction Environmental deterioration, declining energy supplies, and global energy usage have recently become pressing challenges. As the Industrial Revolution advanced, we unintentionally harmed our environment. We should be ready to deal with the horrible and horrifying effects of this harm in the future if it is not decreased, as it has now reached an alarming level. We must act as though there were an emergency on our planet because the existing environmental issues are rising globally for several reasons. It takes nature millions of years to purify the land, water, and air of toxins. But the majority of pollutants come from vehicle and industrial exhaust (Pandit et al., 2022). Environmental pollutants such as methylene blue (MB), 4-nitrophenol (4-NP), and bisphenol A (BPA), which may be released from various industries, and toxic organic polycyclic aromatic hydrocarbon (PAH) compounds, are highly reactive (Khan et al., 2022; Roy & Bharadvaja, 2019; Pansambal et al., 2022; Yadav et al., 2022). These pollutants include heavy metals such as Pb, U (VI), and Cr (IV) and air pollutants such as NOx and SO2. Depending on the level of exposure, they can poison a living being either acutely or permanently (Das et al., 2018; Rahman et al., 2021). Malignancies, heart issues, central nervous system (CNS) dysfunctions, asthma, bronchiolitis, and skin conditions are just a few of the diseases caused by the chemicals mentioned above (Raina et al., 2020). To preserve a sustainable environment, we must take a fresh perspective and tackle disasters with new ideas and methods, as well as with complete awareness N. Alebachew (*) · H. C. Ananda Murthy · B. Abdisa Department of Applied Chemistry, School of Applied Natural Sciences, Adama Science and Technology University, Adama, Ethiopia T. B. Demissie Department of Chemistry, University of Botswana, Gaborone, Botswana © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_1

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and seriousness. To accomplish this, various methods have been tried over the years. The universal procedures that are widely used include sand filtration, flocculation, condensation, and froth flotation. However, the drawbacks of using these procedures include ineffective metal ion scarping, high energy requirements, and the production of nonrecyclable chemicals. All forms of organic and hazardous waste are treated by using conventional technologies, including adsorption, biological oxidation, electrochemical treatment, and thermal treatment, to reduce these challenges (Taifa et al., 2022; Ahmed et al., 2021). Nanotechnology is the synthesis and application of extremely small materials at the nanoscale for use in chemistry, biology, physics, material science, and other areas (Roy et  al., 2022b; Salve et  al., 2022). These uniquely designed nanoscale materials exhibit various chemical, physical, electrical, and mechanical properties. Engineered nanomaterials are employed in nanoremediation to clean up polluted media, which are less expensive and more effective than most conventional methods. Nanomaterials are useful adsorbents, catalysts, and sensors thanks to their high reactivity and significant specific surface area, notwithstanding the challenges associated with the remediation of toxins in water and in the air (Roy et  al., 2022a). Moreover, they work as a vector in the detection and eradication of pests and in the storage, production, and conversion of energy, improving agricultural productivity, diagnosing and screening diseases, the development of drug delivery systems, processing and storage of food, the control of air pollution, construction, and maintaining human health. Nanomaterials stand out for their superior electrical properties, high surface-to-mass ratio, catalytic activity, random distribution of active sites, and various coating modification choices (Guerra et al., 2018; Roy, 2021; Barage et al., 2022; Islam et al., 2022). Recent review works have focused exclusively on the synthesis, functionalization, and applications of carbon-containing NCs, specifically NCs based on graphite carbon nitride (g-C3N4), with their use as photocatalysts, chemical, and biological sensors; adsorbents; and biomedicines for diagnostics and therapy (Rono et  al., 2020; Liu et al., 2021; Alaghmandfard & Ghandi, 2022). The g-C3N4 band gap (2.7 eV) provides a versatile channel for attaining both the lowest manageable unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) and for streamlining the modification procedure by adding nonmetals such as sulfur (S) and nitrogen (N) during the elemental doping process (Padhiari et al., 2021; Rajkumar et al., 2018; Bogireddy et al., 2019). Recently, various techniques have been reported to advance the optical, electrical, and physicochemical properties of g-C3N4-based NCs doped with noble metals and metal oxide nanoparticles (NPs), for the remediation of environmental pollution (Fig. 1.1). These include CuO (Zou et al., 2018), ZrO2 (Ke et al., 2014), Fe2O3 (Sahoo et al., 2020), CeO2 (Tan et al., 2015) and MoS2 (Wang et al., 2021). One of the best approaches to changing the electronic property structure of g-C3N4 and improving its photocatalytic activity was in prior studies thought to be element doping. Ragupathi, Panigrahi, and Ganapathi Subramaniam (2020) comprehensively outlined and evaluated several methods for modifying g-C3N4 to increase band gap engineering. Rono et  al. (2020) explained the significance of

1  Important Features of Nanomaterials for Environmental Remediation

Nanoremediation

Pollution Air NH3,CO,CO2 NOX, CH4, SO2, H2S, VOCs, carboxylic acids, and aldehydes

Fullerences graphene, carbon nanotubes (SWNT, MWNT),and activated carbon

Heavy metals Chlorinated compounds, food waste, and oil

Soil

3

Bacteria, virus, heavy metals, petroleum hydrocarbons, oil, pesticides, dye and solvents

Nanoscale zero-valent iron. Supports such as activated carbon, zeolites, polymers and SiO2,AI2O3,TiO2 nanoparticles

Silica based materials, alkaline ceramics, and apatite

Metalic, biometalic and metal oxides nanoparticles: Fe,Ag,Au Activated carbon and carbon nanotubes (SWNT,MWNT)

Graphene, graphite oxide,and carbon nanotubes (SWNT,MWNT)

Polymer nanoparticles, nanocomposites and nanofiltration membranes

Water

Fig. 1.1  Types of nanomaterials employed for nanoremediation. (Source: Del Prado-Audelo et al., 2021)

computational tools in the study of applying g-C3N4. They noted that these techniques save time, provide more information about the properties, and support appropriate material tuning. Recently, the prospective research potential of nano-based materials and technologies has been underlined. Along with the current commercialization state, Khan et al. (2021) have described how different metal oxides may be doped on g-C3N4-­ based NCs to improve the basic properties in light absorption, speed up the separation and transport of charges, and lengthen carrier lifetime of photocatalysts and biosensor applications. Recently, Alaghmandfard & Ghandi (2022) have clarified various metal oxides doping on g-C3N4-based NCs to improve light absorption, accelerate the separation and transport of charges, and extend the carrier lifetime of photocatalysts and sensing applications. The creation of g-C3N4-doping components to bind more-effective photocatalysts for practical applications in environmental pollution management has been thoroughly covered by Liu et  al. (2021). Additionally, the general nonmetal-doped g-enhanced photocatalytic activity of C3N4 has been consistently documented (Starukh & Praus, 2020).

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Focusing on recent studies utilizing nanomaterials, this chapter will explore the applications of various nanomaterial types for environmental remediation, such as treating polluted water, soil, and air. The general approaches that can enhance the selectivity of photocatalysis, adsorption, and electrochemical sensors are presented with their key benefits and drawbacks, to inspire and promote further research.

1.2 Types, Causes, and Consequences of Environmental Pollutants When undesirable, harmful substances are released into the environment, the atmosphere or the ecosystem’s physical and biological foundations are negatively impacted. This is referred to as environmental pollution. Both natural events like volcanic eruptions and human actions like oil spills or industrial waste disposal can cause pollution. It might also become apparent when societal wastes reduce the environment’s capacity to sustain life. Hazardous pollutants like smoke, smog, particulate matter, and other substances generated by factories, automobiles, and other sources have contributed to environmental pollution. In addition to these chemical compounds, this activity is also being driven by other energy sources, such as the heat and light that contribute to global warming, radioactive pollution, and noise pollution from traffic and businesses, vehicles, and entertainment in cities. Various forms of environmental pollution issues, such as air pollution, water pollution, soil contamination, and many more, are categorized according to their causes (Nagore et al., 2021). The most prevalent and harmful type of pollution is air pollution. Every day, many hazardous chemicals are released into the atmosphere from excessive fuel burning, which is necessary for our daily activities, such as driving and cooking. Particulate matter (PM10 and PM2.5), nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), lead, and ground-level ozone, which is produced by chemical interactions between NOx and volatile organic compounds, are the six most prevalent volatile organic compounds (VOCs) in outdoor air pollution. For example, carbon dioxide (CO2) lowers the amount of oxygen in the blood, while sulfide and nitrogen oxides generate acid rain, which harms plant growth and degrades soil quality. Chlorofluorocarbons (CFCs) damage the ozone layer, which increases the risk of skin cancer, among other problems (Manisalidis et al., 2020). The presence of hazardous pollutants in the atmosphere, such as smoke, particulate matter, and toxic gases, is one of the main causes of environmental pollution (Mittal & Roy, 2021; Garg & Roy, 2022). If these pollutants are not managed, they may produce undesirable environmental effects, such as ozone layer thinning and other related difficulties like global warming. Such pollutants can gravely harm the respiratory systems of living organisms. Additional fields of study contribute to air pollution, such as radioactive waste released into waterways, nuclear weapon testing, and radioisotopes in labs and medicine. Water pollution, one of the biggest environmental problems, endangers aquatic life and the entire food chain by negatively affecting the living beings that depend

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Scheme 1.1  Schematic illustration of three key parameters that regulate the physical and chemical properties of noble metal nanomaterials (NMNs) and the main environmental catalytic applications of NMNs. (Source: Lin et al., 2020)

on them. Water bodies, including rivers, lakes, and oceans, can become polluted by human activities when toxic waste from numerous sources is introduced into them, when untreated sewage is discharged, and when industrial waste is disposed of in water bodies. After reviewing the types, sources, methods, and treatments of organic pollutants in wastewater, several authors (Ganie et  al., 2021; Khan et  al., 2021; Buckner et al., 2018; and Roy et al., 2021a, b, 2022a, b) have concluded that conventional water treatment facilities have failed to effectively degrade persistent contaminants in wastewater. However, the expensive capital treatment of these resistant pollutants through sophisticated water treatment methods such as activated carbons, membrane bioreactors, and advanced oxidation processes is well recognized (Scheme 1.1). Soil pollution refers to soil contamination from hazardous waste, such as plastics, garbage, textiles, and metals, thrown into landfills. Soil pollution is the result of these contaminations’ degrading the soil’s quality. Some elements that cause soil pollution include unplanned solid waste disposal, mining operations, deforestation, and the loss of soil fertility owing to excessive fertilizer use. Thanks to their high reactivity, high surface-to-volume ratio, surface functionalization, and ability to alter physical parameters such as size, shape, porosity, and chemical composition, nanomaterials have recently gained attention for soil remediation. The combination

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of these attributes improves efficiency and selectivity in the capture of pollutants. Thanks to the in situ application, the intercalation of nanoparticles in the soil enables the cleaning of large areas while lowering costs and time. Environmental pollution is also brought on by many human activities, such as burning fossil fuels, testing nuclear weapons, mining ore, leaking waste into water bodies, and using radioisotopes for medicinal and laboratory purposes. Chemical pollution, one of the most harmful environmental pollutants, is primarily brought on by industrial waste in the form of chemical leaks from mines and landfills. Without suitable treatment, chemicals like colors, oils, and grease end up in industrial trash. Chemical pollution contributes to air pollution and is visible in the atmosphere. Burning causes the release of particular chemical contaminants into the atmosphere. Recent technical advancements and the expansion of the industrial sector have made this a significant problem. Pesticides and fertilizers applied to plants are also converted into toxic chemicals. These adversely affect plants, which will then affect us. Generally, various factors, such as pollution and drastically declining air and water quality, have led day after day to global warming, which raises the Earth’s temperature. As a result of ice melting because of rising temperatures, the sea level is rising. Environmental cleanup is the most important duty for the survival of people and other species. The key approaches for using nanomaterials to clean up the environment will be covered in the following section.

1.3 Nanoremediation of the Environment: Basic Aspects of Nanomaterials 1.3.1 Materials Based on Graphitic Carbon Nitride (g-C3N4) Following the initial study by Wang et al. (2009) on graphitic carbon nitride (g-C3N4) with a band gap of 2.7 eV, one potential field is photocatalysts. Several researchers have dedicated their efforts to altering the surface of g-C3N4 via various methods, such as pyrolysis at various temperatures (Dong et al., 2013), modified by doping with nonmetals (Guo et al., 2016; Stolbov & Zuluaga, 2013), doping with metal and metal oxides (Chafi et al., 2018) by studying the effects of precursors (Tian et al., 2019), applying computational methods (Chen & Gao, 2012; Ahmad, 2016), and band gap determination (Xu & Gao, 2012). Table 1.1 summarizes the research on the possible uses of different nanomaterials, their synthesis pathways, and potential applications with general techniques, including photodegradation, adsorption, and electrochemical sensing technologies. These conventional methods can be functionalized or embedded with functional groups that can mark specific molecules of concern (pollutants) for efficient remediation. The nanoparticles’ unique properties enable them to control unique surface chemistries. Today, novel ideas for creating nanoparticles are emerging, one where

C3H6N6, Ti (OC4H9)4

Graphite powder, titanium(IV) isopropoxide

ZrOCl2·8H2O, Melamine

Melamine, sulfuric acid

g-C3N4/I-TiO2

RGO- TiO2

ZrO2/g-C3N4 NC

O-g-C3N4

Urea, FeCl3·6H2O, FeCl2·4H2O Graphite

Fe3O4/g-C3N4

GCE/rGO

Pt g-C3N4

Melamine, zirconium oxychloride –

ZrO2/g-C3N4

Fe3O4/g-C3N4/MoO3 NCs Melamine, FeCl3, FeCl2

Nitrogen-doped oxidized Citric acid carbon dots Urea g-C3N4/CeO2 NCs Melamine, CeO2

Precursor ZrOCl2·8H2O, urea

Type of nanomaterials g-C3N4/ZrO2

4-NP

Detection of tetracycline (TET) Detection of (4-NP)

4-NP

Hummers l

Hydrothermal

Detection of 4-NP

Rhodamine B

Ke et al. (2014)

He et al. (2020)

Tan et al. (2015)

Mammadova et al. (2022) Bogireddy et al. (2019)

Zarei (2020)

Nehru et al. (2020)

Alfaifi and Bagabas (2019)

References Bi et al. (2020)

Electrochemical

Wiench et al. (2017) (continued)

He et al. (2019) Hydrogenation of nitrobenzene into aniline photocatalyst Photocatalytic Jia et al. (2016)

Photoelectrochemical

Photocatalytic

Quenching of fluorescence Thermal decomposition

Photoelectrochemical (PEC) sensor Electrochemical

Electrochemical sensor

Remediation method Photocatalytic degradation Methylene blue (MB) Oxidative degradation

Application Rhodamine B (RhB)

Ammonium perchlorate (AP) Doping Degradation of tetracycline Calcination (process) MB and hydrothermal Computational Nitrobenzene methods

Mixing calcination

Hydrothermal

Chemical oxidation

Hydrothermally, calcination and sonication Hummers’ method, sol–gel sono chemical Ultrasonication

Synthesis method –

Table 1.1  Graphite carbon–based nanomaterials and their applications in environmental remediation

1  Important Features of Nanomaterials for Environmental Remediation 7

Urea, FeCl2, FeCl3

Cu(CH3COO)2·H2O, C3N3(NH2)3 –

GO/g-C3N4 -Fe3O4

2Dg-C3N4/CuO nanocomposites MIP/g-C3N4/FTOa photoanode

a

Fluorine-doped tin oxide

g-C3N4 nanoparticle porous g-C3N4

g-C3N4/Ag2S

Polymerization

Pyrolysis

A one-pot sonochemical Electrostatic self-assembly method Hydrothermal

Thermal oxidation

Melamine, folic acid, tyramine, tryptamine, phenethylamine Silver nitrate, sodium sulfide nonahydrate, melamine Melamine

g-C3N4 assembled with graphene oxide (GO)

g-C3N4

Precursor Synthesis method Thiourea, sodium molybdate Calcining, hydrothermal Dicyandiamide, melamine Heating

Type of nanomaterials MoS2/g-C3N4

Table 1.1 (continued)

Bisphenol A (BPA)

Electrochemical detection Sensor

Adsorption

Photocatalytic

MB degradation

Toxic tetracycline (TC) antibiotic, methylene blue (MB) dye Dopamine (DA)

Catalytic reduction

Adsorption, photocatalysis Electrochemical sensor

Remediation method Photocatalytic

MB, methyl orange (MO) Ascorbic acid (AA), dopamine (DA), uric acid (UA) Reduction of 4-NP

Application Rhodamine B

Yan et al. (2018)

Zou et al. (2018)

Sahoo et al. (2020)

Ayodhya and Veerabhadram (2019) Shen et al. (2020)

Zhang et al. (2020)

Xu et al. (2015)

References Wang et al. (2021)

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the characteristics of the NPs don’t harm the environment. For instance, nanocomposites based on graphite carbon nitride (g-C3N4) and integrating metal and metal oxides like CuO, ZrO2, TiO2, CeO2, and MoO3 have been thoroughly studied for environmental cleanup. Through several methods, such as adsorption, photoelectrochemical sensors (PES), and reduction procedures, NCs are being used for environmental remediation. Graphite carbon nitride has several qualities, such as nontoxic behavior, excellent stability, ease of synthesis, ecofriendly preparation, and superior photoelectric properties, that make it a top candidate for use as photocatalysts and sensors and for excellent pollutant degradation (Yan et  al., 2018). As Xu et  al. (2015) explains, the electrons photogenerated by g-C3N4 can react with oxygen to generate superoxide radicals by creating holes that can react with OH− to generate hydroxyl radicals. Finally, these active radicals can oxidize dye molecules and make them decompose. The reaction’s products are diffused into a solution, and dye molecules are sequentially adsorbed onto g-C3N4-based NCs surfaces to reach a new equilibrium. The increased surface area of the synthesized catalyst can facilitate the diffusion of reaction products and the adsorption of reactants. Thus, the interaction between adsorption and photocatalysis controls the rapid breakdown of dye molecules. In addition to being a great photocatalyst, g-C3N4-based NCs have been created as prospective adsorbents with a greater capacity for heavy metal ions. Therefore, g-C3N4-based NCs might be used to treat industrial wastewater containing organic pollutants and heavy metal ions, which would broaden the substance’s usefulness. The benefits of using semiconductor photocatalytic activity in nanomaterials outweigh those of doing so in bulk materials, by a wide margin. The best scientific data suggest that a graphene-based catalyst can enhance the conversion of oxygen to hydrogen dioxide, helping to hasten the inactivation of bacteria (Khan et  al., 2021). Table 1.1 demonstrates the wide range of modification techniques available for g-C3N4-based NCs to improve the activity of the material intended for environmental cleanup. Several studies have shown that the synthesizing method plays a great role in removing various pollutants. For example, g-C3N4/ZrO2 (Chand and Mondal 2023) and MoS2/g-­C3N4 (Li et al., 2016) have been synthesized for degrading rhodamine B (RhB) by using different precursors, urea, and thiourea, respectively, with various morphologies. Given such radical advantages, researchers have been devoted to improving fundamental properties such as surface area, pore volume, surface modification, and the adjustable pore size of g-C3N4-based NCs. According to Alaghmandfard and Ghandi (2022), the combination of g-C3N4 with various metal oxides, such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, and SnO2, causes the heterojunctions of nanocomposites to have a type II or a Z-scheme system, which have been proven to be outstanding for different applications, including water splitting, CO2 reduction, the photodegradation of organic pollutants, nitrogen fixation, catalysis, sensing, bacterial disinfection, energy storage, etc. As shown in Table 1.1, hydrothermal and mixing calcination or pyrolysis are simple and suitable methods for the most common synthesizing methods (Alfaifi & Bagabas, 2019; Ke et al., 2014; Sahoo et al., 2020; Tan et al., 2015; Zou et al., 2018; Jalil et al., 2021). Among so many metal oxides, Cu, Zr, Ce, and Fe are conventional metals used to

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improve the performance of the bulk g-C3N4 nanosheets. This shows that the surface metals influenced the basic characteristics of the g-C3N4 structure and metal oxide modification. Therefore, new properties like band gap, conductivity, light absorption in the UV-vis range, the electron-hole recombination rate, and photoluminescence intensity can be improved. The use of nonmetal oxides and metal oxides, such as O, S, N, CuO, ZrO2, and P-doped g-C3N4 NCs, for the restoration of contaminated soil and groundwater, is a good example of environmental remediation mediated by nanotechnology. According to the literature (Shylo et al., 2019), nonmetal oxides can be utilized to tune the structure, textural characteristics, and electrical properties of g-C3N4 and thus enhances its responsiveness to the full visible light spectrum, allowing for easier charge separation and extending the charge carrier lifetime. These are also vital for CO2 reduction, H2 evolution, and organic pollutant detection (Starukh & Praus, 2020). Hence, pollutant adsorption on the surface of metal oxide–doped g-C3N4 NCs is due to one of three possible interactions: π–π interaction, electrostatic interaction, and hydrogen bonding (Sahoo et al., 2020). We and the ecosystem are at grave risk from heavy metals and other inorganic elements. Heavy metals may be found in wastewater effluents from numerous industrial sectors. Using typically established techniques, like high-performance liquid chromatography (HPLC) and gas chromatography, several environmental poisons (phenolic compounds, pesticides, and heavy metal ions) in wastewater have been identified. However, such types of detecting methods have some limitations. According to Rajkumar et al. (2018) and Teodoro et al. (2019), these techniques are time-consuming and expensive, and more toxic solvents are needed to conduct a complete analysis. Nevertheless, these methods are ineffective for the onsite detection of environmental pollutants. Recent electrochemical methods have received much interest because of their ease of use, quick reaction, onsite detection, affordability, high sensitivity, and selectivity (Demming, 2011). Thanks to their unique physicochemical properties, small size, and high surface-­ to-­volume ratio properties, highly electrochemical sensors have been developed by using carbon-based materials, such as g-C3N4, GO, and rGO, synthesized from various precursors to remedially control environmental pollution (Petryayeva & Krull, 2011). Several scholars have been dedicated to developing highly electrochemical sensors for detecting nitro-group organic pollutants like 4-NP and bisphenol A (BPA) (Nehru et al., 2020; Mammadova et al., 2022; Wiench et al., 2017). Others have focused on detecting tetracycline (TET) (Sahoo et  al., 2020), ascorbic acid (AA), dopamine (DA), and uric acid (UA) (Zhang et al., 2020). At the same time, still others have contributed to sensing dangerous metal ions (Maduabuchi Ezealisiji et al., 2019). The majority of authors have worked on popular electrochemical techniques such as square wave voltammetry (SWV), differential pulse voltammetry (DPV), and cyclic voltammetry (CV).

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1.3.2 Metal-Based and Metal Oxide–Based Nanomaterials To enhance environmental remediation, another group of researchers is developing metal-based and metal oxide–based nanomaterials, such as TiO2, CuO, Fe2O3, ZrO2, silver, gold, copper, and zirconium nanoparticles. As shown in Table 1.2, various NPs made from various precursors have been used in applying the most popular synthetic techniques, including sol–gel, hydrothermal, and precipitation, to effectively remove harmful compounds. According to one review (Zhou & Li, 2012), some fundamental properties should be addressed when exploring such nanomaterials: Surface atoms located on corners and edges are usually active sites for many reactions, and special consideration should be paid to the stability of exposed crystal planes of shape-controlled NCs during a reaction and their influence on the catalytic activity. In addition, capping or morphology-controlling agents are indispensable for the controlled synthesis of NCs with various shapes. Thanks to their diverse crystallographic features, metal nanoparticles (NPs) are intriguing candidates to study how shape impacts catalytic activity. Because of their intriguing properties, particularly their excellent catalytic performance in various reactions, ranging from CO oxidation to hydrogenation/dehydrogenation and from inorganic to organic reactions, noble metal NPs (Au, Ag, Pt, and Pd) have attracted the most attention within this broad category. These active noble metal nanomaterials are recognized for their antibacterial properties and therefore are widely suggested for wastewater treatment (Lin et al., 2020). The geometries of such metal NPs are primarily cubes, tetrahedrons, and octahedrons, typically with low-index facets (Zhou & Li, 2012). Compared with low-index facets, the high-index facets of face-­centered cubic metals (such as Au, Pt, and Pd) have higher densities of low-coordinate surface atoms, and as a result, they feature greater catalytic activity. However, chemically producing metal nanocrystals with high-index facets is still difficult because of their high surface energy. Some researchers (Kamal et  al., 2021; Ayad et  al., 2020) have conducted a study on the removal of 4-NP and MB pollutants by applying copper, nickel, and palladium NPs thanks to their unique characteristics, cost-­ effectivity, and degradation contaminants. Figure  1.2 illustrates how metallic nanoparticles (NPs) can break down toxic pollutants by taking a photocatalyst approach. This technique is being explored as a potential advanced oxidation technology (AOP) to resolve the challenging issues of air pollution, energy restoration, and water decontamination. Because of organic chemicals’ rapid rates of degradation, the complete conversion of organic chemicals to green products, and the simultaneous treatment of numerous pollutants, photocatalysts have been verified to be exceptional alternatives to the conventional treatment methods for reducing environmental-­related problems (Jiang et  al., 2012; Krishnan et  al., 2017; Ganie et al., 2021) (Fig. 1.3). Magnetic nanoparticles, metallic nanoparticles, and nanomaterials formed from mixed metallic oxide are all great examples of nano-adsorbents, according to the literature. Numerous academics have produced metallic oxide NPs, which are efficient adsorbents, photocatalysts, and electrochemical sensors. The nanomaterials

Al(NO3)3·9H2O, Fe(NO3)3·9H2O, ZnSO4·7H2O Streptomyces, Zirconium(IV) oxynitrate, hydrate, silver nitrate CuSO4·5H2O, Solanum torvum L

Al0.88 Fe0.67 Zn 0.28 O3

a

Carbon paste electrode Cds Cadmium sulfide, QD quantum dots modified

ZrOCl2·8H2O, Cu(NO3)2

Elimination of As (III) Electrochemical

Removal target MB & RhB Food packaging Sorption

Remediation method used Photocatalytic –

Electrochemical sensor Catalytic reduction

H2O2 4-NP

Xia et al. (2015)

Electrochemical and photoelectrochemical biosensor

Ayad et al. (2020)

Benvidi et al. (2017)

Nanda et al. (2017)

Wang et al. (2016)

Biocompatibility

Photocatalytic reduction

Jalil et al. (2021)

Photocatalytic degradation

Tetracycline antibiotic Biomedical applications Glucose

Cr(VI)

Photocatalytic, under UV-vis Wang et al. (2018) light Hydrogenation Shao et al. (2021)

Methylene orange degradation Catalytic

Sol–gel

Adsorption

Radium (VI)

Maduabuchi Ezealisiji et al. (2019) Rahman et al. (2021)

Balraj et al. (2017)

References Kianfar et al. (2021) Gvozdenko et al. (2022) Subhan et al. (2011)

Mixing

Biochemical assisted Catalytic applications hydrothermal method Phyto-extract assisted Toxicity of CuO NPs Phytochemicals

Synthesis method Impregnation Chemical precipitation Coprecipitation

Precipitation, impregnation CuO/ZrO2 ZrOCl2·8H2O, CuSO4·5H2O Hydrothermal, nanocomposites sonochemical ZrO2 nanoparticles ZrCl4 Vapor-phase hydrolysis modified CDs = Cadmium Cu (NO3)2·3H2O, Cd (NO3)2·4H2O Sol–gel sulfide and QDs= quantum dots modified CuO CuO/ZrO2-MCM-41 Zirconium butoxide Cu (NO3)2 Sol–gel, wetness impregnation RGO/CuFe2O4/CPEa Cu(NO3)2·3H2O, Fe(NO3)3·9H2O, Coprecipitation graphite Pd NPs Na2PdCl4 Ecofriendly

Cu/ZrO2 NPs

Polydopamine/hydrous ZrOCl2·8H2O zirconium oxide (PDA/ZO) N-doped ZrO2 Ethylene diamine

ZrO2–AgO nanocomposites CuO NPs

Precursor ZrOCl2·8H2O, Cu(NO3)2 Copper sulfate, chloride, acetate

Type of nanomaterials CuO-ZrO2 CuO

Table 1.2  List of recent reports on metal and metal oxide nanomaterials for environmental remediation

Fig. 1.2  Schematic illustration of the material preparation and applications of the GO/TiO2 nanocomposite for the detection of hazardous 4-NP. (Source: Nehru et al., 2020)

Fig. 1.3  Photocatalytic degradation of various pollutants by sustainable approaches using metallic nanoparticles. (Source: Ganie et al., 2021)

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shown in Table 1.2 possess the desired qualities, including high surface area, high reactivity, rapid diffusion, and easy dispersibility, and use a sustainable environmental cleanup technique, making them excellent photocatalysts, adsorbents, and sensors. Metal oxide NCs such as zirconia (ZrO2) have been fabricated by scholars (Rahman et al., 2021), Al2O3 (Ismail et al., 2019; Jalil et al., 2021), CuO (Maduabuchi Ezealisiji et al., 2019) and CuO/ZrO2 (Shao et al., 2021) and are nanosized particles with large surface areas relative to their volumes; they are therefore good candidates to remove toxic environmental poisons such as rhodamine B (RhB) tetracycline (TC) and methylene blue (MB) dye, and Tanium (VI). The importance of metal oxide NPs synthesized by using a chemical technique applied for the deposition of some toxic byproducts on the surface of the metal nanoparticles has been reported by Gvozdenko et al. (2022) and Maduabuchi Ezealisiji et al. (2019). Thanks to the wide surface area of the fabricated materials, the coprecipitation approach was used to generate the multicomponent metal oxide Al0.88 Fe0.67 Zn0.28 O3, to maximize the removal efficiency of As (III) from aqueous solutions.

1.3.3 Principles of Environmental Pollutant Remediation In addition to synthesizing techniques, using NPs to remove pollutants is influenced by several supplementary parameters. Numerous studies have discussed the synthesis and characterization of NPs for environmental remediation that use the adsorption process instead of coagulation, flocculation, electrochemical methods, degradation, membrane filtration, ion exchange, or bioremediation. The critical review by Liosis et al. (2021) on the quantitative effects of heavy metal adsorption by nanoparticles presented parameters for pH, contact time, temperature, adsorbent dose, and beginning ion concentration to identify how heavy metals are removed from industrial wastewater. The best performance for detecting a specific environmental reductant, oxidant, or volatile organic compound depends on the type of precursor, morphology, electronic properties, the surface functional group, the scheme for the hierarchical structures of nano-oxides, and the ideal composition of additives such as VOCs as gases (Chavali & Nikolova, 2019; Yunus et al., 2012). For example, the temperature at which precursors like urea and thiourea are pyrolyzed significantly impacts the band gap. The ability of g-C3N4-based nanomaterials to capture light and perform photocatalysis at specific temperatures also substantially influences their structural shape (Xu et al., 2015). Thanks to the synergistic effects of photocatalysis and electrostatic adsorption under UV-visible light, dye molecule dissolution is made easier. As a result, the adsorption of dye molecules takes place in the photocatalytic degradation processes. The more adsorbed dye molecules are, the more decomposed they are (Ragupathi et al., 2020). According to Ke et al. (2014) and Alfaifi and Bagabas (2019), because metal oxides like ZrO2 and TiO2 are unable to absorb visible light, g-C3N4 NCs boost p–p* transition and transfer the excited-state electrons of the more negative

1  Important Features of Nanomaterials for Environmental Remediation Fig. 1.4  The mechanism of the photocatalytic degradation process. (Source: Ke et al., 2014)

O2 O2

e- e-

15

e- eEg=2.76eV

Eg=3.76eV

g-C3N4

OH+H+

ZrO2 h+ h+

H2O

h+ h+

Conduction band (CB) (−1.12 eV) edge—compared to the Conduction band (CB) edge of ZrO2 (−1.09 eV)/TiO2 (−0.35 eV)—from Valance band (VB) to (CB). The excited electrons subsequently transfer to the surface of the photocatalyst to react with oxygen to form •O2− and •OH, which can photo-oxidize the organic pollutant into H2, O, CO2, and other molecules that take place on the surface of g-C3N4. the schematic diagram below, which is based on this transfer, shows how pollutants are adsorbed onto the surface of g-C3N4-based nanocomposites. The activity of the metal oxide/g-C3N4 composite in the adsorption and photodegradation of dyes is much higher than that of pure/g-C3N4 or pure metal oxides thanks to the superior electron-hole separation (Fig. 1.4). Several academics have proposed ways to detect nanocomposites, even though there is a plethora of research on removing environmental toxins. Currently, numerous research groups are focusing on improving the capacity of carbon-based nanocomposites to detect pollutants. It is crucial to research cost-effective methods, in addition to improving the efficiency of sensing materials for monitoring. Recently, there has been much attention paid to using the inexpensive, metal-­ free, and easily manufactured g-C3N4 (band gap 2.70 eV), combined with metals and metal oxides, to perform selective catalytic activity in order to reduce 4-NP. In addition to the synthesis technique and the kind of precursor used, the concentration of NaBH4 directly affects the reduction levels of 4-NP, acetone, and MB. Numerous scholars have looked into how the concentration of NaBH4 affects the catalytic reduction process of 4-NP.  The decrease in pollutants 4-NP acetone and MB increased up to a restricted concentration of NaBH4. Thanks to the steric effect caused by NaBH4’s oversaturation, which prevents further hydrogenation, 4-NP, acetone, and MB might be connected with the hydrogenation or reduction process even though NaBH4 is the hydrogen source (Ayodhya & Veerabhadram, 2019; Din Sheikh et al., 2016; Kamal et al., 2021; Ayad et al., 2020). When NaBH4 is ionized in an aqueous media, borohydride ions are produced. Many academics have supported the general reduction mechanism of 4-NP. The following steps are used to understand the mechanism’s precise process:

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Fig. 1.5  Summary of common environmental remediation methods using nanomaterials

1. These borohydride ions adhere to the surface of a composite consisting of g-C3N4, metal, and metal oxide, where they combine to form hydride complexes. At the same time, 4-NP binds to the surface of the composite. Because both processes can be reversed, adsorption is followed by desorption. 2. Adsorption equilibrium on the catalyst’s surface causes the hydrogen transfer from the hydride complex to 4-NP and the following synthesis of the 4-­nitrophenolate ion because Ag2S is a direct semiconductor with a narrow band gap of 1.1 eV. Metal oxides, nonmetal oxides, and g-C3N4-based nanomaterials, which were discussed above, have attracted much interest for their potential use in precisely detecting harmful contaminants. The electrochemical sensing of environmental toxins such as 4-NP, BPA, tetracycline, dopamine, and mercury (II) is growing for improved practical use in the continuing research on composites of various metal oxides with carbon. Researchers advocate for straightforward and practical solutions despite the difficulties of large-scale use. According to Prabakaran and Pillay (2021), chemically modified electrodes using nanomaterials have been proven to have a better ability to detect contaminants than biologically modified electrodes do. Thus, to improve the electrocatalytic reduction and increase the sensing efficiency of common environmental pollutants, graphene oxide (GO)/TiO2 NCs, g-C3N4/CeO2, ZrO2/g-C3N4, RGO/CuFe2O4/CPE, and g-C3N4/GO were developed by Nehru et al. (2020), Tan et al. (2015), Zarei (2020), Benvidi et al. (2017), and Zhang et  al. (2020), respectively, as simple electrochemical sensors on a glassy carbon (GC), a carbon paste electrode (CPE), and a fluorine-doped tin oxide (FTO) electrode (Fig. 1.5).

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1.4 Conclusions and Future Perspectives Pollution severely harms our environment. To achieve a clean environment, better living conditions, and a world free from pollution, various research groups have increased the efficacy of nanomaterials in removing hazardous contaminants by taking the photocatalysis, adsorption, and electrochemical approaches. Doping metals, nonmetals, and metal oxides into carbon-based NCs has increased their activity, but in certain cases, attempts to modify pure g-C3N4 have widened band gaps. Metal, nonmetal, and metal oxide atoms must be doped into g-C3N4 matrices to decrease the band gap for the desired application. Surface doping is the only way for band gap–localized states to develop. It is important to increase the application of various nanotechnology approaches to assess the harm that different contaminants have on the environment before they are released into the ecosystem. The development of graphitic carbon nitride–based NC technology has led to significant breakthroughs, but more research is still needed if extensive environmental remediation applications are to be achieved. The relationship between the doped properties of g-C3N4 and metal, nonmetal, and metal oxide dopants and their influence on photocatalytic, adsorption, and electrochemical activities should be explored because the literature was not sufficiently clear in this regard. By examining the link between various forms of nonmetal and metal elements, academics must be able to develop unique materials with specific properties to develop proper application techniques. The release of nanomaterials into contaminated environments, such as soil, drinking water, or the air, are still speculative and unpredictable, which has significantly hampered researchers’ ability to quantify the risk posed by the nanomaterials. The potential risks to human and ecological health are correlated with nanoparticle dispersion, ecotoxicity, persistency, bioaccumulation, and reversibility. These notions require background knowledge, but the fundamental concepts still need to be developed. Furthermore, no suitable national or international legislation or regulatory guidelines govern the use of nanomaterials. Governments have recently passed many laws to reduce pollution, even though numerous programs and efforts exist to lessen the sources of environmental degradation. The environment must be protected and preserved for the benefit of future generations. One of the cornerstones of green chemistry is that “the materials utilized in the restoration process must not be another source of pollution.” It is generally recommended to put this into practice. Green Chemistry: A Framework for a Sustainable Future https://doi.org/10.1021/acs.oprd.1c00216. Acknowledgments  The authors thank Adama Science and Technology University (ASTU) for supporting this project with research grant number ASTU/SP-R/082/20 through the Ministry of Education (MoE) of Ethiopia. Declaration of Competing Interests  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work described in this paper.

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References Ahmad, F. (2016). First principle calculation of electronic, optical properties and photocatalytic potential of CuO surfaces. KnE Engineering, 1(2015), 1–7. https://doi.org/10.18502/keg. v1i1.504 Ahmed, H.  M., Roy, A., Wahab, M., Ahmed, M., Othman-Qadir, G., Elesawy, B.  H., et  al. (2021). Applications of nanomaterials in agrifood and pharmaceutical industry. Journal of Nanomaterials, 2021, 1472096. Alaghmandfard, A., & Ghandi, K. (2022). A comprehensive review of graphitic carbon nitride (g-C3N4)–metal oxide-based nanocomposites: Potential for photocatalysis and sensing. Nanomaterials. https://doi.org/10.3390/nano12020294 Alfaifi, M. Q., & Bagabas, A. A. (2019). Preparation, characterization, and application in water purification of g-C3N4/I-TiO2 composite photocatalysts. Advanced Material Science, 4(1), 1–10. https://doi.org/10.15761/ams.1000148 Ayad, A. I., Luart, D., Dris, A. O., & Guénin, E. (2020). Kinetic analysis of 4-nitrophenol reduction by ‘water-soluble’ palladium nanoparticles. Nanomaterials, 10(6), 1–16. https://doi. org/10.3390/nano10061169 Ayodhya, D., & Veerabhadram, G. (2019). Synthesis and characterization of g-C3N4 nanosheets decorated Ag2S composites for investigation of catalytic reduction of 4-nitrophenol, antioxidant and antimicrobial activities. Journal of Molecular Structure, 1186(June), 423–433. https:// doi.org/10.1016/j.molstruc.2019.03.048 Balraj, B., Arulmozhi, M., Siva, C., & Krithikadevi, R. (2017). Synthesis, characterization and electrochemical analysis of hydrothermal synthesized AgO incorporated ZrO2 n­ anostructures. Journal of Materials Science: Materials in Electronics, 28(8), 5906–5912. https://doi. org/10.1007/s10854-­016-­6264-­9 Barage, S., Lakkakula, J., Sharma, A., Roy, A., Alghamdi, S., Almehmadi, M., et  al. (2022). Nanomaterial in food packaging: A comprehensive review. Journal of Nanomaterials, 2022, 6053922. Benvidi, A., Nafar, M.  T., Jahanbani, S., Tezerjani, M.  D., Rezaeinasab, M., & Dalirnasab, S. (2017). Developing an electrochemical sensor based on a carbon paste electrode modified with nano-composite of reduced graphene oxide and CuFe2O4 nanoparticles for determination of hydrogen peroxide. Materials Science and Engineering: C, 75(June), 1435–1447. https:// doi.org/10.1016/j.msec.2017.03.062 Bi, X., Sirong, Y., Liu, E., Yin, X., Zhao, Y., & Xiong, W. (2020). Nano-zirconia supported by graphitic carbon nitride for enhanced visible light photocatalytic activity. RSC Advances, 10(1), 524–532. https://doi.org/10.1039/C9RA08540H Bogireddy, N. K. R., Cruz Silva, R., Valenzuela, M. A., & Agarwal, V. (2019). 4-nitrophenol optical sensing with N doped oxidized carbon dots. Journal of Hazardous Materials, 386, 121643. https://doi.org/10.1016/j.jhazmat.2019.121643 Buckner, C.  A., Lafrenie, R.  M., Dénommée, J.  A., Caswell, J.  M., & Want, D.  A. (2018). Complementary and alternative medicine use in patients before and after a cancer diagnosis. Current Oncology, 25(4), e275–e281. https://doi.org/10.3747/co.25.3884 Chafi, F. Z., Salmani, E., Bahmad, L., Hassanain, N., Boubker, F., & Mzerd, A. (2018). First principle calculations with SIC correction of Fe-doped CuO compound. Computational Condensed Matter, 16(September), e00304. https://doi.org/10.1016/j.cocom.2018.e00304 Chand, S., & Mondal, A. (2023). g-C3N4/ZrO2 composite material: A pre-eminent visible lightmediated photocatalyst for rhodamine B degradation in the presence of natural sunlight. Ceramics International. 49, 5419. Chavali, M. S., & Nikolova, M. P. (2019). Metal oxide nanoparticles and their applications in nanotechnology. SN Applied Sciences. Springer International Publishing. https://doi.org/10.1007/ s42452-­019-­0592-­3

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Part I

Green Nanoremediation: Generating Eco-­friendly Nanoremediators

Chapter 2

Green Synthesis of Nanomaterials for Environmental Remediation Kindnew Demssie Dejen, Fedlu Kedir Sabir, H. C. Ananda Murthy, Gezahegn Tadesse Ayanie, Minale Shegaw Shume, and Eneyew Tilahun Bekele

2.1 Introduction The word “environment” is defined by many scholars as a physical system that may interact with other systems by the exchange of both matter and energy. Environmental concerns are today piling up across the globe as one of the greatest problems facing humanity and have been found to be one of the first ranked leading causes of mortality and morbidity. Nowadays, environmental pollution is part of a huge series of issues that the world is confronting. The developments of widespread factories and agricultural activities are the main causes of the contamination of natural environment such as soil, water, and air, which might be contributed to by main sources originating naturally or artificially. Pollutants are substances that contaminate or pollute water, soil, noise, and air. These pollutants have unsolicited effects, or hostile effects on the use of resources in the environment (Mohamed, 2017). The various forms of hazardous waste such as heavy and toxic metal ions, nondegradable organic dyes, pesticides and insecticides, fossil fuels, oxides of NO, SO2, CO, and many others, are considered to be high contributors to environmental pollution (Roy & Bharadvaja, 2019; Raina et al., 2020; Roy et al., 2022a). The pollution of such classes of the environment could result in the creation of a hostile and K. D. Dejen Department of Chemistry, College of Natural & Computational Science, Wolkite University, Wolkite, Ethiopia F. K. Sabir · H. C. Ananda Murthy · G. T. Ayanie · E. T. Bekele (*) Department of Applied Chemistry, School of Applied Natural Science, Adama Science and Technology University, Adama, Ethiopia e-mail: [email protected] M. S. Shume Department of Physics, School of Natural and Computational Science, Wolaita Sodo University, Wolaita, Ethiopia © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_2

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harsher environment, which is not suitable for the well-being of all living things (Verma et  al., 2020; Roy et  al., 2021a). Specifically, human beings are predominantly affected by the pollution of the natural environment compared with other living things, as the pollution of water has become one of the basic sources of carcinogenic-­caused diseases for human beings (Roy & Bharadvaja, 2021; Roy et al., 2021a, b, c). Moreover, air pollution, which might be attributed to poisonous gases, could again be one of the main causes of respiratory-related diseases and harms different parts of human body. Similarly, if the soil is poisoned, this might lead to the discharge of beneficiary micro-organisms that could be used for the development of fertile soil; crop production could then become too low and this in turn leads to famine and the death of humans (Roy et al., 2021c).

