Drinking Water: Quality Control, Distribution Systems and Treatment 153618070X, 9781536180701

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WATER RESOURCE PLANNING, DEVELOPMENT AND MANAGEMENT

DRINKING WATER QUALITY CONTROL, DISTRIBUTION SYSTEMS AND TREATMENT

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WATER RESOURCE PLANNING, DEVELOPMENT AND MANAGEMENT

DRINKING WATER QUALITY CONTROL, DISTRIBUTION SYSTEMS AND TREATMENT

CÉCILE MARCIL EDITOR

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Library of Congress Cataloging-in-Publication Data Title: Drinking water : quality control, distribution systems and treatment. Description: New York : Nova Science Publishers, Inc., 2020. | Series: Water resource planning, development and management | Includes bibliographical references and index. | Summary: "Drinking Water: Quality Control, Distribution Systems and Treatment focuses on some of the technologies involved in water treatment processes, such as adsorption, co-precipitation, flocculation, and coagulation. The authors emphasize the newest easy processes, inadequacies, and prospects of drinking water treatment. In one study, a simple effective intervention for biochanin A in influent water using ZSM-5, a nano-porous crystalline zeolite, is described. In closing, a Sphingomonas paucimobilis strain isolated from an Indian drinking water system was evaluated for its ability to co-aggregate and form mixed biofilms with Salmonella typhimurium, Shigella flexneri, and Escherichia coli O57:H7"-- Provided by publisher. Identifiers: LCCN 2020022911 (print) | LCCN 2020022912 (ebook) | ISBN 9781536180701 (paperback) | ISBN 9781536180718 (adobe pdf) Subjects: LCSH: Water-supply engineering | Water--Distribution. | Water quality management. | Drinking water. Classification: LCC TD345 .D75 2020 (print) | LCC TD345 (ebook) | DDC 628.1/62--dc23 LC record available at https://lccn.loc.gov/2020022911 LC ebook record available at https://lccn.loc.gov/2020022912

Published by Nova Science Publishers, Inc. † New York

CONTENTS Preface Chapter 1

Chapter 2

Chapter 3

vii New Generation Materials for the Adsorption of Toxic Metal Ion from Drinking Water Rekha Sharma, Sapna and Dinesh Kumar Water Treatment Methods for Detoxification of Metal Ions: State-of-the-Art, Future Scenario and Challenges Kritika S. Sharma, Rekha Sharma and Dinesh Kumar A Rapid, Nanoporous Zeolite Based Approach for Removal of Biochanin A in Potable Water Destined for Distribution Pawandeep Singh, Vivek Sharma and Moushumi Ghosh

1

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vi Chapter 4

Index

Contents The Role of Sphingomonas paucimobilis in Intergeneric Co-Aggregation and Mixed Biofilm Formation with Water Borne Pathogenic Bacteria in the Distributed Drinking Water System: Implications of Public Health Risk Parul Gulati and Moushumi Ghosh

83 109

PREFACE Drinking Water: Quality Control, Distribution Systems and Treatment focuses on some of the technologies involved in water treatment processes, such as adsorption, co-precipitation, flocculation, and coagulation. The authors emphasize the newest easy processes, inadequacies, and prospects of drinking water treatment. In one study, a simple effective intervention for biochanin A in influent water using ZSM-5, a nano-porous crystalline zeolite, is described. In closing, a Sphingomonas paucimobilis strain isolated from an Indian drinking water system was evaluated for its ability to co-aggregate and form mixed biofilms with Salmonella typhimurium, Shigella flexneri, and Escherichia coli O57:H7. (Imprint: Nova) Chapter 1 - Nowadays, heavy metal ion pollution in water has gained considerable attention from many research groups across the world. These are highly carcinogenic even at comparatively low concentrations because of their tendency toward bioaccumulation and non-biodegradable nature. Thus, water contamination has also increased public concern. Although, various methods are being used to treat the water and waste water, which are fast and cost-effective. In this continuation, effective water treatment methods have been manufacturing; intense research has been carried out, those having an insignificant effect on the environment and the minimum use of chemicals at a lower cost. The three primary factors have been utilized for the implementation and development of water treatment technologies,

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i.e., the proclamation of new water quality standards, cost efficiency, and the discovery of new rarer contaminants. Previously, the only treatment processes that have been virtually utilized in municipal water treatment are granular media filtration, chlorination, and chemical clarification. Though, in water treatment processes, a dramatic change has been seen in consideration of alternative treatment technologies to the traditional chlorination/filtration purification method from the past 20 years. This chapter categorizes and focuses on some of these technologies such as adsorption, co-precipitation, flocculation, and coagulation at substantial scale water treatment. This chapter will focus on adsorption technologies to treat water and wastewater. Chapter 2 - Approximately two million people die annually because of contaminated drinking water and unsafe sanitation practices. The generation of heavy metal ions is one of the prominent causes of water pollution. Heavy metals such as lead, mercury, chromium, and arsenic exist naturally, but anthropogenic activities cause contamination in water. The World Health Organization (WHO) reports that approximately 1 billion people across the world don’t have an approach to clean drinking water. This count is presumed to eventually increase with increasing population i.e., 7.7 billion (2019) from 7.5 billion (2018), energy requirement and climate change. There are many commercially available methods to detoxify water from heavy metals, while they are liable to rejection because of: less efficient, expensive, generate hazardous toxic waste and energy-consuming. This chapter will explore some advanced treatment methods, which are in use like metal-organic frameworks (MOFs), UV irradiation, etc. Some traditional techniques are still in use like adsorption, reverse osmosis, electrodialysis and so on. Although they serve the purpose, either cannot address these problems quickly, economically, long-term stability or high performance despite development on the technical side. The challenge is to provide solutions which are a universal or single solution, inexpensive, has ease of implementation, cent percent efficiency, and domestic use. The functional integration of different technologies or treatments may solve the current water hazards. Impending water shortage will lead to detoxifying the water, which is now considered undrinkable. This chapter will emphasize the