2.2 Major Classes of Environmental Pollution 2.2.1 Soil Pollution Soil pollution is the main environmental issue as it causes numerous health risks, which may be attributed to the existence of high-level concentration of contaminates such as petroleum hydrocarbons, heavy and toxic metal ions, pesticides, and various solvents. Soil pollution could be described as the accumulation of tenacious toxic and heavy metal-containing compounds, various classes of chemicals, and the compounds that may be detrimental to crop productivity and plant health as well as growth, and also to animal health. As soil, being an “entire basin,” endures the greatest responsibility of all the parts of environmental contamination and this confirms that it needs herculean, urgent, and serious guidelines to control soil contamination and poisons in order to maintain the fertility of soils and this in turn enables the growth of a country to be improved (Pinilla et al., 2016). Numerous anthropogenic activities, which may include the development of industrial processes associated with improvement in urbanization, enhancement of manufacturing activities, and the use of agrochemicals, have been identified as the major human resources, which leads to the presence of a high level of metals in the soil (Yuting Qian). Soil pollution in general could be attributed to sources of agricultural and industrial by-products. The agricultural bases that cause the pollution of soil basically encompass animal waste, the persistent use of pesticides, fertilizers, and related agricultural activities (Shrivastava et  al., 2019). Furthermore, non-­ agricultural soil pollution sources directly result from urban area, which may be due to the increase in population size followed by improvements in industrialization development and a rapid increase in per capita output of waste related to modern ways of life. Nowadays, a number of advanced physico-chemical techniques have been employed for the removal and cleaning of contaminated soil. However, the use of nanotechnology by employing emerging nanomaterials has been found to be the most effective and efficient way of preventing soil pollution (Barzegar et al., 2017).

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As a previous report supports, one of the contaminants of agricultural soil is cadmium (Cd), which is a global environmental problem, especially in the vicinity of agriculture. Recently, the report by Wang et  al. (2020), showed that mercapto-­ functionalized nano-silica-based materials showed deep-rooted, stabilized Cd in poisoned parts of soil.

2.2.2 Air Pollution Maintaining the wellbeing of the environment, one of the main tasks for sustainably supporting the well-being of humans and other forms of life, can be identified as one of the most serious global challenges of our time. The rapid growth of the population size with enhancement of industrial development has had a negative effect on atmospheric air conditions. It has been perceived that the increase in industrialization has led to the release of poisonous contaminants into the atmosphere, is currently found to be a serious issue worldwide and is ongoing. This again confirms that the major origin of atmospheric air contaminant are industrial-related activities, which may involve the release of toxic and poisonous pollutants and gas particles. Basically, the atmospheric air contaminants are classified as primary and secondary pollutants. The primary contaminants of atmospheric air are directly caused by human activities, has been directly connected via the respiratory system, whereas secondary pollutants of atmospheric air are caused by the interaction of components of the primary pollutants. As an example, SO2 gas is generated by the burning of fossil fuels from industrial units and also by vehicles. Primary pollutants present in atmospheric air, in turn, can be combined to initiate smog formation (Idrees & Zheng, 2019). Previous reports showed that there are regulations that control and manage the degree of atmospheric air contamination and the amount of gas that can be released from different industries and that enter into the atmospheric air can be measured or identified using automatized gas analyzer (Padmaja, 2016). The various natural atmospheric conditions, which may include wind, direction, humidity, temperature, synoptic processes, and speed, make a critical contribution to the pollution of air. Immensely advanced techniques of air contaminant protection have been investigated in the past few decades in order to eliminate and monitor the discharge process of various contaminants such as volatile gases and in order to eradicate the serious risks of these gases on the environment and in turn on human health. However, the majority of the techniques have limitations such as low effectiveness, creation of secondary pollutants, high cost, and require complicated and advanced protocols. Instead, the creation and development of nanotechnology and nano-­ science has been found to have an advanced and environmentally friendly handling protocol for not only controlling but also remediating the contamination present in atmospheric air by using diverse techniques, which may utilize nanomaterials such as nanocatalysts, nano-adsorbents, sensors, and membranes/nano-filters that can completely purify the polluted atmospheric environment (Saleem et al., 2022).

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2.2.3 Water Pollution The nature of human activities connected to improvement in economic expansion results in the increase in waste production and thus result in the pollution of the environment, specifically for the various classes of water bodies. The problem of water contamination, which may result in numerous pollutant sources, has been found to be a global concern that has no national boundaries, and which needs an immediate international solution (Zelekew et al., 2021). Different types of industries such as petrochemicals and other chemical producers are important and major sources of contaminants of the environment, especially for water and soil resources. To have clean and sustainable water sources, researchers around the world have designed and developed different physico-chemical methods to remove and degrade pollutants of wastewater, which is becoming one of the top ranked and urgent challenging issues throughout the world (Olana et al., 2022), because, compared with other environmental types of pollutions, water pollution has been found to be the most serious and hazardous problems that needs the contributions of researchers and scientists throughout the world. This is because water contamination has a direct effect on human beings and any other living things within the ecosystem. Therefore, the various physicochemical techniques for eradicating pollutants have been intensively and widely explored and used throughout the world. However, as recent reports support, the majority of those physico-chemical wastewater treatment techniques have their own limitations such as the formation of secondary pollutants, and they are not effective and efficient enough in eradicating and removing waste from polluted water. Currently, the introduction of nanotechnology provides an auspicious approach to the efficient treatment of waste from water containing waste such as a highly adsorbent surface area, catalyst, and photocatalyst (Tilahun et al., 2022). Among the various classes of nanomaterials, those fabricated via green methods have shown an efficient potential approach to treating waste from polluted water because of the enhanced physico-chemical behaviors (Nasrollahzadeh et al., 2021).

2.3 Biosynthesis Techniques of Nanomaterials The numerous benefits of nanomaterials and their biosynthesis components including solvents, raw materials, reagents, and templating agent materials are driving up demand in the chemical industries. These chemicals and reagents have produced hazardous intermediates and products (Mittal & Roy, 2021; Roy et al., 2022a, b, c; Garg & Roy, 2022). Green chemistry is intercalated into the chemical industries to reduce the production of undesirable products, which could result in the pollution of the environment (Taylor et  al., 2008; Khan et  al., 2022; Pansambal et  al., 2022). According to the report by Mandal et al., one of the basic difficult issues in current nanotechnology and nanoscience is the development of reliable experimental advanced and environmentally friendly protocols for the fabrication of different

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types of nanoparticles (NPs) with a diverse variety of chemical compositions, size, and high surface area, morphology, optical and electrical properties, and charge mobility or diffusion rate (Grieger et al., 2012; Yadav et al., 2022). One of the most important aspects of nano-science, which studies materials with sizes in the nanometer grade (10−9 m), is the synthesis of various classes of NPs with specific morphologies and properties (Anandjiwala et al., 2007; Michael et al., 2022). Several physico-chemical synthesis methods have been used to obtain nanomaterials with improved properties, with the goal of having better control over particle size and distribution (Khan et al., 2017; Salve et al., 2022). For the manufacturing of these materials, several methods have been developed. Because of their capacity and shape, the ability to obtain and influence the properties of nano-sized materials has resulted in the expansion of comprehensive new possibilities in nearly all industries and scientific endeavors (Maganga & Taifa, 2022). As nanotechnology is substantially a collection of techniques for manipulating very small-scale properties (Sahoo et  al., 2021; Barage et  al., 2022), a number of advanced techniques have been explored for the development of various classes of NPs that have been recently used, primarily in the biological, chemical, and physical fields even if their method of synthesis was thought to be too expensive, and the use of pernicious chemicals as well as reagents in their synthesis makes bio-based synthesis the preferred method (Ahmed et al., 2021; Roy, 2021; Islam et al., 2022). The biogenesis method could involve the use of microbials (fungi and bacteria, for example) and plant (biomass and/or extract) sources for synthesis; this type of fabrication is very cost-effective, reliable, and eco-friendly (being considered nontoxic) (Mittal et al., 2013; Nagore et al., 2021; Pandit et al., 2022). Owing to their advantages in controlling particle morphology and size, the chemical devaluation and bio-based synthesis methods were widely used compared with the counterparts, which provide nanomaterials that have improved and enhanced properties with great potential for the desired applications.

2.3.1 Different Approaches for the Development of Nanomaterials According to various studies, the current research trends in the area of nanotechnology and nanoscience, which are used to develop reliable experimental processes for generating nanomaterials that have various sizes, properties, applications, and chemical compositions, have significantly attracted the attention of researchers worldwide. Indeed, despite the fact that Michael Faraday’s conventional strategies of a blend of metal soils are still utilized to create metal NPs, there have been a few enhancements and adjustments to the strategies that give superior control and management over the measurement, shape, and other related properties of the NPs. Analysts and scholars around the world have been able to examine quantum control, as well as other properties that are influenced by shape, and composition, since this progression. The exciting potential of nanomaterials can only be realized in

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Nanoparticles

Top-Down

Bulk material

Powder

Mechanical milling/ ball milling Chemical etching Thermal ablation/laser ablation Explosion process Sputtering etc.

Bottom-up UPS-synthesis-nanoparticles

Nanoparticle

Clusters

Atoms

Atomic/molecular condensation Vapour deposition So-gel process Spray pyrolysis etc.

Plants,microorganisms, and macrofungi Metal/metal oxide salt

Bioreductions

Fig. 2.1  Schematic representation of a protocol dedicated to the synthesis of nanoparticles (both bottom-up and top-down approaches) (Padi & Cernik, 2013)

nanomaterials-­based device applications through a blending of nano-building units and assembly strategies (Thiruvengadathan & Korampally, 2013). Nanomaterials can be created with two approaches: bottom-up and top-down. The method of top-­ down approach synthesis involves mechanically reducing large materials in their bulk form to the nanoscale, and large particles to NPs. This method is not safe because it results in particles with a broad dimension distribution, and the NPs produced may be impure. The bottom-up thinking entails joining atoms with atoms to form NPs, which is the most well-known method of NPs synthesis for the targeted applications and processes as can be depicted in Fig. 2.1 (Saba, 2014). The typical solid-state processing of materials includes top-down routes, which could be applied for the desired applications. This route begins with the bulk material and reduces its size, which involves the disintegration of larger particles through crushing, milling, and grinding. The most serious issue with the top-down approach is surface morphology structural imperfection. Such blemishes would have a significant effect on the physico-chemical properties and the surface chemistry of the biosynthesized materials in nanoscale. The ordinary top-down approach of nanomaterial synthesis is well known for causing critical crystallographic harm to the prepared designs (Jalilian et al., 2020; Gao et al., 2016). Bottom-up implies building

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Fig. 2.2  General synthesis methods of nanoparticles (Jadoun et al., 2021)

material from the bottom-up particle by iota and atom by particle. This strategy is found to be more commonly utilized for creating most nano-scale materials with uniform surface morphology and shape, enhanced optical properties, more crystalline materials that have good dispersion nature, which is also favorable for the targeted applications and activities. It covers a chemical blend viably and accurately controls the response to anticipate and encourage molecule development. In spite of the fact that the bottom-up approach is not novel, as can be shown in Fig. 2.2, it is basic in the manufacturing and preparation of nanostructures and nanomaterials (Thakkar et al., 2010). 2.3.1.1 Chemical Synthesis Methods Chemical precipitation is a fundamental bottom-up technique used to create nanomaterials. The sol-gel, hydrothermal, chemical vapor deposition as well as the plasma-enhanced chemical vapor deposition is the most frequently employed chemical synthesis protocol of nanomaterials. These methods could be used to generate NPs following a relatively cost-effective and simple sequence of steps, and at the same time is an environmentally friendly technique (Kida et al., 2007). According to research findings, with those chemical synthesis methods it is difficult to control the distribution of the shape and size of the particle, and the average crystalline size,

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which prevents the harness of the synthesized nanomaterials used in applications. Nanoscale precipitates can be obtained using a variety of techniques, including controlling solid-state diffusion and composite method approaches (mixing of two different materials and mechanically stirring them). In addition to those adapted methods, other approaches could include utilizing internal oxidation of materials, thin film coating deposition, and sputtering (Santhoshkumar et al., 2011). 2.3.1.1.1  Sol-Gel Processing Predominantly, the sol-gel process as can be supported in Fig. 2.3, involves engaging transitioning coordination from the state of liquid to the “sol” phase to a gelatinous network like “gel” phase formation. This in turn allows for the creation of a broad spectrum of low-temperature ceramic and related glass materials. It is a well-­ established advanced industrial step that is both economical and versatile for researchers (Thakkar et  al., 2010). Sol-gel processes are well known as they are suited to the development of oxide NPs and composite nanopowder, as well as access to organic–inorganic composite materials that have a nano-scale size (Allred et al., 2005; Ajmera et al., 2002). The treatment of the sol alters based on the proposed product. Dipping or spinning techniques, for example, can result in a thin-film coating process and exposing the resulting sol to a surfactant can result in powders. Extra condensation steps can result in very different polymeric and related nano-based structures such as direct, clusters, and colloidal particles, depending on the water-alkoxide molar proportions including temperature and pH. Simple procedure of nanomaterials synthesis using sol-gel method. During nanoparticles synthesis, once suspension is formed, the dried samples maintain their shape. This brings about within the order of a strong structure (e.g., aerogels and xerogels) within the shape of the form with huge surface-to-volume proportions, a tall pore network, and limited pore estimated dispersion.

Fig. 2.3  The basic flow of the sol-gel process (Dörner et al., 2019)

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2.3.1.1.2  Chemical Vapor Deposition Chemical vapor deposition (CVD), technique is currently the most likely general bottom-up approach to nanomaterial synthesis. It is now used to grow different types of nanostructures using a variety of components. Using spoiled gaseous materials such as reagents and solvents for the synthesis of nanoparticles creates two opportunity. One is used to clean the environment from pollution by changing into usable form and the second is used to easily access those materials (Adachi et al., 2003b). The CVD synthesis process can be carried out using temperature (TCVD) or alternatively plasma. Plasma also allows for the generation of more directional or aligned growth of the nanomaterials of interest. According to research reports, CVD processes are the popular synthesis routes for carbon nanotube (CNT) fabrication and preparation as can be presented in Fig. 2.4, because this process could be used for the production of large-scale CNTs with a good yield and high purity (Adachi et al., 2003a). Accordingly, in the TCVD process, a carbon-containing precursor salt is decomposed in a high-temperature furnace. The occurrence of a catalyst that can be placed on the samples’ surface area could be used to activate the growth and the reaction kinetics too. The most common and widely used carbon sources during the TCVD growth of CNTs are acetylene (C2H2) and ammonia (NH3) mixtures, with the presence of cobalt, iron, or nickel as the catalyst metal. 2.3.1.1.3  Hydrothermal Synthesis Method These types of synthesis protocol are widely used to create NPs of metal oxides such as iron, zinc, titanium, and those related to their corresponding precursor salts while maintaining control over particle properties. During nanoparticle synthesis in

Fig. 2.4 Schematics of the temperature chemical vapor deposition process furnace (Adachi et al., 2003b)

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the presence of water as solvent, the supercritical behavior of water will be changed by changing the reaction mechanism and the factors such as temperature, pressure, and concentrations. The synthesis of various classes of nanomaterials using this method can be done using either batch or continuous hydrothermal systems. The batch technique can accomplish a system with the desired ratio phases, whereas the continuous system can be used to achieve a higher rate of reaction within a shorter period of time. NPs are formed in a chemical suspension via a colloidal system composed of more than two phases of matter, which is mixed under controlled reaction parameters. The benefit of this synthesis method is the capacity to synthesize a large number of NPs that have optimized morphology, size, composition, optical and electrical properties, and surface chemistry at a reasonable cost. The hydrothermal synthesis method is in general both a facile and a fast method for the development of different NPs with enhanced applications (Gan et al., 2020). 2.3.1.2 Bio-assisted Methods of Nanoparticle Synthesis Nowadays, biological synthesis is a more appealing alternative to traditional methods (physical and chemical approaches) for manufacturing NPs. The bioreduction synthesis employs a number of bioactive ingredients such as plant extracts and microorganisms. Biosynthesis, also known as a green or biological synthesis protocol, is currently found to be the most environmentally friendly and cost effective and at the same time efficient method of synthesizing nanomaterials. High energy and pressure are not required as external experimental conditions (these lead to the energy-saving process), which also makes it cost effective. The active biological components act as surfactant (lowering the overall cost of the synthesis process); it can be used for large-scale NPs production, as well as to prevent overgrowth and maintain the stability of the nanomaterials, as supported in Fig. 2.5. There are three types of bio-assisted synthesis methods: (I) Biogenic synthesis with microorganisms as templates; (II) Biogenic synthesis using bio-molecules as templates, and (III) Biogenic synthesis that involves different parts of green plant extracts. 2.3.1.2.1  Plant Metabolites for NP Synthesis Plant concentrate is utilized because it is necessary for producing excess amounts of nanomaterials that have well-defined sizes with the best crystallinity, chemical composition, high purity, homogenized surface morphology, and are environmentally friendly too. Despite the utilization of bioactive molecules as a green alternative template to obtain small nanomaterials that have a small average crystalline size and uniform surface morphology having been known for a long time, the nature of the reducing agents has been obscure. Processes for synthesizing nanomaterials in the presence of plant extracts are easy and scalable with lower costs than the microbial processing technique or whole plants (Belcher et al., 2004). Plant extracts are vital within the setting of NPs amalgamation as they are used to diminish and stabilize

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Fig. 2.5  Schematic representation of the biogenic synthesis of nanoparticles (Jadoun et al., 2021)

Fig. 2.6  Some of the common plants used to synthesize various nanoparticles (Belcher et al., 2004)

the material. The nature of the synthesized NPs is decided by the source of the plant extract (Fig. 2.6). This can also be utilized to make the desired NPs. This happens as distinctive plant sources contain changing concentrations and combinations of natural reducing agents. The extract obtained from the plant is essentially attached to the precursor of metal salt during the synthesis process without applying of any energy during the easily manageable fabricating process (Arokiyaraj et al., 2017). The concentration of bioactive ingredients and the precursor salt as well as other related parameters such as contact time, temperature, and pH are the major factors that influence NP properties and production times, and their applications too. Eukaryotic organisms, such as mushrooms, have been extensively studied for their ability to form NPs of various compositions and sizes. Because of the variety of enzymes and their relatively simple manipulation, mushrooms are excellent candidates for the construction of metallic NPs and metallic sulfides, according to research. Furthermore, their ability to generate semiconductor NPs is well known and is being researched. The degree of development of NPs is very high when the aqueous plant suspensions are involved instead of microorganisms for the synthesis

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of biomediated NPs, which is a faster and more reproducible process (Mittal et al., 2013). 2.3.1.2.2  Bio Reduction Method Using Microorganisms Microorganisms can persist and develop in a high mediation of poisonous metal salts because of their energy-dependent efflux within the cell by film protein, which has capacities as ATPASE proton anti-transporter specialists and has chemical detoxification nature. Biosynthesis could be an organic or enzymatic response that takes place. As diverse organic agents utilize distinctive instruments with distinctive metals, and there are different bimolecular reactions for NPs amalgamation, the precise instrument for the amalgamation of NPs utilizing natural specialists has not, however, been completed (Fig. 2.7) (Rajput et al., 2020). 2.3.1.2.3  Bacteria-Mediated Synthesis Nanoparticles, especially metal oxide nanoparticles, could be synthesized using bacteria suspension in both intracellular and extracellular conditions (Saeed et al., 2020). However, culture contamination, lengthy procedures, a slow rate of synthesis, and less control over NP size and shape all pose risks to the process (Li et al., 2011).

Fig. 2.7  Bio reduction method using microorganisms

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Table 2.1 Comparison between chemically and biogenic synthesized nanomaterials (Gokulakrishnan et al., 2012; Gowramma et al., 2015; Menon et al., 2017; Smirniotis et al., 2018; Stoimenov et al., 2002) Properties Nature Reducing agents Method Ecological impact Antibacterial activity

Chemical method Expensive, toxic PEG, PVA, PVP, NH3, and others

Biological method Cost-effective, nontoxic Biomolecules of plants

A stabilizer (surfactant) is added to the first solution to control accumulation of NPs Environmental contamination is a drawback of chemical processes and chemical reduction processes are energy intensive Relatively low antibacterial activity

No need to add a stabilizing agent Sufficiently safe and do not have a negative impact on the environment Showing better antimicrobial activity

2.3.1.2.4  Alga-Mediated Synthesis Green growth, an assorted gathering of sea-going microorganisms, has been broadly utilized and detailed to synthesize NPs. They range in size from minuscule (picoplankton) to plainly visible (tiny fish) (Rhodophyta). Previously, the microalgae Isochrysis galbana, Chaetoceros calcitrans, Tetraselmis gracilis, and Cuscuta salina were utilized to fabricate Ag NPs for various purposes (Merin et al., 2010). Prasad et al. utilized Cystophora moniliformis marine green growth as a reducing and stabilizing agent to synthesize Ag NPs (Prasad et al., 2013). 2.3.1.2.5  Fungus-Mediated Synthesis Fungi extracellular construction of NPs is also a viable option owing to their cost-­ effective large-scale production (Guilger-Casagrande & de Lima, 2019). Because of their greater tolerance to metal-bioaccumulation properties, high binding ability, and intercellular uptake, fungal strains are preferred over bacterial species (Anandjiwala et al., 2007), as Table 2.1.

2.3.2 Current Advantages and Challenges of Green Synthesis Methods Nowadays, nanoscale materials are primarily synthesized using various types of physico-chemical methods, which have unpremeditated consequences such as pollution of the natural environment, the use of high amounts of energy sources, as well as potential health problems. Green amalgamation, which employs plant extracts rather than mechanical chemical specialists to decrease metal particles, was created in reaction to these challenges. Green blend is best for a conventional chemical blend as it is less costly, produces less contamination, and moves forward natural

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and human wellbeing and security (Ijaz et  al., 2020). There is an escalation of research being conducted on the construction of nanoscale metals using physical, chemical, and bio-assisted approaches (Horwat et  al., 2011; Wang et  al., 2007). Because of problems that are directly related to the application of huge amounts of energy (Banerjee et  al., 2020), the discharge of harmful toxicants (Hoag et  al., 2009), and the utilization of complex hardware and amalgamation processes (Ahmed et al., 2016a; Baruwati et al., 2009), physico-chemical synthesis methods are continuously used and replaced by green supported techniques (Alsammarraie et al., 2018). Aerosols (Smirniotis et al., 2018), ultraviolet radiation (Wojnarowicz et  al., 2018), and thermal decomposition (Ahmed et  al., 2016b) are all physical methods that require high temperatures and pressure. The vaporized strategy requires a firing temperature of almost 2400 K to deliver atomized vaporized beads and in turn NPs. The union promoted by the plasma-assisted physical vapor deposition method of PdO NPs requires three warm cycles between 250 and 800 °C. Chemical processes always involve the use of sodium borohydride along with dispersants (Hussain et  al., 2016). However, the green synthesis methods employ natural and environmentally friendly templates as both capping and reducing agents. Some biomaterials can be used as both surfactants and at the same time as dispersants (Devi et al., 2019), which can be used to save energy as well as avoiding the use of reagents that are too harmful and toxic. At the moment, biosynthesis primarily employs biomolecules of microorganisms (Bahrulolum et  al., 2021; Garole et al., 2019) or extracts of various plants (Jalilian et al., 2020; Leili et al., 2018), flowers (Ganesan et al., 2020; Khalil et al., 2017), roots, peelings (Ehrampoush et al., 2015), fruits, and seeds (Gao et al., 2016; Dhand et al., 2016). Green materials that contain the molecules of polyphenols and proteins (Nadagouda et al., 2009) can act as reducing agents to diminish metal particles to a lower valence state (Dowlath et al., 2021; Samuel et al., 2022). Green amalgamation has a few focal points over chemical and physical strategies: it is environmentally friendly (Alsammarraie et al., 2018) and pollution free (Devi et al., 2019; Nasrollahzadeh & Mohammad Sajadi, 2016). However, there are still a number of problems and challenges with raw material extraction, reaction time, and final product quality control. For example, ingredients are in limited supply (Devatha & Thalla, 2018). The synthesis time is long, and the product particle size is highly uniform (Gao et al., 2016). Major discoveries uncover the difficulty in topographical and regular dispersions of plants and their compositions. Green synthesis, in contrast, provides an alternative that is environmentally friendly approach that have potential applications in light of current environmental pollution associated with chemical synthesis (Ijaz et al., 2020). Biosynthesis of nanoscale materials has much potential compared with the counterparts, but still it has some drawbacks owing to the selection of materials, synthesis parameters, quality control of products, and application. These selected parameters pose a hindrance to the adoption of industrial applications and large-­scale applications of green-synthesized nanomaterials (Fig. 2.8). Although research suggests that local plants can be fully utilized, large-scale worldwide production of green-synthesized materials in nanoscale has been currently found to be a challenging issue. Intemperate vitality utilization, long response

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Limitations Material

Plant distribution

Increase in production cost

Raw material value Seasonality of plants

High temperature

Synthesis process

High pressure Long reaction time

Increase in energy consumption

Use of chemical reagents

NPs Quality

Uneven and irregular shape and size Low yield

Less ideal quality of product

Low removal efficiency

Application

Limitted application conditions

Practical difficulties in application

Fig. 2.8  Challenges and limitations in the green synthesis of nanomaterials

times, and the utilization of other industrial chemical reagents are the greatest concerns with regard to amalgamation preparation. The heat energy that might be required for a few green synthesized nanomaterials is very high and at same time the blend time is very long, requiring serious vitality utilization, which means the capacity of cationic species from the salt precursor that can live and develop into metal oxides, which will be harmful to the environment. Despite the utilization of naturally and environmentally available crude materials (nanoparticles based on different classes of capping and reducing agents that can be easily and highly accessible), the method does not continuously follow the principle of a green technology. On the other hand, extracts of green plants must be conserved before use (González-­ Ballesteros et al., 2017). Another critical restrictive issue in green synthesis could be a need for an indulgence of the green/biosynthesis procedures, and it is found to be troublesome to access the most precise chemical responses to clarify the blend preparation. Pomegranate (Punica granatum L.) peel extract was utilized as both a reducing and a capping agent to maintain the stability and overgrowth of the combination of Cu/Cu2O/CuO/ZnO nanostructures (Fuku et al., 2016). As a reducing and capping agent, an extract of Zingiber officinale (ginger) root can be utilized to develop Ag NPs (Kora & Rastogi, 2016), and as a chelating operator, Sageretia thea (Osbeck.) can be utilized to synthesize Fe2O3 NPs (Khalil et  al., 2017). In other words, current investigations can conclude that green extracts play a part within the amalgamation, but the particular response instruments included remain a secret. Furthermore, from the standpoint of industrial large-scale production, biomediated synthesized nanoscale materials lack mass balance and stoichiometric ratio production guidance. In terms of engineering, scaling up the green synthesis process is a

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major challenging issue in the current green-mediated synthesis of various nanomaterials. In terms of the quality of NPs, the size, the morphology, the optical and electronic band-gap energies of NPs generated using different extracts of green biomolecules vary greatly, and the properties determined are inadequate enough. According to the recently published reviews and reports, there are large variations in the case of particle size, making the green synthesis technique unsuitable for large-scale production and controlling the particle size of the fabricated nanomaterials during their production is a major challenge (Gao et  al., 2016; Jalilian et  al., 2020). For this reason, current knowledge of the green synthesis of nanoscale materials for different applications such as energy, batteries, waste treatment, and degradation, as well as in vitro activity, is highly limited.

2.4 Characterization of Synthesized Nanoparticles These days, many more sorts of nanoscale materials are developed than in the past decade, and in excess sums compared with more recently, the advancement of more exact and sound conventions for their characterization and checking-up of formation are needed. Typically, because the distinguishing problems of nanomaterials are needed to be legitimately analyzed and then compared with their corresponding bulk forms (Grieger et al., 2012). In reality, a more extensive analysis of NPs is essential and this requires a wide-ranging approach by combining the necessary strategies in a complementary way. Nanoscience is still experiencing consistent development, and the logical community is or may be mindful that there may be certain variations between the way in which explanatory characterization strategies work for materials that are within the nano size range, and their intense “traditional” ways of utilizing more “conventional” (plainly visible) materials (Wang et al., 2013). Even if a number of parameters are given serious consideration, two of the parameters examined during the analysis of NPs are estimate and shape. We are able to measure degree of conveyance, level of accumulation, surface charge and region, and to check the surface phonomenon (Otero et  al., 2017). Measurement, estimate dissemination, and natural ligands loaded onto the layer of the NPs may alter other properties and conceivable applications of the corresponding particles. Furthermore, the crystal structure and its chemical composition should need to be thoroughly investigated and analyzed before performing other characterization as the first step after NP synthesis before using for the targeted applications (Sharma et al., 2019).

2.4.1 Methods of Characterization The synthesized NPs are checked and confirmed depending on their average crystalline size, morphology, and surface charge by using powder X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, ultraviolet visible diffuse

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reflectance spectroscopy (UV-Vis/DRS), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) techniques. It is explored that characterization followed by analysis of NPs is assessed fundamentally by the molecule measurement conveyance and surface morphology. Nowadays, with the help of electron microscopy, it is conceivable to elucidate the morphology as well as the estimate of NPs (Harte et al., 2017; Liu et al., 2019). 2.4.1.1 Thermal Analysis Regarding NPs, many studies report the importance of studying the thermal properties of NPs. This thermal analysis is the heating of synthesized samples at different temperatures to attain the stability and identification of the calcination temperature of synthesized NPs (Anandjiwala et al., 2007). 2.4.1.2 X-Ray Diffraction X-ray diffraction is a well-known explanatory strategy, which is used to promote the analysis of crystal structures, subjective distinguishing proof of different compounds, measuring the stage of crystallinity, quantitative determination of chemical species, molecule sizes, isomorphs substitutions, etc. (Sadeghi & Gholamhoseinpoor, 2015). Initially, at the point when X-ray radiation reflects on any particle, it prompts the improvement of various diffraction plans, and a design reflects the physico-­ chemical feature of gem structures. In a gunpowder test, diffracted designs mostly start from the example and reflect its basic physical-compound highlights. In such manner, XRD can look at the essential highlights of a comprehensive assortment of materials, for example, biomolecules, inorganic impetuses, polymers, superconductors, glasses, etc. (Nyoman Rupiasih et al., 2013; Santhoshkumar et al., 2011). XRD is an ordinary method for the determination and analysis of crystallographic structures and morphology of nanomaterials. There is a variation in intensity with the number of constituents. The instrument dedicated to obtaining XRD data is implemented to collect the intensities of the scattered signals to achieve the diffraction pattern of the measured nanomaterials. The signal intensity versus the phase angle is normally the result obtained. When this pattern is used to perform the calibration of the crystal surface for the material’s crystalline structure, which might include the orientation and phase angles, it can be obtained exactly and easily for analysis and interpretation. Perceiving proof of the stages was carried out with the assistance of the Joint Committee on Powder Diffraction Guidelines records. An advantage of utilizing XRD estimation is that it can analyze the material while avoiding harmful effects on it (Saba, 2014).

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2.4.1.3 Scanning Electron Microscopy with Field Emission The FESEM lens may be a sort of electron-magnifying instrument that pictures the test layer by proofing an intense-energy bar of electrons in a raster check design. The electrons (e−) associated with the surfaces in particles made the test creating signals, which include data approximately the particle surface geology, composition, and alternative features such as conductivity nature (Belcher et al., 2004). The nature of signs resulted in backscattered electrons, cathodoluminescence, SEM including secondary electrons, specimen current, and transmitted electrons. The most common discovery mode is SE imaging. The spot estimate with a field emanation SEM is smaller than the ordinary one and can subsequently create exceptionally intense images, uncovering subtle elements within the range of 1–5  nm in estimate (Valenzuela-Muñiz et al., 2014). Electron magnifying instruments utilize a bar of more excited electrons to maintain materials on a fine scale. For this reason, the FE-SEM is a mandatory spectroscopic machine for intensive surface imaging in the nanoscience discipline (Wang, 2000). The SEM analysis is used to estimate the dimension and shape of synthesized NPs. SEM outputs intense images of the layer of a desired sample (Umer et al., 2012). An SEM spectroscopic machine works on the same principle as a light microscope, but measures electrons scattered by the sample rather than photons. 2.4.1.4 UV-Vis Spectroscopy Characterization The absorption spectroscopy is used for analysis of solution intensity. A beam is generated in the sample solution and the amount of light detected is measured (Raj & Trivedi, 2020). Mostly, particles may take in either UV or Visible light. Absorbance of UV-Vis light is used by the excitation of external e− from the conduction band to the valance band of the material. The Lambert–Beer law is the mathematical and physical foundation for measuring optical absorption in gases and solutions. Concurring with its foundation, absorption is straightforwardly relative to length l, and the concentrations of the retaining substance, c, and can be communicated as A = εbc, where ε could be consistent with absorptivity coefficient. In addition, the type and environment of the sample can influence absorption in a strong way. For instance, structural groups present in the analyzed structures influence the capture of light wavelengths promoted by particles and consequently indicate many different absorption bands in the spectrum. The dissolvable components into, which the retaining species is broken up, moreover, has an impact on the range of the species. The dimension of the particle is also important. If it is highly superior to λ, the light is partially scattered and partially reflected because instead of being a target for absorption, it preferentially interacts with the samples. Light penetrates into the sample when dealing with solids; it undergoes numerous diffractions, refractions, and reflections, and finally emerges diffusely at the surface. Solid samples cannot be handled using the Bouguer–Lambert–Beer law. It is because it considers that there is no light intensity loss related to refraction and scattering (Dowlath et al., 2021).

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45

The Kubelka–Munk equation is commonly used to analyze diffuse reflectance measurements:



F  R  

K 1  R  , s 2R 2

where R is the reflectance at the front face and k and s are coefficients related to absorption and scattering respectively. The Kubelka–Munk function (F(R∞)) is proportional to the concentrations of the adsorbate molecules. From the onset of the plot of the Kubelka–Munk function versus wavelength or photo energy, the energy gap of a semiconductor can be easily calculated. However, if the intention is to obtain a diffuse reflectance spectrum, an integrated sphere, reflected light, should be used to collect the diffuse reflectance light, also using a reference standard (BaSO4 or white standard) (as presented in Fig. 2.9). 2.4.1.5 Photoluminescence Spectroscopy Photoluminescence spectroscopy is the continuous discharge of radiation on the material surface beneath photoexcitation. Photoluminescence analyses are part of impressive and nondestructive methods, which are carried out in massive semiconductors, especially nano-sized materials, to analyze their stability. When a pump laser is used to provide pulsed excitation, the lifetime condition of the excited state can result. The setup will be called time-resolved photoluminescence (TRPL). While sufficient energy light illuminates a material, photons are absorbed and excitation processes are initiated. The excited carriers relax and generate radiation. The absorption can happen in materials while the energy of the photons is equivalent to or higher than the band-gap. Hence, we need to select diverse excitation sources to do the estimations concurring with distinctive materials with distinctive electronic band structures. Other exogenous variables such as temperature, excitation power, and applied external perturbation such as magnetic field and/or electrical field ­and/ Fig. 2.9  Interaction of light source with a nano-sample (Benhaliliba et al., 2012)

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K. D. Dejen et al.

or pressure, can help us to comprehensively understand the electronic states and bands that can be changed during the photoluminescence measurement (Benhaliliba et al., 2012). 2.4.1.6 Characterization Using Fourier Transform Infrared Spectroscopy The Fourier transform infrared (FTIR) spectroscopy characterization and analysis technique results in exactness, reproducibility, and an ideal signal-to-noise ratio. FTIR spectroscopy can distinguish small absorption changes on the arrangement of 10−3, which ensures spectroscopic performance, and may recognize the digested samples/suspensions that represent the whole components during synthesis of nanoparticles (Lin et al., 2014). FTIR spectroscopy is regularly utilized to check that biomolecules are similar to the amalgamation of NPs, which is more verbalized in insightful and advanced inquiries. This technique has moreover been extended to the examination of nano-sized materials, for example, the assertion of valuable iotas covalently joined together onto carbon nanotubes, silver, gold NPs, and graphene, or co-operation occurring between catalyst and substrate in the midst of the reactant strategy (Gurunathan et al., 2014). FTIR is a convenient, meaningful, cost-effective, non-invasive, and basic strategy aimed at promoting recognition of the role of biological molecules in silver nitrate reduction. Infrared measurements versus wavelength of light are utilized to decide the nature of related utilitarians and auxiliary highlights of natural extracts with NPs. The determined spectrum briefly reflects known reliance on the optical properties of NPs. The bio-assisted Ag NPs, by utilizing various leaf extracts, were analyzed using FTIR spectroscopy and appeared as distinctive crests (Preetha et al., 2013).

2.5 Applications of Nanomaterials The leading applications included the utilization of NPs for biomedical activities, which includes medication and quality conveyance, medication of cancer-caused disease, demonstrative devices, nutrition, etc., have been broadly examined throughout the past decade. Conjointly, NPs caused enormous intrigue owing to their exceptionally small estimate and huge surface versus volume proportion, and show completely novel extraordinary differentiation for huge particles of bulk material (Mittal et al., 2014). Exceptionally, as of late, NPs have gained importance in the field of natural remediation (Zhang et al., 2020). Pollution of soil, water, and air have made the ecosystem worse to live in. Pollutants poison food and affect eco-­ diversity and there are new threats to aquatic fauna and flora, water security, as well as community and public health. In order to provide solutions to these issues, nanotechnology has proposed innovative materials in nanoscale to not only sense but also mitigate recalcitrant toxic pollutants that can be present in soil and water (Dörner et al., 2019).

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2.5.1 Applications of Bio-assisted Nanomaterials for Wastewater Remediation Wastewater that can be discharged from factories (industrial and commercial ones) the same as sludge coming from residences in an untreated way and related to synthetic contaminants that can be added to aquatic resources is extremely harmful not to only humans but also to the ecosystem in general. Overwhelming metal NPs, natural compounds, and oils are essential to water toxins in this respect and they can render any water stream unfit for utilization (Chen et al., 2020). Through the progression of nanotechnology and nanoscience, a vast area of novel nanomaterial-­ based innovations has been discovered and utilized for a number of applications, especially in the area of waste treatment and in vitro activities. Nanomaterials as adsorption systems have an enormous surface area for reactions at a very low relative weight, are manufactured at a lower cost than activated carbon, and can effectively remove pollutants. Green nanotechnology has diverse applications in various fields (Fig. 2.10). In any case, development of bio assisted NPs should be broadly utilized in the treatment of distinctive sorts of wastewater. Table 2.2 shows the application of bio-­ assisted NPs in dye and wastewater remediation. Current wastewater foundations and promptly accessible secure water generation within both the progressed and emerging countries are battling to preserve the expanding requirements for higher-purity water direction. This implies that extraordinary proficiency requires low-cost innovation for water treatment (Wang et  al., 2014) (Fig. 2.11). The utilization of NPs, obtained through a green blend for treating wastewater and effluents, can be considered a promising and strategic elective connection to the current shape of treatment techniques. There are a number of bioactive compounds of plants that play essential parts within the union of different types of NPs, which has been found to have numerous applications. ZnO NPs, which could be obtained using the extract obtained from the leaves of eucalyptus for the treatment of industrial waste containing dyes: malachite green and also Congo red (Raota et al., 2019) obtained amazing results comes in sanitization of effluents with the presence of green union of silver NPs utilizing as a base the grape marc extract, of the species Vitis labrusca. Peternela et al. (2018) tended to the adsorption productivity of CuO NPs, which is generated by applying extract from pomegranate leaf to evacuate atrazine, caffeine, diclofenac, and nitrate. Moreover, Vidovix et al. (2019) utilized pomegranate leaf extract to deliver copper NPs and accomplished an evacuation proficiency of 166.02 mg/g of methylene blue color. Cusioli et al. (2020) created an adsorbent utilizing Moringa oleifera Lam. seed husks functionalized with presence of NPs to evacuate metformin from contaminated water. In their consideration, the researchers achieved a decrease of more than 99% of the sedate, hence demonstrating the viability of the modern material. Hassan et al. (2019) utilized chitosan, a compound extracted from shellfish as a premise for the improvement of an adsorbent able to evacuate methylene blue color from wastewater. The researchers

48

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Fig. 2.10  Applications of green nanotechnology in numerous areas

utilized a consortium of chitosan and silica to immobilize ZnO NPs and accomplished 293  mg/g of color evacuation. The utilization of chitosan in phosphorus expulsion has been increasing considerably owing to the proficiency accomplished by analysts, such as Chen et al. (2020) who assessed the execution of phosphorus adsorption through the utilization of the chitosan zirconium compound joined with polyethylene polyamine. The authors arrived at the greatest adsorption capacity of 103.96 mg−1/g of the adsorbent, in this way, illustrating promising utilization of the bio-adsorbent within the expulsion of phosphorus shown in wastewater. Xu et al. (2020) developed an adsorption method that proved to be effective in promoting the removal of phosphorus in excess present in certain water bodies; to do that, an adsorbent composed of a mixture of clay (bentonite) and chitosan impregnated with lanthanum could be used after being generated at a low cost. The author significance occurred because the unused adsorbent was able to expel 93% of phosphate at a starting concentration of 50  mg/L in 20  min of operation. The utilization of the principle of nanotechnology employing a nanocomposite of zero-valent press and clay is an amazing elective for expelling oxyanions in sea-going frameworks. Suazo-Hernández et al. (2021) accomplished the evacuation of 68.43% and 42.76% for arsenic and selenium respectively, beneath a starting concentration of 200 mg/L. The utilization of the nano-adsorbed composed of montmorillonite clay and zero-valent NPs appears to come about from As and Se diminishment prevalent

Au

Ag

Silver nanocomposite hydrogel Fe3O4 Iron

3

4

5

Leaf extract Leaf extract Peel extract

Lemon juice

Peel extract

Petal extract

11 ZnO

12 Cu

13 Ag

Seaweeds (algae) Tea extract

Rosa “Andeli”

Citrus grandis

Lemon fruits

Zanthoxylum armatum Amaranthus spinosus Tangerine

PP and SA Tieguanyin

4–29 nm, spherical

22–27 nm spherical

~21.5 nm, spherical

10–19.5 nm, spherical 6.58 ± 0.76 nm, spherical 15–50 nm, spherical 91 nm, spherical 50 nm, spherical

11–20 nm

60–105 nm

Properties Spherical from 10 to 20 nm (anatase) Piliostigma thonningii Spherical from 50 to 114 nm Lagerstroemia speciosa 41–91 nm, hexagonal

Templates Jatropha curcas L.