Preface

ix

newest easy process, inadequacy, hurdles, and prospects of drinking water treatment. Chapter 3 - The presence of Endocrine disrupting chemicals or EDCs in water poses a serious threat to human health and several food production systems. Apart from EDCs of synthetic origin, phytoestrogens which are plant derived have received little attention in terms of affordable interventions in potable water destined for distribution. This study reports a simple effective intervention for Biochanin A in influent water using ZSM5, a Nano porous crystalline zeolite. The adsorbent ZSM-5 was prepared in laboratory and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer– Emmett–Teller (BET) adsorption and Fourier transform infrared (FTIR) spectroscopy. ZSM-5 was nonporous with a surface area of 653 m2 g-1. The effect of different parameters such as contact time, adsorbent dose and initial solute concentration for removal of Biochanin A by ZSM-5 was evaluated. The equilibrium data for the adsorption of Biochanin A on ZSM-5 was tested in Langmuir and Freundlich adsorption models. Results indicated that Langmuir isotherm model fitted well to equilibrium data in contrast to Freundlich isotherm model. Complete removal of Biochanin A using ZSM5 in water indicated the possibility of application in drinking water. Chapter 4 - Sphingomonas a resident microorganism, is often encountered in the drinking water systems (DWDS). Its capability of growth over a range of temperatures, tolerance to chlorination and antimicrobial resistance patterns have recently raised health concerns. Several physiological aspects, for instance role of co-aggregation and biofilm formation especially with water borne pathogens by Sphingomonas remains largely unknown and deserve attention. In this study, a Sphingomonas paucimobilis strain isolated from Indian drinking water system was evaluated for its ability to co-aggregate and form mixed biofilms with Salmonella typhimurium, Shigella flexneri, Escherichia coli O57:H7. Strong co-aggregation of Sphingomonas with the waterborne pathogens Escherichia coli O157:H7 ATCC 32150, Shigella flexneri 2a and Salmonella typhimurium ATCC 25315 was observed by qualitative and quantitative methods with individual pathogens as well with a cocktail of the

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above three water borne pathogens. Highest aggregation index was observed with Shigella flexneri 2a followed by Salmonella typhimurium and Escherichia coli O157:H7. The aggregation with Escherichia coli O157:H7 could not be reversed by heat, protease and sugars (lactose and galactose). The results of this study have a strong implication on risk of mixed biofilms of these water borne pathogens in DWDS which may have re-grown or introduced (either through leakage or faulty treatment processes) and eventually develop into biofilms with preexisting Sphingomonas. An effective, noninvasive treatment strategy preferably aimed in disrupting signalling molecules of Sphingomonas may be of value, for assuring safety of drinking water.

In: Drinking Water Editor: Cécile Marcil

ISBN: 978-1-53618-070-1 © 2020 Nova Science Publishers, Inc.

Chapter 1

NEW GENERATION MATERIALS FOR THE ADSORPTION OF TOXIC METAL ION FROM DRINKING WATER Rekha Sharma1, PhD, Sapna1 and Dinesh Kumar2,*, PhD 1

Department of Chemistry, Banasthali Vidyapith, Rajasthan, India 2 School of Chemical Sciences, Central University of Gujarat, Gandhinagar, India

ABSTRACT Nowadays, heavy metal ion pollution in water has gained considerable attention from many research groups across the world. These are highly carcinogenic even at comparatively low concentrations because of their tendency toward bioaccumulation and non-biodegradable nature. Thus, water contamination has also increased public concern. Although, various methods are being used to treat the water and waste water, which are fast and cost-effective. In this continuation, effective water treatment methods have been manufacturing; intense research has been carried out, those having an insignificant effect on the environment and the minimum use of

*

Corresponding Author’s E-mail: [email protected].

2

Rekha Sharma, Sapna and Dinesh Kumar chemicals at a lower cost. The three primary factors have been utilized for the implementation and development of water treatment technologies, i.e., the proclamation of new water quality standards, cost efficiency, and the discovery of new rarer contaminants. Previously, the only treatment processes that have been virtually utilized in municipal water treatment are granular media filtration, chlorination, and chemical clarification. Though, in water treatment processes, a dramatic change has been seen in consideration of alternative treatment technologies to the traditional chlorination/filtration purification method from the past 20 years. This chapter categorizes and focuses on some of these technologies such as adsorption, co-precipitation, flocculation, and coagulation at substantial scale water treatment. This chapter will focus on adsorption technologies to treat water and wastewater.