Extract obtained from Ficus benjamina the plant’s leaves Extract obtained from Mukia maderaspatana the plant’s leaves

Biological materials Extract obtained from the plant’s leaves Extract obtained from the plant’s leaves Extract obtained from the plant’s leaves

8 Ag 9 FeO 10 Iron oxide

6 7

Ag

2

Sr. no NPs 1 TiO2

Table 2.2  Applications of green nanomaterials for wastewater treatment

Khan et al. (2017)

Choudhary et al. (2017)

Shittu and Ihebunna (2017)

Reference Goutam et al. (2018)

Bio removal of lead Deterioration of bromothymol removal Deterioration of dyes Decolorization of dyes Treatment of contaminated solution Photocatalytic degradation of dyes Degradation of methyl red, 96% Degradation of commercial dye Putnam sky blue 39

(continued)

Suárez-Cerda et al. (2015)

Ahmed et al. (2016b)

Rajput et al. (2020)

Kora and Rastogi (2016) Arokiyaraj et al. (2017) Ehrampoush et al. (2015)

El-Kassas et al. (2016) Zhang et al. (2020)

Removal of methylene blue Karthiga Devi et al. (2016)

Applications Photocatalytic tannery wastewater treatment Remediation of heavy metal pollution Remediation (photocatalytic) of pollutants of organic nature Cd remediation in water

2  Green Synthesis of Nanomaterials for Environmental Remediation 49

Leaf extract

Leaf extract Leaf extract

Stem extract

15 α-Fe2O3

16 Ag soil NCs 17 ZnO

18 Au and Ag

5–15 nm, spherical 33–192 nm, cubic

Sapindus mukorossi

Au, ~25 nm; Ag, ~64 nm; spherical

20–40, 32.58 nm 88 nm, rod shape

4 and 5 nm, spherical

Properties 20–80 nm, spheroidal

Camellia sinensis

Ocimum tenuiflorum Plectranthus amboinicus Breynia rhamnoides

Curcuma and tea

Templates Eucalyptus sp.

PP plant waste extract rich in polyphenols, SA Sargassum aqueous

19 Nano zerovalent Tea extract iron Natural surfactant 20 Potassium zinc hexacyanoferrate nanocubes

Biological materials Leaf extracts

Sr. no NPs 14 Fe

Table 2.2 (continued)

Mittal et al. (2013) Fu and Fu (2015)

Alagiri and Hamid (2014)

Reference Wang et al. (2014)

Gangula et al. (2011) Catalytic conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) Degradation of Hoag et al. (2009) bromothymol blue Photocatalytic deterioration Jassal et al. (2015) of organic dyes

Applications Treatment of eutrophic wastewater Degradation of methylene orange Treatment of textile dye Degradation of methyl red

50 K. D. Dejen et al.

2  Green Synthesis of Nanomaterials for Environmental Remediation

51

Fig. 2.11  Water defilement sources and wastewater treatment strategies

to other substrates displayed by the creators. Bio-assisted NPs are profoundly capable of reusing and expelling overwhelming metals from wastewaters without damaging and debasement of an assortment of natural contaminants from wastewaters; in this way, filtering the wastewaters for reuse seems to unravel different water quality issues around the world (Goutam et al., 2020).

2.5.2 Wastewater Remediation Via Photocatalysis Photocatalysis holds a remarkable guarantee as a proficient and economical oxidation innovation for application in wastewater treatment. Quick advances in the design and synthesis of novel nanomaterials have moved photocatalysis to the cutting edge of feasible wastewater decontamination (Ren et al., 2021). The primary step of a photocatalytic waste treatment techniques is the excitation of photo-­ generated electron–hole sets with adequate vitality (up to or higher than the band-­ gap vitality (Eg) of the semiconductor). In other words, the excitation of e− within the valence band of the semiconductor in this way exchanges with the conduction band, leaving holes (h+) behind within the valence band. Next, a photocatalyst with a smaller band gap helps to capture more photons in visible light. In the next step appears the division of photo-generated electrons and gaps. Nevertheless, bulk e− carriers experience a recombination stage with the generation of phonons or warmth, coming about within the decrease in the number of energized charge carriers. Electrons and holes can participate in various surface chemical reactions; these

52

K. D. Dejen et al.

charge carriers may also be combined on the surface. Among them, the photo-­ generated electrons are broadly considered a reductant for specifically decreasing a few overwhelming metal particles. The isolated gaps may respond with a hydroxyl particle (OH−) or a water particle to create hydroxyl radicals (·OH), and directly take an interest in the oxidative deterioration due to their solid oxidizability, which is the essential pathway of the generation of ·OH. In expansion, the isolated electrons can react with broken-up oxygen within the water to create superoxide radicals (·O2−); upon an encouraging response, the deterioration produces OH.  This foreign matter in water are immediately adsorbed on the layer of the catalytic material, which increases the charge portability and encourages upgrades of its redox capacity, and after that, the arrangement of chemical responses occurs with the dynamic species created by the catalyst to obtain the debasement items. The redox responses specified above are recorded below (Conditions (2.1)–(2.9)): A comparative photocatalytic process can moreover happen within the so-called photo-Fenton response. The first stage of preparation/entail step of fabrication is to prepare ·OH radicals from Fenton reagents (H2O2 and Fe2+) beneath UV-Vis radiation (λ 99

Kaliraj et al. (2019)

(continued)

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Table 9.1 (continued) Photocatalyst Bimetallic ZnOSnO2 nanoparticles

Copper nanoparticles Nickel oxide nanoparticles Tin dioxide nanoparticles

Zinc oxide nanoparticles Titanium oxide nanoparticles

Gold nanoparticles Zinc oxide nanoparticles Silver nanoparticles Bismuth oxychloride Gold nanoparticles Bismuth oxyiodide Zinc sulfide nanostructures Bismuth oxybromide

Contaminant Methylene blue dye Sulfisoxazole Sulfamethoxazole Methylene blue dye Evans blue dye Methyl orange dye Methylene blue dye Rhodamine B dye Methylene blue dye Methylene blue dye Methyl orange dye Malachite green dye Malachite green dye Rhodamine B dye Methyl orange dye Methylene blue dye Methyl orange dye Rhodamine B dye Malachite green dye Methyl orange dye

Degradation efficiency (%) 88

References Mahlaule-Glory et al. (2022)

66 70 90

Mali et al. (2020)

88.13 100

Karthik et al. (2019) Luque et al. (2021)

98.6

Chen et al. (2019)

95

Al-Hamoud et al. (2022)

81.14

Hosny et al. (2022a)

100

Brindhadevi et al. (2020) Awad et al. (2021) Garg et al. (2018a) Ahmad et al. (2020)

93 91.8 92.55 95.15 99.47 90

Garg et al. (2018b) Munyai et al. (2022)

95.91

Garg et al. (2018c)

synthesis of the ZnO nanoparticles; this may have been responsible for the enhanced degradation efficiency of the synthesized ZnO nanoparticles from Phoenix roebelenii compared with other plant extracts. Furthermore, the molecular weight of the target pollutant can be a significant factor influencing the efficiency of the photodegradation process. For example, the photocatalytic performance of copper oxide (CuO) nanoparticles synthesized from Psidium guajava leaf extract for the degradation of reactive yellow and Nile blue 160 under exposure to solar light was investigated in a study by Singh et al. (2019). While 97% of Nile blue was degraded in 100 mins, only about 80% of reactive yellow 160 was degraded, even at longer times (120 mins). Nevertheless, the use of similar reaction conditions of dye concentration, catalyst loading, and irradiation source and time achieved a removal efficiency of 93% and 81% for Nile blue and reactive yellow 160, respectively. The complex structure and the relatively higher molecular weight of reactive yellow 160 were reported to be responsible for its

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lower degradation efficiency. On the other hand, the surge in the degradation efficiency of Nile blue was explained in terms of its rapid diffusion toward the photocatalyst’s surface, owing to its relatively low molecular weight. This demonstrates that the efficiency of the photocatalytic process is equally driven by the target pollutant’s molecular weight. Moreover, another notable factor that controls the efficiency of the photocatalytic remediation is the exposure duration to the light source. In a study by Ramasamy et  al. (2021), the efficiency of titanium dioxide (TiO2) nanocatalysts synthesized from Ludwigia octovalvis leaf extract in the degradation of several pollutants was evaluated. The research findings revealed maximum degradation efficiency values between 72.4% and 93.1% for alizarin red, crystal violet, methylene blue, and methyl orange, separately, after 6 hours of exposure. The efficiency of the breakdown of methyl orange and methylene blue were around 60 ± 5% after 1 hour of exposure to solar irradiation, but this increased with increasing exposure duration. This finding charts a pathway for tuning the large-scale application of biogenic TiO2 nanoparticles in the photodegradation of dyes and other recalcitrant contaminants from water resources. Interestingly, the doping of other metals onto nanomaterials synthesized from plant extracts has shown remarkable efficiency compared to undoped nanomaterials. For example, the utilization of the Ag NP/Degussa nanocomposite by El-Desouky et al. (2021) in the degradation of methylene blue was 100% efficient. Similarly, Lu et al. (2019a) reported a 100% degradation of phenol by using a copper oxide/titanium oxide composite. Also, methylene blue and Congo red exhibited 99.3% and 98.5% degradation, respectively, after using a Ag-doped ZnO nanocomposite (Sharwani et al., 2022). The comparative photocatalytic efficiency of CuO and Ag-CuO nanomaterials biosynthesized with Cyperus pangorei leaf extract was evaluated in the photodegradation of rhodamine B, with removal efficiencies of 74% and 92%, respectively (Parvathiraja & Shailajha, 2021). It is believed that the metal-doped nanoparticles exemplify altered band-gap and optical properties as well as enhanced surface properties and photogenerated carriers, and they consequently show improved photocatalytic activity (Huang et  al., 2016; Indira et al., 2021). According to previous reports, the efficiency of the photocatalytic degradation of chemical contaminants depends on the phytochemical type and concentration present in the precursor plant, the duration of exposure to the light source, the particle size and surface area of the catalyst, the band-gap energy of the biosynthesized photocatalyst, and the molecular weight of the target pollutant. Tuning these properties to the optimal conditions is fundamental to the complete mineralization of organics in polluted water. In addition, for most of the photocatalysts synthesized from plant materials, it is unclear whether extracts from other parts of the plants (such as bark, apart from the leaf) will find potential applications in the degradation of chemical pollutants. Table 9.1 provides a summary of different noncarbonaceous materials used for the photocatalytic remediation of pollutants.

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217

9.3 Green Noncarbon-Based Adsorbents for Heavy Metal Decontamination The adsorbent and the adsorbate physically and chemically interact at the surface during adsorption (Fig. 9.2). Temperature, the sorption mechanism between adsorbent and adsorbate, the medium’s pH, chemical interferences, sorbate concentration, and other factors all influence the sorption performance (Adeola et al., 2022; Iwuozor et al., 2022). Owing to their high sorption capacity and ecofriendly nature, chitosan and selected metal-based materials have long been used in the water purification process. Chitosan is the second most prevalent substance in the environment (Gusain et al., 2019). Due to its easy metal ion binding and powerful reaction with metal ions, chitosan has great potential for heavy metal removal. Abukhadra et al. (2019) reported that a composite of bentonite and chitosan, supported by green-fabricated Co3O4, was synthesized via a green approach, and its physicochemical characteristics were examined by using a variety of analytical tools. The morphological elucidation by FTIR, SEM, HRTEM, and XRD supports the formation of the composite. Bentonite/chitosan Co3O4 adsorbs Cr(VI) ions. The composite surface was saturated with Cr(VI) ions after 480 minutes, according to the kinetic studies. The sorptive interaction is a chemisorption type, best described

Fig. 9.2  Chitosan-magnetite nanocomposite strip’s elimination of chromium ions. (Adapted with permission from Sureshkumar et al. (2016))

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A. O. Adeola et al.

by the pseudo-second-order model. The isotherm parameters showed the monolayer adsorption of Cr(VI) ions, which was mostly represented by the Langmuir model. The theoretically determined adsorption maximal (qmax) value was 250 mg/g. Cr(VI) ions can be efficiently decontaminated in six runs by using the composite, which has high reusability. Moreover, it has high oxidation properties and can be used in the photocatalytic removal of Cr(VI) ions from water. Furthermore, bentonite/chitosan Co3O4 green composite can be used to treat real water samples, which makes it suitable for field application (Abukhadra et al., 2019). The successful synthesis and application of the MgO-bentonite composite for lead adsorption from wastewater was reported by Elkhatib et al. (2022). In 5 minutes at 298 K, a nanocomposite (MgO-bentonite) absorbed 94% of Pb(II), demonstrating a quick adsorption response. The produced nanocomposite has a 4.5-fold greater maximum Pb(II) adsorption capacity than bentonite (qmax = 75 mg/g). The Pb(II) sorption process is feasible, and the computed thermodynamic characteristics point to chemisorption as the main reaction controlling lead sorption by a nanocomposite. It is suggested that cation exchange and precipitation reactions are the main mechanisms for Pb(II) adsorption by the nanocomposite, according to FTIR/EDX studies. The effectiveness of a nanocomposite for lead removal from industrial wastewater and sewage was shown by using field samples in batch and column experiments. Adsorption performance levels of 93% and 95% from industrial wastewater and drainage wastewater, respectively, were recorded (Elkhatib et al., 2022). Therefore, a nanocomposite’s great efficacy in removing Pb(II) from wastewater shows that it is a good choice for effective Pb(II) removal from contaminated water. Adsorbents synthesized from rare earth metal (REM) offer outstanding sorption capabilities for arsenic, as demonstrated in numerous experimental findings (Lee et al., 2015; Li et al., 2010). These REM-based adsorbents are more efficient than ion exchange resins and other commercially available sorbents in terms of adsorption performance. Some of them have recorded adsorption capacities that is as high as 348.5 mg/g (Ti-loaded basic yttrium carbonate, at a pH of 7) and 480.2 mg/g (hydrated yttrium oxide, at a pH of 5). Additionally, the process of adsorption can be  completed quickly (Yu et  al., 2018). As a result, the REM-based sorbents are particularly well suited for treating wastewater that is heavily contaminated with arsenic, in order to reduce the arsenic to an acceptable level.

9.4 Green Noncarbon-Based Adsorbents for Removal of Organic Pollutants Recent studies have looked at nanoclay as a sorbent for the sorption of pollutants from water. Several types of clays, including bentonite, illite, pyrophyllite, sepiolite, kaolinite, and montmorillonite, are environmentally benign for eliminating toxins from water (Ighalo et  al., 2022). Sepiolite is a fibrous clay mineral containing silanol-surface-active sorption sites and has a highly porous structure. There have

9  Green Noncarbon-Based Nanomaterials for Environmental Remediation

219

been reports of its molecular sieving and adsorptive properties (Sabah & Ouki, 2017). Sepiolite is an effective material for the cleanup of polluted water, thanks to its high specific surface area (358 m2/g), total pore volume (0.559 cm3/g), and mean pore diameter (47.3 Å). Its 3D crystalline structure lends it rigidity, sturdiness, and robustness, and the adsorption of polycyclic aromatic hydrocarbons did not significantly alter its morphology (Cobas et  al., 2014). Pyrene and naphthalene were adsorbed onto sepiolite and organo-sepiolite via chemisorption and H-type sorption, with a maximum capacity of 8 mg/g. With activation energy ranging from 26.3 to 31.2 kJ/mol and a Gibbs free energy (G) of −29.35 kJ/mol, the reaction was fully endothermic (Adeola & Forbes, 2021a). Aluminosilicates called zeolites come in a variety of Si/Al ratios that are found in nature and reproducible in the laboratory. They are significant because of their crucial physicochemical characteristics, which include specific surface area, stability, high ion exchangeability, sorption, and sieving capacity (Fletcher et  al., 2017). Zeolites has various applications, including their utilisation as adsorbents, ion exchangers, membranes, and molecular sieves for soil and water treatment. This modified clay mineral is an effective, affordable, and accessible sorbent (Lee & Tiwari, 2012). Although geosorbents, such as sepiolite and zeolites, are naturally occurring and ecofriendly, one significant drawback of geosorbents is the difficulty faced in incredibly diverse systems. Because a geosorbent is a geochemical, developing a physicochemical sequestration model for its interaction with pollutants is complex. Mesoporous silica has a consistent twodimensional hexagonal pattern of channels and is a highly organized substance. Mesoporous silica has pores with a size range of 2 to 10 nm and a large surface area, making it effective for removing cadmium (Renu et al., 2016). Natural organic materials (NOMs) have the potential to produce harmful disinfection byproducts during the water treatment process. However, the removal of NOM from water is still insufficient. Fang et al. (2018) examined the effectiveness of layered double hydroxide (LDH) and its calcined forms in the removal of humic acid and fulvic acid (HA and FA) under different conditions. This study demonstrates that LDH may be efficiently calcined at 500 °C to increase the elimination of NOM, with adsorption capabilities of 98.8 mg/g for HA and 97.6 mg/g for FA at a pH of 9.5. Electrostatic interactions control how much HA and FA are removed by CLDH, and intercalation into LDH’s interlayers was not seen (Fang et al., 2018). A summary of ecofriendly and efficient noncarbon-based materials for the remediation of organic pollutants is provided in Table 9.2.

9.5 Noncarbonaceous Coagulants and Flocculants for Treating Water Flocculation is a process that occurs when a chemical coagulant is added to water, which facilitates the binding together of tiny particles, resulting in larger aggregates that are simpler to separate. It tends to transform tiny flocs into observable

220

A. O. Adeola et al.

Table 9.2  Summary of various metal-based adsorbents prepared via ecofriendly methods for remediation of organic pollutants Adsorbent γ-Fe2O3/chitosan composite Fe3O4 nSiO2 mSiO2 Fe-loaded SiO2

Contaminant Methyl orange

Adsorption capacity (mg/g) 29.50

Dichlorodiphenyltrichloroethane 97% Nitrobenzene 1155

Magnetic chitosan-Fe(III) CI acid red 73 hydrogel Zinc oxide nanoparticles/ Direct blue 78, acid black 26 chitosan Fe3O4/ZrO2/chitosan Amaranth

294.5

Chitosan-coated Reactive yellow 145 magnetite nanoparticles Fe3O4/Al2O3/chitosan Methyl orange composite Chitosan-MgO composite Methyl orange

70.10

Mg/Al double layered hydroxide CS-AL (aliquat-336 impregnated chitosan beads) Chitosan/ZnO nanorod composite (CS-ZnO) Bentonite/chitosan Co3O4

Humic and fulvic acid

98.8 and 97.6%

Alizarin, Methyl orange

126.58, 42.55

Alizarin red S

111.11

Congo red

303

Mesoporous MnFe2O4 NPs

Roxarsone

51.49

34.5, 52.6 99.6

416 60

References Zhu et al. (2010) Liu et al. (2014) Mangal et al. (2013) Shen et al. (2011) Salehi et al. (2010) Jiang et al. (2013) Kalkan et al. (2012) Tanhaei et al. (2015) Haldorai and Shim (2014) Fang et al. (2018) Ranjbari et al. (2019)

Abukhadra et al. (2019) Hu et al. (2017)

suspended particles. Pin floc particles are created when microfloc particles collide, and these particles eventually grow larger and thus become observable (Hanif et al., 2021). The inclusion of coagulants, constant agitation, and the collision of particles lead to the growth of flocs. Coagulants improve the settling rate and floc stability and aid in interparticle bridging. When the water reaches a certain floc strength and size, it is ready for sedimentation. To reduce the impact of negatively charged particles present on the surface of nonsettlable particles, such as color-producing organic molecules and clays, charge balance in the water is typically maintained by introducing coagulant chemicals of opposite charges in comparison to suspended solids (Yu et al., 2011). Decontamination procedures must be carried out on contaminated water  to ensure environmental and public health safety. Electrofloatation, ion exchange, incineration, rain, extraction, evaporation, membrane filtration, oxidation, membrane filtration, adsorption using activated carbon, advanced oxidation techniques,

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biodegradation, and coagulation are the methods most frequently used to clean up contaminated water. After charge neutralization is accomplished, lower  molecular weight suspended particles bind with one another. These somewhat larger particles, which are often invisible to the naked eye, are referred to as microflocs. Because water is constantly surrounding these particles, the water surrounding the new microflocs must be pure (Aguilar et al., 2003). More chemical coagulants must be added to the impure water surrounding the flocs to achieve charge particle neutralization and coagulation, which have not yet been accomplished. Coagulants also include the inorganic salts of polyvalent metals. Ferric chloride, calcium chloride, magnesium chloride, alum, ferrous sulfate, and polyaluminum chloride have all been widely utilized as coagulants thanks to their affordability (Brown & Emelko, 2009). Because of a few drawbacks, the use of inorganic coagulants in industrial wastewater treatment is constrained and relatively restricted. The increasing levels of metal (such as aluminum) in treated water have negative impacts on human health, and the production of enormous amounts of metal hydroxide sludge poses disposal problems (Hanif et al., 2021). Other significant challenges include the need for large amounts of water for improved flocculation, the technique’s limited applicability in different dispersed systems, its sensitivity to pH levels, its inefficiency in cold water (such as polyaluminum chloride), and its inefficiency for very small particles. Table 9.3 lists several inorganic coagulants for wastewater treatment, along with their likely benefits and drawbacks.

9.6 Conclusion and Future Perspectives On a laboratory scale, several nanomaterials have been developed and successfully used to remove hazardous pollutants from wastewater. However, before industrial wastewater is discharged into natural water reservoirs, the efficiency of the elimination of dyes, organic compounds, toxic metals, inorganic particles, and many other suspended particles present in the industrial effluents must be enhanced in order to meet environmental regulations. This chapter has covered natural noncarbon-based materials and nanomaterials that are based on inorganic materials. The use of these cutting-edge nanotechnologies holds promise for enhancing water treatment techniques and addressing some of the current major issues with water contamination and remediation. However, it is necessary to re-evaluate the overall wastewater treatment process for its cost-effectiveness. To reduce costs, increase purification performance, and lessen the drawbacks of the current treatment technologies, modern treatment technologies should be simple to integrate with existing wastewater treatment facilities.

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Table 9.3  Noncarbon-based coagulants with plausible merits and demerits. Adapted from Hanif et al. (2021) Noncarbonaceous coagulant Lime

Ferrous sulfate

Merits Most prevalent High efficiency No salt required Independent of pH

Ferric chloride

High efficiency between pH values 4–11

Ferric sulfate

High efficiency between pH values 4–6 High efficiency between pH values 8.8–9.2 Rare application Formation of denser flocs Increased settling rate Works well in hard water Only a small dosage required

Polyaluminum chloride

Sodium aluminate

Aluminum sulfate

Easy to apply and handle Low amount of sludge produced Highly effective between pH values 6.5–75

Demerits pH controlled Generation of large sludge Salt added to water Often requires improved alkalinity Undesirable increase in dissolved salts Often requires twice the alkalinity over Al Undesirable increase in dissolved solids Often requires addition of a base Less scientific data for validation

Useful with Al Expensive Low efficiency in soft water Useful only in a narrow range of pH Increases dissolved solids

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Chapter 10

Green Iron Nanoparticles for Nanoremediation Christopher Santos Silva, Vinicius Marx Silva Delgado, Vitória de Oliveira Lourenço, Flávia Cristina Policarpo Tonelli, Larissa Cristiane Souza Prote, Celso Judson Tadeu Batista Ferreira, Danilo Roberto Carvalho Ferreira, Antônio Pereira Ribeiro Arantes, Bryan da Paixão, Eduardo Thomaz, and Fernanda Maria Policarpo Tonelli

10.1 Introduction Environmental pollution, especially in recent decades, has alarmed the world’s population. Substances of different chemical natures (for example, f.ex., inorganic, and organic) or biological contaminants have decreased air, water and soil quality (Pansambal et al., 2022). Persistent pollutants are a grave concern once they can accumulate, and they are difficult to remove, threatening people with their toxicity (Mittal & Roy, 2021; Grover et al., 2022; Okoye et al., 2022; Khan et al., 2022; Prata, 2022; Michael et al., 2022). This type of pollution is responsible for a large number of premature deaths worldwide (Landrigan et al., 2019) and is a negative consequence of fast industrialization ignoring sustainability (Sulaymon et al., 2020). Environmental protection agencies have set threshold limit values (TLVs) for various environmental contaminants, aiming to offer a reference for safe levels of pollutants and their toxicity for human beings (Manisalidis et al., 2020; Uddin & Jeong, 2021). However, it is necessary to address the problem in a holistic way, such as through a specific health approach that accounts for environmental, animal and human health, and to propose solutions to remediate pollutants and restore contaminated areas.

C. S. Silva · V. M. S. Delgado · V. d. O. Lourenço · F. C. P. Tonelli · L. C. S. Prote Celso Judson Tadeu Batista Ferreira · A. P. R. Arantes · B. da Paixão · E. Thomaz F. M. P. Tonelli (*) Department of Biochemistry, CCO, Federal University of São João del Rei, Divinópolis, Brazil e-mail: [email protected] D. R. C. Ferreira Department of Materials, CDTN/CNEN, Federal University of Minas Gerais, Belo Horizonte, Brazil © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_10

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10.1.1 Main Threats of Environmental Pollution to Humans As previously mentioned, pollutants can be organic, inorganic or biological (Fig. 10.1). Among the inorganic ones, heavy metals have been used by human society since 9000 BCE for a variety of purposes. Nowadays, they are broadly used in the industrial scenario due to their various chemical properties (Cortizas et  al., 2016). Examples of these substances include As, Cr, Cd, Hg, Mn, Pb, Sb and Zn. Heavy metals are useful, especially as cofactors that allow and/or optimize the activity of enzymes, not only in humans but also in other living beings (Verma et al., 2020; Roy et al., 2021a; Roy & Bharadvaja, 2021). In all six classes of enzymes, zinc can act as cofactor (Gupta et al., 2016; Łukowski & Dec, 2018). However, because people have do not properly dispose those elements, commonly wrongly discharging them into water  from rivers, lakes and oceans, pollution from high concentrations of heavy metals has been made an urgent global concern. Few organisms are able to purge metals from their bodies by associating them with a protein or encapsulating them within a hydrophobic vesicula. So, they are toxic to most organisms in any ecological system and can intoxicate human beings, even when humans have not been in direct contact with these pollutants (Briffa et  al., 2020). This last scenario  might occur when heavy metals bioaccumulate. This means that when an organism takes in these contaminants, they accumulate inside their cells and might

Fig. 10.1  Environmental pollutants from different chemical nature

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never be expelled. As a consequence, they can accumulate even in higher level in animals higher up on the food chain and end up entering the human body through food, especially fish products (Alnashiri, 2022). Independent of the metal, they are safe for our physiology only when their concentrations are below certain thresholds. Even at low concentrations, if out of recommended limits, these hazardous metals can cause problems in living beings as a consequence of long-term exposure (Mitra et al., 2022). Heavy metal contamination in an organism may lead to many pathological adversities, depending on the organ affected and the level of exposure. These substances can induce neurodegenerative disorders, arthritis, cancer and respiratory diseases, even causing death. Exposure to arsenic, for example, may lead to malfunctions in cell replication, respiration and enzymes  in general because its ions attach to sulfhydryl groups. It can cause ischemic cardiovascular diseases, atherosclerosis, hypertension and ventricular arrhythmias. Heavy metal contamination stimulates the production of oxygen-reactive species and inflammatory mediators. It can also damage the liver and kidneys as a result of oxidative stress, causing also apoptosis. Arsenic can contribute to carcinogenicity and diabetes mellitus development in human beings as it is genotoxic, impairs DNA repair and reduces the expression of peroxisome proliferator–activated receptor gamma (Ohiagu et  al., 2022). Common sources of heavy metals include mining wastewater and industries that apply, for example, dyes that contain heavy metals (Xie & Ren, 2022). These dyes can be classified into chrome acid dyes, metal complex acid dyes, direct metal-­ containing dyes and reactive metal-containing dyes and can be found in some types of textile wastewater, for example (Velusamy et al., 2021). Pollution by organic contaminants is also a threat. Examples of these molecules include polycyclic aromatic hydrocarbons (PAHs), pesticides, dyes, phenol and its derivatives, polychlorinated biphenyls and pharmaceuticals. Among PAHs, benzo(a) pyrene exhibits the potential to be teratogenic, mutagenic and carcinogenic and is harmful to fetal development, especially fetal neurodevelopment, once it has crossed the placenta (Lawal, 2017). PAHs, as same as dioxins and volatile organic compounds, can pollute the air, causing bronchiolitis, asthma, chronic obstructive pulmonary disease, lung cancer, central nervous system dysfunctions and cardiovascular events (Manisalidis et al., 2020). Exposure to pesticides can cause acute poisoning and also contribute to the development of chronic illnesses such as allergies, cancers and asthma (Aziz et al., 2021). When it comes to dyes, most of these substances are carcinogenic and mutagenic and might not be retained/removed by water treatment. The majority of dyes are used in the textile industry to dye fabrics but can also be applied to cosmetics, food, paints, paper, plastic and pharmaceutical products. The wastewater generated and commonly discharged without any type of treatment into rivers can contribute to decreasing levels of dissolved oxygen content, causing death in aquatic ecosystems and eutrophication (Gurses et  al., 2021). Emerging contaminants of an organic chemical nature are also a concern once they have the potential to disrupt the endocrine system. They originate from the inappropriate disposal of pharmaceuticals and personal care products, and provided that they have enough affinity, these micropollutants might alter the transport

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procedures and properties of biological membranes (Pozza et al., 2022). For example, estrogens as pollutants have been associated with breast cancer and are harmful substances not only to humans (Adeel et al., 2017; Regnault et al., 2018). Ibuprofen, for example, might disturb the enzymatic, hormonal and genetic systems of human beings, and it has been found in water systems in big cities, turning into pollutants (Ali et al., 2016). Biological pollutants are especially concerning when it comes to underdeveloped countries and countries in development. The main source of this type of pollutant is the fecal contamination of water and soil from waste leachate, due to poor sanitation, causing fecal material to enter rivers (Prata, 2022). Recently, this fecal pollution has been related to resistant bacterial genes, and researchers are recommending taking a more holistic approach to understanding antibiotic resistance related to this type of pollution (Karkman et  al., 2019). Microorganisms such as Bacteroides spp., Bifidobacterium spp., Campylobacter spp., Clostridium perfringens, Cryptosporidium spp., Escherichia coli, Salmonella spp., Shigella spp., Toxoplasma gondii and Trichinella spirallis can be considered environmental contaminants and have as their sources not only human feces but also animal feces (Bianco et al., 2020). The main concerns related to this type of pollutant are the diseases they have the potential to cause in living beings, especially humans (Delahoy et al., 2018).

10.1.2 Nanoremediation of Environmental Pollution The abovementioned pollutants urgently need to be removed from polluted areas, and it is also necessary to reduce their production and their discharge into the environment. Different solutions are being proposed to do so, and these include nanomaterials once they present low cost, elegance and efficiency  in promoting remediation (Rajput et al., 2022; Roy et al., 2022b). Nano-based solutions to environmental restoration can involve photocatalysis, nanoadsorption, hybrid nanoremediation and/or nanofiltration. The nanoscale materials feature unique physicochemical properties for use in optical and electrical devices that can  detect pollutants (Roy & Bharadvaja, 2019; Roy et  al., 2021b; Yadav et al., 2022). Their high surface-to-volume ratio improves performance that can also be optimized  through chemical surface modification (functionalization) (Boulkhessaim et al., 2022). Nanoparticles can be used in nanoremediation and there are already a large array of protocols using them to detoxify different types of pollutants (Roy et al., 2021c, 2022a; Taifa et  al., 2022). These nanomaterials can, for example, also favor the biodegradation of contaminants performed by hyperaccumulators and soil microbes; they can  positively contribute to nanophytoremediation and microbial-­mediated nanoremediation, respectively (Raina et  al., 2020; Rajput et  al., 2022; Roy et al., 2022c).

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Among nanoparticles, the ones generated using iron can be used in different areas such as delivery (e.g., drugs), electronics and catalysis and are useful for remediating environmental contaminants too (Xu et al., 2022; Pandit et al., 2022; Garg & Roy, 2022). Iron nanoparticles (Fe NPs) can perform sustained removal (involving absorption), converting dangerous substances into less-toxic forms or degrading them and thus neutralizing their negative effects on living beings (Machado et al., 2015).

10.2 Characteristics of Iron Nanoparticles for Nanoremediation Especially in recent years, the use of Fe NPs to promote the remediation of environmental pollution has been receiving increasing attention, and their high potential to remediate different types of pollutants derives from their capacity to perform nanofiltration, nanocatalysis and nanosorption, for example (Saif et al., 2016). Fe NPs come in a large variety of forms, such as oxides, metallic and bimetallic structures. Each form has its own characteristics that make it suitable for certain types of applications. However, Fe NPs in general have relevant chemical and physical features, such as large surface areas and high reactivities (at much higher levels compared with those of bulk Fe-based materials), that make them suitable for nanoremediation (Gil-Díaz et  al., 2021). These nanoparticles’ capacity to work as adsorbents, for example, surpassess the capacity of traditional ones (such as biochar), and their surfaces can be chemically modified to optimize their performance (Gomaa, 2018). Among Fe NPs, zero-valent iron nanoparticles (nZVIs), iron sulfide nanoparticles and Fe3O4 nanoparticles are the most relevant for nanoremediation (Xu et al., 2022). Further, nZVIs have shown strong redox activity (as they can efficiently react with not only inorganic substances but also organic ones) and good adsorption capacity, and they can be produced at a low cost. So far, nZVIs have proven to be able to, at a concentration of 2%, adsorb 89.5% of As from polluted soil samples without causing negative impacts on soil parameters such as electrical conductivity and pH while reducing As phytotoxicity (Baragano et al., 2020). These nanostructures are commonly capped or attached to supports to avoid undesirable aggregation (Pasinszki & Krebsz, 2020). In addition, nZVIs stabilize with chitosan and can be prepared in a packed stream-rotating bed. Hexavalent chromium could be adsorbed at 101.837 mg/g to the nanomaterial (in a selective way in the presence of NO3−), and the nanoparticle could be reused more than four times (Fan et al., 2020). Also, nZVIs can be used to generate other iron nanostructures to remediate pollutants. After aging in a solution for 2 h, these nanostructures generated an Fe2O3 shell. The Fenton-like system Fe(@)Fe2O3 /NaHSO3 could promote the decomposition of more than 99% of the orange II present after only 30 s at a pH of 3 (Yang et al., 2020). Iron sulfide nanoparticles can be successfully applied in a wide range of areas, such as nanoremediation and medicine (as thrombolytic agents) (Fu et al.,

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2019; Gong et al., 2016). FeS (mackinawite), for example, can remediate inorganic pollutants (such as heavy metals) and organic pollutants (such as tetrachloroethene) (Chen et al., 2019). Fe3O4 nanoparticles (magnetite) feature magnetic properties that can be very useful; for example, magnetite can attach to heavy metals to recover them after remediation (Konate et  al., 2017). Particle suspension can be exposed to magnetic separators (ferromagnetic filaments in a column, for example), in order to recover magnetite in a fast, selective, and efficient way (Gomaa, 2018). However, there is also an important limitation in that: magnetic dipole–dipole attraction is able to facilitate aggregation. These particles exhibit good biocompatibility (Gu et  al., 2022) and can contribute to the microbe-based remediation of dyes, for example, helping electrons to flow from donating microbes to accepting microbes, serving as electron conductors contributing to the biodecolorization of methyl orange, for example (Qin et al., 2021).

10.3 Synthesizing Iron Nanoparticles Fe NPs can be synthesized through two categories of methods: top down or bottom up. Top-down methods start using larger structures and break them down into smaller ones, at the nanoscale. They can involve, for example, mechanical milling and/or grinding. The size reduction is continued until the desired dimensions have been reached. Synthesis can be performed by using sonication, for example, and commonly require a specific device, which can make the procedure expensive. Bottom-up methods are more cost-effective and involve the synthesis of larger structures from smaller ones. For example, chemical synthesis protocols commonly use salts containing the metal of interest to generate metallic nanoparticles by applying this type of method (Saif et al., 2016). Different physical and chemical methods can allow the production of Fe NPs; however, they can end up generating toxic waste, such as residues of NaBH4(a reducing agent). So greener methods are necessary to generate ecofriendly nanoparticles capable of being used in remediation. Green synthesis protocols can use biomaterials such as plants, microorganisms, biomolecules obtained from living organisms, etc. Some of the substances in these types of raw materials are toxic chemicals that generate and stabilize the nanomaterial (Bolade et al., 2019).

10.4 Green Iron Nanoparticles for Nanoremediation Fe NPs can be generated by using different types of bio-based raw materials. Thanks to specific properties that allow for the efficient remediation of pollutants (such as heavy metals) and thanks to magnetic properties that allow for the recovery and reuse of these nanoparticles, they can be successfully applied as ecofriendly nanoremediators (Table 10.1). The extract obtained by using Trigonella foenum-graecum

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Table 10.1  Examples of green Fe NPs that perform nanoremediation Biomaterials or organisms Plants Corchorus olitorius with Penaeus semisulcatus Hybrid of Eucalyptus urophylla and Eucalyptus grandi Moringa oleifera

Pollutants Cr3+, Cd2+, Ni2+, methyl orange, methylene blue and Congo red

Ref. Gomaa (2018)

Arsenate

Wu et al. (2019)

Cd2+ and Pb2+

Vázquez-Guerrero et al. (2021) Sravanthi et al. (2018)

Calotropis gigantea Methylene blue and aniline with Pithecellobium dulce Acacia nilotica Lead ions Catharantus roseus

Methyl orange and Escherichia coli

Trigonella foenum-graecum Black tea leaf Apple peel

Methyl orange Ibuprofen Malachite green

Green tea leaf

Methylene blue and methyl orange

Mentha spicata L.

As3+ and As5+

Moringa oleifera

Nitrate and Escherichia coli

Prangos ferulacea and Teucrium polium Bacteria Bacillus subtilis, B. pasteurii and B. licheniformis Algae Chlorococcum sp. MM1 Jania rubens, Sargassum vulgare and Ulva fasciata Algae present in the lichen Ramalina sinensis Algae in the lichen Ramalina sinensis

Arsenic

Da’na et al. (2022) Roy et al. (2022a, b, c) Radini et al. (2018) Ali et al. (2016) Ting and Ching (2020) Shahwana et al. (2011) Prasad et al. (2014) Katata-Seru et al. (2018) Karimi et al. (2019)

Cr6+

Daneshvar et al. (2018)

Cr6+

Subramaniyam et al. (2015) Salem et al. (2020)

Marine bacterial biofilm

Pseudomonas aeruginosa and Staphylococcus aureus

Safarkar et al. (2020)

Cd and Pb

Arjaghi et al. (2020) (continued)

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238 Table 10.1 (continued) Biomaterials or organisms Fungi Aspergillus niger BSC-1 Penicillium pimiteouiense Aspergillus terreus Penicillium oxalicum Fusarium proliferatum Fusarium oxysporum

Pleurotus florida

Penicillium spp.

Saccharomyces cerevisiae

Pollutants Cr6+ Cr6+ Congo red and direct blue-1 Methylene blue Malachite green, methyl violet and crystal violet Bacillus cereus, Listeria monocytogenes, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi, Candida albicans, Cd, Cr, Ni, Pb and Zn Candida albicans, C. glabrata, Candida sp., Bacillus cereus, Staphylococcus aureus, Micrococcus mucilaginosus, Klebsiella pneumoniae, K. terrigena, Pseudomonas aeruginosa and Escherichia coli Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Shigella sonnei, and Pseudomonas aeruginosa Bacillus subtilis and Escherichia coli

Ref. Chatterjee et al. (2020) Mahanty et al. (2019) Singh et al. (2022) Mathur et al. (2021) Schuster and Su Yien Ting (2021) Darwesh et al. (2021)

Manikandan and Ramasubbu (2021)

Zakariya et al. (2022) Ranjani et al. (2022)

seeds, for example, allowed the synthesis of magnetic iron nanoparticles capable of degrading 95% of the dye methyl orange, an environmental contaminant, in 90 min (Radini et al., 2018). This dye could also be degraded by Fe NPs generated by using the extract from Catharantus roseus. These nanoparticles have also shown good antibacterial activity against Escherichia coli (Roy et al., 2022a). It is possible to optimize nanoparticles’ characteristics by conjugating them with other nanomaterials. For example, Fe NPs generated by using the extract obtained from Corchorus olitorius leaves could detoxify heavy metals and microbes, but their results are inferior to that obtained from conjugating them with chitin nanoparticles generated from Penaeus semisulcatus. For absorptive capacity, the conjugate in fact produced results superior to any of the nanoparticles on their own. The conjugate could, in 30  min, remove 98.9%, 94.2% and 90.3%, respectively, of Cr3+, Cd2+ and Ni2+. Regarding the conjugate’s capacity to promote the degradation of the dye methyl orange, in 150 min, it offered a 95% removal rate; 90% of degradation was achieved when remediating pollution induced by methylene blue and Congo red. In this type of remediation, involving the organic structure of dyes, iron nanoparticles can promote the catalysis of a Fenton reaction, Fe2+/H2O2, releasing reactive oxygen species that can attack chromophore bonds, promoting its decolorization (Gomaa, 2018).