Keywords: water treatment, adsorption technologies, efficient, contaminants

1. INTRODUCTION For the survival of any life on earth, water is necessary to accomplish daily life purposes. Unfortunately, quality of water systems are continuously degrading because of population growth, industrial development, use of a pesticide in agricultural fields, and domestic proposes [1−3]. In recent years, water pollution has existed as a severe issue that disturbs the physiology of all living creatures, fisheries, and many more commercial activities [4−6]. Widely, researchers, scientists, and supreme government bodies are taking part in resolving this severe water pollution issue [7]. In last few decades thousands of water contaminants found in water in the form of organic, inorganic, and biological have caused lethal carcinogenic effects on the living organism present in the aquatic medium and all over in the ecosystem [8−10]. Many heavy metals are responsible for water pollution because of their high carcinogenicity [11-13]. Since ancient times, arsenic considered as the severe carcinogenic element. The total of 35 elements relates to the environmental concern of toxicity. Out of these 23 metals categories into the heavy metal series according to their specific gravity five times higher than the water. For instance, As, Cd, Pb, Hg, showed 5.7, 8.65, 11.34, 13.54,

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comes into the hazardous top 20 elements list provided by the US Agency Disease Registry (ATSDR) in cooperation with USEPA. The flourished animal and plants present in the ecosystem is exposed with the heavy metals which comes from various sources such as the industrial activity, coal power plant, agricultural fields, coal and stone mining, acid mine, drainage, and landfill leachates municipal wastewater treatment plants [14]. Different arsenic species found in the water possesses the following toxicity order like dimethyl arsenic acid (DMA) < monomethyl arsenic acid (MMA) < arsenate < arsenite) [15, 16]. These heavy metals, when present in water beyond their permissible limit, causes severe diseases such as vomiting, nausea, asthma, and thyroid, gastrointestinal, and liver problems caused by cobalt [17−19]. Although zinc is the essential element which required for the nourishment of the human body but causes poor growth and mental fever when exceeds their permissible limit 3.0 mg L-1 which recommended by world health organization (WHO) [20, 21]. Some other ions also show the toxic effect, for instance, F-, NO3-, Cl-, SO42-, PO43-, etc. Excess intake of nitrate produces the methemoglobinemia disease in children, also known as the blue babies’ disease [22]. Alternately, fluorosis occurred because of the higher concentration of the fluoride. Besides these pollutants several other organic pollutants, for example, plasticizers, biphenyls, pesticides, phenols, greases, hydrocarbons, pharmaceuticals, fertilizers, oils, and detergents, etc. originate from the different water resources. Several other harmful pathogenic bacteria, fungi, microbes, viruses, amoebas, algae, planktons, and bacteria also create water pollution and cause severe waterborne disease. It has been estimated that the till 2020, the world population reach up to 7.9 billion may be world face the problem of water scarcity [23]. So, there is an urgent requirement to develop an efficient strategy for the removal of toxicants to supply safe drinking water to the world [24]. In previous research, lots of methods and techniques were implied to resolve this major issue which belongs to the ultra-filtration, filtration, flotation, adsorption, crystallization, centrifugation, reverse osmosis, sedimentation and precipitation, electrodialysis, distillation, ion-exchange, gravity separation, and electrolysis, etc. Figure 1 shows various techniques for the purification of water. This chapter will focus on new generation techniques, including

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adsorption, co-precipitation, flocculation, and coagulation. Among all these, adsorption-based methods are best and proper for wastewater treatment because of their wide range availability because of smooth handling and available in different forms. Researchers have used a variety of adsorbents to absorb insoluble and soluble inorganic, biological, and organic pollutants. With all these vital applications, this efficient method involves some limitations, therefore not as much suitable for the commercial application. Shortcomings like low adsorption ability, commercial-scale columns were showed with many adsorbents.

2. REMEDIATION TECHNIQUES 2.1. Adsorption Adsorption is the process through which toxicant as an adsorbate adsorbed on the adsorbent surface. Adsorption is a surface-based phenomenon which occurred because of physical forces. The pollutant also adsorbed on the solid surface via weak chemical interaction like chemical bonding responsible for adsorption [25]. It might depend on various factors such as reaction temperature, pH, amount of adsorbent dose, contact time, presence of the other pollutants, and the nature of the adsorbate and adsorbent. After reaching a certain level in the adsorption process, equilibrium achieved where the concentrations of adsorbed ion and water become constant. It occurred the more adsorption when the concentration of substance was according to their surface to the mass transfer process [26]. It is a very eminent, efficient, and economically viable process to eliminate the heavy metals from wastewater and exhibited the maximum adsorption. The maximum adsorption occurs because of a specific area, which is a crucial factor for the adsorption process, along with nanoparticles, showed a high surface-to-volume ratio, which makes it perfect aspirants [27]. It has considered that adsorbents mostly used to make the potable water are carbon nanotube, graphene, polymers, metal oxide, and zeolite-based materials.

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Liu et al. reported a novel biomimetic SiO2@CS composite for the exclusion of As5+ and Hg2+ showed an excellent adsorption capacity. Here, SiO2 exhibits good mechanical strength and stable chemical properties, which attributes the prohibition of the agglomeration of the adsorbent. The amino and hydroxyl functional groups of chitosan played a key role in the removal of heavy metal by supplying many active sites. The FESEM technique determined a leaf-like morphology of SiO2@CS composite. It was a notice that at even minute concentration of heavy metal showed the heavy metal removal and found 204.1 and 198.6 mg g-1 regarding the Hg2+ and As5+. This biomimetic composite attained up to 60% removal within a short time interval of around 2 min. The minimum time period limit and excellent adsorption capacity showed potential behavior. The good adsorption properties show its potential for removing heavy metal ions [28].

Figure 1. Various techniques to treat water. [Reproduced by permission of The Royal Society of Chemistry@ https://pubs.rsc.org/en/content/articlelanding/ 2012/ra/c2ra20340e#!divAbstract]

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Yan et al. introduced the hollow gangue microspheres into the geopolymer matrix using the geopolymeric approach to remove various heavy metal ions like lead cadmium, copper, and zinc from aqueous solution. It is a green and low-cost method using industrial solid waste abbreviated as GM. The GM/KGP (Gangue microspheres into a geopolymer matrix) adsorbent showed an amorphous structure and included different functional groups like Si–O–Si, Si–O–Al, and–OH. The geopolymer matrix comprises the hollow gangue microspheres consistently. They used the BET surface area analyzer to determine the surface area, which was found up to 26.41 m2 g-1. The preferential adsorption order of heavy metal was lead > copper > cadmium > zinc. The Langmuir isotherm model and the pseudosecond-order kinetic model were best fitted for the adsorption and kinetic data of the adsorption process, respectively. Adsorption of heavy metal over the surface of the GM/KGP adsorbent was totally the endothermic process. The adsorption process for the removal of metal ions is electrostatic attractions, physical, ion-exchange, and chemical interactions. Authors concluded that GM/KGP adsorbent is cost operative, safe, and active effort to remove hazardous heavy metals from wastewater [29]. Wang et al. adsorbed heavy metal ions on incinerated sewage sludge ash. The initial solution pH displayed an important part for the remediation of heavy metal and higher adsorption found at pH six within the initial 15 min in the single and dual component systems of heavy metal. The presence of other competing ions may diminish the rate of adsorption, which delays the equilibrium state. The adsorption data were followed the Freundlich isotherm explained the multilayer adsorption. Targeted heavy metal followed the affinity order for adsorption as copper > cadmium > zinc and showed the maximum adsorption capacity for copper, cadmium, and zinc heavy metal ions as 0.13, 0.11 and 0.06 mmol g-1, respectively. They considered the cation exchange mechanism to be the primary adsorption mechanism. The adsorption process is mainly managed by ISSA (Incinerated sewage sludge ash). Because of the practical solid-liquid separation technique, additional studies must be attentive to the adsorption performance of other metals ions [30].

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Chen et al. utilized the modified cellulose derivative by a different functional group like a secondary amino group, amide, carboxyl, and carbonyl sulfide to mitigate the removal of heavy cadmium metal. The modified cellulose derivative was characterized by the XPS, FTIR, 13C NMR, and XRD analytical tools. The changed form showed good adsorption capacity was 401.1 mg g-1 than the bare cellulose exhibited greater affinity with cadmium resulted from three times better performance than cellulose. The adsorption experiment carried out spontaneous, well fitted with the Freundlich model and followed the pseudo-second-order kinetics model with high regression coefficient value R2 = 0.994, R2 > 0.997, respectively. The DFT calculation characterized the affinity of functional groups with Cd2+, and these groups showed synergistic interactions with the cellulosebased adsorbent [31]. Wu et al. showed the adsorption of heavy metals includes copper, cadmium, and lead by using magnetic polysaccharide gel beads made up of a combination of the carboxymethyl chitosan, sodium alginate, with magnetic graphene oxide. Various tools like SEM, FTIR, VSM, XRD, XPS, and TGA were utilized to know the physicochemical properties of the composite beads. Because of its magnetic behavior, it could easily separate from wastewater and showed the 90% removal after the five-consecutive adsorption-desorption cycle. To explain the adsorption process kinetics, the obtained data were linearized, and according to a higher regression factor value with a particular model order declared. Here the Langmuir isotherm model and pseudo-second-order model best fitted for the adsorption and they considered kinetics data as a chemical process. Based on FTIR and XRD analysis assumed that they involved the chelation interaction among the carboxyl groups, hydroxyl groups, and nitrogen groups with the lead ions. It confirmed the magnetic polysaccharide beads had selectively worked for the lead ion with maximum and minimum adsorption capacity 189.04 55.96, and 86.28 mg g-1 for lead, copper, and cadmium, respectively. Good regeneration ability and recyclability make it a right candidate for wastewater treatment [32]. Jia et al. synthesized a magnetically separable iron silica core-shell adsorbent where Fe3O4 act as core and SiO2 as shell further immobilized the

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amine and anhydride including polyethyleneimine (PEI) and 1,4,5,8naphthalene tetracarboxylic-dianhydride (NTDA). After synthesis, SEM, TEM, FTIR, XRD, VSM analyzed the adsorbent. SEM analysis attributes the homogenous core-shell structure with three layers of 300 nm comprising Fe3O4, nSiO2, PEI-NTDA layer was 200 nm, and 20 nm in diameter. During the batch study, it favored the adsorption of lead simultaneously other heavy metals such as nickel, cadmium, copper, and zinc present in the aqueous solution. The largest adsorption was 285.3 mg g-1 at perfecting parameters at an adsorbent dose 0.5 g L-1, pH 6.0, contact time 3 h, initial concentration 200 mg L-1. The Langmuir isotherm model and the pseudo-second-order model were well fitted with the adsorption data. By applying the external magnetic field, these nanoparticles easily recovered and used for the next six cycles [33]. Arshad et al. prepared the graphene oxide incorporated polyethyleneimine in the form of calcium bead showed removal towards the lead, mercury, cadmium from wastewater. The Langmuir adsorption model and the pseudo-second-order model were best fitted for the adsorption process on functionalized-GOCA (Graphene oxide embedded calcium alginate) beads. At room temperature, the adsorption capacity was demonstrated up to 602, 374, 181 mg g-1 for lead, mercury, and cadmium, respectively. They ascribe better adsorption capacity because of the accessibility of active adsorption sites in varied functionalities as GO, and polyamine exhibited complexation with alginates carboxylate groups. All may synergistically reinforce the adsorption of metal ions. The preferential order of removal of heavy metal by functionalized GOCA beads as follows lead > mercury > cadmium. The five repetitive adsorption-desorption studies displayed a similar trend after the studied of other ions showed the removal efficiency of 75-80% for lead ions [34]. Xiao et al. employed magnetic Loofah sponges for the elimination of chromium and copper ions from the polluted water. Here biochar obtained from the Loofah sponges and pyrolyzed in a tube furnace in the N2 atmosphere further make accessible to support with chitosan. SEM morphology depicts the smooth surface of the bare biochar, while CMLB (chitosan combined with magnetic biochar) has a rough and mesopores