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Fe NPs have also demonstrated the potential for arsenic removal from aqueous systems (Majumder et al., 2019). Iron nanoparticles could be synthetized by using the leaves of a eucalyptus hybrid of the species Eucalyptus urophylla and Eucalyptus grandi, for arsenate (As5+) treatment in domestic sewage. The proposed mechanism suggests that the nanoparticle acts by forming a monodentate chelating ligand and a bidentate binuclear complex. Despite the considerable adsorption of As5+ in a deionized water solution (55.9%), the adsorption in simulated wastewater was lower (27.7%), probably due to the presence of other organic compounds that interfered with the remediation (Wu et al., 2019). To remove Cd2+ and Pb2+, iron nanoparticles conjugated with cellulose nanofibers (NFCs) were synthesized by using Moringa oleifera wood and leaf extract, by Vázquez-Guerrero et al. (2021). In the proposed mechanism, the adsorption of Cd2+ and Pb2+ ions occur at metallic and nonmetallic sites through ion-exchange processes, electrostatic bonds and hydrogen bonds, and the negative characteristic of the adsorbent contributes to the better adsorption of ions. The Fe NP/NFC conjugation was able to remediate 14,489 mg/g of Cd2+ and 89,088 mg/g of Pb2+ at a constant pH of 5. However, the synthesis of Fe NP/NFC applied ultrasound techniques, hydrolysis with 40% sulfuric acid and cryo-crushing with liquid nitrogen. Although these techniques and reagents pose no danger when properly handled, reproducing this protocol requires ultrasound equipment, and its cost increases due to the acid and especially the nitrogen. It was possible to remove methylene blue and aniline by using nZVI generated from an extract of Calotropis gigantea flowers (Sravanthi et al., 2018). To overcome the loss of effectiveness in the nanoparticle caused by aggregation, it was immobilized by chitosan (extracted from the seed of Pithecellobium dulce). The results revealed a remediation level of 85.5% for methylene blue and 74.8% for aniline, both under a 1:1:2 ratio for the biomaterial, chitosan and the nanomaterial. Ting and Ching (2020) successfully degraded malachite green dye with iron nanoparticles synthesized from apple peel extracts (APE-Fe NPs). The synthesized APE-Fe NPs came in elliptical and spherical shapes, promoting 71.51% of dye decolorization in the first minute of remediation; the removal rate increased with time and with a higher rate of exposure to nanoparticles. The results of APE-Fe NPs’ promoted remediation were promising according to degradation tests on other molecules, especially dyes. Da’na et  al. (2022) synthesized Fe NPs functionalized with diamine, from extracts of Acacia nilotica, in order to test their effectiveness in removing lead ions from aqueous media. The addition of diamine occurred by attaching N-[3(trimethoxysilyl)propyl]ethylenediamine (DA) to the surface of the nanoparticles, using two methods—post-synthesis (Fe NP-DA-G) and one-pot synthesis (Fe NP-DA-P)—and both chemically modified nanoparticles were compared with conventional Fe NPs. It was found that the Fe NPs produced via the one-pot synthesis process (Fe NP-DA-P) had the highest lead ion removal capacity, followed by the conventional Fe NPs and finally the nanoparticles formed via the post-synthesis process (Fe NP-DA-G).

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The improper disposal of medicines and other therapeutic substances pollutes the soil and water bodies with chemical substances; the drugs, as previously discussed, can cause environmental imbalances and put the health of the entire ecosystem at risk. In that regard, Ali et al. (2016) managed to synthesize Fe NP capable of absorbing ibuprofen. The nanoparticle was produced by applying black tea extract conjugated with carboxymethyl cellulose by using epichlorohydrin as a crosslinker. It managed to remove 92% of the ibuprofen, and the nanoremediators were recyclable.

10.4.1 Fungi-Based Synthesis of Fe NPs for Nanoremediation Among microorganisms, fungi have distinct and unique characteristics for use in green chemistry and sustainability. The synthesis of Fe NPs by using fungi commonly occurs from the extracellular hydrolysis of anionic iron-based compounds by various cationic proteins secreted by microorganisms (Anyanwu et al., 2021). Water bodies polluted by heavy metals are threatening sources of contamination, not only for humans but also for the entire ecosystem. Pollution by hexavalent chromium (Cr6+), for example, can cause extensive damage to kidneys and livers, in addition to being extremely carcinogenic and having the ability to accumulate in animals higher up on the food chain (Chatterjee et al., 2020; Avudainayagam et al., 2003). In order to mitigate this problem, aqueous solutions contaminated by Cr6+ could be successfully treated by using superparamagnetic iron oxide nanoparticles synthesized from extracts of the fungus Aspergillus niger BSC-1. This nanomaterial’s ability to remove Cr6+ maintained most of its efficiency for five test cycles (only 19.3% of removal capacity was lost during cycles) (Chatterjee et al., 2020). Iron oxide nanoparticles with Cr6+ remediating properties were also synthesized from fungi of the species Penicillium pimiteouiense, extracted from mangroves. The nanoparticles could be applied in the remediation of hexavalent chromium for 2 h, degrading about 90% of the pollutant at a pH of 2. Reuse tests were conducted, and the NPs exhibited efficiency offering reduction rates: 81.39% and 69.42% for the fourth and fifth cycles, respectively (Mahanty et al., 2019). Dyes are often discarded into water bodies at the end of industrial production chains. Azo dyes, such as Congo red (CR) and direct blue-1 (DB-1), regularly have toxic, mutagenic and carcinogenic properties, and as a consequence of their structure, they are persistent environmental pollutants that can barely be degraded naturally (He et  al., 2018). Iron nanoparticles synthesized by strains of the fungus Aspergillus terreus were used for the remediation of CR and DB-1 dyes. Fe NPs, which have demonstrated excellent efficiency in the degradation of dyes near a neutral pH value, have also exhibited the ability to be reused for five cycles, at which point a significant loss in efficiency had been reached (Singh et al., 2022). A culture of the endophytic fungus Penicillium oxalicum, extracted from the leaf of the plant Tecomella undulata, could be used to synthesize spherically shaped Fe NPs for the

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treatment of methylene blue–polluted samples. The Fe NPs degraded 99.17% of the dye in 6  h of reaction, proving to possess remarkable efficiency compared with other metallic nanoparticles (Mathur et al., 2021). Triphenylmethane-based dyes such as malachite green, methyl violet and crystal violet were also used in degradation tests using nanoparticles synthesized from fungi. Extracts of the endophytic fungus Fusarium proliferatum were able to synthesize Fe NPs, exhibiting an efficient capacity to decolorize triphenylmethane dyes. Fe NPs exhibited an efficiency of 18.3% for malachite green degradation, 28.9% for methyl violet and 23.8% for crystal violet. The studies revealed, after an analysis of the catalysis’ kinetics, that the rate of dye degradation was extremely efficient in the first 24  h, but after this period, no significant improvement was observed (Schuster & Su Yien Ting, 2021). Urban centers generate large amounts of chemical and organic waste that are often improperly disposed of, in that they are released into rivers and lakes within the vicinity of municipalities. In this context, samples of the fungus Fusarium oxysporum were used in the synthesis of Fe NPs, aiming to treat contaminated municipal waters. The fungus samples synthesized nanoparticles of small sizes, contributing to the efficiency of the treatment against biological contaminants such as bacteria, specifically Bacillus cereus, Listeria monocytogenes, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi. They could also treat pollution caused by the yeast Candida albicans and the heavy metals Cd, Cr, Ni, Pb and Zn (Darwesh et al., 2021). Pleurotus florida mushroom extracts successfully synthesized spherical-shaped Fe NPs with the capacity to act against yeasts such as Candida albicans, C. glabrata and Candida sp. It could also treat biological pollutants such as gram-positive (Bacillus cereus, Staphylococcus aureus and Micrococcus mucilaginosus) and gram-negative (Klebsiella pneumoniae, K. terrigena, Pseudomonas aeruginosa and Escherichia coli) bacteria. The best inhibitory performance was observed against Candida glabrata at 200  μg/mL (Manikandan & Ramasubbu, 2021). Aqueous extracts of the fungus Penicillium spp. were used in the green synthesis of iron oxide nanoparticles with antibacterial efficiency. Using 250 μg of the nanomaterial, the best antibacterial performance was observed when assayed against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Shigella sonnei and Pseudomonas aeruginosa (Zakariya et al., 2022). Importantly, yeasts can also be used to generate iron nanoparticles, serving as green materials in ecofriendly synthesis protocols. The yeast Saccharomyces cerevisiae, popularly used in fermentations for bread, can be used to generate green Fe NPs. The nanoparticles produced from it have proven to be able to remediate the bacteria Bacillus subtilis and Escherichia coli. However, the results from the remediation of B. subtilis were more efficient, proving that these nanoparticles exhibited better antimicrobial performace against gram-positive organisms (Ranjani et al., 2022).

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10.4.2 Plant-Based Synthesis of Fe NPs for Nanoremediation Current research on applying plant-based materials such as plant extracts for nanometal biosynthesis has started a new era of rapid and nontoxic protocols for producing nanoparticles (Iravani, 2011). Obtaining nanoparticles from plants is a fast-growing route to reduce costs and promote environmental sustainability. The green synthesis of iron nanoparticles mediated by plants guarantees greater stability compared to that performed by using microorganisms; this may be due to the natural presence of biomolecules such as flavonoids, terpenoids, polyphenols and other phytochemicals capable of promoting efficient metal-ion reduction. Different aspects can influence the properties of the generated nanoparticles. For example, by using Azadirachta indica extract and iron chloride, iron nanoparticles could be produced. However, extract and precursor salt concentration, temperature and pH impact the synthesis process. To prevent agglomeration, the concentration of the extract should be set at approximately 15% and the precursor salt at 1.0 mM of FeCl3. The temperature, an essential factor in determining and adjusting the size of the particles, was set at approximately 60 °C; salt reduction increases as a function of temperature but at high temperatures Fe NPs agglomerate. Finally, another key factor for the green synthesis of Fe NPs is the pH: in an acidic medium, the synthesis produces a smaller number of particles in the spectral reading, whereas in an alkaline medium, the synthesis produces large agglomerates of nanoparticles. The ideal pH for the synthesis of Fe NPs using Azadirachta indica was 6.0. Thanks to alterations in these parameters, new characteristics can be produced as desired in substitution to classic ones (Rathore & Devra, 2022). Almond shells served as raw materials to generate nZVI biochar, which remediated samples polluted by hexavalent chromium. Its removal efficiency achieved high rates—for example, 99.8% at a nanoparticle dosage of 10  mg/L in the first hour. Here, pH proved to be an important parameter. This result was achieved at a pH of 2–6, but at a pH of 7–11, the efficiency was approximately 20% lower (Shu et al., 2020). Green iron nanoparticles could be successfully generated by using green tea leaf extract, and the thus-generated nanomaterial proved to be able to promote the decolorization of the dyes methyl orange and methylene blue. The ecofriendly nanoparticle exhibited a performance level superior to that of those generated by using borohydride reduction (Shahwana et al., 2011). Aquatic environments can be negatively impacted by As from natural processes or result of mining and metallurgy activities. Exposure to this element is related to different types of damage to human health, such as cancers, skin diseases, and infertility. Chemical and biological methods for the removal of arsenic from aqueous solutions are used as ways of minimizing human exposure to this element. However, these methods come with limitations, such as their ineffectiveness in removing arsenite ions. Green-based iron nanoparticles, on the other hand, can reduce these limitations. For example, Mentha spicata leaves could be used to generate an extract that could synthesize green iron nanoparticles. The generated nanomaterial was

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entrapped in beads made of chitosan and was able to promote the efficient removal of As3+ and As5+ (Prasad et al., 2014). Prangos ferulacea and Teucrium polium could provide substances that acted as reducing and capping agents, allowing the green synthesis of Fe NPs capable of removing arsenic from aqueous samples in a nontoxic, low-cost and ecofriendly way. The essential parameters for synthesing these NPs and using them as nanoremediators were pH, contact time, stirring speed, arsenic concentration, adsorbent dosage and temperature. The best removal result was obtained at a pH of 6.0 and a contact time of 20 min (93.18% removal) (Karimi et al., 2019). Contaminants such as NO3 also threaten the drinking water supply. Iron nanoparticles generated through a green protocol using Moringa oleifera (which also offers properties such as coagulation and antimicrobial activity, such as against Escherichia coli) could act as decontaminating agents against this type of pollution. Current nitrate decontamination techniques (e.g., reverse osmosis, adsorption, ion exchange, precipitation and electrocatalysis) are not capable of ensuring complete removal, consume a large amount of energy and produce toxic byproducts such as iodine. The nanoparticle produced using M. oleifera offered efficient removal potential and synthesis when using lower-pH-generated materials with increased capacities for nitrate removal from the water (Katata-Seru et al., 2018).

10.4.3 Algae-Based Synthesis of Fe NPs for Nanoremediation Other organisms with promising applications in green protocols for Fe NP synthesis include algae: a polyphyletic group of organisms with wide biodiversity. Algae are eukaryotes and photosynthesizing organisms that can be macro- or microorganisms, both of which are able to synthesize metal nanoparticles. Their biological simplicity and mass production with high cost-effectiveness will be welcome advantages in the production of Fe NPs for nanoremediation once they can avoid generating waste consisting of hazardous chemicals and can mitigate the production of byproducts that can act as pollutants (Mukherjee et al., 2021). Algae are easy-to-handle and potentially biocompatible materials that not only promote remediation but also act as free radical scavengers exhibiting anticancer potential, for example. In nanoremediation, their capacity to reduce, cap and stabilize ions in protocols aiming to generate metallic nanoparticles is relevant (AlNadhari et al., 2021). Algae’s impressive potential to generate Fe NPs derives from their abundance in nature and easiness to reproduce under lab conditions (in a broad range of temperatures, taking a small amount of time to reproduce and generate the substances necessary to produce the nanomaterials). Living beings are not the only sources for synthesizing these NPs; the dry biomass of dead algae also can serve as a green raw material in the synthesis of NPs (Negi & Singh, 2018; El-Sheekh et al., 2021). Chlorococcum sp. MM1 could be applied to promote the synthesis of 20–50 nm spherical Fe NPs. The nanoparticles were attached to polysaccharides and

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glycoproteins hypothesized to be reducing and capping agents during synthesis. The nanomaterial was able to remediate pollution caused by Cr6+, surpassing bulk iron’s capacity to do so; while the latter reduced 25% of the Cr6+ to Cr3+, the Fe NPs reduced 92% (Subramaniyam, 2015). In order to fight biofilm formation, algae-based material was used to synthetize Fe NPs. Different nanomaterials were generated by applying aqueous extracts of Jania rubens, Sargassum vulgare and Ulva fasciata, separately. Fe3O4 NPs proved to be efficient against the biofilm generated by marine bacteria in the following order of efficiency: S. vulgare > J. rubens > U. fasciata. Interestingly, this was not the order of seaweeds fighting the biofilm alone (that order was J. rubens > S. vulgare > U. fasciata), and the presence of Fe NPs not only altered the order of effectiveness but also offered better results than the organisms when working alone (Salem et al., 2020). Importantly, algae can also serve as green materials in the synthesis of Fe NPs when integrating lichens. In fact, 10% of lichens are formed by associations involving symbiotic reunions featuring fungi and microalgae  cyanobacteria  and the other 90% are generated by associations involving fungi and other algae, and only (Grimm et al., 2021). The lichen Ramalina sinensis can contain algae species such as Trebouxia impressa and Trebouxia potteri (De Oliveira et  al., 2012). It could extracellularly generate Fe NPs from ferric chloride salts (Safarkar et al., 2020), and this nanomaterial exhibited the capacity to remediate biological pollutants, offering results similar to those of tetracyclin when remediating Pseudomonas aeruginosa or Staphylococcus aureus. The same lichen species allowed the extracellular reduction of ferric chloride salts to generate 20–40 nm Fe NPs capable of removing Pb (82%) and Cd (77%) from aqueous samples (Arjaghi et al., 2020).

10.4.4 Bacteria-Based Synthesis of Fe NPs for Nanoremediation Different nanoparticles have powerful antimicrobial properties against a variety of organisms. Fe NPs, in particular, which are commonly smaller than silver nanoparticles and can also feature superparamagnetism, can interact with the membranes of pathogens and can cause instabilities. Fe NPs can change a membrane’s permeability by disrupting its metabolic activity and causing its rupture (Gomaa et al., 2018). Their antibacterial potential may increase with increases in Fe concentration (Jegadeesan et al., 2019), and this trait may also be influenced by the Fe ion’s positive charge (Katata-Seru et al., 2018). However, bacteria can be not only the target of Fe NPs but also the green raw materials used to generate this nanomaterial in an ecofriendly manner (Bolade et al., 2019). Magnetic iron oxide nanoparticles could be generated by applying Microbacterium marinilacus (Mukherjee, 2017), Desulfovibrio magneticus strain

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RS-1 (Baumgartner et al., 2016) or Magnetospirillum magneticum AMB-1 in the synthesis protocol (Yoshino et al., 2018). Fe NPs capable of remediating environmental pollution could already be produced by using bacteria. Superparamagnetic iron nanoparticles could be generated by using Bacillus subtilis, B. pasteurii or B. licheniformis, offering a protocol capable of generating more nanomaterial than the chemical one and requiring less investment. The nanomaterial (37–97 nm in size) could efficiently remove Cr6+ from polluted samples. Fe NPs generated by using B. pasteurii offered removal rates above 99% (adsorbing 190 mg/g of nanomaterial) (Daneshvar & Hosseini, 2018).

10.5 Conclusion According to the data available in the literature, it is possible to ensure that Fe NPs are important and versatile tools to promote the nanoremediation of organic, inorganic and biological pollutants. When these particles are produced via green synthesis, the use of bio-based raw material allows for the mitigation of negative effects on the ecosystem, thus avoiding the use of harmful chemicals to generate the nanomaterial. This type of nanoparticle, generated from plants, fungi, bacteria and/or algae, has great potential to be used as an ecofriendly nanoremediator of contaminated environments.

10.6 Future Perspectives Studies should continue to develop new green synthesis protocols that can generate Fe NPs capable of efficiently and cost-effectively remediating environmental pollution. There are still important limitations that deserve to receive attention in order to turn green synthesis into a more attractive alternative for the large-scale production of iron nanoparticles. Ecofriendly methods that produce high yields of a nanomaterial are still needed. Reproducibility is also important because Fe NPs need to be produced with efficiency, presenting a uniform particle size, and with the required characteristics. Although these nanoparticles are not yet used in strategies for remediation in large scale or in the field, it is expected that this type of experiment will start being developed soon, in order to allow researchers to understand the impact of the nanoremediator in polluted ecosystems, where it will interact with not only pollutants but also living beings. The field of nanoparticles offers great potential for the development and future production of green Fe NPs on an industrial scale, aiming for the ecofriendly restoration of polluted ecosystems.

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Chapter 11

Green Silver Nanoparticles for Nanoremediation Kajalben Patel, Yogita Abhale, Rajeshwari Oza, Kun-Yi Andrew Lin, Alejandro Perez Larios, and Suresh Ghotekar

11.1 Introduction A breakthrough in modern nanotechnology has marked a crucial turning point in history. Modern nanotechnology deals with developing, altering, and imaging nanostructures that range in size from 1 to 100 nm. In 1959, Feynman made the first discovery of nanotechnology. Numerous industries, including food packaging, agriculture, electronics, medicine, animal husbandry, and health care, now have new potentials thanks to nanotechnology. Additionally, it is a modern industrial development (Roy et al. 2021a, b, c; Pansambal et al., 2022b; Aswathi et al., 2022; Dutta et al., 2022b; Sudheer et al., 2022; Tran et al., 2022). Because of atomic interactions on the surfaces of nanoparticles (NPs), which provide less coordination than bulk materials do, nanoscale particles have improved K. Patel · Y. Abhale Department of Chemistry, Government College Daman (Affiliated to Veer Narmad South Gujarat University, Surat), Daman, UT of DNH & DD, India R. Oza Department of Chemistry, S.N. Arts, D.J.M. Commerce and B.N.S. Science College (Autonomous), Savitribai Phule Pune University, Sangamner, Maharashtra, India K.-Y. A. Lin Department of Environmental Engineering & Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, Taichung, Taiwan A. P. Larios Research Laboratory in Nanomaterials, Water and Energy, Engineering Department, University of Guadalajara, Campus Los Altos, Tepatitlán de Morelos, Jalisco, Mexico S. Ghotekar (*) Department of Chemistry, Smt. Devkiba Mohansinhji Chauhan College of Commerce and Science (University of Mumbai), Silvassa, UT of DNH & DD, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_11

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characteristics. Depending on their fundamental shapes, NPs can be formed of metals or nonmetals (Michael et al., 2022; Barage et al., 2022; Kelele et al., 2021; Ghotekar et al., 2022; Mohammadzadeh et al., 2022; Pansambal et al., 2022a; Roy et al. 2022a, b, c; Prakash et al., 2022). Palladium, gold, platinum, silver, iron, copper, and semiconducting minerals make up the majority of metallic NPs (Soni et  al., 2021). Nonmetallic NPs, on the other hand, are predominantly made of carbon-­based compounds. Metallic NPs have been the subject of extensive research because they have eclectic optical, electrical, magnetic, and catalytic capabilities (Roy et al. 2021a, b, c, 2022a, b, c; Singh, 2022). Silver nanoparticles (Ag NPs), among other NPs, have drawn a lot of attention thanks to their distinct features (Roy & Bharadvaja, 2019; Roy, 2021; Salve et al., 2022). Because of their biological, optical, and electrical features, Ag NPs are crucial nanomaterials (NMs) that have been widely explored. As a result, these NPs have multifarious uses, such as in biosensing, environmental cleanup, the creation of nanodevices, medication delivery, and biomedicine (Ghotekar et al., 2019; Raina et al., 2020; Alharbi et al., 2022; Huq et al., 2022; Roy et al. 2022a, b, c). In the environmentally friendly synthesis of Ag NPs, diverse renewable natural resources are used in place of hazardous chemicals, such as bacteria, plant extracts, and yeasts (Rafique et  al., 2017; Abdelghany et  al., 2018). So-called biosources, made of natural materials, are incredibly rich in bioactive elements, including carbohydrates, amino acids, and polyphenolic chemicals that can function as reducing agents and restrain the formation of Ag NPs (Chung et  al., 2016; Ahmad et  al., 2019). Thanks to their natural origins and biodegradability, these biological compounds are comparatively safer than dangerous chemicals (Rajeshkumar & Bharath, 2017). Consequently, it is thought that this environmentally friendly synthetic technique will one day offer a viable option for the industrial and commercial manufacture of Ag NPs (Mousavi et al., 2018). The current status of water resources demonstrates the predominance of contamination by industrial wastewater drainage. An appropriate alternative is required to address the consequences of the serious health and environmental risks from polluted waters (Roy & Bharadvaja, 2021; Roy et al. 2021a, b, c; Garg & Roy, 2022). The several physical and chemical treatment processes now used to handle dye wastewater are more time-consuming, expensive, and inefficient. As an alternative, NPs have become better options for dye mitigation and decomposition because of their superior surface characteristics and chemical reactivity (Pagar et al., 2021; Dutta et al., 2022a; Lal et al., 2022; Khan et al., 2022). In this context, Ag NPs’ potential for treating dye wastewater has been thoroughly investigated (Marimuthu et al., 2020). Ag NPs can be produced by applying both top-down and bottom-up strategies. The top-down strategy entails using methods such as laser ablation and sputtering to reduce a bulk material to nanosizes. The bottom-up strategy, in contrast, involves generating NPs from smaller components through chemical and biological processes, among others. Biological techniques, also referred to as green synthesis techniques, which are generally carried out by using therapeutic plants, have merits that make them superior to physical and chemical processes because the former are more affordable, more accessible, and more environmentally beneficial (Beyene et al., 2017; Garg et al., 2020; Ijaz et al., 2020). This chapter analyses the implications of various parameters on green synthesis and covers new advancements in

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biogenic fabrication, optimization factors, and characterization approaches for Ag NPs, notably employing diverse plant extracts. Additionally, various uses for herbal plant–derived Ag NPs that have been biosynthesized for environmental remediation are explored.

11.2 Synthesis of Ag NPs Using a Diverse Approach The bottom-up and top-down strategies are the ones most usually employed for NP synthesis. Top-down processes involve physically milling, cutting, and shaping materials with tools. Bottom-up processes, which use chemicals or biological processes, are thought to be the best ways to manufacture NPs because they allow atoms or molecules to self-assemble into larger particles.

11.2.1 Chemical Approach The most popular technique for creating Ag NPs is chemical reduction employing both inorganic and organic reducing agents. Numerous reducing agents, including ascorbate, sodium borohydride, elemental hydrogen, sodium citrate, poly(ethylene glycol)-block copolymers, and polyol, can assist in the reduction of Ag ions to metallic Ag and the subsequent clustering of the metal, which produces Ag NPs (Merga et al., 2007). AgNO3 was employed as a metal precursor and trisodium citrate and sodium borohydride as stabilizers, and the end product was Ag NPs. Trisodium citrate and sodium borohydride are effective reducing agents for the synthesis of Ag NPs, with diameters ranging from 60 to 100 nm and from 5 to 20 nm, respectively (Agnihotri et al., 2014). Additionally, Ag NPs have been created by utilizing polyvinyl alcohol and hydrazine hydrate as reducing and stabilizing agents (Patil et al., 2012). The biomedical and biotechnology fields can also utilize spherical NPs. Chemical approaches have a substantial advantage over physical ones in that they can produce high yields of NPs (Ghotekar et al., 2015). However, chemical processes are expensive, and the chemicals needed to make Ag NPs, like citrate, are frequently poisonous and dangerous. Additionally, creating Ag NPs with well-­ defined sizes is exceedingly challenging, and different procedures must be taken to prevent particle aggregation (Zhang et al., 2016).

11.2.2 Physical Approach Evaporation-condensation and laser ablation are the most popular physical processes used to create nanoparticles. With such physical procedures, Ag NPs can create a little ceramic heater (Jung et al., 2006). In one work, for example, massive

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metallic particles were laser-ablated in solution to create Ag NPs (Sylvestre et al., 2004). There are benefits to using physical methods, such as rapid synthesis without radiation or other perilous reagents as reducing agents. However, these approaches have diverse limitations, such as significant energy consumption, low yield, uneven distribution, and solvent contamination (Elsupikhe et al., 2015).

11.2.3 Green Approach Ag NPs are produced through biological processes, also called green synthesis, by using organisms like microbial agents, plants, or biological agents (Pandit et  al., 2022). Plants and microbes (such as algae, bacteria, and fungi) are considered effective biological nano-factories for Ag NPs. Thanks to the potential for high yields and considerable protein concentrations, the synthesis of Ag NPs by employing microbes has garnered a lot of interest (Tarannum & Gautam, 2019; Alharbi et al., 2022; Huq et  al., 2022). Nevertheless, there are obstacles with this approach in terms of maintaining culture and progress. The utilization of diverse plant extracts in the bio-inspired fabrication of NPs has various benefits over other environmentally friendly synthesis techniques because plants are benign to the environment and simple to work with (Ghotekar et  al., 2018, 2019; Bangale & Ghotekar, 2019). Additionally, this use provides availability, low costs, great yields, minimal toxicity, and energy efficiency (Ghotekar, 2019; Ghotekar et al., 2021; Kashid et al., 2022). Amino acids, steroids, saponins, glycosides, flavonoids, tannins, and other polyphenols are phytochemicals in plants that act as reducing, capping, and stabilizing agents during the biogenic fabrication of NPs (Korde et  al., 2020; Nikam et  al., 2019; Singh et  al., 2018a; Cuong et  al., 2022). Figure  11.1 and Table  11.1

Fig. 11.1  Schematic layout for plant-assisted green fabrication of Ag NPs and their uses

Fruit

Seed

Fruit

Latex

Alstonia scholaris

Annona squamosa L.

Berberis vulgaris

Calotropis procera

UV-vis, TEM, FT-IR, FE-SEM

UV-vis, EDX, XRD, SEM

Peel

Fruit

Citrus reticulata

Citrus X sinensis

UV-vis, XRD, FT-IR, DLS, SEM

XRD, UV-vis, FE-SEM, TEM, EDX, FT-IR UV-vis, FT-IR, HR-TEM, XRD

Flower

Aerva lanata

Chloroxylon swietenia Leaf

Characterization technique XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), zeta potential, AFM, EDAX, UV-vis, FT-IR XRD, TEM (Transmission Electron Microscopy), SEM, EDAX, DLS (Dynamic Light Scattering), zeta potential, UV-vis, FT-IR XRD, SEM, EDS, HR-TEM, DLS, zeta potential, UV-vis, FT-IR XRD, UV-vis, TEM, FT-IR

Plant part Leaf

Botanical name Aegle marmelos

Quasi-spherical

5–50

Spherical

35.4

10–35

6.9

Spherical

Dispersed spherical and rod-shaped Spherical

22.14 ± 0.42 Spherical

50 ± 5

Spherical

Spherical

7 ± 3

22

Shape Spherical and irregular

Size (nm) 5–30

Table 11.1  Diverse plant-mediated NPs with physicochemical parameters References Sampath et al. (2021)

Catalytic reduction

Dye degradation

Antibacterial, larvicidal, and catalytic activities Catalytic, antibacterial, and anticancer studies Antibacterial, and photocatalytic activities Antibacterial and dye degradation

Catalytic degradation

(continued)

Jaast and Grewal (2021) Yadav and Chauhan (2022)

Chandhru et al. (2022) Nga et al. 2022)

Hashemi et al. (2022)

Jose et al. (2021)

Rajasekar et al. (2021)

Antibacterial, antioxidant, Palithya et al. (2022) and catalytic activities

Application Antimicrobial, larvicidal, and photocatalytic activities

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Characterization technique UV-vis, XRD, SEM, EDS, FT-IR, DLS, zeta potential XRD, FT-IR, UV-vis, PL, TEM, EDX, XPS XRD, FT-IR, UV-vis, TEM, SEM-EDAX

UV-vis, XRD, FT-IR, HR-TEM, XPS UV-vis, XRD, SEM with EDS, TEM, FT-IR UV-vis, XRD, FE-SEM, TEM, EDS, FT-IR XRD, UV-vis, HR-TEM, FE-SEM, zeta potential UV-vis, XRD, FT-IR, SEM, DLS, zeta potential, HR-TEM, BET, EDS XRD, TEM, SAED, UV-vis, EDX, FT-IR, TGA–DSC UV-vis, FE-SEM, EDX, FT-IR, TEM-SAED, DLS

UV-vis, XRD, FT-IR, SEM, EDX, TEM, AFM UV-vis, XRD, FT-IR, TEM, SEM, EDX

Plant part Pod

Leaf

–

Flower

Flower

Fruit

Leaf

Seed

–

Leaf

Leaf

Fruit

Botanical name Clitoria ternatea

Cyperus pangorei

Ferula assafoetida

Heterotheca subaxillaris Jasmine

Jujube

Kalanchoe pinnata

Nigella Sativa

Panax vietnamensis

Ruellia tuberosa

Sida retusa

Syzygium malaccense

Table 11.1 (continued)

17

20–40

55.65

Spherical

Spherical

Spherical

Spherical

Spherical

10–12

10

Spherical

Spherical

Nanofiber

Quasi-spherical

Spherical

Spherical

Shape Spherical

38

25–35

22

20–30

8

32–60

Size (nm) 62.51

Antibacterial, and catalytic activities Antimicrobial, anticancer, and photocatalytic activities Antibacterial and catalytic activities Antibacterial catalytic activities

Antibacterial and photocatalytic activities Antibacterial, anticancer, and catalytic activities Antibacterial and photocatalytic activities Photocatalytic activities

Anticancer, antioxidant, and photocatalytic activities Catalytic activity

Photocatalytic activities

Application Dye degradation

Herbin et al. (2022)

Sooraj et al. (2021)

Seerangaraj et al. (2021)

Tran et al. (2021)

Chand et al. (2021)

Naghizadeh et al. (2021) Mehata (2021a, b)

Rajasekar et al. (2022) Aravind et al. (2021)

References Varadavenkatesan et al. (2020b) Parvathiraja et al. (2021) Subramaniam et al. (2022)

258 K. Patel et al.

Rhodiola imbricata and Withania somnifera Tulsi

Punica granatum

Poria cocos

Botanical name Syzygium samarangense Thunbergia grandiflora Trigonella foenum-graecum Zingiber officinale Decaschistia crotonifolia Fucus gardener

Leaf

UV-vis, BET, HR-TEM, XRD, SAED, EDX

Characterization technique UV-vis, XRD, SEM, EDS, TEM, FT-IR, XPS Flower UV-vis, XRD, SEM, EDX, FT-IR, DLS Seed UV-vis, XRD, FT-IR, TEM, SEM, EDX – UV-vis, XRD, FT-IR, TEM Leaf UV-vis, XRD, TEM, EDAX, FT-IR, DLS, zeta potential Whole UV-vis, XRD, HR-TEM, plant SAED, EDX, FT-IR Mushroom UV-vis, XRD, FT-IR, TEM, FE-SEM, EDX, DLS Seed UV-vis, XRD, FT-IR, SAED, HR-TEM Root FT-IR, UV-vis, DLS, HR-TEM, SAED, EDX

Plant part Flower

Spherical Spherical Spherical Spherical Spherical Spherical Spherical

82 10–20 13.6 19.39 20 10–35 32–42

–

Spherical

–

5–10

Shape Spherical

Size (nm) 9

Catalytic reduction

Singh et al. (2018b)

Application References Antibacterial and catalytic Basalius et al. (2022) activities Catalytic activity Varadavenkatesan et al. (2020a) Antibacterial and Awad et al. (2021) photocatalytic activities Dye degradation Mehata (2021a, b) Antibacterial, antioxidant, Palithya et al. (2021) and catalytic activities Catalytic reduction Princy and Gopinath (2021) Metal sensing and Doan et al. (2022) catalytic reduction Photocatalytic and Muthu et al. (2021) catalytic reduction Catalytic, antioxidant, and Kapoor et al. (2022) cytotoxic study

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demonstrate how various plant parts, such as bark, fruit, seeds, leaves, flowers, roots, and stems, can be used to create Ag NPs.

11.3 Plants Extract–Mediated Green Production of Ag NPs Thanks to the availability of several plants and their straightforward and secure application, the plant-assisted biosynthesis of Ag NPs is an extensively used approach. For the biogenic fabrication of Ag NPs, various plant materials, including leaves, roots, fruit, peels, flowers, etc., have been successfully used (Table 11.1). Numerous bioactive substances, including alkaloids, terpenoids, flavonoids, phenols, vitamins, and tannins, as well as different amino acids, enzymes, and proteins, can be found in plant broths (Ghotekar et al., 2018, 2019). Plant extracts include these functional biomolecules, which make it simpler and more stable to synthesize bioactive Ag NPs utilizing plants. Numerous studies have been conducted in the past few years for the bioproduction of Ag NPs employing diverse plant parts, including leaves, seeds, fruit, flowers, roots, peels, stems, etc. For instance, the simple, quick, and environmentally friendly production of bioactive Ag NPs was accomplished by using the leaf extract of Aegle marmelos (Sampath et al., 2021). They also looked into the effectiveness of biosynthesized Ag NPs for clinical and environmental applications. By using a flower extract from the Aerva lanata plant, Naidu (Palithya et al., 2022) created Ag NPs. Raman et al. (Rajasekar et al., 2021) employed Alstonia scholaris fruit extract to quickly produce Ag NPs. The fruit of Berberis vulgaris and the seeds of Annona squamosa were employed for the green fabrication of Ag NPs (Jose et al., 2021; Hashemi et al., 2022). Depending on the plant or section of the plant that was utilized for fabrication, the amount of time required for synthesis, the size, the shape, and the bioactivity of the generated Ag NPs vary significantly. For instance, utilizing Panax ginseng root extract and a 2 h reaction, Ag NPs with a size range from 10 to 30  nm were created (Singh et  al. 2016a, b). However, utilizing Panax ginseng leaf extract, Ag NPs of 5–15 nm were created within 45 minutes of the reaction (Singh et al. 2016a, b). The leaf extract of Chloroxylon swietenia created spherical or rod-shaped Ag NPs, according to Nguyen et al. (Nga et al., 2022). Also, Clitoria ternatea and Cyperus pangorei plant extracts generated spherical Ag NPs (Varadavenkatesan et al., 2020b; Parvathiraja et al., 2021). The simple, quick, high-quality, and stable fabrication of Ag NPs utilizing plant extracts has been significantly impacted by several factors, including the concentration levels, incubation periods, pH, and temperature, among others. (Aravind et al., 2021; Rajasekar et al., 2022; Subramaniam et al., 2022). The chemistry of reduction and oxidation is the most likely mechanism for producing Ag NPs by using plants. According to some theories (Chand et al., 2021; Mehata, 2021a, b; Naghizadeh et al., 2021; Tran et al., 2021), the plant broth contains alkaloids, vitamins, enzymes, organic acids, terpenoids, flavonoids, polyphenols, amino acids, and polysaccharides that play important roles in the synthesis of Ag NPs.

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11.4 Critical Factors for Sustainable Green Synthesis of Ag NPs 11.4.1 Optimal pH An earlier study looked into ways to modify the pH during the fabrication of Ag NPs to alter their size, topology, and stability. The maximum quantity of synthesized NPs was achieved at pHs of 7–9, and a pH of 7 was optimal to assure the reduction of Ag+ to Ag0 during Ag NP formation. Numerous investigations have demonstrated that as the pH rises, Ag NP production rates rise (Ghotekar et  al., 2018, 2019; Mehata, 2021a, b; Naghizadeh et al., 2021). Additionally, Ag NPs were nearly spherical at higher pH levels, and increasing the pH to 8 significantly accelerated the reaction rate (He et  al., 2017). According to other authors (Joshi et  al., 2018), synthesizing Ag NPs at an alkaline pH has several benefits, such as a high yield, stability, a quick growth rate, and an enhanced reduction reaction. A basic pH enables more -OH groups to participate in the reduction process, boosting the yield. Generally, -OH groups in plant broths play important roles during the production of Ag NPs (Singh et al., 2009).

11.4.2 Temperature One of the most crucial factors influencing the topology and size of bio-fabricated Ag NPs is temperature. Several investigations have demonstrated that Ag NPs’ shape changes and their dimensions decrease as the reaction temperature rises (Verma & Mehata, 2016; Asimuddin et al., 2020; Nasaruddin et al., 2021). To create Ag NPs, the authors used olive leaf extract. They discovered that raising the temperature of the process might cause a rapid reduction in Ag+ ions and the nucleation of Ag nuclei, resulting in the formation of tiny and spherical NPs. A different study (Kredy, 2018) also showed that whereas high temperatures create small NPs, lower reaction temperatures yield larger NPs. Furthermore, even at the low temperature of 40 °C, Vitex agnus-castus leaf extract was found to quickly reduce Ag+ ions. In contrast, another study found that creating Ag NPs was most effective at temperatures between 60 °C and 80 °C (Stavinskaya et al., 2019). As a result, high temperatures encourage nucleation, whereas low temperatures encourage growth in the synthesis of NPs.

11.4.3 Concentrations of Plants Extract and AgNO3 The concentration of plant extract in the reaction solution can be increased to increase the absorbance levels of the samples (Anandalakshmi et al., 2016). Higher concentrations of plant extract cause biomolecules to function as reducing agents

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and cover the surfaces of the NPs, which keeps them from agglomerating and boosts their essential stability (Khalil et al., 2014). The AgNO3 concentration significantly influences the biogenic fabrication of AgNO3. The concentration level of AgNO3 can enhance the absorption level, and 1 mM is thought to be the ideal concentration for NPs (Vanaja et al., 2013). A higher AgNO3 concentration can also result in larger NPs (Bar et al., 2009).

11.4.4 Incubation Time A crucial factor for improving the stability, yield, and size of produced Ag NPs is incubation time. Within 2  min of incubation, a rapid color shift was seen when Anana scomosus extract was utilized to create Ag NPs (Ahmad & Sharma, 2012). Within 2 min, the concentration of AgNO3 in the solution rapidly fell, producing NPs. Up to 5 min passed while the response continued before the hue somewhat changed. The NPs had a median size of 12 nm and were spherical. Another study (by Jain & Mehata, 2017) used Ocimum Sanctum leaf extract to create stable Ag NPs that were about 17 nm in size. After 15 min of incubation, the yield of biogenically fabricated Ag NPs started to rise and kept rising over the next few hours. Thanks to a rise in the quantity of the generated Ag NPs, the absorption level rose as the incubation period increased. Ag NPs were also produced by using Origanum vulgare extract, and the NP yield improved with a reaction time of up to 3 h (Shaik et al., 2018). As Ag NPs formed, the reaction mixture’s color intensity slowly shifted from yellow to brown.

11.5 Characterization Tools An essential part of green synthesis is characterizing the Ag NPs to examine their topology, size, purity, surface chemistry, stability, etc. Diverse tools, including X-ray diffraction (XRD), UV-visible spectrophotometry, scanning electron microscopes (SEMs), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopes (TEMs), zeta potential analyzers, and dynamic light scattering (DLS), have been applied to explore green fabricated Ag NPs. Because of the initial color change, Ag NP fabrication can be initially seen with the naked eye. Typically, the reaction mixture’s dark brown hue denotes the formation of Ag NPs. Next, UV-visible spectrophotometry is employed to validate the fabrication of Ag NPs. In UV-visible spectrophotometry, fabricated Ag NPs displayed a significant peak between 400 and 470 nm. The topology and size of biogenically fabricated Ag NPs affected the absorption spectra (Huq & Akter, 2021). Effective technologies for characterizing NPs include SEMs and TEMs. Such microscopic techniques are

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applied to examine the topology, size, shape, purity, and level of particle agglomeration of produced NPs (Du et al., 2016). The structural characteristics of NPs, such as their particle sizes, degrees of crystallinity, etc., have been assessed by using the analytical technique XRD (Akter et al., 2020). The polydispersity index and hydrodynamic size of the produced NPs are investigated by employing dynamic light scattering (DLS). Zeta potential measurements determine whether Ag NPs in aqueous solutions are stable. Investigating the biomolecules in charge of capping and stabilizing NPs using FT-IR spectroscopy is crucial. The perfect crystal structure of Ag NPs was also visible in the XRD profile. The FT-IR spectrum demonstrated that different biomolecules served as capping, stabilizing, and reducing agents throughout the fabrication experiment (Alharbi et al., 2022; Huq et al., 2022).

11.6 Applications of Biosynthesized Ag NPs for Bioremediation 11.6.1 Photocatalytic Activity Because photocatalysis reduces organic pollutants in aquatic environments, it is an efficient and environmentally benign technology for a rising pollution (David & Moldovan, 2020). Among different NPs, Ag NPs have received the most attention as photocatalysts for wastewater treatment (Marimuthu et  al., 2020). Kayalvizhi et al. suggested a biogenic technique to produce Ag NPs and applied it as an active photocatalyst for methylene blue (MB) dye degradation (Sampath et al., 2021). The presence of MB dye demonstrated effective photocatalytic activity (Palithya et al., 2021). According to Hashemi et  al., Ag NPs made from Berberis vulgaris are acceptable photocatalysts for degrading methyl orange (Hashemi et  al., 2022). Similar to this, Ag NPs made from Calotropis procera have been used for the photocatalytic decomposition of methyl orange (Chandhru et al., 2022). Ag NPs generated from Chloroxylon swieteni have been used for the effective photocatalytic degradation of azo dyes, namely Congo red, Coomassie blue, and crystal violet under sunlight irradiation (Nga et al., 2022). Ag NPs have high photocatalytic capabilities against dyes, allowing for effective wastewater treatment (De et al., 2021). Phytonanomaterials have shown promise as remediation agents for hazardous contaminants and industrial effluents (De et al., 2021). The MB dye was photodegraded by the Ag NPs produced from Citrus x sinensis, and up to 82.2% of the dye was removed after 75 min (Yadav & Chauhan, 2022). Ag NPs that demonstrated photocatalytic reactivity against Rhodamine B in visible light were created by using Cyperus pangorei extract (Parvathiraja et al., 2021). The Ag NPs from Ferula assafoetida exhibits decolorization activity against MB dye (Subramaniam et al., 2022). Table 11.2 lists a few selected plant-based Ag NPs with good potential for the photocatalytic degradation of contaminants and colors.

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264 Table 11.2  Diverse dye degradation using biosynthesized Ag NPs Ag NP Aegle marmelos

Dye Methylene blue Aerva lanata Cotton blue and Congo red Alstonia Methylene scholaris blue Annona Coomassie squamosa L. brilliant blue Berberis vulgaris Methyl orange Calotropis Methyl procera orange Chloroxylon Congo red swietenia Coomassie blue Crystal violet Citrus reticulata Malachite blanco green Citrus X sinensis Methylene blue Clitoria ternatea Methylene blue Cyperus Rhodamine B pangorei Ferula Methylene assafoetida blue Heterotheca Methyl subaxillaris orange Jasmine Methylene blue Jujube Rhodamine b Eriochrome black T Kalanchoe Rhodamine B pinnata Nigella sativa Congo red

Panax vietnamensis

Source Visible light Sunlight

Degradation efficiency (%) Time References 49.9 180 min Sampath et al. (2021) – 30 min Palithya et al. (2022)

UV-visible light Sunlight

97

27 min

–

30 min

Sunlight

97.82

9 min

UV-visible light Sunlight

98

–

>95 90

24 h

Sunlight

Sunlight irradiation –

>90 Wastewater: 71; total N: 84.5 82.2 –

UV irradiation UV irradiation –

86

Sun light

72

96 –

UV & visible 90.9 light 84.7 irradiation UV irradiation Solar irradiation

Methyl – orange Rhodamine B Rhodamine B

83 87 96 97 98.5 –

120 h

Rajasekar et al. (2021) Jose et al. (2021) Hashemi et al. (2022) Chandhru et al. (2022) Nga et al. (2022)

Jaast and Grewal (2021)

75 min

Yadav and Chauhan (2022) 18 min Varadavenkatesan et al. (2020b) 2 h Parvathiraja et al. (2021) 90 min Subramaniam et al. (2022) 11 min Rajasekar et al. (2022) 120 min Aravind et al. (2021) 80 min Naghizadeh et al. (2021) 45 min Mehata (2021a, b) 150 min 20 min Chand et al. (2021) 15 min 13 min – Tran et al. (2021)

(continued)

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Table 11.2 (continued) Ag NP Ruellia tuberosa

Sida retusa

Trigonella foenumgraecum Zingiber officinale

Dye Crystal violet Coomassie brilliant blue Methylene blue Methyl orange Methylene blue Congo red Rhodamine B Methylene blue

Source Sunlight irradiation

Degradation efficiency (%) Time 87 – 74

Sunlight

–

–

Sunlight

80

120 min Sooraj et al. (2021)

– UV light

– 93

– 216 h

Awad et al. (2021)

–

99.9

10 min

Mehata (2021a, b)

References Seerangaraj et al. (2021)

11.6.2 Reducing Nitrophenols Aerva lanata flower extract–mediated spherical Ag NPs were used by Naidu et al. (Palithya et  al., 2022) to minimize 4-nitrophenol (4-NP). Additionally, Palithya et  al. reported producing Ag NPs by utilizing the Decaschistia crotonifolia leaf extract, which was evaluated as a homogeneous catalyst for reducing 4-NP (Palithya et al., 2021). The concentration of the catalyst, its size, and several atoms on its surface were all parameters that affected the rate of the reduction reaction. Later, using the leaves of Dalbergia spinosa, Muniyappan et al. (Muniyappan & Nagarajan, 2014) created Ag NPs and examined their ability to decrease 4-nitrophenol. They also performed 1 H NMR spectroscopy in addition to absorbance measurements to validate the reduction of 4-NP and the production of 4-aminophenol (4-AP). Numerous additional organizations have also conducted research using Fucus gardneri, Punica granatum, Tulsi, and other green fabricated Ag NPs to reduce 4-nitrophenol (Singh et al., 2018b; Muthu et al., 2021; Palithya et al., 2021; Princy & Gopinath, 2021; Sooraj et  al., 2021; Doan et  al., 2022; Kapoor et  al., 2022). Table 11.3 lists the features of the biogenically fabricated Ag NPs that were utilized as catalysts to decrease 4-NP and 4-NPs’ respective reactions.

11.7 Challenges and Future Research Opportunities Ag NPs’ potential for use is vast, and research on their synthesis utilizing green technology is expanding. The green manufacturing of NPs and phytochemicals obtained from plants can help researchers create effective bioremedial agents. However, the complexity and the diversity of phytochemicals present enormous

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Table 11.3  Catalytic reduction of nitrophenols by using Ag NPs Sr. No. 1

Reaction NO2

NO2

AgNPs

NaBH4

2

OH

O

NO2

NO2

OH NH2 O

OH

NaBH4

3

NaBH4 OH

Tran et al. (2021) OH

AgNPs

NO2

NO2

References Singh et al. (2018b), Muthu et al. (2021), Palithya et al. (2021), Princy and Gopinath (2021), Sooraj et al. (2021), Doan et al. (2022), Kapoor et al. (2022)

NH2

NH2

Tran et al. (2021)

AgNPs O

OH

technological hurdles. Additionally, the surface charge, topology, and size of Ag NPs play major roles in determining their physicochemical activity, and these characteristics are challenging to control throughout various experimental methods. To examine their toxicity and distribution, it is necessary to understand their pharmacokinetics and pharmacodynamics. Ag NPs might also be discharged into the environment; hence, this issue requires additional investigation. Additionally, a recent study found that Ag NPs were harmful to macrophages. Nevertheless, the outcomes of in vivo experiments were distinct from those of in vitro studies. Therefore, further research into Ag NP toxicity is necessary. Furthermore, over the past few years, there has been a surge in the number of goods using NPs, mostly Ag NPs. Therefore, it is crucial to look into Ag NP toxicity in living things. When using Ag NPs for environmental remediation applications, it is critical to consider how the materials, preparation techniques, stability, and toxicology affect living things. For instance, Ag NPs showed significant promise for the treatment of wastewater; several approaches have been thought of to look into this matter. Such initiatives can aid in developing innovative environmental remediation systems that use several components. In order to create safe and effective technologies and goods, it is crucial to pinpoint the main reason for the toxicity brought on by NPs.

11.8 Conclusion Ag NPs are predicted to be used more often in various fields in the future. Further research is necessary, nevertheless, because of their harmful effects on the environment, animals, and people after prolonged contact. Ag NPs should also be tested for their toxicity and biocompatibility in vivo to help develop fresh and perhaps helpful

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bioremedial agents. Ag NP toxicity is still unknown because there are inadequate data to make reliable judgments at this time. Until the toxicity of Ag NPs is properly explored, it is challenging to determine the effective processes for manufacturing innocuous Ag NPs. Therefore, more research is needed to identify the precise physical or chemical characteristics of Ag NPs that contribute to toxicity. Ag NPs’ physicochemical qualities can be improved to produce innocuous Ag NPs with low toxicity and increased bioremedial efficacy. Future research should concentrate on how biological systems are affected by Ag NPs, how living things respond to acute and chronic exposure to Ag NPs, and the many exposure routes. This will contribute to the development of additional environmental and biological protection measures.

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Jung, J. H., Oh, H. C., Noh, H. S., Ji, J. H., & Kim, S. S. (2006). Metal nanoparticle generation using a small ceramic heater with a local heating area. Journal of Aerosol Science, 37(12), 1662–1670. Kapoor, S., Sood, H., Saxena, S., & Chaurasia, O. P. (2022). Green synthesis of silver nanoparticles using Rhodiola imbricata and Withania somnifera root extract and their potential catalytic, antioxidant, cytotoxic and growth-promoting activities. Bioprocess and Biosystems Engineering, 45(2), 365–380. Kashid, Y., Ghotekar, S., Bilal, M., Pansambal, S., Oza, R., Varma, R. S., Nguyen, V.-H., Murthy, H. A., & Mane, D. (2022). Bio-inspired sustainable synthesis of silver chloride nanoparticles and their prominent applications. Journal of the Indian Chemical Society, 99, 100335. Kelele, K. G., Tadesse, A., Desalegn, T., Ghotekar, S., Balachandran, R., & Murthy, H. C. A. (2021). Synthesis and characterizations of metal ions doped barium strontium titanate (BST) nanomaterials for photocatalytic and electrical applications: A mini review. International Journal of Materials Research, 112(8), 665–677. Khalil, M.  M., Ismail, E.  H., El-Baghdady, K.  Z., & Mohamed, D. (2014). Green synthesis of silver nanoparticles using olive leaf extract and its antibacterial activity. Arabian Journal of Chemistry, 7(6), 1131–1139. Khan, A., Roy, A., Bhasin, S., Emran, T. B., Khusro, A., Eftekhari, A., et al. (2022). Nanomaterials: An alternative source for biodegradation of toxic dyes. Food and Chemical Toxicology, 164, 112996. Korde, P., Ghotekar, S., Pagar, T., Pansambal, S., Oza, R., & Mane, D. (2020). Plant extract assisted eco-benevolent synthesis of selenium nanoparticles-a review on plant parts involved, characterization and their recent applications. Journal of Chemical Reviews, 2(3), 157–168. Kredy, H. M. (2018). The effect of pH, temperature on the green synthesis and biochemical activities of silver nanoparticles from Lawsonia inermis extract. Journal of Pharmaceutical Sciences and Research, 10(8), 2022–2026. Lal, S., Verma, R., Chauhan, A., Dhatwalia, J., Guleria, I., Ghotekar, S., Thakur, S., Mansi, K., Kumar, R., & Kumari, A. (2022). Antioxidant, antimicrobial, and photocatalytic activity of green synthesized ZnO-NPs from Myrica esculenta fruits extract. Inorganic Chemistry Communications, 141, 109518. Marimuthu, S., Antonisamy, A. J., Malayandi, S., Rajendran, K., Tsai, P.-C., Pugazhendhi, A., & Ponnusamy, V. K. (2020). Silver nanoparticles in dye effluent treatment: A review on synthesis, treatment methods, mechanisms, photocatalytic degradation, toxic effects and mitigation of toxicity. Journal of Photochemistry and Photobiology B: Biology, 205, 111823. Mehata, M. S. (2021a). Green route synthesis of silver nanoparticles using plants/ginger extracts with enhanced surface plasmon resonance and degradation of textile dye. Materials Science and Engineering: B, 273, 115418. Mehata, M. S. (2021b). Green synthesis of silver nanoparticles using Kalanchoe pinnata leaves (life plant) and their antibacterial and photocatalytic activities. Chemical Physics Letters, 778, 138760. Merga, G., Wilson, R., Lynn, G., Milosavljevic, B. H., & Meisel, D. (2007). Redox catalysis on “naked” silver nanoparticles. The Journal of Physical Chemistry C, 111(33), 12220–12226. Michael, A., Singh, A., Roy, A., & Islam, M. (2022). Fungal-and algal-derived synthesis of various nanoparticles and their applications. Bioinorganic Chemistry and Applications, 2022, 3142674. Mohammadzadeh, V., Barani, M., Amiri, M. S., Yazdi, M. E. T., Hassanisaadi, M., Rahdar, A., & Varma, R.  S. (2022). Applications of plant-based nanoparticles in nanomedicine: A review. Sustainable Chemistry and Pharmacy, 25, 100606. Mousavi, S.  M., Hashemi, S.  A., Ghasemi, Y., Atapour, A., Amani, A.  M., Savar Dashtaki, A., Babapoor, A., & Arjmand, O. (2018). Green synthesis of silver nanoparticles toward bio and medical applications: Review study. Artificial Cells, Nanomedicine, and Biotechnology, 46(sup3), S855–S872.

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Muniyappan, N., & Nagarajan, N. (2014). Green synthesis of silver nanoparticles with Dalbergia spinosa leaves and their applications in biological and catalytic activities. Process Biochemistry, 49(6), 1054–1061. Muthu, K., Rajeswari, S., Akilandaeaswari, B., Nagasundari, S., & Rangasamy, R. (2021). Synthesis, characterisation and photocatalytic activity of silver nanoparticles stabilised by Punica granatum seeds extract. Materials Technology, 36(11), 684–693. Naghizadeh, A., Mizwari, Z.  M., Ghoreishi, S.  M., Lashgari, S., Mortazavi-Derazkola, S., & Rezaie, B. (2021). Biogenic and eco-benign synthesis of silver nanoparticles using jujube core extract and its performance in catalytic and pharmaceutical applications: Removal of industrial contaminants and in-vitro antibacterial and anticancer activities. Environmental Technology & Innovation, 23, 101560. Nasaruddin, R. R., Engliman, S., & Mastuli, M. S. (2021). Green synthesis of silver nanoparticles using coffee extract for catalysis. Malaysian NANO-An International Journal, 1(2), 13–25. Nga, N. T. A., Raghavendra, V. B., Sindhu, R., Alshiekheid, M., Sabour, A., Krishnan, R., Chi, N. T. L., & Pugazhendhi, A. (2022). Green fabrication of silver nanoparticles using Chloroxylon swietenia leaves and their application towards dye degradation and food borne pathogens. Food and Chemical Toxicology, 165, 113192. Nikam, A., Pagar, T., Ghotekar, S., Pagar, K., & Pansambal, S. (2019). A review on plant extract mediated green synthesis of zirconia nanoparticles and their miscellaneous applications. Journal of Chemical Reviews, 1(3), 154–163. Pagar, T., Ghotekar, S., Pagar, K., Pansambal, S., & Oza, R. (2021). Phytogenic synthesis of manganese dioxide nanoparticles using plant extracts and their biological application. In Handbook of greener synthesis of nanomaterials and compounds (pp. 209–218). Elsevier. Palithya, S., Gaddam, S.  A., Kotakadi, V.  S., Penchalaneni, J., & Challagundla, V.  N. (2021). Biosynthesis of silver nanoparticles using leaf extract of Decaschistia crotonifolia and its antibacterial, antioxidant, and catalytic applications. Green Chemistry Letters and Reviews, 14(1), 137–152. Palithya, S., Gaddam, S.  A., Kotakadi, V.  S., Penchalaneni, J., Golla, N., Krishna, S.  B. N., & Naidu, C. (2022). Green synthesis of silver nanoparticles using flower extracts of Aerva lanata and their biomedical applications. Particulate Science and Technology, 40(1), 84–96. Pandit, C., Roy, A., Ghotekar, S., Khusro, A., Islam, M. N., Emran, T. B., Lam, S. E., Khandaker, M.  U., & Bradley, D.  A. (2022). Biological agents for synthesis of nanoparticles and their applications. Journal of King Saud University-Science, 34(3), 101869. Pansambal, S., Oza, R., Borgave, S., Chauhan, A., Bardapurkar, P., Vyas, S., & Ghotekar, S. (2022a). Bioengineered cerium oxide (CeO2) nanoparticles and their diverse applications: A review. Applied Nanoscience, 1–26. Pansambal, S., Roy, A., Mohamed, H.  E. A., Oza, R., Vu, C.  M., Marzban, A., Chauhan, A., Ghotekar, S., & Murthy, H. (2022b). Recent developments on magnetically separable ferrite-­ based nanomaterials for removal of environmental pollutants. Journal of Nanomaterials, 2022, 15. Parvathiraja, C., Shailajha, S., Shanavas, S., & Gurung, J. (2021). Biosynthesis of silver nanoparticles by Cyperus pangorei and its potential in structural, optical and catalytic dye degradation. Applied Nanoscience, 11(2), 477–491. Patil, R. S., Kokate, M. R., Jambhale, C. L., Pawar, S. M., Han, S. H., & Kolekar, S. S. (2012). One-pot synthesis of PVA-capped silver nanoparticles their characterization and biomedical application. Advances in Natural Sciences: Nanoscience and Nanotechnology, 3(1), 015013. Prakash, M., Kavitha, H. P., Abinaya, S., Vennila, J. P., & Lohita, D. (2022). Green synthesis of bismuth based nanoparticles and its applications-a review. Sustainable Chemistry and Pharmacy, 25, 100547. Princy, K., & Gopinath, A. (2021). Green synthesis of silver nanoparticles using polar seaweed Fucus gardeneri and its catalytic efficacy in the reduction of nitrophenol. Polar Science, 30, 100692.

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Rafique, M., Sadaf, I., Rafique, M. S., & Tahir, M. B. (2017). A review on green synthesis of silver nanoparticles and their applications. Artificial Cells, Nanomedicine, and Biotechnology, 45(7), 1272–1291. Raina, S., Roy, A., & Bharadvaja, N. (2020). Degradation of dyes using biologically synthesized silver and copper nanoparticles. Environmental Nanotechnology, Monitoring & Management, 13, 100278. Rajasekar, R., Samuel, M., Edison, T. N. J. I., & Raman, N. (2021). Sustainable synthesis of silver nanoparticles using Alstonia scholaris for enhanced catalytic degradation of methylene blue. Journal of Molecular Structure, 1246, 131208. Rajasekar, R., Thanasamy, R., Samuel, M., Edison, T. N. J. I., & Raman, N. (2022). Ecofriendly synthesis of silver nanoparticles using Heterotheca subaxillaris flower and its catalytic performance on reduction of methyl orange. Biochemical Engineering Journal, 187, 108447. Rajeshkumar, S., & Bharath, L. (2017). Mechanism of plant-mediated synthesis of silver nanoparticles–a review on biomolecules involved, characterisation and antibacterial activity. Chemico-­ Biological Interactions, 273, 219–227. Roy, A. (2021). Plant derived silver nanoparticles and their therapeutic applications. Current Pharmaceutical Biotechnology., 22(14), 1834–1847. Roy, A., & Bharadvaja, N. (2019). Silver nanoparticle synthesis from Plumbago zeylanica and its dye degradation activity. Bioinspired, Biomimetic and Nanobiomaterials, 8(2), 130–140. Roy, A., & Bharadvaja, N. (2021). Efficient removal of heavy metals from artificial wastewater using biochar. Environmental Nanotechnology, Monitoring & Management, 16, 100602. Roy, A., Murthy, H. A., Ahmed, H. M., Islam, M. N., & Prasad, R. (2021a). Phytogenic synthesis of metal/metal oxide nanoparticles for degradation of dyes. Journal of Renewable Materials, 10, 1. https://doi.org/10.32604/jrm.2022.019410 Roy, A., Elzaki, A., Tirth, V., Kajoak, S., Osman, H., Algahtani, A., et al. (2021b). Biological synthesis of nanocatalysts and their applications. Catalysts, 11(12), 1494. Roy, A., Sharma, A., Yadav, S., Jule, L. T., & Krishnaraj, R. (2021c). Nanomaterials for remediation of environmental pollutants. Bioinorganic Chemistry and Applications, 2021, 1. Roy, A., Pandit, C., Gacem, A., Alqahtani, M. S., Bilal, M., Islam, S., et al. (2022a). Biologically derived gold nanoparticles and their applications. Bioinorganic Chemistry and Applications, 2022, 8184217. Roy, A., Roy, M., Alghamdi, S., Dablool, A. S., Almakki, A. A., Ali, I. H., et al. (2022b). Role of microbes and nanomaterials in the removal of pesticides from wastewater. International Journal of Photoenergy, 2022, 1. Roy, A., Singh, V., Sharma, S., Ali, D., Azad, A.  K., Kumar, G., & Emran, T.  B. (2022c). Antibacterial and dye degradation activity of green synthesized iron nanoparticles. Journal of Nanomaterials, 2022, 3636481. Salve, P., Vinchurkar, A., Raut, R., Chondekar, R., Lakkakula, J., Roy, A., et al. (2022). An evaluation of antimicrobial, anticancer, anti-inflammatory and antioxidant activities of silver nanoparticles synthesized from leaf extract of Madhuca longifolia utilizing quantitative and qualitative methods. Molecules, 27(19), 6404. Sampath, G., Govarthanan, M., Rameshkumar, N., Vo, D.-V.  N., Krishnan, M., Sivasankar, P., & Kayalvizhi, N. (2021). Eco-friendly biosynthesis metallic silver nanoparticles using Aegle marmelos (Indian bael) and its clinical and environmental applications. Applied Nanoscience, 13, 1–12. Seerangaraj, V., Sathiyavimal, S., Shankar, S.  N., Nandagopal, J.  G. T., Balashanmugam, P., Al-Misned, F. A., Shanmugavel, M., Senthilkumar, P., & Pugazhendhi, A. (2021). Cytotoxic effects of silver nanoparticles on Ruellia tuberosa: Photocatalytic degradation properties against crystal violet and coomassie brilliant blue. Journal of Environmental Chemical Engineering, 9(2), 105088. Shaik, M. R., Khan, M., Kuniyil, M., Al-Warthan, A., Alkhathlan, H. Z., Siddiqui, M. R. H., Shaik, J. P., Ahamed, A., Mahmood, A., & Khan, M. (2018). Plant-extract-assisted green synthesis

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of silver nanoparticles using Origanum vulgare L. extract and their microbicidal activities. Sustainability, 10(4), 913. Singh, A. K. (2022). A review on plant extract-based route for synthesis of cobalt nanoparticles: Photocatalytic, electrochemical sensing and antibacterial applications. Current Research in Green and Sustainable Chemistry, 5, 100270. Singh, M., Sinha, I., & Mandal, R. (2009). Role of pH in the green synthesis of silver nanoparticles. Materials Letters, 63(3–4), 425–427. Singh, P., Kim, Y. J., Wang, C., Mathiyalagan, R., & Yang, D. C. (2016a). The development of a green approach for the biosynthesis of silver and gold nanoparticles by using Panax ginseng root extract, and their biological applications. Artificial cells, Nanomedicine, and Biotechnology, 44(4), 1150–1157. Singh, P., Kim, Y. J., & Yang, D. C. (2016b). A strategic approach for rapid synthesis of gold and silver nanoparticles by Panax ginseng leaves. Artificial Cells, Nanomedicine, and Biotechnology, 44(8), 1949–1957. Singh, J., Dutta, T., Kim, K.-H., Rawat, M., Samddar, P., & Kumar, P. (2018a). ‘Green’synthesis of metals and their oxide nanoparticles: Applications for environmental remediation. Journal of Nanobiotechnology, 16(1), 1–24. Singh, J., Mehta, A., Rawat, M., & Basu, S. (2018b). Green synthesis of silver nanoparticles using sun dried tulsi leaves and its catalytic application for 4-Nitrophenol reduction. Journal of Environmental Chemical Engineering, 6(1), 1468–1474. Soni, V., Raizada, P., Singh, P., Cuong, H. N., Rangabhashiyam, S., Saini, A., Saini, R. V., Van Le, Q., Nadda, A. K., & Le, T.-T. (2021). Sustainable and green trends in using plant extracts for the synthesis of biogenic metal nanoparticles toward environmental and pharmaceutical advances: A review. Environmental Research, 202, 111622. Sooraj, M., Nair, A.  S., & Vineetha, D. (2021). Sunlight-mediated green synthesis of silver nanoparticles using Sida retusa leaf extract and assessment of its antimicrobial and catalytic activities. Chemical Papers, 75(1), 351–363. Stavinskaya, O., Laguta, I., Fesenko, T., & Krumova, M. (2019). Effect of temperature on green synthesis of silver nanoparticles using Vitex agnus-castus extract. Chemistry Journal of Moldova, 14(2), 117–121. Subramaniam, S., Kumarasamy, S., Narayanan, M., Ranganathan, M., Rathinavel, T., Chinnathambi, A., Alahmadi, T. A., Karuppusamy, I., Pugazhendhi, A., & Whangchai, K. (2022). Spectral and structure characterization of Ferula assafoetida fabricated silver nanoparticles and evaluation of its cytotoxic, and photocatalytic competence. Environmental Research, 204, 111987. Sudheer, S., Bai, R. G., Muthoosamy, K., Tuvikene, R., Gupta, V. K., & Manickam, S. (2022). Biosustainable production of nanoparticles via mycogenesis for biotechnological applications: A critical review. Environmental Research, 204, 111963. Sylvestre, J.-P., Kabashin, A. V., Sacher, E., Meunier, M., & Luong, J. H. (2004). Stabilization and size control of gold nanoparticles during laser ablation in aqueous cyclodextrins. Journal of the American Chemical Society, 126(23), 7176–7177. Tarannum, N., & Gautam, Y. K. (2019). Facile green synthesis and applications of silver nanoparticles: A state-of-the-art review. RSC Advances, 9(60), 34926–34948. Tran, M.-T., Nguyen, L.-P., Nguyen, D.-T., Cam-Huong, L., Dang, C.-H., Chi, T. T. K., & Nguyen, T.-D. (2021). A novel approach using plant embryos for green synthesis of silver nanoparticles as antibacterial and catalytic agent. Research on Chemical Intermediates, 47(11), 4613–4633. Tran, T. V., Nguyen, D. T. C., Kumar, P. S., Din, A. T. M., Jalil, A. A., & Vo, D.-V. N. (2022). Green synthesis of ZrO2 nanoparticles and nanocomposites for biomedical and environmental applications: A review. Environmental Chemistry Letters, 20, 1–23. Vanaja, M., Rajeshkumar, S., Paulkumar, K., Gnanajobitha, G., Malarkodi, C., & Annadurai, G. (2013). Kinetic study on green synthesis of silver nanoparticles using Coleus aromaticus leaf extract. Advances in Applied Science Research, 4(3), 50–55.

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Part III

Conjugating Nanoremediation to Other Remediation Strategies

Chapter 12

Green-Based Nanomaterials and Plants in Nano-Phytoremediation Strategies Bargavi Purushothaman and Saranya Kannan

12.1 Understanding of Nano-Phytoremediation Owing to the rapid technological advancement in the past century, hazardous waste pollutants accumulate in the environment (Singh et al., 2017; Roy & Bharadvaja, 2019). Remediation is the science that deals with the elimination of environmental pollutants into harmless products with the aid of chemical or biological means (Khan et al., 2022). Nanotechnology involves the formation and utilization of nanomaterials with any one of the proportions within the range of 1–100 nm (Roy et al., 2021a, 2022a; Taifa et al., 2022). Nanoremediation is the involvement of nanoparticles in the remediation process. It acts as a nanocatalyst, nanosensor, nanocontainer, or chemical oxidant to remove environmental pollutants (Fei et  al., 2022; Rajput et  al., 2022). Phytoremediation involves higher plants in the remediation process, which aids the transfer, stabilization, detoxification, and removal of environmental contaminants from soil, groundwater, sediments, etc. (Verma et al., 2020; Mittal & Roy, 2021). Nano-phytoremediation is an upcoming field that possesses the characteristics and advantages of both nanoremediation and phytoremediation. The usage of nanomaterials in the remediation process for the elimination of organic and chemical containments together with organic pollutants enhances the rate of conversion of harmful products owing to the huge surface area and elevated surface energy (Raina et al., 2020; Roy et al., 2021a, b, c; Yadav et al., 2022). However, the B. Purushothaman Department of Oral Pathology, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences (SIMATS), Saveetha University, Chennai, Tamil Nadu, India S. Kannan (*) Functional Nanobiomaterials Laboratory (Green Lab), Department of Periodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences (SIMATS), Saveetha University, Chennai, Tamil Nadu, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_12

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contrary ideology on the accumulation of nanoparticles due to environmental remediation is regarded as toxic (Ihtisham et al., 2021). Phytoremediation is a relatively slow process and the damage to the environment is almost nil (Garg & Roy, 2022). To hasten the elimination of the containments, nanomaterials are involved in the initial conversion of toxic products into a suitable form that can be taken up by the plants, thereby completely eliminating the pollutants from the environment (Nwadinigwe & Ugwu, 2018).

12.2 Green-Based Nanomaterials in Remediation Industrial wastewater is heavily loaded with antibiotics, toxic dyes, pesticides, etc., that affect the environment. The discharge of wastewater directly into the environment has a direct impact on aquatic life, useful microorganisms, deterioration of crops, and so on. Hence, a proper treatment and efficient disposal system are required. Metallic nanoparticles are widely employed for the degradation of toxic dyes owing to their catalytic activity (Garg et  al., 2020; Pandit et  al., 2022; Roy et al., 2022a, b, c; Pansambal et al., 2022). As the motto is to decrease the load of toxic materials that are dumped into the environment, the synthesis of nanoparticles for remediation should not generate toxic chemical by-products during the synthesis. Green synthesis of nanomaterials developed with various plant extracts, algae, fungi, bacteria, etc., has been investigated (Roy & Bharadvaja, 2017, 2019; Singh et al., 2018; Nagore et al., 2021; Roy, 2021; Michael et al., 2022; Roy et al., 2022a, b, c; Salve et al., 2022). The synthesis of different nanoparticles and their employment in environmental remediation, along with their beneficial use in plants, are detailed below.

12.2.1 Silver Nanoparticles The wide applications of silver nanoparticles (AgNPs) in medicine, sensors, electronics, textiles, wastewater management, etc., along with lower toxicity, make them an irresistible material. Figure 12.1 details the AgNPs synthesized with the plant extracts of onion, tomato, and acacia catechu, which were employed for the degradation of various toxic dyes including methyl orange, methyl red, and Congo red with an average degradation rate of 90% after 30  min of degradation time (Chand et al., 2020). Nigella sativa extract aided the formation of AgNPs within the size range 10–12  nm and showed strong photocatalysis against Congo red dye (Chand et  al., 2020). Various other plant extracts including Parkia speciosa (Ravichandran et  al., 2019), Sophora mollis leaf extract (Nazir et  al., 2021), and jujube core extract-mediated AgNPs supported the photodegradation of anionic and cationic contaminants (Naghizadeh et  al., 2021). Anabaena variabilis, Spirulina platensis (Ismail et al., 2021), Bacillus pumilus, B. paralicheniformis, Sphingomonas

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Fig. 12.1  Schematic representation of the mechanism of nanoparticle formation and the photocatalytic degradation of dye (Chand et al., 2020)

paucimobilis (Allam et al., 2019) etc. were involved in the synthesis of the AgNPs, which were eventually employed for wastewater management. Also, the combination of dye degradation was facilitated by them. The degraded dye products are smaller colorless molecules such as SO42−, CO2, and H2O (Gola et  al., 2021). Diospyros lotus-mediated AgNPs were effective in degrading the colorants in effluent and causing a considerable decline in the concentration of sulfite, sulfates, and chlorides that has been attributed to the adsorption of AgNPs (Yasmin et al., 2020). Also, AgNPs removed Co(II) and Pb(II) ion contaminants from groundwater (Attatsi & Nsiah, 2020). Despite the removal of the toxic compounds, AgNPs were retained in the treated water as metal ions do not biodegrade. The high concentration of AgNPs dumped into the environment destroys the beneficial bacteria and causes an imbalance in the ecology. To overcome the problems, AgNPs should be removed from the environment through phytoremediation in such a way that it benefits the plants. AgNPs are reported to support plant metabolism and growth. The shoot length, number of

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leaves/plant and shoot dry weight of the fenugreek plant have improved. The biochemical contents and the number of seeds in the pods have also increased (Sadak, 2019). Pistia stratiotes, a floating macrophyte, was efficient in the removal of Ag from the water resource (Akahir et al., 2021).

12.2.2 Cobalt Nanoparticles Cobalt oxide nanoparticles are one of the transition metal oxides that belong to the magnetic p-type semiconductors with potential catalytic properties. CoO, cobalt oxide (Co2O3), and cobaltosic oxide (Co3O4) are the important types of cobalt-based nanoparticles with different oxidation states (Singh, 2022). The variable oxidation state of cobalt oxide nanoparticles was employed for the light-driven degradation of environmentally harmful chemicals such as malachite green (Verma et al., 2021), methylene blue (Majid et  al., 2020), murexide dye, and eriochrome black-T (Adekunle et al., 2020). The green synthesis of cobalt nanoparticles was performed using green extracts (Vitis rotundifolia (Samuel et al., 2020), Raphanus sativus var. Hibiscus cannabinus, Vitis vinifera, Phoenix dactylifera L. (Rajeswari et al., 2021)), bacteria (Bacillus thuringiensis, Micrococcus lylae, B. subtilis), fungi (Aspergillus nidulans, Nothapodytes foetida, etc.), and biological extract (ferritin (Hosein et al., 2004), peptide threonine–leucine–valine–asparagine–asparagine (Thanh et  al., 2005), egg albumin) (Waris et al., 2021). Cobalt is an essential micronutrient of terrestrial and aquatic plants including diatoms, chrysophytes, dinoflagellates, and the Leguminosae family. Co is an integral micronutrient of vitamin B12, which supports the enzymatic reactions in the nitrogen fixation process in legumes (Hu et al., 2021).

12.2.3 Iron Oxide Nanoparticles Iron is a vital microelement to all living organisms and is important for chlorophyll formation in plants. However, the high concentration of iron causes toxicity in plants (Morrissey & Guerinot, 2009). Various plants, bacteria, fungi, and algae are employed for the synthesis of iron nanoparticles. Plant extract aids the formation of iron oxide nanoparticles in combination with other elements, e.g., okra extract-­ mediated cobalt–iron oxide nanoparticles (Kombaiah et  al., 2018), magnesium oxide-decorated iron oxide (Sahoo et al., 2020) etc., were employed for remediation. The biological resources aid the formation and stabilization of the nanoparticles with ketones, aldehydes, flavonoids, terpenoids, carboxylic and phenolic groups, etc. (Kaur & Sidhu, 2021).

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12.2.4 Classification of Phytoremediation 12.2.4.1 Phytoextraction The eviction of non-natural contaminators by plants is known as phytoextraction. Current research articles have examined the chance of phytoextraction, and show that the forceful adding of both the biomass yield and the alloy is essential to form the productive process (Hu et al., 2021). Accumulation of chelating mediator in soil augments the bioavailability of contaminators and it rarely has the ability to forcibly warn the addition of similar plants, but it can produce harmful refer to methods or strategies that do not adversely affect the risk of the environment (Morrissey & Guerinot, 2009). As a result, it is obtained by testing the engine designed for forceful development and moving about open forceful accumulators as a form of model plant. Modern advancements have impacted our understanding of the bigger picture that are under the responsibility of the forceful addition of Zn, Cd, Ni, and As by plants (Kombaiah et al., 2018). Attempts to convince the block of metal fighting and development to file charges against previously only involved Hg, As, and Cd, but the happy outcome was quietly brought about by a few tendencies from rational purpose. Following the potential goal of phytoextraction, a more fundamental understanding of the features and patterns complex in forceful addition is beneficial. 12.2.4.2 Phytostimulation Phytostimulation is also known as supported rhizosphere biodegradation, rhizodegradation, or plant-aided bioremediation; it is the collapse of elementary contaminators in the soil rerouting improved microbial movement in the plant root region or rhizosphere. Microbial movement is aroused in the rhizosphere in many tendencies: (1) compounds, hindering sugars, carbohydrates, amino acids, acetates, and enzymes, disperse for specific ancestries enhanced in accordance with first microbiological concepts (Sahoo et al., 2020); (2) Providing oxygen to the rhizosphere through the roots, that guarantees aerobic conversions; (3) fine-root biomass-accessible elementary ingredients; (4) mycorrhizae fungi that are cultured inside the rhizosphere can flush out basic contaminants that, due to their particular relationship to iota and fragment change pathways, cannot be specifically exchanged by microorganisms; and (5) plants serve as an improved home for embellished microbial societies and venture. 12.2.4.3 Phytostabilization Phytostabilization enhances the reduction of the adaptability of troublesome metals in soil. Immobilization of metals is possibly consummated by wind-dropping jolted just, underestimating soil degeneration, and to the strengthening relationships

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between structures, contaminant solubility or bioavailability is falling. The addition of soil change, via timber, phosphates, alkalizing capacities, and biosolids, can lower the solubility of metals in soil and reduces discharge to groundwater (Kaur & Sidhu, 2021). With each successive development of contaminants caused by plant ancestries, inclusion to ancestries, or sleet inside the root precinct, the elasticity of contaminants decreases. In a few occurrences, plants used hydraulic control to prevent leachate migration, which they feared may be unavoidable and affect ordinary people’s access to water (Ishikawa & Bach, 1999). The use of phytostabilization to claim metals in their current position is extremely attractive when supplementary processes to remediate corruption weakened by substantial communities’ position are not feasible. Due to soil toxicity, remediation is challenging at locations where considerable amounts of extreme metals have been collected (Das, 2018). The development of root biomass after the ability to stop contaminants and the tendency to keep contaminants in the ancestries has been lauded; plants endure inside financial ways that lead to very high levels of contaminants. 12.2.4.4 Phytotransformation/Phytodegradation Phytotransformation, still as much a concern as phytodegradation, is the division of elementary contaminators sheltered by plants as well as (1) metabolic processes inside the plant or (2) the result of compounds, hindering those enzymes, assembled in each plant (Chandra et al., 2017). The contaminators are degraded into plainer compounds that are held following green cover, which, in the correct series, supports plant growth. Remediation by phytotransformation is powerless against the immediate, crude response of contaminants from the facilities’ adding and emitting. The influence, frequency, and collection of the artificial in soil water are likely to have an impact on the direct crude response of composite into plant structure around the root order. (Goutam et al., 2018). Uptake influence depends on artificial adjustment progress, material/artificial controls, and plant characteristics when really the occurrence rate depends on the plant type, leaf field, mineral, soil liquid, heat, wind atmospheres, and relative humidity (Bhati & Rai, 2018). Following the transfer of each plant’s elementary compound, two remediation steps can be taken: (2) Complete conversion to uninteresting without scent vapour and water; and (1) storage of the fake and alluring trash into the plant travelling around lignifications. 12.2.4.5 Rhizofiltration Rhizofiltration is the planned and devoted removal of hazardous metals from contaminated groundwater using plant ancestries. In the beginning, suitable plants with opposing root systems are abounding with blended water to accustom the plants. These plants are accordingly transported to the debased or dirty ground to expand the contaminators, and later the ancestry is vague, and they are collected. Rhizofiltration permits in situ movement, underestimating the clamour in the air

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(Godheja et al., 2016). An appropriate plant for rhizofiltration purposes can eliminate harmful metals in response to allure active-progress root meaning over a clean range. Cu2+, Cd2+, Cr6+, Ni2+, Pb2+, and Zn2+-blocking hazardous metals have been successfully removed from liquid solutions by a number of plant varieties. Further potential distance from liquid streams for low-plane living contaminants (Allam et al., 2019). Nanotechnology and phytoremediation are two related topics where knowledge for harmonised contaminants from soil was developed. Nanotechnology uses a more exaggerated technique, while phytoremediation uses an extra, well-established method (Bhati & Rai, 2017). These are optimistic surroundings following the sunny approach of reasonable outdoing following the upgraded influence of the old practice of phytoremediation and remodeling and in the present, computers may have outperformed after learning of earlier plans to develop capabilities. Soil adulteration is enhanced in an anthropogenic (land, mechanics, wastewater) occupancy that engages the toxic of minerals, pesticides, and sediments to the soil, and in another habitat, production and urbanization contaminate the soil following spatial waste, heavy metals, solid, and plentiful additional sluggish, cruel, and lacking in fundamentals (Madhavi et al., 2013). Metals such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), are essential enduring processes, in view of the fact, like cadmium (Cd), nickel (Ni), and lead (Hg), have no physiological purpose but often result in a destructive commotion at a superior collection. High sounds that are appropriate are cruel and appropriate for animals as well, preventing that Cd, Cr, Hg, and Pb can cause liver damage, piece of animate skeleton degeneration, kidney dysfunction, and other problems, even though soil acts as a clean material by attraction puzzle movement (Swarnavalli et al., 2017). In contrast to air pollution that has direct contact with human lives, customers and additional animals get a wordy itch as a result of soil adulteration. Any increase in a substance that has the potential to have a detrimental effect on exercise may be seen as a contaminator of soil. Phytoremediation has urgently occurred as an optimistic approach to the in situ discharge of many contaminators (Ebrahiminezhad et al., 2018).

12.2.5 Phytoremediation Technology for Heavy Metal Contaminants from Soil Nano-phytoremediation is a process that includes nanotechnology and phytotechnology for the remediation of material contaminators. Nano-phytoremediation for the same and removal of TNT 2, 4, 6-trinitrotoluene polluted soil is more effective than either nanoremediation or phytoremediation alone. The exploitation of nanoparticles for material requests is growing very rapidly (Weng et al., 2016). For that reason, the large surface area of the particles corresponds to the magnitude of the force of the particles; then, the responses to material requests that are artificially or simply mediated greatly correct allure awareness. Knowledge of phytoremediation for water contaminators.