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network. The formation of a lined porous interconnection occurred because of the breakdown of the lignocellulosic material because of temperature at the time of heating in the furnace. Chitosan functionalized with different weight ratios of biochar, which are assigned as 20-50 wt% composition. During the adsorption experiment, 40 wt% changed biochar composition achieved the best adsorption 30.14, 54.68 mg g-1 for chromium and copper. FTIR, XPS, and XRD methods were used to understand the mechanism of adsorption. Based on changing intensities and peak area after the modification and the adsorption confirmed heavy metal ion removal. Kinetics and isotherm studies showed that CMLB defined by pseudosecond-order and the Freundlich models. They reduced the adsorption capacity very less after the three-sorption experiment by CMLB were 23.34, 42.6 mg g-1 for chromium and copper, respectively. Alternatively, the XPS analysis elucidated the primary adsorption mechanism of CMLB occurred. The ion exchange and surface complexation, signifying that CMLB can be a potential and environmental-friendly removal of heavy metal ions from the wastewater [35]. Mnasri-Ghnimi showed the application of the mixed pillared and single natural clay to remove inorganic pollutants in polluted water. Further, the adsorption experiment was conducted by including various effective parameters, such as initial ion concentration, amount of dose, the effect of pH, temperature, and contact time. By comparing the pillared and natural clay, pillared clay showed a higher affinity towards the heavy metal ion i.e., cadmium, cobalt, copper (M2+). Controlled pH attributes the adsorption of cobalt, copper, at a particular pH. The pH ranges from 6.0 to 10.0 favored the removal of cobalt and copper and 8.0 – 10.0 for cadmium. Alternatively, with increasing initial concentration, the extent of adsorption of M2+ enhanced until the concentration of the M2+ increased in the solution. Langmuir isotherm model and Second-order kinetics were associated with the adsorption of heavy metal M2+, and the process seemed to endothermic nature. Obtained coefficients well favored the adsorption process with M2+ ion interaction. Various characterization methods like BET, ZPC, CEC, and FTIR were carried out to test the texture of adsorbent and draws the experimentally changes occurred after adsorption. Desorption study also

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performed to check reusability; it can also be regenerated. The application of other isotherms such as Toth or Sips studied to find out the accuracy of the adsorption process, and weight of adsorbent also tested in the presence of the ions in the solution [36]. Wang et al. synthesized the 3D flower-like shape with sulfide functional groups inserted LDH (Layered Double Hydroxide) ordered micro composite sorbent to remove the lead, copper, zinc, cadmium, manganese selectively. The affinity order of removal of divalent heavy metal was for removing heavy metals, which displays an effective selective order toward various divalent metal ions lead > copper > zinc > cadmium > manganese. Particularly, lead and copper show high kd values as ~ 106, 105 mL g-1, respectively. A systematic batch study was carried out to confirm the selective removal of heavy metal, and they evaluated adsorption capacity through the Langmuir isotherm. The Langmuir isotherm predicts the monolayer adsorption in between the M2+ and NFL-S, while, kinetic study shows the chemisorption was the rate-limiting step [37]. Dong et al. synthesized the hydrochar impregnated Ti3AlC2-derived nanofibers by the carbonization of the biomass through the hydrothermal process. To certify a manageable future, it becomes necessary to use rich biomass to produce chemicals, transport fuels, and other raw materials. Hydrochar is evolved as promising is candidates resulted by hydrothermal carbonization of cellulose biomass, pinewood, sawdust in hot water at high pressure. XRD, BET, SEM, TEM, and FTIR were used to characterize formed hydrochar derived Ti3AlC2 adsorbent to investigate the crystal structures, textural properties, morphologies, and surface nature. The resulting product selectively targeted cadmium and copper [38].

2.1.1. Carbon-Based Nanoadsorbents Nowadays, nanoadsorbents based on carbon has been extensively utilized as a promising candidate for the removal of heavy metal ions from wastewater and water. Recently, various carbon-based nanomaterials have appeared as effective nanoadsorbents for wastewater treatment applications. For example, activated carbon (AC) making up with graphene and carbon nanotubes (CNTs) which is the utmost communal carbon-based practical

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adsorbent [39]. In the aqueous systems for the removal of inorganic and organic pollutants, AC is documented as a common and effective adsorbent because of a high surface reaction affinity, highly porous structure, and higher surface area up to 3000 m2 g-1. In the last decade, researchers have stalled the escalation of additional carbon adsorbents and have emphasized the development of cheaper AC precursors, and it is coupled with other adsorbents or chemical functionalization [40–45]. On the foundation of their developed heavy metal elimination presentation, CNTs have a shorter intraparticle diffusion distance and more available adsorption sites per unit mass compared to AC [46]. To remove toxic heavy metals from water and wastewater such as As3+, Cd2+, Cr3+, Co2+, Cu2+, Eu3+, Pb2+, Mn2+, Hg2+, Ni2+, Sr2+, Th4+, U6+, V2+ and Zn2+ CNTs are accessible in the form of their allotropes i.e., multi-walled (MWCNTs) and single-walled (SWCNTs) carbon nanotubes. Various methods such as sorption, precipitation, electrostatic attraction, and chemical interaction are ascribed to the mechanisms to absorb heavy metal ions onto CNTs that are multifaceted. Several factors handle the adsorption possessions of CNTs. Among these issues, the significant morphological features are the role of discrete adsorption sites and the fraction of unlocked and opened nanotubes [47]. The number of active sites in the capped CNTs is fewer than the opened CNT bundles [48]. Interstitial channels, grooves, outer surfaces, and internal sites are the four types of adsorption sites in CNTs. The purity of CNTs is likewise a significant feature. Contaminants, for example, carbon-based pollutants, soot, and catalyst particles may decrease the number of CNT active adsorption sites by coating the surfaces of CNT bundles. Earlier studies have shown that CNTs adapted thru oxygen display importantly enhanced adsorption ability. During the oxidation or synthesis, a few oxygen moieties, for instance, –COOH, –CO, and –OH might be accompanied with the CNT surface through various plasma treatments, acids, and ozone. A negative charge induces on the surface of CNTs by oxidation along with advancing dispersibility in aqueous solution. Thus, the capacity of cation exchange augmented [49]. As per, SWCNTs have enhanced adsorption performance for Zn2+ and Ni2+ with functional acidic sites on negative zeta potential and their surface. CNTs were changed using various metal oxide

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materials, for example, aluminum oxide, [50, 51] manganese dioxide, [52] and iron oxide [53], which resulted in favorable heavy metal ion removal. The synergistic effect amongst metal oxides and CNTs is the key part of the mechanisms for improved adsorption capacity. To absorb the toxic heavy metals from water and wastewater streams, manufacturing novel adsorbents [54, 55] such as graphene adsorbents incorporated with metal oxides have been used as the newest affiliate of the allotropes of the carbon family. Smart magnetic graphene was fruitfully synthesized by Gollavelli et al. thru ferrocene precursors and graphene oxide (GO) using microwave irradiation for the removal of heavy metals ions such as As5+, Pb2+, and Cr6+. The adsorbent showed high established removal efficiency (99%) ppm level down to the ppb level. For innocuous water intake in imminent regionalized systems of water, the virtuous adsorption possessions, lucrative nature, and effectual disinfection control accomplish it a potential adsorbent [56]. For heavy metal adsorption, GO has also been extensively utilized in different forms such as foam, aerogel, and powder. For the removal of Cu2+ ions, the GO aerogel compared to AC (40 min) and oxidized CNT sheets (24 h) with a 15 min adsorption rate to reach equilibrium. Various compounds, for instance, poly(amidoamine), poly-3-aminopropyltriethoxysilane, chitosan, polydopamine, ethylene diamine tetraacetic acid (EDTA), and cyclodextrin have been used for effective surface functionalization of GO to reach further heavy metal adsorption capacity. For heavy metal ion adsorption, EDTA was displayed to advance the recital of GO through the formation of stable metal ions chelates [57].

2.1.2. Zeolite Based Nanoadsorbents In heavy metal ion remediation, zeolites and its associated crystalline inorganic constituents play a key role in adsorption [58, 59]. Because of their ion-exchange, unique catalytic, and adsorption properties, zeolites have been extensively used in several industrial applications which are made of crystal-like hydrated aluminosilicate materials having uniform pore size [60]. Though owing to their pore sizes which deceits amongst 0.4-1 nm, zeolite particle sizes usually range amongst 1-10 mm, and they are considered as nanomaterials. Though, approximate outcomes with synthetic

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zeolites, for instance, zeolite X106 and zeolite 4A105 have also been chosen as the natural zeolite clinoptilolite which has been frequently utilized for heavy metal treatment. The removal of Cu2+, Cd2+, Pb2+, and Ni2+ ions has been examined on natural zeolites by Sprynskyy et al. [61]. They determined that the adsorption arises because of three discrete steps of fast adsorption i.e., inversion stage, dispersion, and clinoptilolite microcrystal surface and also has an ion-exchange nature. Furthermore, the ion-exchange adsorption proves a major role in the removal of these metal ions. Because of the competition of hydrogen ions, the adsorption process diminished sharply at a lower pH. By associating the synthetic zeolites (NaPl) and the natural zeolite clinoptilolite, removal competence on zeolite exchangers of the heavy metal ions was examined [62, 63]. In comparison to natural zeolites, synthetic zeolites have significantly enhanced exchange capacity. For the remediation of Cr3+, Zn2+, Ni2+, Co2+, and Cu2+ ions, zeolite 4A have been manufactured by Hui et al. These zeolites displayed an excellent adsorption capacity and a good recital to re-mediate these above-mentioned heavy metal ions. The hydration free energy, crystal structure of zeolite 4A, and metal ions’ hydrated radii handle the difference in adsorption performance [64]. For the fabrication of zeolites comparable to a needle-like nanocrystalline shape, Luo et al. reported green and sustainable method using metakaolin (MK) as a precursor clay mineral. Because of a specific needle-like shape associated with raw MK with a layered structure, the hydrothermally produced zeolite showed developed the specific surface area and porosity. Therefore, the synthesized zeolites exhibited a 20-fold augmentation associated with raw MK and remove the Pb2+ and Cu2+ metal ions having a good adsorption capacity of 337.8 mg g-1 and 431.0 mg g-1, respectively. The ion exchange reactions amongst heavy metal ions and the sodium ion of zeolites are proved the adsorption mechanism of MK-based zeolites [65].