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12.2.6 Phytoremediation Technology for Water Contaminants Modernization keeps transforming the collective public by presenting discounted solutions to various fields. Nanotechnology is one of the final intelligent transformations in agreement to phytoremediation, an older process, and one bioremediation (Natarajan & Suuki, 2013). Sophisticated nanomaterials such as zeolites, nanofibers, carbon nanotubes, nanocatalysts, illustration nanoparticles, and nano sponge-­ready nanofiltration plans can catalytically attack artificial contaminators and toxins regrettable civil service; the illustrated nanoparticles can remove metals as a result of their interaction competencies. Nanomaterial uses are not limited to washing; by using nanomaterial probes in water hearing forms, thinking components like probes have improved sense and bias. Although these requests are for nanotechnology, the main strategy for reasonable advancement is also the green television approach (Ali et al., 2017). Nanotechnologies will produce huge profits in environments of water leadership and position by recovering, cleansing, washing, desalination, maintenance, reusing, and leakage procedures, and extending a confidential dossier or conducting hearings (Yadav et al., 2017). According to various chemists who discuss and document the use of phytogenic magnetic nanoparticles (PMNPs) in water and wastewater (WWT) environments, factors like crucial expression rules, desired amount, wonderful paramagnetic manner, and extreme fullness magnetization profit are important factors (Stampoulis et al., 2009). This green lie of PMNPs design is as fast, cautious, accidental, and clean as many physicochemical computers. Commercialization features connected to this talent are operating wastewater movement. Wisdom’s limits continue to widen as means, adaptation, and reusability are taken into account. These studies similarly present a model of PMNPs immunity settled nothing overflow. This green skill is accurately more feasible and economically reasonable (Shekhawat & Arya, 2009). The following parameters should be added to the result carriage for this function and incidence of PMNPs: extract volume, fit type, pH, the essence of sign, real parameters like heat, etc. As stated in numerous publications, skilled is currently a viable study option for a longer noble following a wide variety of active groups by changing plant metabolites and lying contracts (Ankamwar, 2010). Other appropriate articles define that everything is constantly molded for the development of nanoparticles from a variety of origins in individual outcomes by linked zero-­valent iron nanoparticles from Eucalyptus globulus, allocated for adsorption of hexavalent chromium (Cr (VI)) following extreme-order adsorption ability (Beattie & Haverkamp, 2011). Green alliance/bio-linked results of nanoclusters from Mediterranean cypress, following about 2 nm in the breadth of nanoparticles is highly applicable in the relocation of dyes. These nanoclusters consist of extremely restricted zero-valent iron nanoparticles (Saif et al., 2016).

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Raina, S., Roy, A., & Bharadvaja, N. (2020). Degradation of dyes using biologically synthesized silver and copper nanoparticles. Environmental Nanotechnology, Monitoring & Management, 13, 100278. Rajeswari, V. D., Khalifa, A. S., Elfasakhany, A., Badruddin, I. A., Kamangar, S., & Brindhadevi, K. (2021). Green and ecofriendly synthesis of cobalt oxide nanoparticles using Phoenix dactylifera L: Antimicrobial and photocatalytic activity. Applied Nanoscience, 1–9. Rajput, V. D., Minkina, T., Upadhyay, S. K., Kumari, A., Ranjan, A., Mandzhieva, S., & Verma, K. K. (2022). Nanotechnology in the restoration of polluted soil. Nanomaterials, 12(5), 769. Ravichandran, V., Vasanthi, S., Shalini, S., Shah, S.  A. A., Tripathy, M., & Paliwal, N. (2019). Green synthesis, characterization, antibacterial, antioxidant and photocatalytic activity of Parkia speciosa leaves extract mediated silver nanoparticles. Results in Physics, 15, 102565. Roy, A. (2021). Plant derived silver nanoparticles and their therapeutic applications. Current Pharmaceutical Biotechnology, 22(14), 1834–1847. Roy, A., & Bharadvaja, N. (2017). Qualitative analysis of phytocompounds and synthesis of silver nanoparticles from Centella asiatica. Innovative Techniques in Agriculture, 1(2), 88–95. Roy, A., & Bharadvaja, N. (2019). Silver nanoparticle synthesis from Plumbago zeylanica and its dye degradation activity. Bioinspired, Biomimetic and Nanobiomaterials, 8(2), 130–140. Roy, A., Murthy, H.  A., Ahmed, H.  M., Islam, M.  N., & Prasad, R. (2021a). Phytogenic synthesis of metal/metal oxide nanoparticles for degradation of dyes. https://doi.org/10.32604/ jrm.2022.019410 Roy, A., Elzaki, A., Tirth, V., Kajoak, S., Osman, H., Algahtani, A., et al. (2021b). Biological synthesis of nanocatalysts and their applications. Catalysts, 11(12), 1494. Roy, A., Sharma, A., Yadav, S., Jule, L. T., & Krishnaraj, R. (2021c). Nanomaterials for remediation of environmental pollutants. Bioinorganic Chemistry and Applications, 2021, 1764647. Roy, A., Pandit, C., Gacem, A., Alqahtani, M. S., Bilal, M., Islam, S., et al. (2022a). Biologically derived gold nanoparticles and their applications. Bioinorganic Chemistry and Applications, 2022, 8184217. Roy, A., Roy, M., Alghamdi, S., Dablool, A. S., Almakki, A. A., Ali, I. H., et al. (2022b). Role of microbes and nanomaterials in the removal of pesticides from wastewater. International Journal of Photoenergy, 2022, 2131583. Roy, A., Singh, V., Sharma, S., Ali, D., Azad, A.  K., Kumar, G., & Emran, T.  B. (2022c). Antibacterial and dye degradation activity of green synthesized iron nanoparticles. Journal of Nanomaterials, 2022, 3636481. Sadak, M. S. (2019). Impact of silver nanoparticles on plant growth, some biochemical aspects, and yield of fenugreek plant (Trigonella foenum-graecum). Bulletin of the National Research Centre, 43(1), 1–6. Sahoo, S. K., Dhal, J. P., & Panigrahi, G. K. (2020). Magnesium oxide nanoparticles decorated iron oxide nanorods: Synthesis, characterization and remediation of Congo red dye from aqueous media. Composites Communications, 22, 100496. Saif, S., Tahir, A., & Chen, Y. (2016). Green synthesis of iron nanoparticles and their environmental applications and implications. Nanomaterials, 6(11), 209. Salve, P., Vinchurkar, A., Raut, R., Chondekar, R., Lakkakula, J., Roy, A., et al. (2022). An evaluation of antimicrobial, anticancer, anti-inflammatory and antioxidant activities of silver nanoparticles synthesized from leaf extract of Madhuca longifolia utilizing quantitative and qualitative methods. Molecules, 27(19), 6404. Samuel, M. S., Selvarajan, E., Mathimani, T., Santhanam, N., Phuong, T. N., Brindhadevi, K., & Pugazhendhi, A. (2020). Green synthesis of cobalt-oxide nanoparticle using jumbo Muscadine (Vitis rotundifolia): Characterization and photo-catalytic activity of acid Blue-74. Journal of Photochemistry and Photobiology B: Biology, 211, 112011. Shekhawat, G., & Arya, V. (2009). Biological synthesis of Ag nanoparticles through in vitro cultures of Brassica juncea C. zern. Advanced Materials Research, 67, 295–299.

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Singh, A. K. (2022). A review on plant extract-based route for synthesis of cobalt nanoparticles: Photocatalytic, electrochemical sensing and antibacterial applications. Current Research in Green and Sustainable Chemistry, 5, 100270. Singh, M., Pant, G., Hossain, K., & Bhatia, A. (2017). Green remediation. Tool for safe and sustainable environment: A review. Applied Water Science, 7(6), 2629–2635. Singh, J., Dutta, T., Kim, K. H., Rawat, M., Samddar, P., & Kumar, P. (2018). ‘Green’ synthesis of metals and their oxide nanoparticles: Applications for environmental remediation. Journal of Nanobiotechnology, 16(1), 1–24. Stampoulis, D., Sinha, S. K., & White, J. C. (2009). Assay-dependent phytotoxicity of nanoparticles to plants. Environmental Science & Technology, 43(24), 9473–9479. Swarnavalli, G. C. J., Dinakaran, S., Raman, N., Jegadeesh, R., & Pereira, C. (2017). Bio inspired synthesis of monodispersed silver nano particles using Sapindus emarginatus pericarp extract– Study of antibacterial efficacy. Journal of Saudi Chemical Society, 21(2), 172–179. Taifa, S., Muhee, A., Bhat, R. A., Nabi, S. U., Roy, A., Rather, G. A., et al. (2022). Evaluation of therapeutic efficacy of copper nanoparticles in Staphylococcus aureus-Induced rat mastitis model. Journal of Nanomaterials, 2022, 7124114. Thanh, N. T., Puntes, V. F., Tung, L. D., & Fernig, D. G. (2005). Peptides as capping ligands for in situ synthesis of water soluble Co nanoparticles for bioapplications. Journal of Physics: Conference Series, 17, 70. Verma, A., Roy, A., & Bharadvaja, N. (2020). Remediation of heavy metals using nanophytoremediation. In Advanced oxidation processes for effluent treatment plants (pp. 273–296). Elsevier. Verma, M., Mitan, M., Kim, H., & Vaya, D. (2021). Efficient photocatalytic degradation of Malachite green dye using facilely synthesized cobalt oxide nanomaterials using citric acid and oleic acid. Journal of Physics and Chemistry of Solids, 155, 110125. Waris, A., Din, M., Ali, A., Afridi, S., Baset, A., Khan, A. U., & Ali, M. (2021). Green fabrication of Co and Co3O4 nanoparticles and their biomedical applications: A review. Open Life Sciences, 16(1), 14–30. Weng, X., Jin, X., Lin, J., Naidu, R., & Chen, Z. (2016). Removal of mixed contaminants Cr (VI) and Cu (II) by green synthesized iron based nanoparticles. Ecological Engineering, 97, 32–39. Yadav, K., Singh, J., Gupta, N., & Kumar, V. (2017). A review of nanobioremediation technologies for environmental cleanup: A novel biological approach. Journal of Materials and Environmental Science, 8(2), 740–757. Yadav, V. K., Gnanamoorthy, G., Ali, D., Bera, S. P., Roy, A., Kumar, G., et al. (2022). Cytotoxicity, removal of Congo red dye in aqueous solution using synthesized amorphous iron oxide nanoparticles from incense sticks ash waste. Journal of Nanomaterials, 2022, 5949595. Yasmin, S., Nouren, S., Bhatti, H. N., Iqbal, D. N., Iftikhar, S., Majeed, J., & Nazir, A. (2020). Green synthesis, characterization and photocatalytic applications of silver nanoparticles using Diospyros lotus. Green Processing and Synthesis, 9(1), 87–96.

Chapter 13

Main Interaction of Green Nanomaterials and Microorganisms on Nanoremediation Protocols Devaraja Gayathri and Rajanna Soundarya

13.1 Introduction Global developmental activities such as industrialization and a rising population have provoked research on several inorganic and toxic contaminants, and they represent a high risk to human health and the environment (Prado-Audelo et al., 2021). Many anthropogenic activities like mining, discharging industrial effluents, and burning fossil fuels has increased organic and inorganic pollutants in the environment, especially persistent organic pollutants (POPs) that bioaccumulate in nature for longer durations and that cause enormous health hazards (Fei et al., 2022). This is an alarming and urgent problem for environmentalists, scientists, and researchers, encouraging them to search for and apply a novel strategy to solve this problem. Nanotechnology, which is the branch of science that encompasses the study of nanosized (1–100 nm) materials, is one such promising field (Gaur et  al., 2018; Ahmed et al., 2021; Barage et al., 2022). Nanotechnology (and nanoparticles) has become a significant field of study and research because of its extensive use in various areas, including cancer therapy, antimicrobial agents, diagnostics, drug delivery, biomarkers, etc. (Mousavi et al., 2018; Nagore et al., 2021; Roy, 2021; Islam et al., 2022; Taifa et al., 2022; Salve et al., 2022). Nanoremediation is a novel concept and a promising strategy to address pollution (Roy & Bharadvaja, 2019; Roy et al., 2021a, b, c). Nanoremediation is defined as the engineered, synthetic, or bio-based materials applied to reduce the toxicity of pollutants in the environment, which is an effective and rapid measure and possibly a better technology to resolve most persistent pollutants like pesticides, chlorinated solvents, halogenated chemicals, and heavy metals (Verma et  al., 2020; PradoAudelo et al., 2021). Over the past few decades, the conventional method of D. Gayathri (*) · R. Soundarya Department of Studies in Microbiology, Davangere University, Shivagangothri, Davangere, Karnataka, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_13

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nanoparticle synthesis used physical and chemical means. Because conventional methods require high pressure, temperature, electricity, and the use of inorganic toxic chemicals in the reduction of metals, the green synthesis of nanoparticles is preferred (Wu et al., 2019). Green chemistry involves the production of safe, ecofriendly nanoparticles with broad acceptance in various fields (Raina et al., 2020; Roy et al., 2021a, b, c). The green synthesis of NPs is a biocompatible method that uses a variety of sources like plant extracts, bacteria, fungi, actinomycetes (e.g., streptomyces), algae, and many more (Ahmad et  al., 2019; Pandit et  al., 2022; Pansambal et  al., 2022; Roy et  al., 2022a, b, c; Michael et  al., 2022). The green synthesis of nanoparticles is most widely accepted because it decreases the usage of harmful and depleting materials; increases the effectiveness of time, space, and energy; and offers ecofriendly solutions (Mousavi et al., 2018; Mittal & Roy, 2021; Roy et al., 2021a, b, c; Khan et al., 2022). Biological materials such as plants and microorganisms synthesize nanoparticles with their enzyme machineries by reducing the metals and accumulating the metal and metal oxide intracellularly or extracellularly. The major nanoparticles produced from green synthesis are gold, silver, selenium, zinc oxide, tellurium, zirconia, platinum, palladium, magnetite, quantum dots, uraninite, and silica, among others (Narayanan & Sakthivel, 2010). Conventionally, the process of nanoparticle synthesis includes two methods, namely the top-down and bottom-up methods (Singh et al., 2019). These two methods of synthesis produce nanoparticles of uniform sizes, shapes, and dimensions. The top-down approach includes mainly the degradation of bulkier particles into smaller particles; the size reduction is achieved through various technical methods, like grinding, milling, sputtering, thermal or laser ablation, etc. In the bottom-up approach, the synthesis of nanoparticles involves chemical and or biological methods, where upon self-assembly, the atoms form new nuclei, which subsequently grow to become nanosized particles. The bottom-up approach also includes sono-­ decomposition, electrochemical methods, and chemical reduction methods (Gaur et  al., 2018). It is necessary to green synthesize NPs by taking novel, innovative approaches and using nanoremediation strategies to achieve environmental cleanup processes like nano-sensing and nanophotocatalysis (Roy et al., 2022a, b, c; Yadav et al., 2022; Garg & Roy, 2022). Nanomaterials such as nanoscale zero-valent iron/ carbon nanotubes, magnetic and metallic NPs, silica NPs, graphene oxide, covalent organic frameworks, and metallic inorganic frameworks (Fei et al., 2022) are currently being synthesized. However, for effective remediation, the availability of novel NPs and their in situ applications need to be urgently addressed.

13.2 Types of Nanomaterials Materials in the range of 1–100 nm are referred to as nanomaterials. Nanomaterials range in size from bulk materials to small molecules, and most nanomaterials have different features, including size, shape, surface area, and reactivity, depending mainly on their applications (Shahid et  al., 2022). Various nanomaterials are

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categorized according to their size, dimensions, morphology, and properties (Salem et al., 2022a, b). Some of the characteristics of nanomaterials are listed below. Sl. Types of no. nanomaterials Examples 01 Metal/metal Silver, gold, oxide based copper, titanium, zinc, magnesium, iron, alginate

02 Carbon based Fullerene, nanotube, graphene, oxides, nanodiamond, carbon-based quantum dot 03 Polymer Chitosan, poly based lactic glycolic acid, poly glutamic acid

04 Silica based

Properties Fast kinetics, high adsorption capacity, high surface-to-volume ratio

Remediation mechanism Adsorption, oxidation, reduction, photodegradation, photocatalysis

Easier Adsorption biodegradation, high surface area, nontoxic nature, high adsorption capacity

Simple to Nano filtration produce, cost-effective, biocompatible, biodegradable, generally nonimmunogenic Si(OEt)4, SiO2, Controllable pore Catalysis and SiO5, SiO2 size, large surface absorption area, tunable and tailorable structure

Applications Removal of pollution-causing toxicants from industrial contaminated water and waste water, heterogenous photocatalysis nanoremediation, biological chemical sensors Therapeutic delivery, biomedical imaging, biosensor/tissue engineering, cancer therapy Drug delivery, biosensors, stimuli responsive cargo delivery, nano composites, agricultural, environmental Removes variety of pollutants from water

13.2.1 Methods of Nanoparticle Synthesis The commercialization of nanoparticles in various field is achieved when high-­ throughput nanoparticles/nanomaterials are synthesized to a good and controlled standard of quality. Two principal approaches, top down and bottom up, are commonly used to prepare nanoparticles (Dhand et al., 2015). The top-down approach features the transformation of bulkier substances or materials into nanosized particles. This method is easy to use, but it does not produce uniform nanoparticles. The bottom-up approach is generally a constructive method and is the opposite of the top-down process. The former is forms nanoparticles through the self-assembly of

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Fig. 13.1  Methods of nanoparticles synthesis

nanosized atoms and nanosized molecules. The NPs formed through this method have well-defined shapes, sizes, and chemical compositions (Abid & Kadhim, 2022). The commonly used top-down methods for the mass production of NPs are photolithography, electron beam lithography, milling techniques, anodization, and ion and plasma etching (Sharma et al., 2017). While laser pyrolysis, sol–gel processing, chemical vapor deposition, plasma- or flame-spraying synthesis, and bio-­ assisted/based synthesis are the bottom-up processes involved in the formation of NPs (Sánchez-Moreno et al., 2018). Several typical methods of nanoparticle synthesis, such as physical, chemical, and bio-assisted syntheses, are shown in Fig. 13.1. 13.2.1.1 Physical Method of Synthesis The physical method of nanomaterial production includes the usage of a strong laser beam through a laser ablation process. Where the strong laser beam impacts the target material or precursor, this high intensity laser irradiation vaporizes the original target molecule and thus leads to the synthesis of nanoparticles (Salem et al., 2022a, b). Generally, different physical methods are in practice to synthesize nanoparticles: lithography, pulsed laser ablation, laser-induced pyrolysis, powder ball milling, gas-phase deposition, electron beam, and aerosol (Xu et al., 2020).

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13.2.1.2 Chemical Method of Synthesis The chemical methods of synthesizing nanoparticles are efficient, simple, and tractable, and the chemical composition and the size of the NPs can be managed efficiently. Sol–gel synthesis, template-assisted assay, reverse micelle, hydrothermal, polyol, chemical vapor, and coprecipitation are the commonly used chemical methods (Ali et al., 2016). Chemical methods use metal alkoxides and other chemicals as precursor molecules and reducing agents (Parashar et al., 2020). 13.2.1.3 Biological Method of Synthesis Currently, the physical and chemical methods of NP synthesis are in practice. The use of highly toxic chemicals and high physical stress has hazardous effects on the environment. To address this issue, the biogenic method evolved as an effective alternative to produce less-toxic and more-ecofriendly high-throughput nanoparticles/nanomaterials (Velusamy et  al., 2016). The bio-based synthesis of NPs has recently become the predominant branch of nanotechnology (Abbasi et al., 2016). The biogenic sources for NPs may include plants, bacteria, fungi, algae, and actinomycetes. The green chemistry, in combination with nanotechnology, helps eliminate the negative impacts of the physical and chemical methods (Salem et al., 2020). In green chemistry, the selected solvent medium, the reducing agent, and the use of less-hazardous stabilizers are the three important concerns in the production of NPs (Fig 13.2). The bio-based synthesis of nanoparticles requires specific parameters, such as optimal conditions for cell growth, the type of biocatalyst, the reducing agent, and optimal reaction conditions for enzyme activity. 13.2.1.4 Bacterial Synthesis of Nanoparticles Prokaryotic eubacteria are most commonly used for the synthesis of metallic NPs. The relative ease of manipulation, level of purification, and high yield are the main reasons for preferring bacteria as sources of NP synthesis. For all these benefits, bacteria have become the preferred choice, often called the factory of NPs (Salem et al., 2018). Soil contains diverse groups of microorganisms; among them, bacteria interact with metal ions in the soil. These metal–microbe interactions contribute to the reduction of environmental pollution thanks to process like bioremediation, bioleaching, biomineralization, and metal corrosion (Velusamy et al., 2016). Singh et al. (2018) listed some examples of bacteria that can efficiently produce silver (Ag) NPs of specific shapes and sizes: Escherichia coli, Lactobacillus casei, Bacillus cereus, Aeromonas sp. SH10 Phaeocystis antarctica, Pseudomonas proteolytica, various species of bacillus (e.g., B. amyloliquefaciens, B. indicus, and B. cecembensis), Enterobacter cloacae, Geobacter spp., Arthrobacter gangotriensis, Corynebacterium sp. SH09, and Shewanella oneidensis. In addition, bacteria involved in synthesis of

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Bottom-up approach Isolation of bio-based extracts (ex. Bacteria, plants, fungi, algae, yeasts etc)

Preparation of metal ion solution

Metal soluon

Reduction of metal ions to zero valent metals/nanoparticles under specific cultural conditions. Indicated by changes in the colour of solutions

Reduction reaction Capping and stabilization of NP using capping and stabilizing agents present in bacteria, plants, fungi, algae and yeasts etc., Fig. 13.2  Mechanism of biosynthesis of nanoparticles

gold (Au) NPs include B. megaterium D01, Desulfovibrio desulfuricans, E. coli DH5a, B. subtilis 168, Shewanella alga, Rhodopseudomonas capsulate, and Plectonema boryanum UTEX 485. The synthesis of gold nanoparticles occurred in the Roman civilization, where Romans used gold nanoparticles for ornamental purposes. Various bacterial species have been well characterized to synthesize NPs, both extracellularly and intracellularly. Javaid et al. reported in 2018 that a dried bacterial cell mass of Aeromonas sp. SH10 can extracellularly reduce Ag+ to AgO in a culture medium. Further, Bacillus licheniformis, B. pumilus, and B. persicus produce Ag NPs extracellularly. Recovering extracellularly synthesized NPs is easy, generally using high-speed centrifugation. The intracellular synthesis of NPs is facilitated by a transport protein in the bacterial cell. The thus-produced NPs accumulate over the cell wall or even in periplasmic space. For example, the Pseudomonas stutzeri AG259 strain reduces a AgNO3 solution and produces Ag NPs and a small number of monoclinic crystalline α-form Ag sulfide acanthites. Similarly, Corynebacterium sp. SH09 produced Ag NPs and combined them with diamine to form complexes. The extraction of intracellular

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NPs uses cell lysis through both physical (ultrasonication, heat treatment) and chemical methods (using salts and detergents) (Murugan et al., 2014) In 2002, Nair and Pradeep showed that Lactobacillus spp. can efficiently form nanocrystals on its cell surface. In 2007, Prasad et al., using a Lactobacillus strain under ambient temperature, synthesized titanium NPs. Srivastava et  al. (2013) reported that by utilizing the E. coli K12 strain, they produced Au NPs. These NPs were used efficiently for the catalytic biodegradation of a nitroaromatic chemical pollutant, 4-nitrophenol, in water. Hennebel et al. (2011) used mixed strains of fermentative bacterial cultures such as Clostridium butyricum, Citrobacter braakii, Klebsiella pneumonia, Enterobacter faecium, and Bacteroides vulgates to synthesize palladium NPs. The NPs produced from these bacteria are highly effective in the degradation of diatrizoate in simulated water. Zeng et  al. (2021) isolated Leclercia adecarboxylata from heavy metal–contaminated soil and used it to synthesize phosphate-­functionalized iron-based NPs. This phosphate-solubilizing bacteria could reduce the toxicity of Pb2+ through a reductive process, followed by precipitation, thus transforming it from the labile fraction of Pb2+ to a residual fraction and playing a significant role in nanoremediation. The protocol for nanoremediation using bacterial species is depicted in Fig. 13.3. 13.2.1.5 Fungal Synthesis of Nanoparticles Fungi-based synthesis of NPs is gaining considerable significance in nanotechnology and green chemistry due to its distinct advantages such as simple isolation and extracellular enzyme secreting characteristic feature. Proteins produced from fungi have the ability to transform dangerous metal ions into nonhazardous zero-valent metals (Saglam et  al., 2016). In addition, the important characteristics of fungal diversity, ability to tolerate high metal tolerate concentration and accumulate metal ions making fungi as versatile over bacterial population. In 2003, Sastry research group reported that acidophilic fungus Verticillium sp. produced Ag nanoparticles in cytoplasm intracellularly. While, Botrytis cinerea was reported to synthesize gold nanoparticles in combination with biomolecules (Castro et  al., 2014). Silver nanoparticles produced using Penicillium citreonigrum Dierckx and Scopulariopsis brumptii Salvanet-Duval extracellulary which were isolated from east of Lake Burullus (Hamad et al., 2018) and AgNP produced from these fungi were found to be efficient. Aureobasidium pullulans, Aspergillus niger, Cladosporium resinae, Penicillium spp, Funalia trogii, Ganoderma lucidum, Rhizopus arrhizus and Trametes versicolor adsorbed heavy metals from polluted area and these organisms were used for NP synthesis (Say et al., 2003). Salvadori et al. (2013), further it was reported that uptake Cu (II) by Hypocrea lixii dead biomass and produced of Cu NP. At the same time, this microbe could also able to produce NiO nanoparticles both extra and intracellularly (Salvadori et al., 2015). Alshehri (2018) synthesized gold nanoparticles using Mucor indicus CBS 226.29 ET. Incubated M. indicus with HAuCl4 salt for 4 h, and change in color from light yellow to violet indicated the formation of gold nanoparticles. While, Fusarium

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Methods of Nanoparticles synthesis

Physical Method (Hazardous)

Biological Method (non hazardous)

Chemical Method (Hazardous)

Bacteria mainly involved in nanoparticles synthesis Isolation of bacteria from soil sample.

Growth of bacteria at 37ºC for 48hrs and other optimum growth conditions in shaking incubator.

The broth is subjected to centrifuged and separate the supernatant

Supernatant is then transferred to reaction vessel containing respective metal ions solution and incubated for 72 hrs.

Colour shift in this reaction mixture will indicate the formation of NP.

Optimum density/absorption spectrum of reduction of respective metal ions is measured through UV-Visible spectrophotometer/nanodrop at 250-800 nm. Morphology and uniformity of respective nanoparticles are measured through XRD, FTIR, SEM and TEM. Fig. 13.3  General protocol of synthesis of NPs from bacteria

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oxysporum could synthesize various NP extracellularly, they reduce aqueous silver ions in water to generate Ag NP and also produce Zirconia NP by using aqueous ZrF62− anions. Likewise F. oxysporum and Verticillium spp, in the presence of ferric and ferrous salts produced magnetite NP and F. oxysporum f. sp. lycopersici was screened and produced platinum NP both by intra-and extracellular forms (Alghuthaymi et al., 2015). General protocol for NP synthesis is given in Fig 13.4 13.2.1.6 Yeast-Based Synthesis of Nanoparticles Similar to bacteria, yeasts are unicellular organisms that significantly contribute to the synthesis of NPs, in which Saccharomyces spp. are the prominent strains used to produce various NPs. The proteins with specific amino acids produced by yeasts can reduce and stabilize nanoparticles. Yeasts produce quinones, which are organic molecules derived from aromatic compounds, and these quinones aid in the production of NPs (Huston et al., 2021). Unicellular eukaryotic fungal species include diverse strains of yeast that can accumulate into observable concentrations of heavy metals thanks to their cell sizes. The detoxification in yeast cells takes place through glutathione, metallothioneins, and phytochelatins mechanisms. Chang et  al. (2021) extracted barium carbonate nanoparticles (nBaCO3) from living yeast cells produced through intracellular biochemical reactions. Further, Salunke et al. (2015), by reducing potassium permanganate, synthesized MnO2 NPs by using the yeast Saccharomyces cerevisiae. For electrochemical sensor fabrication purposes, gold–silver alloy NPs produced from Sacchromyces sp. have been used. These NPs detect the amount of paracetamol in tablet samples and the vanililin content in vanilla bean and vanilla tea samples (Grasso et al., 2019). Magnusiomyces ingens LHF1 was used for the production of selenium NPs (Lian et al., 2019). The production of magnetic spherical nanoparticles of nickel or nickel oxide using dead or inactivated organic matrices of Rhodotorula mucilaginosa (Salvadori et al., 2015) has also been reported. This technique may have commercial value as the induction of magnetic metallic NPs from toxic metals in liquid waste would detoxify the effluents. Recent data have shown that white rot fungi have been used to synthesize nanoparticles and to decontaminate waste water (Kapoor et al., 2021) (Fig 13.5). 13.2.1.7 Algal Synthesis of Nanoparticles Algae are photosynthetic organisms able to heterotrophically assimilate carbon; hence, they are potential alternative sources of energy. In addition, algae have extended their applications to nanotechnology as green sources. With algae, it has been possible to produce various nanoparticles of specific shapes and sizes (Gwala et al., 2021). For example, Tetraselmis kochinensis, Scenedesmus, and Desmodesmus are used for the biosynthesis of metal NPs that have shown antimicrobial activity.

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Major fungal species involved in NPs synthesis (General example: Aspergillus spp., Cladosporium spp., Fusarium sp., Trichothecium spp., Penicillium spp., and Trichoderma spp.

Isolation of Fungal isolates and cultured on PDA media at 28ºC For NP synthesis, 200ml of respective fungal isolates grown in conical flasks containing respective media at 25-28ºC in rotary shaker at 152 rpm for 72 hours.

Filtration to separate mycelial mat and supernatant

10mg of wet biomass + 100ml of aqueous solution containing respective metal salts/100rpm at 28C for 120 hrs.

Reduction of metal ions to respective metals is indicated through change in colour of aqueous solution.

Reduction in metal ions is measured through UV-visible spectroscopy, FTIR, Fluorescence measurements, SEM and TEM.

In situ applications of fungi mediated NPs 1. Environmental remediation 2. Hazardous waste management and metal sequesterization 3. Absorbs heavy metals from polluted sites. Fig. 13.4  General protocol for synthesis of NPs from fungi

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Commonly used Important Yeast species involved in NPs nsynthesis Saccharomyces cerevisiae, Magnusiomyces ingens and Rhodotorula mucilaginosa

Growing of yeasts cells in the form of suspension culture.

Combining of yeast cells and respective metal ions solution

Through NADH dependent reductase activity, and in presence of quinones, reduction of metal ions to respective metals takes place

Optical measurement of NPs produced from the yeasts was done using UV-Visible spectroscopy. Characterization of NP achieved through XRD, FTIR, SEM and TEM. In situ applications of NP from yeasts 1. Magnetite nanoparticles produced from yeasts are used in detoxification of industrial effluents and safe environment. 2. Utilized to treat contaminated water. 3. Used to check amount of paracetamol in tablet samples etc.,

Fig. 13.5  Protocol for yeast-mediated synthesis of NPs

Further, Bhardwaj and Naraian (2021) used cyanobacteria—a blue-green alga—to produce inorganic nanoparticles that have been used as nanopesticides and nanofertilizers. Diatoms are the unicellular microalgae-produced nanomaterials made of biomineralized silica cell walls called frustules; these types of zero-valent nanomaterials are used to control environmental pollution through nanoremediation (Grasso et al., 2019). Additionally, Coccolithophores calcify nanoplankton-produced CaCO3 microparticles (coccoliths) in the form of arrays of nanoscaled structures, and they are used as type II diabetes markers (Skeffington & Scheffel, 2018) Fig. 13.6.

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D. Gayathri and R. Soundarya Microalgae involved in NPs synthesis are (Examples: Tetraselmis kochinensis, Scenedesmus and Desmodesmus )

Cultivation of algae in the ponds at required optimum conditions

Incubation of algal culture in metallic solution at 20ºC for 72 hrs.

Bio-reduction step (Reduction of metal ion to zerovalent metal occurs through 3 phases such as, metal ion reduction and nucleation, amalgamation, and final; step is acquisition of definite shape through termination phase).

Shift in the colour indicate the formation of NP

NP characterisation are achieved through UV-visible spectroscopy, FTIR, SEM and TEM.

Fig. 13.6  Protocol for production of alga-mediated NP synthesis

13.2.1.8 Actinomycetic Synthesis of Nanoparticles Actinomycetes are filamentous, gram-positive, spore-forming actinobacteria and are considered either bacteria or fungi (Gupta et  al., 2019). Actinomycetes have recently been used in nanotechnology to produce nanomaterials/nanoparticles of different shapes (square, rod-like, spherical, triangular, pleomorphic, or even hexagonal). Actinomycetes sp. are used mainly to synthesize silver, gold, copper, selenium, barium, and other metallic NPs, and these NPs have various applications in medicine, pharmaceuticals, ecology, agriculture, and industry (Venkateswaran et al., 2022). Nangia et al. (2009) reported that Nicotinamide adenine dinucleotide hydrogen (NADH) and NADH reductases such as Stenotrophomonas maltophilia and Rhodopseudomonas capsulate produced gold nanoparticles by reducing gold ions to zero-valent gold NPs. However, Sen and Sarkar (2017) reported that the alkali-tolerant actinomycete genus Rhodococcus, tolerant to alkaline environments and slightly high temperatures, has the capacity to synthesize monodispersed Au NPs. Figure 13.7 shows NP production using actinomycetes.

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Actinomycetes such as Stenotrophomonas maltophilia, Streptomyces hygroscopicus, Streptomyces glaucus and Rhodopseudomonas Capsulate known to produce nanoparticles.

Isolation of Actinomycetes from soil, and culturing of actinomycetes on respective media such as ISP and Actinomycetes isolation agar etc.

Inoculation of isolated colonies in to 500ml conical flask containing respective culture medium/incubated on shaking incubator at 120 rpm/5-6 days/27ºC.

After incubation, centrifuge at 8000 rpm/10 min/4ºC

Supernatant collected to be exposed to respective metallic solution and incubated at 37C for 24 hrs.

Biosynthesized nanoparticles studied by measuring absorbance of solution containing nanoparticles by UV-visible spectrophotometer at 300-700 nm, FTIR , SEM and TEM. In- situ applications of Actinomycetes mediated NP. 1. Waste water treatment 2. Green-energy production 3. Pollution monitoring by reducing heavy metals

Fig. 13.7  General protocol for synthesis of NPs from actinomycetes

13.2.1.9 Plant-Based Synthesis of Nanoparticles Over the past few decades, the green synthesis of NPs has been a very popular area of research. Various kinds of natural bio-based extracts are in use to synthesize NPs, out of which plant-mediated nanoparticle synthesis has been employed as the best resource. Plant extracts contain highly efficient stabilizing and reducing substances for the controlled synthesis of nanomaterials (Singh et  al., 2018). Plants contain biomolecules such as proteins, amino acids, terpenoids, flavones, ketones, aldehydes, vitamins, alkaloids, tannins, phenolics, saponins, polysaccharides and other compounds that act like reducing, capping, and even stabilizing agents in the production of NPs (Aslam et al., 2021). Some of the desirable phytochemicals found in various parts of plants, like leaves, fruit, stems, and roots, provide diverse sources

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for NP synthesis (Anyanwu et al., 2021). Iron nanoparticles produced by using various parts of plants were significantly important in reducing environmental pollution by degrading organic dyes, removing chlorinated organic pollutants (e.g., polychlorinated biphenyls), treating ground water, and removing heavy metals (e.g., arsenic). Gold nanoparticles synthesized by using plant extracts from the hydroxyl functional group increased the interaction between hydroxyl ions and Au3 ions to form gold nanoparticles, which were later reduced to zero-valent gold NPs (Akintelu et al., 2021). Okaiyeto et al. (2021), using an aqueous solution of Salvia officinalis leaf extract, produced silver nanoparticles; the produced Ag NPs had good antiplasmodial effects and showed cytotoxic effects against human cervix adenocarcinoma cells. A pod extract of Peltophorum pterocarpum was reported to produce magnetite nanoparticles and had potential absorptive efficiency in reducing the concentration of methylene blue dyes, and it also showed antibacterial activity against Staphylococcus epidermidis and Escherichia coli. In addition, gold nanoparticles synthesized from Cassytha filiformis and Alpinia nigra leaf extract by using HAuCl3.H2O salt (as precursor) had apparent biodegradation activities for the photocatalytic degradation of cationic dye; additionally, Au NPs in the presence of solar radiation mediated the degradation of dyes like methyl orange and rhodamine B (Akintelu et al., 2021). Rasheed et al. (2018) synthesized Ag NPs from a leaf concentrate of Convolvulus arvensis by using NaBh4 as a reducing agent, and these NPs showed catalytic activity in reducing the azo dyes that cause environmental pollution. The general protocol for NP synthesis by using plants is shown in Fig 13.8.

13.3 Nanoremediation Bioremediation is a process involving the utilization of biological forms such as bacteria, fungi, plant extracts, algae, etc. to degrade, detoxify, transform, and stabilize environmental pollutants to the levels below the concentration limits acceptable by regulatory authorities (Rasheed et al., 2018). To reduce the pollutants and heavy metals in the environment bioremediation alone is insufficient; hence, a novel method is needed. Nanotechnology is a technique of producing and then modifying nanoscale materials that are up to 100 nm in size. Recently, the metal nanoparticles produced from bio-based methods have gained attention among scientists and researchers for the bioremediation of environmental pollutants and toxicants (Jeevanandam et al., 2021). Nanoremediation is a promising technology for environmental decontamination, focusing especially on recalcitrant contaminants. Nanoremediation has been attempting to clean up the environment through detection, monitoring, and remediation (Rajan, 2011). Nanoremediation represents a cutting-edge technology for safe and sustainable bioremediation, especially for persistent organic compounds (POCs) such as pesticides, chlorinated solvents like PCBs (polychlorinated biphenyls), brominated and halogenated chemicals, perfluoroalkyl and polyfluoroalkyl

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Many of the plants for example Pinus densiflora, Diospyros kaki, Ginkgo biloba, Magnolia kobus, Camellia sinensis, Desmodium gangeticum , and Platanus orientalis are used in the synthesis of NP, Crude leaves extracts of plants possess many of the alkaloids, phenolic acids, flavonoids and terpenoids helps in conversion of metal ions to zero valent metals.

Addition of leaves crude extract to the metallic salt solution.

Incubation of plant extract and metallic solution for 48-72 hrs.

Colour shift in the metal solution signifies the formation of NP.

Reduction of metal ions to metals are measured by absorption spectra using UV-Visible spectrophotometer at 250-700nm.

Characterization of plants mediated NP are done through XRD, FTIR, SEM and TEM. In situ applications of NP produced from plants. 1. Used in agriculture fields to increase nutrient absorption by plants, detection and control of plant diseases. 2. Manganese oxide nanoparticles (MnONPs) synthesized from the leaves concentrate of plant called Abutilon indicum, has shown efficient absorption activity and photocatalytic activity against the heavy metal CrVI, indicating the potential to remediate various organic and inorganic contaminants Silver NPs produced from the plant Matricaria chamomilla due to its high catalytic activity is effective against rhodamine B dye, thus makes it as a promising source for waste water treatment (Hano et al., 2022). Fig. 13.8  Protocol for the synthesis of NPs from plants

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substances (PFASs), and even heavy metals. In the field of nanotechnology, gifted researchers are highly active in producing innovative, engineered, and structured nanomaterials to reduce the toxicity of heavy metals in soil (Zou et  al., 2016). Nanomaterials include zero-valent irons (nZVI) NMs, carbon nanotubes (CNTs), magnetic and metallic nanoparticles, silica (SiO2) nanoparticles, graphene oxide, covalent organic frameworks, and metal organic frameworks (Fei et  al., 2022). Among these prospective nanomaterials, nanoscale zero-valent iron (nZVI) NMs have garnered the attention of international scientific communities because they possess unique characteristics—such as high surface area, high adsorption capabilities, and high regenerable capabilities—that other nanomaterials lack (Hu et  al., 2017; Gil-Díaz et al., 2017; Xue et al., 2018). Over the past decade, nZVI NMs have been used to immobilize heavy metals thanks to these NMs’ higher stability and effectiveness (Xie et al., 2014). Microorganisms can efficiently synthesize nanoparticles by reducing metal ions. Sharma (2022) explained the mechanism governing the interaction between microbes and heavy metals; different organisms showed varied tolerance responses to environmental parameters. Zero-valent iron is an effective tool in bioremediation because it can treat polluted acidic water, where zero-valent iron nanomaterial quickly neutralizes the acid and thus removes the dissolved heavy metals by immobilizing them (Das, 2018). Additionally, carbon nanotubes have been used in the remediation of polluted water thanks to their specific adsorption properties and affinity with targeted molecules. They have been used widely in the removal of heavy metals such as chromium, lead, and zinc. Carbon nanotubes also assist in the removal of various biological impurities and many types of organic and inorganic compounds (Rajan, 2011).

13.4 Advantages of Nanomaterials With the advent of science and technologies, marked efforts have been recently made to mitigate environmental pollutions. However, innovative and productive ideas to meet the growing environmental challenges are scarce (Ganie et al., 2021). Many approaches have been taken to reduce the risk of toxic contamination, and the use of nanomaterials for nanoremediation/treatment incurs lower costs and is simple and faster than conventional methods. This may be due to their enhanced surface area, transport properties, and sequestration characteristics (Bhandari, 2018). Their high adsorption capacity, their high selectivity, and how easy they are to produce make NPs vital to treating contaminated water and soil (Mukhopadhyay et al., 2021).

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13.5 Disadvantages of Nanomaterials Along with the considerable potential benefits, the usage of nanomaterials also comes with misconceptions and uncertainties. Using zero-valent ions has four main disadvantages: 1. Micron-size clusters produced from the aggregation of high concentrations of zero-valent ions do not exhibit nanoscale effects. 2. Under almost all relevant conditions, the bare nZVI NM will move less than a few meters. 3. Significant risks to human health and ecosystems can be traced (Tratnyek & Johnson, 2006). 4. Two major associated with using nanomaterials/nanoparticles. Among them, the two most significant risks are health-associated and environmental risks. Healthassociated risks occur mainly from the usage of nZVI NMs; the people who handle these types of nanomaterials are those most likely to be affected during the transportation, handling, and injection of NP slurries. The traveling distance of NPs and their ecotoxicity are the two main attributes used to govern the extent of environmental risk.