2.1.3. Metal-Based Nanosorbents For water and wastewater remediation, various nano metal oxides are considered as low-cost and effective materials, for example, aluminum oxides, magnesium oxides, titanium oxides [66], manganese oxides

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comprising hydrous manganese oxide [67], ferric oxides counting hematite (a-Fe2O3) and goethite (a-FeOOH) [68], magnetite (Fe3O4) [69], hydrous ferric oxide, maghemite (g-Fe2O3) [70], zinc oxides [71], mixed-valence manganese oxides [72], and cerium oxides [73]. Fundamentally, in the aqueous condition, the communal adsorption mechanism depends on the interaction amongst oxygen in the metal oxides and heavy metal ions [74]. Currently, because of their high reactivity with heavy metal ions, ease of regeneration, desirable mechanical stability, and outstanding surface-tovolume ratio, hierarchically structured metal oxides have attracted significant attention of researchers [75, 76]. Arsenic has been removed from drinking water on granular ferric hydroxide, which is the most extensively used metal-based materials that previously been commercialized. Essentially, it comprises ferrihydrite (Fe(OH)3) component embedded on akageneite (b-FeOOH) which utilized in fixed bed absorbers showing high adsorption capacity. They show high arsenic adsorption capacity having a specific area and porosity of granules up to 330 m2 g-1 and 75% [77, 78]. Intended for the remediation of toxicants, the several readily available and economically attractive low-cost bio adsorbents have been composed of seafood waste, industrial by-products, cellulose waste materials, food waste, and agricultural waste which shows cost efficiency from moderate to in height competence [79-81].

2.2. Metal-Organic Frameworks Metal-organic frameworks (MOFs)/porous coordination polymers (PCPs) are rising as favorable aspirants in a massive amount of diverse application and multifunctional materials in water remediation [82]. Because of self-assemblage by strong bonds amongst the organic linkers and metal-containing species, the MOFs consist of organic linkers and metal nodes. In the synthesis of MOFs, all the synthetic crystalline materials hold ideal flexibility, a large area to mass ratios, and prominent porosity in alteration of shape from the microporous to the mesoporous scale together with their pore size [83–85]. Farha et al. reported a MOF in 2012 having a

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higher specific surface area reported so far of any porous material i.e., 14 600 m2 g-1 surface area which was the computer-simulated and actual surface area of 7000 m2 g-1 [86, 87]. The performance of MOFs in the existence of water can be accounted for as an adsorbent in an aqueous environment since they might experience hydrolysis [88]. Compared to other covalent materials, for example, zeolites and activated carbon, the MOFs are additionally vulnerable to hydrolysis because of metal-ligand coordination bonds. Though, a rising number of steady MOF structures have been addressed in recent literature because of this reason [89–91]. MOFs are an emerging class of adsorbents to undertake ecological contamination by removing heavy metals from water and wastewater, and they can be synthesized by simple and affordable techniques on a large scale supporting their outstanding stability under harsh conditions [92]. Various heavy metals such as Cd, Pb, As, Hg, and Cr are effectively removed from wastewater using MOFs as an adsorbent [93]. The adsorption performance of MOFs on heavy metal can be categorized into five main methods. These methods comprise (i) the fictionalization of organic linkers and metal nodes to improve selectivity and produce extra adsorption sites contrast to the pristine MOFs (ii) to advantage as of their synergistic effects and properties, (iii) increase their pore size by introducing defects in the structure, (iv) utilization of large organic linkers to advance porosity and to produce additional adsorption sites, and (v) hybridization of MOFs with other functional materials, for instance, magnetic materials. A MOF/polymer composite, which is water stable, has been synthesized by Sun et al. with biological and environmentally friendly materials. This composite is identified as MIL100, as a polydopamine (PDA) and MOF instead a polymer phase composite that comprises 1,3,5-benzenetricarboxylate (Fe-BTC). Fe-BTC/PDA composites established 394 mg g-1 and 1634 mg g-1 of heavy metal adsorption capacities for lead and mercury, respectively, which was found to be 99.8% adsorption capacities of the composite. In addition, these novel composites showed higher water stability, contrary to fouling, high separation, and regenerable performance within short response time [94]. Depending on the composition, their pore size can range from 0.3 to10 nm, which is a further significant characteristic of MOFs towards good

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adsorption capacity. This formulates it promising to manufacture nanofiltration membranes as separating agents based on MOFs [95, 96]. For example, to produce NF hybrid membranes at a pressure of 7 bar with a flux of 31 L m-2 h-1 and a Cu2+ rejection of 90%, a MOF/GO composite functionalized with an amino group embellish with a PDA-coated substrate surface was utilized [97]. The MOFs are a rising water treatment composite material having wide-ranging applications due to high capacity, an outstanding adsorption competence, and the possibility of alteration of their pore size. The removal of several key hazardous contaminants, mainly Cd2+ and Pb2+ in different wastewater reported by Pournara et al. reported on MOF [Ca(H4L)(DMA)2].2DMA (Ca-MOF) in which the MOFs was shown to be an extremely competent and selective adsorbent. Similarly, an economic column based on silica sand and Ca-MOF was set up efficient to remove a moderately huge amount of replicated wastewater having a co-existing ions series in higher concentrations and traces of Pb2+ (100 ppb). The concluding consequence selected that water remediation may be a practical application of Ca-MOF. The pair distribution function (PDF) data can determine the construction of M2+. The authors have synthesized an easy and ready-to-use electrochemical sensor to removal toxicants aggravated by the outstanding adsorption belongings of Ca-MOF based on changed graphite paste with CaMOF. The anodic stripping voltammetry (ASV) was utilized to detect Cd2+, Zn2+, Pb2+, and Cu2+ by this sensor and it showed low detection limits up to 0.64–1 to 4 mg L–1. In fact, the MOF was found to have a dual nature proper for electrochemical determination together with adsorption of heavy metal ions for the first time reported till date. Therefore, to synthesize a series of composite materials, an opportunity is opened that would be utilized in ecological monitoring and remediation [98]. Lv et al. described a simple one-step approach for the development of cost-effective and a scalable fluorescence sensor known as MIL-101-NH2. The outcome confirmed that the detection of Cu2+, Pb2+, and Fe3+ having the detection limit of 0.0016, 0.0052, and 0.0018 mM, respectively was occurred on fluorescent MIL-101-NH2. Prominently, showing this easy manufacturing procedure of luminescent MOFs was of extensive utilities to