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Anyanwu, N. G., Stanley, H. O., Okpokwasili, G. C., & Akaranta, O. (2021). Biogenic nanoparticles and their environmental applications in bioremediation and pollution control. International Journal of Innovative Research in Science and Technology, 6, 113–121. Aslam, M., Abdullah, A. Z., & Rafatullah, M. (2021). Recent development in the green synthesis of titanium dioxide nanoparticles using plant-based biomolecules for environmental and antimicrobial applications. Journal of Industrial and Engineering Chemistry, 98, 1–16. Barage, S., Lakkakula, J., Sharma, A., Roy, A., Alghamdi, S., Almehmadi, M., et  al. (2022). Nanomaterial in food packaging: A comprehensive review. Journal of Nanomaterials, 2022, 20220824. Bhandari, G. (2018). Environmental nanotechnology: applications of nanoparticles for bioremediation. Approaches in Bioremediation: The new era of environmental microbiology and nanobiotechnology, 301–315. Bhardwaj, A. K., & Naraian, R. (2021). Cyanobacteria as biochemical energy source for the synthesis of inorganic nanoparticles, mechanism and potential applications: A review. 3 Biotech, 11(10), 1–16. Castro, L., Blázquez, M. L., González, F. G., & Ballester, A. (2014). Mechanism and applications of metal nanoparticles prepared by bio-mediated process. Reviews in Advanced Sciences and Engineering, 3(3), 199–216. Chang, Y., Zheng, C., Chinnathambi, A., Alahmadi, T. A., & Alharbi, S. A. (2021). Cytotoxicity, anti-acute leukemia, and antioxidant properties of gold nanoparticles green-synthesized using Cannabis sativa L leaf aqueous extract. Arabian Journal of Chemistry, 14(4), 103060. Das, P. K. (2018). Phytoremediation and nanoremediation: emerging techniques for treatment of acid mine drainage water. Defence Life Science Journal, 3(2), 190–196. Dhand, C., Dwivedi, N., Loh, X. J., Ying, A. N. J., Verma, N. K., Beuerman, R. W., et al. (2015). Methods and strategies for the synthesis of diverse nanoparticles and their applications: A comprehensive overview. RSC Advances, 5(127), 105003–105037. Fei, L., Bilal, M., Qamar, S.  A., Imran, H.  M., Riasat, A., Jahangeer, M., et  al. (2022). Nano-­ remediation technologies for the sustainable mitigation of persistent organic pollutants. Environmental Research, 211, 113060. Ganie, A.  S., Bano, S., Khan, N., Sultana, S., Rehman, Z., Rahman, M.  M., et  al. (2021). Nanoremediation technologies for sustainable remediation of contaminated environments: Recent advances and challenges. Chemosphere, 275, 130065. Garg, S., & Roy, A. (2022). Phytoremediation: An alternative approach for removal of dyes. In Phytoremediation (pp. 369–386). Academic Press. Gaur, N., Narasimhulu, K., & PydiSetty, Y. (2018). Recent advances in the bio-remediation of persistent organic pollutants and its effect on environment. Journal of Cleaner Production, 198, 1602–1631. Gil-Díaz, M., Alonso, J., Rodríguez-Valdés, E., Gallego, J. R., & Lobo, M. C. (2017). Comparing different commercial zero valent iron nanoparticles to immobilize As and Hg in brownfield soil. Science of the Total Environment, 584, 1324–1332. Grasso, G., Zane, D., & Dragone, R. (2019). Microbial nanotechnology: Challenges and prospects for green biocatalytic synthesis of nanoscale materials for sensoristic and biomedical applications. Nanomaterials, 10(1), 11. Gupta, A., Singh, D., Singh, S. K., Singh, V. K., Singh, A. V., & Kumar, A. (2019). Role of actinomycetes in bioactive and nanoparticle synthesis. In Role of plant growth promoting microorganisms in sustainable agriculture and nanotechnology (pp. 163–182). Woodhead Publishing. Gwala, M., Dutta, S., & Ghosh Chaudhuri, R. (2021). Microalgae mediated nanomaterials synthesis. In Algae (pp. 295–324). Springer. Hamad, A. F., Han, J. H., Kim, B. C., & Rather, I. A. (2018). The intertwine of nanotechnology with the food industry. Saudi Journal of Biological Sciences, 25(1), 27–30. Hennebel, T., Van Nevel, S., Verschuere, S., De Corte, S., De Gusseme, B., Cuvelier, C., et  al. (2011). Palladium nanoparticles produced by fermentatively cultivated bacteria as catalyst for

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Part IV

Safety Aspects and Analysis of Nanoremediation

Chapter 14

Supporting Nanotechnology Safety Through Nanoinformatics Sesuraj Balasamy, Surya Sekaran, and Rajalakshmanan Eswaramoorthy

14.1 Introduction to Nanoinformatics Nanotechnology is widely used in the world for new inventions and technology. Nanoinformatics aids in the identification of materials and components and their respective compositions. All the information is sequenced in the database to predict the exact value and find suitable materials. In recent years, the development of applications that make use of nanotechnology has rapidly increased. All fields of research are now benefiting from the technical advances of nanotechnology (Liu & Cohen, 2015). Information science is one of the least studied topics, and nanomarker assessment has received even less attention. The combination of information science and nanotechnology is giving rise to the field of nanoinformatics, which has made significant progress. Nanoinformatics performs important functions in its merger with other fields. For instance, the development of computing platforms for screening and predicting substances or chemicals, the development of sensors for national security, the development of online services with much more memory and more-reliable applications, the development of databases, and so on. The transistor was without a doubt one of the most significant inventions of the twentieth century. The development of personal, mobile, and high-performance computers was made possible by the advancement and miniaturisation of semiconductor technologies. Many undertakings in science and business today would be inconceivable without the assistance of computational technologies. Computing power is employed in the construction of cars, ships, and planes, such as in the design of individual components or the modelling of the overall aerodynamic S. Balasamy · S. Sekaran · R. Eswaramoorthy (*) Department of Biomaterials (Green Lab), Centre of Molecular Medicine and Diagnostics (COMManD), Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Science (SIMATS), Saveetha University, Chennai, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_14

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behaviour of a set. A new, emerging field of study has grown in prominence. This is computational nanotechnology, which refers to the use of computer algorithms and methods to enhance nanoscience and nanotechnology. This new field of research deals with matter entities on the order of billionths of a metre. It is difficult to determine when humans began using materials at the nanoscale. The Romans made nanoscale glasses from metals in the fourth century BCE. The existence of nanoparticles of metals such as gold and silver, for example, gives the stained-glass windows of mediaeval churches their stunning variety of colours. The capacity to analyse and manipulate matter at the nanoscale, on the other hand, has only lately been made feasible by the development of advanced technology. This has resulted in an increase in the number of discoveries and technical developments and in extension of research. Two key components of these new scientific and technical achievements were the creation of the scanning tunnelling microscope (STM) in 1981 and the atomic force microscope (AFM) in 1986 (Tanaka, 2018). These instruments are capable of manipulating atoms and molecules, constructing simple nanostructures, and producing photographs of surfaces at atomic resolutions. Computational models of chemical and physical systems that allow researchers to simulate potential nanomaterials, devices, and applications have been developed. These simulations are also becoming much faster and more accurate thanks to advances in computer power and 3D visualisation capabilities. The amount of scientific knowledge that is now readily available (in journals, periodicals, articles, websites, etc.) has also significantly increased in recent years, largely because of the widespread use of the Internet. As a result, the significance of computational nanotechnology has grown tremendously. Some of these nanotechnology-based systems employ computational intelligence methods, which are sometimes referred to as intelligent computational nanotechnology. However, the use of computational intelligence technologies to help the growth of nanotechnology and nanoscience needs to be further investigated. A number of computational intelligence methods are used in the creation of intelligent systems, including genetic algorithms (GAs), Artificial neural networks (ANNs), and fuzzy systems, to name a few. The ideas behind genetic algorithms, which are highly parallel search and optimisation techniques, were inspired by Darwinian natural selection and genetic reproduction, in which the fittest individuals live the longest and are most likely to reproduce. In contrast, neural networks, which are based on the architecture and functionality of the human brain, have been used to solve a number of challenges. By combining these clever methods with nanoscience and nanotechnology, the cost of developing effective devices, some of which are unimaginable even to professionals, can be reduced and their development accelerated. However, in supporting nanoscale device initiatives, these strategies have not been adequately explored. It is expected that they can offer a number of very useful tools to facilitate the rapid growth of this new field of study. In the same way that other computational techniques have been used for the projects of the current generation of engineering systems such as cars, ships, airplanes, and microdevice-integrated circuits, intelligent computational nanotechnology has emerged as a fundamental computational tool for the development of new

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nanodevices. As one of the world’s technological leaders, the United States can benefit from the application of nanoinformatics in a variety of industries. In recent years, the European Commission has worked with the US government to develop novel nanoinformatics materials that can sense and communicate with biological systems. This project can be a great help in planning drug discoveries. It can also effectively improve current medical applications. A nanoinformatics tool that uses mining techniques to extract data from research articles and proposals has also been developed. This tool can more broadly benefit biological databases by bypassing the tedious and time-consuming process of ingesting new information (Afantitis et al., 2018). Nanoinformatics is defined as the science and practice of finding information important to nanoscale engineering and sciences and then creating and implementing sophisticated techniques for recording, verifying, storing, sharing, interpreting, modelling, and using such information. The main disadvantage of nanoinformatics is that it is still in its early phases of development, with data distributed in the form of papers. Recently, various projects in the domain of nanoinformatics to handle nanoparticle data have emerged. Medical informatics, bioinformatics, and other interdisciplinary fields have emerged from the development of computing techniques and applications related to biomedicine. These biomedicine-related informatics disciplines include methods for data and knowledge integration, biomedical theories and vocabularies, data and text mining, systems interoperability, DNA and RNA sequencing, medical decision support, predicting relationships between gene mutations and disease, developing standards for data representation and exchange, and a variety of other scientific and technological approaches to solving complex problems. These sectors have benefited from efforts that have resulted in notable outcomes like the Human Genome Project and other projects, the computerisation of clinical practice, and the creation of computerised decision-support systems (O’Connor et al., 2014). After decades of research on such biomedical systems, the scientific community, including those in informaticians, is beginning to focus on the difficult new subject of nanomedicine. Nanomedicine holds the promise of scientific and technical advancements that have the potential to alter medicine. To our knowledge, nanoinformatics has not yet been addressed in any of the papers published in the computing field. The application of nanoinformatics in this context is a particularly challenging problem that remains largely unexplored. The management of data, information, and knowledge presents significant challenges that need to be addressed to improve research in this area. While research in this field is frequently connected with nanotechnology, computational techniques are vital for extending information and enhancing professional practice in a diversity of other disciplines. In the 1980s, in order to save all published DNA sequences in a central repository, it became necessary to collect all data in the form of publicly accessible databases and make gene and protein sequences freely available to everyone. Numerous researchers have developed effective techniques, resources, and tools for analysing large-scale data thanks to the open accessibility of DNA sequences in databases

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such as Gene Bank and the accessibility of protein structures in databases such as Protein Data Bank. Analyses of biological data have entered a new era as processing speed and storage capacity have simultaneously increased. The effectiveness of this subject is demonstrated by the large number of bioinformatics tools and approximately 1000 datasets that are now made available to the general public. We may draw valuable conclusions on the growth of nanoinformatics by using the same approach as the dissemination and development of bioinformatics (Maojo, 2010).

14.1.1 Information on Nanotechnology and Nanoscience The term nanotechnology was first coined by Richard Feynman in 1959 at a conference at the California Institute of Technology. The lecture “There Is Plenty of Room at the Bottom,” a talk that Feynman gave in advance of the conference, suggested that by manipulating specific atoms and molecules, it might be possible to control the production of nanometre-scale materials for promising technical, industrial, and biological applications. The findings of this conference and its offshoots are now considered the theoretical basis for the advancement of nanotechnology. Since then, nanotechnology has sparked a revolution in a wide range of disciplines, including biotechnology and clinical research, as well as physics, chemistry, materials science, engineering, environmental sensing, manufacturing, and quantum computing (Panneerselvam & Choi, 2014). These initiatives have therefore increased the attention paid to novel synthesis methods, structures, phenomena, and characteristics associated with dimensional length scales between 1 and 100  nm. Scientific nomenclature has employed the word nano, which is taken from Greek, meaning “dwarf,” since 1960. However, atomic, molecular, and ionic interactions affect the behaviour of particles smaller than 100 nm. Macroparticles, particles larger than 100 nm in diameter, exhibit properties similar to those of bulk materials. Thanks to quantum phenomena, nanoparticles exhibit novel and variable properties. There are various definitions in the literature even though the term nanotechnology has been used for almost 40 years. In 1974, Japanese scientist Norio Taniguchi first used it to explain the exact creation of nanoscale materials. Nanoscience and nanotechnology were defined in a 2004 study by the Royal Society and Royal Academy of Engineering: • Nanoscience is the examination of events and the handling of substances at the atomic, molecular, and macromolecular sizes whose characteristics are very different from those of larger scales. • Nanotechnology is the design, characterisation, production, and application of structures, devices, and systems by controlling shape and size at the nanometre scale. Throughout history, it is unclear when humans first developed technology using nanoscale particles. Glasses with metallic nanoparticles were made around the

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fourth century BCE. The Lycurgus cup, for example, is an artefact from this period. It is made of glass and contains gold and silver nanoparticles. Depending on where the light source is positioned, the hue of the cup changes to represent the death of King Lycurgus. The first quantum well was made in the 1970s by researchers at Bell Labs and IBM by using a process called the epitaxial growth of thin films, which allows monolayers of a semiconductor material to be deposited one after another. These quantum dots, which are now among the most popular materials in nanotechnology, originated in this work. However, it was not until the 1980s, with the development of fabrication and characterisation techniques for nanostructures, that research activities significantly expanded. In 1981, a technique for vaporising metals in a heated plasma and forming metal clusters was devised. This technique was used in 1985 to produce fullerenes (C60). The scanning tunnelling microscope (STM) was created in the 1980s by Binnig and Rohrer of the IBM research facility in Zurich. In 1986, they received the Nobel Prize in physics for their creation. Nanostructures may now be visualised, characterised, and manipulated thanks to the advancements of the scanning tunnelling microscope (STM) and the atomic force microscope (AFM) (Seko et al., 2018). The most researched and used nanostructure today was first discovered by Iijima in the early 1990s. In the same decade, several projects were launched to build molecular switches and study the conductivity of molecules. In addition, the first field-effect transistor based on carbon nanotubes was developed. At year’s end, Bill Clinton, then-president of the United States, spoke about the importance of advancing nanoscience and nanotechnology and announced a USD 497 million public investment for (Dalton, 2000). Industrialised countries and, to a lesser extent, emerging economies have since invested in nanoscience and nanotechnology. The creation of computational and experimental methods necessary for the design and production of nanoscale components, such as nanowires, quantum dots, nanosensors, nanocatalysts, etc., is enabled by the evolving fields of nanoscience and nanotechnology. Current tools are still expensive, which discourages many researchers, especially in underdeveloped countries, from using them. A decrease in price always follows technological progress, as has been the case in electronics and telecommunications. Therefore, it is reasonable to expect that in the next decade, with the help of growing public and private investment and the development of new low-cost tools, the number of marketed goods with embedded nanotechnology will significantly increase. Nanotechnology will in the future undoubtedly affect the character of almost everything that humanity has achieved if it is developed and deployed. According to some estimates (Mullard, 2017), the societal impact of nanotechnology could be as great as that of the (first) Industrial Revolution and undoubtedly greater than recent developments in space exploration, nuclear energy, transistor and computer technology, and polymers. For the most part, organic, inorganic, and hybrid nanoparticles are well recognised. In contrast to simple monomeric carbon nanotubes, fullerene particles, and

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metallic nanoparticles, which make up inorganic nanomaterials, organic nanoparticles are the building blocks of polymers like gold and silver nanoparticles. Examples of hybrid nanoparticles include synthetic nanoparticles like DNA-carbon nanotube arrays. Nanoparticles can be used to produce devices for medication administration, treatment, and diagnosis in the biomedical industry because their size is comparable to that of biomolecules like proteins. Nanoparticles are present in a wide range of consumer goods, including bottles, apparel, bicycles, cosmetics, sunscreens, and titanium dioxide nanoparticles. Two nanotherapies for the treatment of cancer, Doxil and Abraxane, are now available and have received food and drug administration (FDA) approval. The unique properties of nanomaterials hold promise for a variety of uses, but they also raise safety questions. Nanoparticles have the potential to be harmful to human health and have undesirable side effects owing to their capacity to enter the body, flow in the blood, and enter cells, so understanding the biological and toxicological effects of nanoparticles is crucial for determining whether products are safe. Nanoscale materials are characterised primarily by two aspects. First, nanoparticles have a substantially bigger surface area than the same mass of a substance in its larger form. The surface area increases a million times. The overall bulk and volume, however, remain unchanged. Second, the behaviour of matter can start to be dominated by quantum effects at the nanoscale, which can change its optical, electrical, and magnetic characteristics (Mullard, 2017).

14.2 Application Framework for Nanoinformatics Nanoinformatics is a method for gathering, organising, analysing, preserving, distributing, modelling, and analysing data pertaining to nanotechnological processes and materials in order to produce actionable knowledge for the nanoscale research and engineering community. The development and use of tools required for simulations, computations, and predictive modelling of nanomaterials, nanodevices, and nanosystems is part of the computational nanoscience community, collectively known by the more general term nanoinformatics. Product development and product manufacturing are other areas where nanoinformatics has much to offer. The industrial process associated with the commercialisation of nanotechnology, while separate from basic research activities, has some commonalities. Production design, logistics, quality control, safety, and the business model are all accelerated by data-driven processes in this sector. Products are also designed for performance and reliability. Indeed, the activities of scientific research in nanoinformatics and those of industrial development can complement each other in various ways and lead to constructive synergy. Today, the development of new technologies relies heavily on knowledge and data from basic research. Feasibility opportunities could be enhanced by access to more-comprehensive data sets than the few illustrative examples found in the published scientific literature, industrial research, and design initiatives. Nanoinformatics tools can accelerate time to market and streamline workflows. Similarly, the application of

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nanoinformatics tools that identify data or modelling deficiencies in industry can stimulate new basic research initiatives to address these needs. From an industrial perspective, the added value of a process step can be better regulated and maximised when it is a data-intensive activity in a production chain. The design and manufacture of products containing nanomaterials requires precise property data that affect overall performance. Raw materials, which may occasionally be nanomaterials themselves, should be supplied with material certification documentation detailing their composition and characteristics. Inputs at each stage of the manufacturing process subsequently influence the structure and quality of the output. Accurate process control and optimisation can be achieved through simulation and modelling that are based on nanoinformatics in conjunction with data from metrological techniques. Manufacturing repeatability can be predicted, and design margins can be generated by using known input distributions, variabilities, and linkages between processes, enabling the feasibility of adaptive manufacturing and process optimisation in nanomanufacturing. Ideally, there should be a stream of process and a characterisation data in the production stream that provide provenance data for standardisation, extensibility, and new manufacturing innovations (Volodin & Omelyanenko, 2017).

14.2.1 Nanoinformatics as Emerging Field of Information Technology The uses of computational technologies, informatics, and molecular simulations have increased as important approaches to research in nanobiotechnology and nanoinformatics. These methods are ideally suited for generating qualitative findings, insights, and design recommendations. While bioinformatics is often used to analyse DNA and protein sequence data by using computational tools, nanoinformatics is used to characterise particles and materials with applications in nanotechnology and biotechnology through modelling and simulation, often at the atomic level, using computational chemistry techniques. The term nanomedicine entered common usage as of 2004. The first nanomaterials for biomedical sciences were developed in 1985. To date, applications for biomedical issues have dominated the development of today’s nano-biomedical sciences. Examples include technological advances through novel synthesis techniques in lipids, polymers, colloid chemistry, and colloid synthesis, as well as the discovery of brand-new chemical processes such as fullerene and quantum dot synthesis. These brand-new molecular systems can be used for therapy and diagnosis. By segmenting the subject into four categories—social aspects, new applications of traditional bioinformatics methods, new modelling challenges, and the emergence of collaborative environments—an analysis of the current state of nanobiotechnology informatics can be carried out. The nanobiotechnology informatics is a defining

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characteristic of nearly every new nanoinformatics initiative (Nwankwo & Ukhurebor, 2021).

14.2.2 Nanoinformatics for Environmental Health and Biomedicine A variety of companies, including those in power generation, electronics, biomaterials, and medicine, have greatly benefited from the development of nanotechnology. The creation and application of nanoscale devices for the secure and efficient transport of medications to their intended sites is one illustration of the quick advancement of nanotechnology in medical treatment and diagnosis. The possible effects of nanotechnology on the environment and human health are also causing considerable worry. Consequently, there is a global drive to ensure the ethical development of practical nanotechnologies in order to avoid adverse effects on the environment and human health. Huge numbers of data are being produced to better understand and map the toxicological and pharmacological properties of nanomaterials so that safe nanomaterials can be constructed for various intended applications. Data on nanomaterials are often sought for their physical, chemical, and structural properties; their environmental effects; their toxicological behaviour; their processing details; their production quantities; their environmental emissions; and more. New informatics tools are urgently needed to collect, manage, analyse, and model the vast numbers of data associated with nanoscale processes and materials. Nanoinformatics currently emphasises mainly nanodata planning and database design, nanodata curation, nanodata intelligent supply assessment, literature searches for nanodata collection and meta-analysis, data mining, and machine learning, such as the development of quantitative structure–activity relationships (QSARs), simulations of nanomaterial fate and transport, nano–bio interactions, and evaluations of possible health and environmental risks. In the past 10 years, the discipline of nanoinformatics, which is essentially made up of nanotechnology and data science, has become more and more significant in the research and development of nanomedicine and the effects of nanomaterials on the environment’s health. Cyberinfrastructures and web platforms, such as nanoinfo.org in the United States and eNanoMapper in the European Union, provide a wide range of tools and resources thanks to research in this area. This thematic series will report on recent developments in the development of databases. These databases contain a valuable collection of information on the physicochemical properties and bioactivity of nanomaterials. One paper describes the latest version of caNanoLab and provides a critical analysis of the difficulties in creating nanomaterial databases and of the biomedical research community’s requirements for organising and sharing nanodata. Another paper summarises the most recent advancements of the eNanoMapper database for information on nanomaterial safety information, and a third

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contribution discusses the Nano E-Tox database, which focuses on the ecotoxicity of nanomaterials (Afantitis et al., 2020). Additionally, there has been tremendous development in the Nanotechnology Consumer Items Inventory, which monitors the promotion and distribution of items with nanotechnological elements in the marketplace. Two other papers address the use of sophisticated literature and text-mining approaches, such as natural language processing and corpus-based automatic information extraction, to automate the discovery and extraction of nanodata. Bibliometric and social media platform analyses are also discussed and utilised in the domain of nanoinformatics to discover cooperative networks and growth for nano-assisted medication delivery to treat brain cancers.

14.2.3 Effective Cancer Treatment Using Nanoinformatics A special synthesis of chemistry, biology, and the natural sciences can be found in nanotechnology, which is a useful tool in medical healthcare for the early diagnosis and personalised treatment of cancer. It has greatly profited from the recognition and description of a number complex molecular processes that offer a better understanding of biological systems and lessen complex illness events. However, the use of computational methods in nanomedicine is still in its infancy and represents an urgent area of research. The topic of nanoinformatics was created in response to the demand for computational applications at the nanoscale and the resulting consequences. Researchers can use nanoinformatics as a useful platform to create and study the effects of nanoparticles (NPs) as drugs at the aggregation, molecular, cellular, tissue, organ, and organism levels. In addition to understanding risk assessment and cytotoxic analysis, it helps to understand the physiological and biochemical characteristics of NPs. Nanoinformatics studies have greatly helped researchers overcome obstacles such as drug resistance, poor retention in tumours, long circulation times, toxicity to nontumorigenic cells, and inadequate pharmacokinetics in malignancy studies. A cheaper and faster alternative to expensive in vitro and in vivo toxicity and safety studies is the computer-aided development and analysis of NP interactions. The computer-aided analysis of the most popular methods for NP optimisation creates compact targeting ligands to replace bulky antibodies against tumour epitopes and the virtual screening of NP libraries for tumour targets. Other well-­ known property assessments performed in nanoinformatics include data mining, network analysis, the quantitative structure–property relationship (QSPR), the quantitative structure–activity relationship (QSAR), and ADMET (absorption, distribution, metabolism, excretion, and toxicity) predictors (González-Nilo et al., 2011). Recent scientific data have demonstrated a significant improvement in the categorisation of nanoparticles in the form of liposomes, polymeric micelles, quantum dots, gold, silicon, polymer shells, dendrimers, etc., but there are still many

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difficulties that require the development of more-efficient NP types, specifically the better utilisation of in vivo behaviour. Application sections have taken the lead in discovering solutions to these problems by assisting with data management and analysis from biomedical applications as well as in silico studies of NP interactions with biological molecules using simulation techniques. It has aided in the storage and computational management of enormous volumes of structural and property data in the field of nanomedicine and encouraged research on data mining, data modelling, and information retrieval. Studies in nanoinformatics have provided in silico novel templates for nanomaterial development and discovery and improved material selection. This has undoubtedly improved the in vitro and in vivo performance of NP products and the accuracy of their drug delivery systems. The ultimate aim in developing anticancer drugs has been to propose specific nanomedicines that ideally attach to cancer cells at the tumour site without harming healthy cells. In the present era, various techniques of nanoinformatics have replaced the traditional methods of nanotechnology and improved the quality of nanomedicines developed for better cancer diagnosis and treatment. Currently, specific bionano-models are being created that take into account important factors such as the binding affinity, the ligand density, the length of the ligand bond, the valence of the bond, the shape of the nanoparticles, and the stiffness of the substrate. Using experimentally verified binding interactions and membrane protein expression, the Monte Carlo simulation approach is used to investigate the binding capability of NPs to the chosen target cancer cells versus healthy cells. Similar delicate pressures must be balanced at the pharmacological and toxicological levels to ensure that the drug is neither too firmly nor too loosely bound. This is necessary for the complex to be safely taken up and released at the appropriate disease site. This balance is achieved by using guided dynamics and methods such as parallel replica dynamics and hyperdynamics to map the path of a molecule freed from its binding site.

14.2.4 Nanoinformatics to Support Precision and Sustainable Agriculture The third agricultural revolution, commonly known as the Green Revolution of the 1950s and 1960s, significantly increased agricultural productivity worldwide and prevented the spread of famine and starvation. However, since the beginning of the Agricultural Revolution, the world’s population has increased by almost five billion, necessitating ongoing increases in food production. Low crop yields, declining soil health and fertility, low efficiency and low agrochemical use primarily owing to pesticide and fertiliser overuse, decreasing arable land per capita, and decreasing freshwater availability for irrigation are just a few of the issues affecting global agriculture and food security. Furthermore, climate change brought on by rising temperatures and rising atmospheric CO2 concentrations is predicted to have

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impacts on agricultural soils’ resilience, their capacity to support output, and their ability to ensure food production for a growing population. The opportunities and limitations of using nanotechnology to enable sustainable and precision agriculture have been addressed in a number of recent reports on crop nutrition improvement methods and smart crop sensors. Nanotechnology can be used to design fertiliser delivery that targets specific organs or tissues in a controlled manner via stimulus-­ dependent release, which can increase nutrient-use efficiency by releasing the nutrient for plant uptake. In addition, nanotechnology-assisted agriculture is expected to more effectively control pests with fewer pesticides, avoid wide-ranging impacts on soil health and biodiversity, and improve the soil microbiome that optimising nitrifying and denitrifying bacterial communities, thereby improving soil function and nutrient cycling. Creating smart “sensor” plants that can detect abiotic stress through tailored nanomaterial distribution is one of the longer-term applications of this technology (Maojo et al., 2012). 14.2.4.1 Models for Nano-enabled Agriculture Using Nanoinformatics In recent years, much research has been conducted to use machine learning to analyse the risks associated with nanomaterials and to develop safe, environmentally friendly nanomaterials. For example, an increasing number of nano-QSAR models relate certain properties of nanomaterials to their uptake by cells or organisms and their effects. These models can be used to define targeted methods in precision nano-agriculture. These models enable the identification of surface functionalisations that, for instance, enhance protein binding and cellular interaction. Using QSARs, the ecotoxicity of pesticides to targeted and nontarget species has been predicted, although nano-QSARs have not yet been developed for plants. However, given the exponential increase in data on nanomaterials in plants and soil species, it is only a matter of time before the first nano-QSARs are produced for plants and soil microbiota. Similar to how improvements in nanomedicine will facilitate the development of the optimally controlled release of agrochemicals, the same will be true for precision nano-agriculture. For example, to predict the best pharmaceutical formulations and dosages, deep learning has been developed by using an autonomous data-partitioning technique and evaluation criteria suitable for pharmaceutical formulation data. From an agricultural perspective, the selection of formulation parameters and the determination of whether an application is appropriate for a particular site or climate can be informed by knowledge of relevant factors, including nanomaterial, plant, soil, and climate factors that control the rate of the release of the active ingredient and the factors that determine the transport of the carrier. The development of such data-driven models remains difficult because they require a large number of data to be trained and validated. Pesticides and the potential use of computational chemical-modelling technologies to accelerate insecticide risk assessment that can be applied at the nanoscale have led researchers to conclude that quantum chemistry is a suitable method for determining the structure and relative stability of organic compounds and for

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investigating deterioration routes. To assess its suitability for nano-based agriculture, a new evaluation is needed using quantum nanomaterial descriptors for QSAR development. 14.2.4.2 The Challenges in Nano-agriculture Despite the great potential for various applications of nanotechnology in agriculture, several hurdles still need to be overcome before many advanced nanomaterials can be fully exploited on a commercial basis. This includes the lack of mechanistic understanding of connections at the nanomaterial plant root level as well as the uptake and hybridisation of nanomaterials in the plant’s vascular systems and organs. Additionally, there is a lack of information on the risks to human health and the environment associated with the purposeful use of nanomaterials (Wang et al., 2021).

14.3 Emerging Databases and Tools for Nanoinformatics The databases and technologies discussed here show that more and more resources are available to users. Their further development is supported by the constant growth of databases and various computer programs. According to the data on nanomaterials, new-database efforts such as ISA-TAB-Nano, caNanoLab, and the Nanomaterial Registry will promote data sharing, data standards, and the creation of tools and procedures tailored to the nanoscale. The development of these areas essentially requires that journals and other organisations adopt the ISA-TAB-Nano standard to enable a uniform presentation of nanotechnology data. Importantly, researchers have developed useful methods, instruments, and resources that have considerably benefited the field of bioinformatics thanks to the flexibility of using released DNA sequences in databases like Gen-Bank and thanks to open accessibility. Another challenge is the dearth of research journals from subscription-­based publications in nanotechnology, especially in chemistry, where even abstracts are not available for large-scale studies like text mining. This is a huge disadvantage for text mining and investigations into nanoinformatics. A recent review on QSAR provided an overview of various developments, outlined a precise course for future studies, and highlighted the most pressing research gaps. Although modelling the behaviour of nanomaterials poses different difficulties than modelling the behaviour of drugs, it is still possible to develop new techniques and specialised tools from existing ones. A probable reduction in the necessity for animal testing is one benefit of continuing to develop nanoinformatics. The recent initiatives of the nanotechnology sector are encouraging (Wang et al., 2021).

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14.3.1 Text Mining Text mining is a computational method for using the knowledge found in books. In the discipline of biology, three significant text-mining techniques are now in use: (I) approaches based on co-occurrence; (II) approaches based on rules or knowledge; and (III) approaches based on statistics or machine learning. Co-occurrence-based approaches look for particular words or concepts that, although they may be abstract, appear in the same sentence and then speculate on a relationship between them. The structure of language, the way physiologically meaningful information is expressed, and the connections between these two categories of knowledge are all factors that rule-based systems take into account. The way statistical or machine-learning-based systems work, however, is by creating classifiers that can work at any level. The majority of scientific journals still do not have free full-text access. The few text-­ mining methods that are currently accessible are listed below. The following search engines were used: (1) Google Scholar; (2) GoPubMed; and (3) Textpresso. 14.3.1.1 Databases Despite the advent of new technologies utilising semantic web ontologies and capabilities for the management of scientific data, databases continue to be fundamental components in the infrastructure in nanoinformatics and in the other e-science areas. Relational databases currently house the majority of the data. By defining fundamental concepts and common structures, the development of these data bases (DBs) starts the process of producing a variety of classifiers and taxonomies that are used as a foundation for the construction of conceptual DB schemes, which organise an initial array of data (Volodin & Omelyanenko, 2017).

14.3.2 Artificial Intelligence and Machine Learning in Nanoinformatics The vast output of data has been used in the development of new computational techniques for their exploitation imperative, which is now being efficiently organised and stored in numerous sectors of health and materials research. Cheminformatics research has already made a significant contribution to the resolution of many issues in the drug-finding field, including interactions among surface proteins and receptor inhibition or affinity. It is also constantly evolving and adapting to the unique requirements arising in various research domains, such as nano-safety. Several steps in the drug development pipeline have been greatly accelerated by in silico tools, but more work is still needed to combine the techniques by creating a clear framework and standardising the processes. Parallel to this, new informatics techniques created for the study of materials have inherited cheminformatics, which is a rapidly

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expanding area, and new methods and algorithms are being developed to meet the specific needs of substances whose properties span several scales. In order to quantify the safety of nanomaterials and their effects on living things and the environment, nanoinformatics, which focuses on materials at the nanoscale, adapts and expands the in silico tools and methods already available. It also develops new approaches to address the equilibrium, dynamic, interactive, and quantum properties of nanomaterials. It has never been more critical to create split computational techniques and algorithms for NMs, in part to enable the management of the broad features of NMs that have emerged from combinatorial methods used to build mega libraries with fundamentally different compositions. The community urgently needs to develop low-cost nanoinformatics models and tools based on AI and machine learning (ML) to foresee essential NM capacities, interactions with environmental and biological milieus, and possible adverse effects. Particular focus should be placed on the creation of data-driven meta-models and prediction models that reveal complex relationships between NM characteristics and physical qualities, as well as their functions and detrimental biological impacts. With new models expected to be published in the literature in the coming months, interest in artificial intelligence methods and deep-learning techniques on big datasets of NMs and their effects on organisms is also growing. The discipline is aggressively pursuing the creation of methods that enable the creation of nontoxic materials for a variety of applications, from smart farming to environmental cleaning to nanomedicine (Lewinski & McInnes, 2015).

14.3.3 Overcoming Nanoinformatics Flaws and Issues The interdisciplinary nature of this knowledge domain and the ongoing expansion of its definitions to reflect the emergence of new materials, devices, and applications had to be taken into consideration by the projects that were actually put into action. The most thorough and detailed strategy has currently been established in the framework of the Nanoinformatics 2020 Roadmap, which was agreed upon at the 2015 seminars. The development of the nanoinformatics concept itself occupies a sizeable space in this document. The authors believe that, like bio- and ecoinformatics, nanoinformatics is tasked with synthesising techniques for data collection, processing, and dissemination while taking into account the unique characteristics of nanotechnologies, such as their interdisciplinary nature, the multifactor description of materials and devices, changes in the nomenclature of properties as new objects are created, etc. As a result, nanoinformatics cannot be viewed as merely applying informatics to nanotechnologies. One presentation at the 2015 seminar made the point that a specialist in nanoinformatics is unintentionally a bridge between two fields and as such must gain a solid understanding of the scientific core of issues while looking beyond auxiliary factors like databases and ontologies. On the one hand, the method of the natural integration of NM data through well-­ established facilities of biomedical informatics has accelerated the formation of

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nanoinformatics as an emerging field with its own databases, classifiers, ontologies, etc. and has also led to a certain pertinent imbalance, which has had an influence on the selection of pretty standard nanostructures, the nomenclature of characteristics, and the selection of tools and techniques for operation with data. As a result, the majority of projects completed in compliance with the roadmap do not take into consideration the particular data features found in the other application fields of nanomaterials, like electronics, mechanical engineering, and power engineering. Because bulk macroscopic materials exhibit nanoscale properties only in their internal or surface structure, nanoinformatics rarely applies to them (Maojo, 2010).

14.4 Cyberinfrastructures for Nanoinformatics The application of computer systems and algorithms, as well as their development, to the advancement of nanoscience and nanotechnology is known as computational nanotechnology. Researchers have chosen to divide this new field into five subareas, namely molecular modelling, nanodevice simulation, high-performance computing, nanotechnology, and computing inspired by nanotechnology, in order to make computational nanotechnology easier to describe and comprehend.

14.4.1 Computational Intelligence in Nanoinformatics A subfield of computer science known as computational intelligence develops systems that in some ways resemble intelligence by using algorithms and methods that mimic cognitive processes such as recognition, education, and growth. Fuzzy logic, artificial neural networks, and evolutionary algorithms are some of the best-known algorithms. 14.4.1.1 Genetic Algorithms Darwinian natural selection and genetic replication, which favour the fittest because they live the longest and have the highest possibility of reproducing, serve as the basis for genetic algorithms, which are essentially extremely parallel search and optimisation approaches. These algorithms draw ideas from the genetic cycles of living things to find the best solutions. The process is as follows. A chromosome is a structure made up of a collection of bits or symbols that can encode each potential solution to a problem. Chromosomes represent individuals who have evolved over many generations, much like living organisms, in accordance with the theories of natural selection and survival of the fittest, as outlined by Charles Darwin in his book The Origin of Species. Genetic algorithms are able to develop solutions to urgent issues by mimicking these processes.

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The initial population of arbitrary beings, which serves as the starting point for evolution, is created. Individuals for the reproductive phase are selected through a selection process based on the fitness of each individual, using a series of genetic operators to generate new solutions. The chances of survival in future generations are determined by these new solutions and their capabilities. The number of generations that receive a certain score, or an optimal processing time, and the degree of similarity between population members can be numerous factors that determine the algorithm’s breakpoint. 14.4.1.2 Fuzzy Logic One of the main components of information is imprecision. The other is uncertainty. Set theory and probability theory are the two most commonly used theories to deal with uncertainty and scepticism. Although these ideas are helpful, they often do not do justice to the vast numbers of data that people provide. Humans are capable of managing extremely complicated operations by using incomplete or approximate knowledge. Human operators can also apply a strategy, but they can usually formulate it in language. To translate information that is mathematically ambiguous but described by a set of language norms, fuzzy logic and fuzzy set theory can be used. The result is an inference-based system where fuzzy set theory and fuzzy logic provide the mathematical tools for interacting with these language principles. Fuzzy set theory provides a mathematical basis for dealing with the fuzzy and imprecise information that humans provide. This approach is increasingly used in systems that incorporate data, and it has proven successful in a number of applications. 14.4.1.3 Neural Networks Artificial neural networks (ANNs) are computer models that can learn, associate, generalise, and abstract. They are modelled after the complex network of connected, coupled neurons found in the human brain. Artificial neurons, which make up the bulk of processing units in neural networks, are highly coupled and perform basic operations while passing the results to neighbouring processors. Complex system modelling and pattern recognition have greatly benefited from neural networks’ ability to make complex mappings between inputs and outputs. Neural networks excel at extracting patterns from complex, imperfect, or noisy data because of their structure. Different neural network types use various learning methods. One approach to training changes the weights of the artificial neural networks by minimising the error between the target and network output to obtain a satisfactory input–output connection. Many of these patterns are also called input patterns or target patterns. From this data, three sets of training, validation, and test patterns are created. To improve the weights of the network and to reduce errors, the patterns are first supplied to artificial neural networks. Using the validation set prevents

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overfitting and gives the model the ability to generalise. The effectiveness of the data fitting is evaluated by using the test set, which contains a database that has never been provided to artificial neural networks. 14.4.1.4 Cloud Platform for Informatics An essential outcome of the Nano-Solve-IT project is the e-platform, which is made accessible to users as a cloud application that can be accessed over the Internet or installed as an independent platform on the local servers of interested stakeholders. With an enhanced method for data entry and prediction production in response to particular client questions, this platform offers all computational modelling abilities and tools created as part of the project in a single framework. The final objective is to fully integrate the technologies to make it feasible to build comprehensive computational processes. For particular applications and requirements, these diverse models and tools will also be made available as stand-­ alone components. The e-platform will have a strong system architecture that is adaptable, user-friendly, simple to maintain, and open to cooperative interaction with other tools and databases. Our objective is to provide a single, readily extendable, web-based platform that guarantees sustainability and can be customised to meet the demands of each unique user while also taking regulatory and research needs into account (Maojo, 2010).

14.4.2 Infrastructure for Nanoinformatics Development and Requirements This infrastructure ought to offer users consistent access to a variety of databases containing data on nanomaterials, as well as information on the databases. The nano-portal should provide tools for researchers to share information and materials by giving them access to nanomedical databases, academic publications, demonstrations, ontologies, and terminologies. It would also operate as a channel for the diffusion of characterisation information and aim to investigate various evaluation methods and profiles. To hasten the discussion and verification of nanomedical research data, the infrastructure should be able to support data annotation, data curation, and proper data-grading tools that could improve the accuracy of published experimental results. The curation process will be influenced by descriptions found in the literature and by observed experiments and findings. In addition, the infrastructure will help researchers track their experiments tools, parameters, and protocol specifics and apply computational techniques and procedures to evaluate and draw conclusions from such data. There could be two sections of this infrastructure. The first would be a data archive that makes it easier for experts to share data for nanoscale research, that

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publishes these data, and that makes them freely accessible. All of these data would be kept in a database and available online. A higher-level ontology would be utilised to contain the complete data collection, and each nanomaterial would be shown together with any associated metadata. The tool repository, containing tools and services categorised into the following groups, would make up the second part: instruments for data collection, calibration; quality-control uploading, storing, and managing data; tools for data analysis and processing tools for data sharing and collaboration; and ontologies, terminologies, and standards. It is possible to automatically categorise publications that describe nanomaterials by using text mining and natural-language-processing methods to extract pertinent data. Clustering engines can also aid in this categorisation by employing standard procedures and strategies including normalisation, the extraction of features, agreement clustering, and multidimensional scaling. The following components would also have to be developed in order to create such a nanoinformatics platform: • A set of reference data sets and tools for research data processing and visualisation. • Tools for simulation and modelling focused on nanotechnology. • Services for user communication, such as the creation of instruments for the sharing of information and resources among researchers working in the field: This flexible, new paradigm has already been used in biomedicine, successfully integrating information collected from databases using semantic web technologies, sharing a similar ontology, and ensuring that data are searchable through normalised URL. • The repository of documentation, including services for version control and tools for academics to use to conduct intelligent searches. • Resources and tools for managing recently released regional information, notifications, and news. • Educational tools and discussion fora (De la Iglesia et al., 2013).

14.4.3 Nanoinformatics’ Emerging Role in the United States The use of nanoinformatics can improve several industries. The European Commission and the US government recently collaborated to develop novel nanoinformatics materials that can recognise and communicate with biological systems. This project could be very helpful in drug discovery and effectively improve current medical applications. In addition, a nanoinformatics tool has been developed that uses mining techniques to extract data from research papers and proposals, which can benefit biological databases and bypass a tedious and time-consuming process. Applying the principles of nanoinformatics can help in the development of kits for onsite disease detection, prediction of early-stage diseases leading to preventive measures,

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development of biosensors, etc. In addition, the United States has always been a leader in the development of advanced instrumentation in the biomedical field. The purpose of this minireview is to highlight the use of nanoinformatics in the United States on the basis of these brief facts and concerns. Big data science has improved the new information knowledge in the United States, which has increased interest in a variety of scientific topics. Along with information science, the emergence of nanotechnology has expanded the scope of these sciences. Because it accelerates scientific discovery and provides an easy way to circumvent risk assessment, nanoinformatics research has recently attracted the interest of scientists. Before products can be commercialised, certain factors, such as the use of research tools, the start of numerous activities, and the translation of information, will be required (Nadikattu, 2020).

14.5 Conclusion As was already mentioned, a plethora of knowledge is being produced by studying nanoinformatics and developments in the nanotechnology field. Given that this information is diverse in type, when evaluating these data, studies of various scales face a number of challenges. As a result, the creation and development of novel analyses using computational methods have steadily become more important, necessitating additional resources that are available to the public. This study examines the pressing requirement for automated management approaches. Fresh information produced in nanoinformatics studies comes from collaborations between research teams doing fieldwork. The ongoing publication of fresh findings in this field calls for consistency. Because data resources cannot be manually improved so that resources offer new techniques, it is crucial that these sources be automatically updated. Along with other fields, including material science and engineering, chemistry, physics, medicine, and the pharmaceutical industry, these fields closely collaborate with technology inventors and producers. It is crucial to take social aspects into account as well, because these affect how well consumers adopt nanotechnology. It affects them on a worldwide scale. In light of this, much effort should be put into studying nontoxic, agricultural, environmental, and biomedical engineering studies, which should be based on the findings of prior studies and successful results. The drawback is that a full set of information is controlled and easily accessible. Understanding behaviour and interactions requires modelling and simulation in nanoinformatics. Because many novel nanomaterials are manufactured, an open approach to methods and publishing new research data is critical. Computer scientists and researchers should work with public–private partnerships in a variety of critical areas to ensure the long-term viability of research projects. It all depends on how firmly nanotechnology is adopted in both industry and medicine. As we’ve seen, nanoinformatics is one of these elements that is essential for expanding the scope of research.

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References Afantitis, A., Melagraki, G., Tsoumanis, A., Valsami-Jones, E., & Lynch, I. (2018). A nanoinformatics decision support tool for the virtual screening of gold nanoparticle cellular association using protein corona fingerprints. Nanotoxicology, 12, 1148–1165. Afantitis, A., Melagraki, G., Isigonis, P., Tsoumanis, A., Varsou, D.  D., Valsami-Jones, E., Papadiamantis, A., Ellis, L.-J. A., Sarimveis, H., & Doganis, P. (2020). NanoSolveIT Project: Driving nanoinformatics research to develop innovative and integrated tools for nanosafety assessment. Dalton Clinton, R. (2000). Proposes $2.8 billion increase in science funding. Nature 403, 349. https://doi.org/10.1038/35000362. De la Iglesia, D., Cachau, R. E., García-Remesal, M., & Maojo, V. (2013). Nanoinformatics knowledge infrastructures: Bringing efficient information management to nanomedical research. Computational Science & Discovery, 6, 14011. González-Nilo, F., Pérez-Acle, T., Guínez-Molinos, S., Geraldo, D.  A., Sandoval, C., Yévenes, A., Santos, L. S., Laurie, V. F., Mendoza, H., & Cachau, R. E. (2011). Nanoinformatics: An emerging area of information technology at the intersection of bioinformatics, computational chemistry and nanobiotechnology. Biological Research, 44, 43–51. Lewinski, N. A., & McInnes, B. T. (2015). Using natural language processing techniques to inform research on nanotechnology. Beilstein Journal of Nanotechnology, 6, 1439–1449. Liu, R., & Cohen, Y. (2015). Nanoinformatics for environmental health and biomedicine. Beilstein Journal of Nanotechnology, 6, 2449–2451. Maojo, V. (2010). Nanoinformatics in Europe: The ACTION-Grid White Paper. Maojo, V., Fritts, M., de la Iglesia, D., Cachau, R.  E., Garcia-Remesal, M., Mitchell, J.  A., & Kulikowski, C. (2012). Nanoinformatics: A new area of research in nanomedicine. International Journal of Nanomedicine, 3867–3890. Mullard, A. (2017). The drug-maker’s guide to the galaxy. Nature, 549, 445–447. Nadikattu, R.  R. (2020). The emerging role of nano-informatics in America. Available SSRN 3614535. Nwankwo, W., & Ukhurebor, K. E. (2021). Nanoinformatics: Opportunities and challenges in the development and delivery of healthcare products in developing countries. In IOP conference series: Earth and environmental science (p. 12018). IOP Publishing. O’Connor, B., Berry, R., & Goguen, R. (2014). Nanotechnology environmental health and safety. Elsevier Inc. Panneerselvam, S., & Choi, S. (2014). Nanoinformatics: Emerging databases and available tools. International Journal of Molecular Sciences, 15, 7158–7182. Seko, A., Toyoura, K., Muto, S., Mizoguchi, T., & Broderick, S. (2018). Progress in nanoinformatics and informational materials science. MRS Bulletin, 43, 690–695. Tanaka, I. (2018). Nanoinformatics. Springer Nature. Volodin, D., & Omelyanenko, V. (2017). Nanoinformatics application framework for R & D and industrial analisys. In 2017 IEEE 7th international conference nanomaterials: Application & properties. Wang, E. Y., Mao, T., Klein, J., Dai, Y., Huck, J. D., Jaycox, J. R., Liu, F., Zhou, T., Israelow, B., & Wong, P. (2021). Diverse functional autoantibodies in patients with COVID-19. Nature, 595, 283–288.

Chapter 15

Conventional Strategies of Bioremediation Versus Green Nanoremediation Mehreen Shah

and Sirajuddin Ahmed

15.1 Introduction Pollution has widely and rampantly increased with an exponentially increasing population. A growing population needs more resources; hence, once these products and resources are utilized or consumed fully, the disposal of their generated waste becomes a challenge (Boopathy, 2000). Many conventional ways to tackle pollution backfire; for example, incineration produces large amounts of smoke, which is rich in carbon monoxide, hemotoxic, and carcinogenic (cancer causing). Excessive chemicals in soil over relative amounts of natural compounds are strong indications of soil contamination leading to pollution (Agnello et  al., 2014). Bioremediation emerges, then, as an attractive and viable tool to reduce pollution as it employs the use of microorganisms to reduce the organic content of the garbage or contamination/pollution. These microorganisms are much easier to reclaim and attenuate once their role in mitigating the contamination has been fulfilled, compared to removing chemicals from the site of pollution (Azubuike et  al., 2016). Bioremediation is incorporated mainly during the degradation, attenuation, immobilization, or detoxification of a plethora of chemical/toxic wastes and physical hazardous contaminants from the surrounding site of pollution through the powerful action of microorganisms (Boopathy, 2000). The main principle is to degrade and convert the pollutants or transform them into less-toxic forms. The process of bioremediation can be carried out in ex situ and in situ manners, depending on several factors, which include (but are not limited to) the cost of remediation, the characteristics of the contaminated site, the type of remediation, and the concentration of hazards to be remediated (Gaikwad, 2022). On the basis of these parameters, a bioremediation technique is then finally shortlisted. Various engineered methods from technological M. Shah (*) · S. Ahmed Department of Environmental Science and Engineering, Jamia Millia Islamia (Central University), New Delhi, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_15

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engineering using machines that are juxtaposed with biotechnology are used, incorporating microorganisms whose potential to degrade pollutants is harnessed in various facilities that are engineered to help these microorganism degrade pollutants at their utmost peaks and potentials in a controlled facility. Bioremediation techniques include biostimulation, bioaugmentation, bioventing, biosparging, and bioattenuation. Ex situ bioremediation involves the use of a facility to treat the polluted media. Slurry-phase bioremediation takes place by using a bioreactor: a contained facility and solid-phase bioremediation involving biopiling, landfarming, composting, and biofilters. Bioremediation emerges as the most optimized, economical, and ecofriendly tool for managing polluted and contaminated environments (Azubuike et al., 2016). All bioremediation techniques have their own advantages and disadvantages because they have their own specific applications. Antagonistic interactions with other microorganisms (such as predation), enzyme activity, the population of the bacteria, sources for carbon, and nutrients affect the rate at which remediation occurs (Naik & Duraphe, 2012). The latest advent of science, green nanoremediation, overcomes the shortcomings. Nanoremediation involves the use of nanoparticles (NPs) that are extremely small in dimension (less than 100 nm). Owing to this characteristic, nanoparticles have an extremely high surface–volume ratio, which can be exploited to remediate the contaminated site. Nanoparticles can be synthesized through the reduction of metal ions by using plant- or microorganism-based enzymes, extracts, or secondary metabolites (Singh et al., 2018). These nanoparticles overcome the various limitations of conventional strategies of bioremediation, hence allowing researchers to explore new avenues to improve efficiency rates and overcome barriers (Akintelu et al., 2021). Nanoparticles have various mechanisms by which they can overcome these hurdles. They can employ various types of absorbent/ascorbate mechanisms, antioxidant action, heavy metal detection, and antibacterial action (Ganapuram et al., 2015).

15.2 Bioremediation Bioremediation can be best understood by the understanding of the term itself: “Bio-” hints at the use of biological microorganisms, and “remediation” refers to the process of remedying a problem. Bioremediation helps us to eradicate or neutralize a harmful contaminant and so allows for the reclamation of wastewater and polluted soil for better use (Naik & Duraphe, 2012). It emerges as a highly useful tool for the remediation of highly polluted soil and water. It involves various techniques in which microorganisms are used in the conversion of polluted organic matter into less-harmful byproducts. More specifically, it uses immobilization, detoxification, attenuation, and the conversion of harmful compounds into harmless byproducts. Anaerobic, aerobic, and facultative bacteria are widely used in this process (Azubuike et al., 2016).

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Bioremediation has various advantages over chemical or physical treatments of polluted sites: • It is cheaper in the long run compared with other methods, such as sifting, incineration, or chlorination. • It uses microorganisms, so its dependence on synthetic chemicals and electricity or other fuels is reduced. Hence, it is cleaner. • Microorganisms can be scaled up in biotechnological facilities. • Microorganisms feed on organic waste content, so no additional food needs to be used (Azubuike et al., 2016).

15.3 Microorganisms Used for Bioremediation Microorganisms are extremely small in size, and those used in bioremediation by environmental scientists cannot be seen with the naked eye. Their beneficial actions help restore ecological balance. They convert pollutants into harmless byproducts (Timmis & Pieper, 1999). Microbes are very hardy and can survive in a plethora of media, such as highly saline conditions, and they can live and replicate at extremely hot and cold temperatures and in the presence of hazardous compounds (Gaikwad, 2022). Certain characteristic qualities of microbes, namely their high adaptability and their ability to utilize carbon (waste material) as their food source, are beneficial for bioremediation. Bioremediation processes can be carried out by different species of microbes in different environmental situations and conditions (Azubuike et al., 2016). The most commonly used microorganisms are Achromobacter, Arthrobacter, Alcaligenes, Bacillus, Corynebacterium, Pseudomonas, Mycobacterium, Xanthobacter, Flavobacterium, and Nitrosomonas (Singh et al., 2014). The microbes used in bioremediation can be categorized as follows: 1. Aerobic bacteria, such as Pseudomonas, Sphingomonas, Nocardia, Flavobacterium, Acinetobacter, Rhodococcus, and Mycobacterium, can degrade complex organic compounds in the presence of oxygen. These microbes can degrade pesticides and insecticides, various hydrocarbons, alkanes, and polyaromatic compounds. These bacteria use carbon as a food source to generate energy for their replication (Vidali, 2001). 2. Anaerobic bacteria degrade pollutants in the absence of oxygen. They are not used as regularly as aerobic bacteria, though. Anaerobic bacteria are used for the bioremediation of chlorinated aromatic compounds and the dechlorination of trichloroethylene, chloroform, polychlorinated biphenyls, and other compounds which are hamful. They generate methane gas as a byproduct, which can be then used as biofuel (Timmis & Pieper, 1999).

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15.3.1 Techniques Used in Bioremediation Bioremediation techniques can be divided into two broad categories according to the mode of application through which they are carried out: ex situ and in situ (Fig.  15.1). The nature of contaminants, depth and amount of pollution, type of environment of pollutant generation, location, laboratorial conditions, and facilities are the selection criteria for selecting any bioremediation technique (Philp & Atlas, 2005). Performance and success are based on oxygen and nutrient concentrations, the physiochemical nature of the site, the types of pollutants, temperature, pH, and other factors that determine the efficiency of bioremediation processes (El Fantroussi & Agathos, 2005). Ex situ bioremediation techniques remove pollutants from polluted sites and successively transport them to another site for treatment (Nano et al., 2003). Ex situ bioremediation techniques are usually considered for use on the basis of the depth of the pollution, the type of pollutant, the degree of pollution, the cost of the treatment, and the physical location of the polluted site (Whelan et al., 2015).

15.3.2 Solid-Phase Treatment Solid-phase bioremediation is an ex situ technology in which contaminated soil is excavated and collected in piles. It also includes organic waste such as plant residues, animal manures and other agriculture wastes, domestic waste, industrial waste, and municipal waste. Bacterial growth is introduced through pipes that are Bioremediation

Ex-situ Bioremediation

In-situ Bioremediation

Intrinsinc Bioremediation

Engineered Bioremediation

Slurry Phase Bioremediation

Biosparging Bioventing Bioslurping Biostimulation Bioaugmentation Natural attenuation

Fig. 15.1  Various techniques used in bioremediation

Bioreactor

Solid Phase Bioremediation Biopiling Land farming Composting Biofilter

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distributed throughout these piles (Nano et al., 2003). Air is also added through the pipes for ventilation and for microbial respiration. A solid-phase system requires a significantly larger amount of space, and this clearing out of space requires more time, energy, and manual labor compared with the requirements for slurry-phase processes. Solid-phase treatment processes include windrows, biopiles, land farming, and composting, among others. Composting is a process in which microbes are used to sequester and break down organic wastes into less-toxic forms, and it is one of the most important solid-phase biological treatment technologies suitable for the treatment of large amounts of solid materials of wastes (Angelucci & Concetta Tomei, 2016). However, many toxic compounds are resistant to microbial degradation because they have complex chemical structures, synthetic origins, high toxicity, and high compound concentrations, which hamper microbial degradation. The growth of microbes is also affected by moisture, pH, inorganic nutrients, etc. The composting of hazardous, toxic waste typically involves substrate-sparse soils, which are inadequate in nutrient media, so support from microbiota requires the addition of sufficient amounts of remedial agents to soil media to make up the deficiency (Namkoong et al., 2002) In 1996, Hogan reported that the mechanisms leading to the removal of hazardous compounds in soil via composting could include volatilization, assimilation, adsorption, polymerization, and leaching. Composting can be carried out in one of two systems: an open system (e.g., land treatment) or a closed system. The open land system is a cost-effective, economical treatment method, but the temperature declines during cold winters: The rate of biodegrading waste materials depends on temperature and thus decreases in winter (Margesin & Schinner, 2001). The land treatment system has various limiting factors, such as oxygen availability, the amount of substrate, the nutrients in the soil, etc. The efficiency of the open treatment systems can be improved by including ventilation—i.e., oxygen. This technique is referred to as engineered soil piles and forced aeration treatment (Hogan et al, 1996).

15.3.3 Composting Process in Bioremediation Composting (Fig.  15.2) is an important part of solid-phase biological treatment, where targeted compounds can be either solid or a liquid associated with a solid matrix. The toxic compounds should be biologically transformed. The waste should be prepared so that the biological treatment potential of the microbes is at its peak potential. The compounds in the waste must be well solubilized so that they can be bioavailable (Namkoong et al., 2002). The organic matter and pollutants in waste serve as sources of carbon substrate (i.e., food and energy) for microorganisms. Enzymes exuded by microbes during this process help to degrade toxic compounds. For example, the microbial species Phanerochaete chrysosporium produces an

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Fig. 15.2  Representation of a closed composting system with aeration

extracellular lignin peroxidase enzyme that helps to degrade benzopyrene and 2,4,6-trinitrotoluene (Sayadi & Ellouz, 1995).

15.3.4 Biopiling Using biopiles (Fig. 15.3) is a technological bioremediation strategy in which soil, which may be covered with sheets to increase temperature, is excavated from its original site of contamination and then brought to a treatment facility that consists of an aeration and leachate system (Whelan et al., 2015). Piles are aerated by using vacuum pumps or air blowers, and composts are placed onto them, which consist of bacterial species that may be supplied with additional nutrients (Gomez & Sartaj, 2014). Using biopiles is a popular method to treat soil that has been contaminated by petroleum and petroleum-based products, volatile organic compounds (VOCs), pesticides, halogenated VOCs, fuel-based hydrocarbons (Dias et  al., 2015; Sanscartier et al., 2009). VOCs are anthropogenic chemicals and are a common pollutant. Moisture levels, pH, temperature, nutrient, and oxygen availability are some of the factors that affect biopile efficiency. Chemlal et  al. (2013) studied biopile efficiency in sandy soil, and Akbari and Ghoshal (2014) studied clayey soil as a factor. Biopiles provide a way to treat contaminated soil by using anaerobic and aerobic bacteria. Some commonly used microorganisms used in biopiles are Pseudomonas putida, Dechloromonas aromatica, Methylibium petroleiphilum, and Alcanivorax borkumensis. Heated air can be introduced into the biopiles: Elevated temperatures help improve the efficiency of remediation, but excessive heat may degrade the bacteria, so the temperature must be controlled, as shown by Aislabie et al. (2006).

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Fig. 15.3  Diagram of biopile method in bioremediation

15.3.5 Limitations • Contaminated soils must be extracted or excavated from their original sites. • Expert knowledge and assessments are required to determine the contaminants’ ability to degrade, and the nutrient loading rates and oxygen levels need to be maintained. • Ensuring similarity among the sizes of treatment areas is more time-consuming than using slurry-phase processes. • Halogenated compounds are only partially treatable. • Biopiles use a static treatment process that is less efficient than processes that use periodic mixing. • Air aeration machinery, nutrient addition, and excavation dramatically increase the cost of treatment. • Expert supervision and testing for the feasibility of a contaminant treatment lengthen the process time. • The pretreatment and post-treatment of contaminated soil increase costs, time, and the labor requirements.

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15.3.6 Slurry-Phase Bioremediation Slurry-phase bioremediation (Fig. 15.4) is a relatively faster process compared with the solid-phase treatment processes. The soil to be remediated is added to water, nutrient substrate, and oxygen in the bioreactor to create the optimal conditions for the microorganisms to thrive and degrade the contaminants in the soil (Tekere et al., 2019). This processing separates from the contaminated soil the stones and plastics that are outside the ambit of bacterial degradation (Nano et al., 2003). The amount of water to be added depends on the concentration of pollutants, the rate of biological degradation, and the physicochemical nature of the soil. After this process is complete, the soil is excavated and dried up to remove moisture by using vacuum filters, pressure filters, and centrifugal systems. The next procedure followed is the disposition of soil (Ross, 1990). Some of the goals of bioreactors for designing slurry-phase remediations are as follows: 1. Reduce microbial growth-limiting factors in the soil environment, such as a lack of organic substrate, nutrients, or oxygen availability. 2. Provide suitable conditions for optimal bacterial growth, such as adequate levels of moisture, pH, and temperature. 3. Minimize the limitations of mass transfer and improve the desorption of organic material from the soil matrix, such as in the 1998 experiment by Christodoultos et al.

Treatment of exhaust gas

Treated gas

Make-up water Recycled water

POLLUTED SOIL

Wastewater treatment

Slurry Bioreactor

Addition of nutrients, inoculum,surfactans and electron acceptors

Clarifier Excess of water

TREATED SOIL

Fig. 15.4  A slurry-phase bioreactor with different components attached

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15.3.7 Factors Affecting Slurry-Phase Biodegradation The following are some of the factors that affect slurry-phase biodegradation (Tekere et al., 2019): 1. Age of the microbes 2. Moisture content 3. Temperature (20–30 °C) 4. pH (optimum: 5.5–8.5) 5. Mixing (mechanical and air mixing) 6. Nutrients (N, P, and other micronutrients) 7. Microbial population 8. Reactor operation (batch and continuous cultures) 9. Oxygen (mainly for aerobic metabolism)

15.3.8 In Situ Bioremediation In situ bioremediation refers to an onsite technique where biological remediation species are applied to the contaminated media at the site of pollution. Toxic chemicals and organic waste are broken down into a less-toxic forms thanks to the activity of biological species (Jørgensen et al., 2007). This is a function of nutrient and air additions, electron donors, and acceptors. Nitrogen and phosphorus are used as nutrients, and orthophosphate may also be supplied. Oxygen is most commonly used as an electron acceptor. Under aerobic conditions, the end products of the bioremediation are CO2, H2O, and cell masses of microbial origin. In the absence of oxygen, alternate electron acceptors include manganese, sulfate, carbon dioxide, and ferrous ions. Because no excavation or transport of contaminated soil is required, a major cost of ex situ techniques is avoided (Rodríguez-Escales et al., 2017). In the case of intrinsic bioremediation, the necessary nutrients and conditions are naturally met, so human intervention is not required. Natural degradation processes occur through the application of aerobic and anaerobic bacteria to the site of contamination. Through air sparging and bioventing, air may be artificially or mechanically introduced at the subsurface soil level to improve the efficiency of the aerobic bacteria. Monitored natural attenuation (MNA) occurs through the application of bacteria, which may be enhanced by introducing nutrients to the soil (Declercq et al., 2012). Soil media can be divided into saturated and unsaturated zones. MNA is used for the saturated zones, which are supplied with air for aerobic bacteria. Anaerobic bacteria have also been successfully used for the degradation of several compounds. Dyes, heavy metals, chlorinated solvents, nutrients, and types of organic waste have been treated by in situ bioremediation techniques (Sarkar et al., 2017). An electron donor is added to supply the activity of a sulfate, and metal-­ reducing bacterial species use carbon sources such as ethanol, molasses, etc. The

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biostimulation helps to reduce Fe (III) to Fe (II). The in situ remediation may be engineered, or it may be intrinsic in nature so human intervention is minimized (Kalantary et al., 2014).

15.3.9 Biosparging Biosparging (Fig. 15.5) adds pressurized air or gas to contaminated soil to promote the aerobic bacterial degradation of contaminants in the soil. It is a suitable technique for treating pollution that occurs from oils such as mineral oil or aromatic compounds such as naphthalene, xylene, toluene, and ethylbenzene (BTEX) (Kao et al., 2008). Biosparging is an effective way to control the infiltration of harmful compounds into the groundwater through capillary action or leaching. It is different from air sparging in that air sparging involves volatilization, whereas biosparging reduces harmful compounds through bacterial aerobic action or biodegradation (Vidali, 2001). Unlike bioventing, air at the saturated zone is injected, and this leads to the upward movement of VOCs to the unsaturated zone to promote biological degradation thanks to the bacterial species in the contaminated soil. The efficiency depends on two factors: (i) the permeability of bacteria inside the soil, which is mandatory for bioavailability, and (ii) the extent to which the pollutant can be biologically degraded (Philp & Atlas, 2005)

15.3.10 Bioventing Bioventing (Fig. 15.6) is an in situ bioremediation technique. In this process, oxygen and nutrients are supplied to the soil microorganisms inside unsaturated zones by using extraction wells or air injections in order to stimulate the process of degrading contaminants in the soil (Philp & Atlas, 2005). In the vadose zone, a low air flow rate is supplied in order to reduce the volatilization of hydrocarbons. The most commonly used technique to achieve this is direct air injection. Fuel-based pollutants/ petroleum hydrocarbons, TPH compounds and volatile compounds, pesticides, and nonchlorinated solvents are easily treated by using this method because vapor is passed through the contaminated soil (Höhener & Ponsin, 2014). The technique must occur under biodegradable conditions so that the aerobic microorganism can degrade the contaminant. The soil particle size and moisture levels influence the permeability of the air inside the soil. Phenanthrene-contaminated soil was observed to be >93% decontaminated after 7 months of bioventing (Frutos et al., 2010). The pH of the soil, the nutrient availability, and the microorganism activity influence the optimal rate of biodegradation. The higher temperatures in summer improves the biodegradation compared with the colder temperatures of winter. The

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Fig. 15.5  Diagram of biosparging process Injection of Air/Oxygen

Vacuum withdrawal

Contaminated Zone

Unsaturated Zone Aerobic Biodegradation of Contaminants by Indigenous Microorganisms Saturated Zone

Fig. 15.6  Diagram of bioventing, showing unsaturated and saturated zones

optimal pH is 6–8. Naturally degrading microorganisms must be present in sufficient quantities in order for the bioremediation to be efficient (Philp & Atlas, 2005). The soil must be on the finer side rather than the coarser side in order to effectively increase the air permeability, and the soil must be adequately moist in order to effect the natural activity of the bacteria in the soil, which will break down the contaminants (Sharma et al., 2020).

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15.3.11 Limitations • • • • • •

Low air permeability in soil reduces the efficacy of bioventing. Chlorinated compounds are not broken down effectively. Moisture may be reduced by excess aeration, thus hampering biodegradation. The presence of nonoxygen gases may hamper this process. The presence of too much vapor build up may also hamper this process. Air-supplying machinery and equipment increase costs.

15.3.12 Bioslurping Bioslurping (Fig. 15.7) incorporates two bioremediation practices, namely vacuum-­ enhanced free-product recovery and bioventing (Gidarakos & Aivalioti, 2007). The process of bioventing adds oxygen to facilitate the bioremediation of contaminants and removes gas from the soil. Vacuum-enhanced free-product recovery degrades light nonaqueous liquid phase liquids (LNAPLs)—such as petroleum, diesel fuel, or derivatives, which are insoluble in water and have lower densities than water—in the water table and capillary fringe. It helps achieve the bioremediation of the vadose zones of the soil, and because there are two processes, there are two remediation potentials, one for each contaminant. Bioslurping helps extract petroleum derivatives from the capillary fringe without the release of trapped gases and prevents the formation of smear zones after the remediation processes (Gidarakos et al., 2001). Air Treatment or Discharge Air/Liquid Separation

Oil/Water Separator

Air Flow in vadose Zone Supporting Biodegradation Flow due to PressureInduced Gradient Horizontal Flow Lines Ground water

Fig. 15.7  Diagram of bioslurping procedure

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15.3.13 Limitations • • • •

It is less effective in low-permeability soil. The presence of chlorinated compounds may slow the biodegradation process. In winters, because of the cold, the activity of the aerobic bacteria is hampered. Bioslurping may reduce moisture content in soil and retard the bioremediation capacity of the bacteria. • Large amounts of water may be removed by the bioslurper system, causing wastage.

15.3.14 Biostimulation Biostimulation refers to the stimulation and propagation of existing bacteria that engage in bioremediation by breaking down compounds. It occurs through the addition of rate-limiting nutrients and electron acceptors such as phosphorus, oxygen, carbon, and nitrogen. Anaerobic microorganisms break down petroleum-derived compounds by using electron donors, which enable it to use halogenated contaminants as electron acceptors, thus enhancing the bioremediation process (Kalantary et  al., 2014). The process of biostimulation is useful for cleaning up oil and gas spills. It takes advantage of the already-present microorganisms in the soil, and additives that enhance their remediation ability are used. Local geology factors such as soil particle size and interparticle spacing may heavily influence the bioremediation process. Soil that is tightly packed and that has low aeration will not be greatly influenced (Adams et al., 2015).

15.3.15 Nanoparticles (NPs) for Bioremediation The results of a lab analysis showed the inhibition of pathogens, indicating the bactericidal capacity of green nanoparticles. The degradation period was very short compared with that of previous remediation tools, affirming the success of this method. Green nanoparticles leave fewer polluting residues compared with conventional remediation tools, such as those used in wastewater management (Akintelu et al., 2021). Those conventional remediation techniques often incur very high costs for postprocessing and often cause pollution once released into water bodies (Azubuike et  al., 2016). Hence, scientists and researchers around the globe have been developing newer remediation tools that work at higher efficiency levels, reduce postprocessing costs, and can later be disposed of without being deleterious to the environment in which they are released. Green nanoparticles also have an effect on the degradation of synthetic dyes and the detection of heavy metal ions. Hence, green nanoparticles show great potential for water remediation and are unique solutions for the future (Singh et al., 2018).

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15.3.16 Biological Components for Green Synthesis These methodologies are dependent on reactions from biologic species and parameters such as pressure, the type of solvent, pH, and temperature. Plant metabolites such as aldehydes, ketones, amides, terpenoids flavonoids, phenols, carboxylic acids, polyphenols, saponins, and ascorbic acids are widely used. These help to reduce metal ions to NPs (Singh et al., 2018).

15.3.17 Catalytic Activity of Nanoparticles A synthetic compound that is indispensable for the manufacture of pesticides, insecticides, drugs, fungicides, and leather tanning is 4-nitrophenol. But if this consumed or inhaled, it can cause harmful effects on human health, such as cyanosis (turning skin, lips, or nail beds blue), dizziness, headaches, and nausea. Despite its toxicity and damage to the health of humans and subsequently to the environment, its need in industrial manufacture has been a problem for scientists and environmentalists worldwide (Han et al., 2019). It is important to promote the reduction of 4-­nitrophenol before it can be properly disposed of, without polluting natural water bodies or letting it seep into groundwater (Lai et al., 2007). When 4-nitrophenol is reduced, the product formed from the reduction is called 4-aminophenol, which is industrially important for the manufacture of sulfur dyes, paracetamol/acetaminophen (a therapeutic drug), rubber, and natural antioxidants; the preparation of black/white films, analgesics, antipyretics; and stoppage corrosion (Han et al., 2019). One way to reduce 4-nitrophenol is to use NaBH4 as a reductant and adding Au NPs as metal catalysts. A potential difference between donor (H3BO3/NaBH4) and nitrophenolate ions or the acceptor molecule may require a higher activation energy barrier that must be reduced so that the reaction may occur at the lower energy provided at substrate level, and its rate of reaction must be optimal (Lin et al., 2013). The rate of reaction can be significantly increased by increasing the adsorption of reactants on their surface because metallic NPs have a high surface– volume ratio, thereby significantly lowering the activation energy. Further, 4-nitrophenol is characterized by a sharp band at 400 nm in its UV-visible spectra, hence affirming the success of using metallic nanoparticles to reduce 4-nitrophenol (Ganapuram et  al., 2015). Green Ag NPs (synthesized by using plant stem extract) lead to an absorption intensity of 400 nm, and a band at 313 nm indicates the formation of 4-­ aminophenol, proving the catalytic reduction potentia (Ganapuram et al., 2015).

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15.3.18 Degradation of Synthetic Dyes by NPs versus Activated Sludge: A Comparative Study Nanoparticles show absorbance for both visible light and ultraviolet light (UV), which leads to an oxidation reaction for the synthetic dye in the sample. NPs exhibit high catalytic action that result in the degradation of the Congo red and methylene blue dyes. NPs display fast degradation for synthetic dyes such as methylene blue. Numerous industries, such as paper, textile, pharmaceutical, food industries, hair coloring, toy production, etc., use synthetic dyes (Toh et al., 2003) and end up in wastewater. And NPs can degrade these contaminants, the synthetic dues, in wastewater. Methylene blue (MB) is a cationic dye, and Congo red (CR) is an anionic dye— both of which are notorious for polluting water. If these dyes are not removed from the discharge of industries, then they can wreak havoc on delicate water systems. Scientists have devised newer techniques for the degradation of synthetic dyes in water, and NPs have the ability to cause the catalytic reduction of these dyes in water, thus enabling scientists to treat the polluted discharge from various industries (Nateghi et al., 2012). There are dipole–dipole interactions between the nitrogen group, or N, in methylene blue and the phenol group, or -OH, from proanthocyanidins chelated to the Nanoparticles. The green synthesis of NPs has been achieved by using a variety of secondary plant metabolites, such as saponins (including those extracted from plants such as G. mangostana, salvinia, etc.). The removal of synthetic dyes is highly important to remediate polluted water because if this water is consumed, it can damage human health and under some conditions can even prove to be fatal (Singh et al., 2018).

15.3.19 Victoria Blue Dye Degradation Using Gold Nanoparticles In a study by Jishma et al. (2018), gold nanoparticles, or Au NPs, were synthesized by using biological precursors. Triphenyl methane blue dyes, namely Victoria blue B (or VBB) and VBR, were photocatalytically degraded or were degraded by using sunlight, by 65% and 52%, respectively, over 8 h. The experiment was ecofriendly and cost-effective and hence worth replicating at a large industrial scale. Toh et al. (2003) showed that chlorine and other synthetic derivatives lead to carcinogen generation in water, hence posing a serious threat.

15.3.20 Decolorization of Textile Effluent Using Inactivated Sludge In an experiment by Patil in 2016, sludge with aerobic bacteria was activated for 15 days and the bacterial culture was increased from its initial cell number of 100 nm). Owing to this characteristic, nanoparticles have an extremely high surface–volume ratio, which can be exploited to remediate contaminated sites. Nanoparticles can be synthesized by using plant- or microorganism-based enzymes, extracts, or secondary metabolites to reduce metal ions. Compared with conventionally used nanoparticle synthesis by using chemicals, green nanotechnology offers a much better alternative as it uses natural and nature-derived sources to reduce metal ions into corresponding nanoparticles. Green synthesis helps us to prevent detrimental losses to the environment that would be caused by conventional methods, which create pollution and hence defeat the original purpose of using nanoparticles for remediation. These nanoparticles overcome the various limitations of conventional strategies of bioremediation, hence allowing researchers to explore new avenues to improve efficiency rates and overcome barriers. Nanoparticles have various mechanisms by which they can overcome these hurdles. They can employ various types of absorbent/ascorbate mechanisms, antioxidant action, heavy metal detection, and antibacterial action.

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Chapter 16

Using Nanoremediation Strategies: Cost–Benefit Analysis Gustavo Alves Puiatti

16.1 Selection of a Remediation Strategy Environmental remediation is the action of removing contaminants or pollutants from environmental matrices, such as soils, groundwaters, rivers, lakes, and oceans (Speight, 2020). The main objective of a remediation action is to protect the environment and human health (Söderqvist et al., 2015; Brusseau, 2019). The high number of locations, the wide range of options for remediation strategies, and the tightening of requirements for the sustainability of remediation actions make decision-­making a nontrivial task (Söderqvist et al., 2015). Successful remediation actions require long-term framing, planning, and management (Burger et al., 2019). Remediation projects are complex because of their multidisciplinary nature, which encompasses social, economic, and environmental aspects (Tilla & Blumberga, 2018). Therefore, identifying the variables that affect the performance of remediation projects is essential to increase their efficiency and ensure their sustainability (Tilla & Blumberga, 2018). Thus, selecting the method of remediation for a contaminated area is not a straightforward process (Brusseau, 2019). The main factors that need to be considered when selecting a remediation alternative are as follows: (i) drivers and goals of the remediation project, (ii) risk management, (iii) technical feasibility, (iv) stakeholders’ satisfaction, (v) costs and benefits, and (vi) sustainable development (Bardos et al., 2002). The international community has sought to produce scientific knowledge, public policy instruments, and ventures that meet the UN Sustainable Development Goals, which address crucial real-world social, economic, and environmental demands (Hou & O’Connor, 2020). In this way, several strategies with a more holistic view of the remediation process have been developed in recent years to subsidize the decision-making process (Söderqvist et al., 2015). G. A. Puiatti (*) Department of Civil Engineering, Federal University of Viçosa, Viçosa, Brazil © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 F. M. Policarpo Tonelli et al. (eds.), Green Nanoremediation, https://doi.org/10.1007/978-3-031-30558-0_16

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Such strategies can be grounded in the following methods: cost–benefit analysis (CBA), cost-effectiveness analysis (CEA), life-cycle analysis (LCA), and multicriteria analysis (MCA) or multicriteria decision analysis (MCDA) (Brinkhoff, 2011). CBA and CEA can also be individually applied or be integrated with an MCA/ MCDA (Brinkhoff, 2011). MCA has been increasingly employed to assess the sustainability of projects and to support decision-making in the environmental sector (Rosén et  al., 2015; Söderqvist et  al., 2015). MCA aims to evaluate whether a project meets specific performance criteria (Söderqvist et al., 2015). MCA is a general term that comprises different qualitative, quantitative, and semiquantitative methods (Rosén et al., 2015; Söderqvist et al., 2015). MCA has been indicated for the sustainability assessment of remediation actions by several authors of the scientific community because it allows the integration of quantitative and qualitative variables (Rosén et al., 2015; Söderqvist et al., 2015). The term MCDA is often adopted when numerical values are used for weighting and scoring criteria to ease the comparison of alternatives in MCAs (Rosén et al., 2015). The sustainable choice of remediation (SCORE) is an MCDA method developed to provide relevant and objective assessments of the sustainability of remediation alternatives, according to the fundamental economic, environmental, and social criteria (Rosén et al., 2015). SCORE employs cost–benefit analysis (CBA) to assess the economic sustainability of remediation alternatives (Söderqvist et al., 2015).

16.2 Cost–Benefit Analysis (CBA) of Remediation Strategies CBA is an assessment technique commonly applied in different sectors, such as the public health, urban planning, and environmental sectors (Wright, 2019). Environmental CBAs are economic assessments of projects and policies that seek to improve the provision of services that may generate (positive or negative) environmental impacts (Atkinson & Mourato, 2008). According to Caliman et al. (2011), CBA is the principal tool for economically evaluating alternatives for soil and groundwater remediation. CBAs are very relevant to incorporate in a single-figure complex information on environmental, social, economic, and engineering aspects related to site contamination, sources of pollution, and the remediation actions and their consequences (Rinaudo & Aulong, 2014). A questionnaire survey conducted in 2016 found that CBA was the most used method among the consulted professionals to assess the sustainability of remediation alternatives (Hou et al., 2016). CBA is used to express positive or negative consequences in monetary units— i.e., costs and benefits—based on welfare economics (Söderqvist et al., 2015). CBA has a simple principle: if the costs surpass the benefits, the intervention is justifiable (Guerriero, 2019). However, CBA might seem complex and intimidating given the diversity of possible intervention alternatives (Guerriero, 2019). Thus, dividing a CBA into the following consecutive steps makes it more manageable: (1) specify the problem, (2) quantify the benefits, (3) assign monetary values to each benefit,

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(4) quantify the interventions costs, (5) include considerations for the duration of costs and benefits and re-express them numerically, (6) compare the estimated costs and benefits, and (7) perform uncertainty analyses to assess the robustness of the obtained results (Guerriero, 2019). The total benefits can be divided into four categories: (i) increased property values; (ii) improvements in human health (reduced risks of morbidity and mortality), (iii) the increased provision of ecosystems, such as the improvement of marketable products (e.g., food harvest), the increased provision of locations for recreational activities and increased biodiversity, and (iv) other positive externalities, such as improved visibility or reduced damage to cultural monuments (Söderqvist et  al., 2015; Guerriero, 2019). However, human health improvements are the most important category (Guerriero, 2019). Because of the limited resources available for an environmental remediation action, determining the direct economic benefits has been one of the main topics of empirical investigation for decades to make pieces of evidence available to justify expenditures on the management of a contaminated site (Li et al., 2022). However, environmental costs and benefits are difficult to relate to monetary values because of their nonconsumptive nature (Li et al., 2022). In this context, the hedonic price method (HPM) has been extensively used as a nonmarket tool to evaluate the externalities of site contamination (Li et al., 2022). The HPM assumes that the price of many market goods, such as properties, is a function of a group of characteristics (Atkinson & Mourato, 2008; Lavee et  al., 2012). In the case of properties, these characteristics may include neighborhood, structural, and environmental attributes (e.g., their proximity to contaminated sites) (Lavee et  al., 2012). The HPM uses econometric and statistical techniques to isolate the implicit contribution of each characteristic to the price of an item (Atkinson & Mourato, 2008). Generally, studies show that proximity to contaminated sites results in the significant depreciation of local property prices, termed stigma (Li et al., 2022). In an HPM, records gathered from real estate markets are analyzed by using statistical regression methods to estimate changes in property values related to several attributes (Lavee et al., 2012). The value of ecological attributes may thus be determined from the variation in prices of properties under distinct ecological conditions, therefore avoiding the need to estimate production functions (Bahman Kashi et al., 2019). The human capital and willingness-to-pay (WTP) approaches are the main methods for assigning monetary values on variations in human health (Guerriero, 2019). The WTP approach considers the amount of money that individuals are willing to pay to decrease the probability of the occurrence of an adverse event (Guerriero, 2019). In the human capital method, an individual’s life is valued on the basis of their future production potential (Guerriero, 2019). Within the human capital method, the cost of illness (COI) method estimates monetary losses resulting from a health outcome (Guerriero, 2019). The COI method, although more straightforward, underestimates the value of health outcomes and ignores their other associated intangible aspects, such as pain and stress (Guerriero, 2019). Furthermore, COI values can be estimated only a posteriori (Guerriero, 2019). Therefore, the WTP approach is used more often in CBAs (Guerriero, 2019).

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Some costs of remediation actions are related to the following: (i) design, (ii) project management, (iii) capital costs (e.g., interest on loans and the depreciation of machinery), (iv) remediation action (e.g., costs associated with mobilization, fieldwork, and demobilization), (v) monitoring programs (during and after remediation); and (vi) project risks (related to previously unforeseen events, such as below-­ estimated removal efficiency, change in public opinion, and authority requirements) (Söderqvist et al., 2015). Additionally, the remediation action per se can cause negative externalities, such as the nonimprovement of health conditions (increased health risks arising from the action onsite or in other locations because of the transport of the contaminant or the storage or final disposal of contaminated material) and the reduced provision of ecosystem services (Söderqvist et al., 2015). Noise, emissions, and heavy equipment traffic can also cause health outcomes (Söderqvist et  al., 2015). A list of the possible costs and benefits resulting from remediation actions is presented in Table 16.1 (Söderqvist et al., 2015). The use of remediation technologies without robust scientific evidence of their being safe can increase the risk to recipients rather than decrease it (Burger et al., 2019)—i.e., the associated benefits and costs might be, respectively, overestimated and underestimated in CBAs. For the SCORE tool, the present value (PV) of each benefit (Bi) and cost (Ci) listed in Table 16.1 is calculated by using Eqs. 16.1 and 16.2 (Söderqvist et al., 2015). T

1

t 0

1  rt 

T

1

t 0

1  rt 

PV  Bi   

PV  Ci   

t

t

Bit (16.1) Cit (16.2)

where rt is the social discount rate at time t and T is the time horizon associated with the costs and benefits. The remediation alternative with the highest net present value (NPV) is the most socially profitable or, if NPV