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manufacturing other four MOFs functionalized by the similar alteration process displayed suitable fluorescence possessions. To gain immense fluorescence emission, this technique merely required to embellish amino groups with an organic linker in which no other fluorescein was indispensable. In addition, the as-synthesized MIL-101-NH2 showed soaked adsorption capacities of Pb2+, Cu2+, and Fe3+ carried out up to 0.9, 1.1, and 3.5 mM/g and had immense adsorption aptitude for these metal ions. Similarly, in water and wastewater, the adsorption of heavy metals on the other four amino-functionalized MOFs displayed virtuous adsorption capacity. In the removal and detection of Cu2+, Pb2+, and Fe3+ via MIL-101NH2 the investigation of FTIR and XPS studies recommended that the chelation amongst metal ions and amine groups showed a vigorous part. In conclusion, in the concurrent removal and detection of heavy metal ions, the suggested process had remarkable potential for applied requests [99]. Zhang et al. reported the removal and detection of Pb2+ from an aqueous solution. The ligands have N, in the structure of a water-stable metal-organic framework (CAU-7-TATB) which offers binding sites for metal ions. For the removal of Pb2+ metal ions, CAU-7-TATB displays fast adsorption kinetics and high adsorption capacity. Noticeably, the potentially applicable CAU-7-TATB remnants in height preceding adsorption towards Pb2+ in the occurrence of interfering ions like Mn2+, Mg2+, Ca2+, Ni2+, Cr3+, Co2+, and Zn2+ which does not interfere in removing Pb2+ from industrial water. In brief, the elimination of Pb2+ ions, the synthesized CAU-7-TATB was proved as an innovative adsorbent. The effect of various parameters, such as the interfering ions, adsorption kinetics, effect of pH, and adsorption isotherms, were thoroughly considered on the adsorption capacity. In conclusion, to absorb Pb2+ ions effectively, the N in triazine was found to be accountable. This study offers an alternate path of fabricating potentially viable prolonged MOFs adsorbents having nitrogen atoms in their ligands towards metal ions [100]. Guo et al. reported BUC-17 ultrafine powder, which was synthesized by the introduction of absolute ethanol and showed ultra-high adsorption capacity toward Cr6+ up to 121 mg g-1. It showed much more adsorption capacity toward Cr6+ ions. The adsorption process was found to be

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endothermic, spontaneous, and randomness increases by the demonstration of equilibrium and kinetic data. The accessible overall data showed that both ion-exchange and electrostatic interactions give Cr6+ adsorption onto BUC17. pH and co-existing anions showed significant characters divulged from the experimental data. To eliminate anionic heavy metals from wastewater, it was predictable to utilize BUC-17 as an effective adsorbent [101]. For the removal of Nd ions in aqueous systems, Najafi et al. reported the solvothermal pathway for the fabrication of hydro stable mixed-lanthanide MOF included with BTC as the ligand and La3+ and Ce3+ as metal ions. To study the possessions of Ce0.8La0.2BTC (DMF), many experimental tests and analyzing approaches have been employed. The fruitful development of lanthanide BTC-MOF was proved using FTIR spectroscopy. The crystalline and microporous structure of MM-MOF showed the XRD and SEM characterization. The specific BET surface area of the synthesized adsorbent was 627 m2 g-1. The largest adsorption capacity was found to be 142.8 mg g1 which has been calculated using Langmuir isotherm which proves the operative cooperation of two lanthanides in the MOF structure and increase of the nonlinear possessions of MOF to absorb Nd3+ ions. They assessed various optimizing parameters, such as initial metal ion concentration, contact time, co-existing ions, temperature, and pH for the adsorption process. The electrostatic interaction amongst a carboxyl group of MOFs and Nd3+ ions shows the adsorption process and is found to be a promising candidate as an adsorbent. The kinetic data and equilibrium data were best fitted to the pseudo-second-order model and the Temkin isotherm model. They found the adsorption process of Nd3+ ions to be spontaneous and endothermic [102]. Mahmoodi et al. reported magnetic eggshell membrane (Fe3O4@ESM), which was considered as a MOF support bed and produced by a lowtemperature co-precipitation method. To synthesize the water-based ZIF67@Fe3O4@ESM composite by ultrasound-assisted method, zeolitic imidazolate framework-67 (ZIF-67) crystals having large porous volume and high surface area up to 1403.7 m2 g-1 subclass of MOFs were successfully stabilized and grown on the surface of the Fe3O4@ESM. Various characterization techniques such as FTIR, EDS-Mapping, XRD,

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BET, VSM, and SEM were utilized to analyze the synthesized samples. For the removal of Cu2+ and BR18 dye from wastewater, the ZIF67@Fe3O4@ESM composite showed better performance and faster adsorption rate due to the high-surface-area contrast to other equipped adsorbents. The adsorption data were best fitted to the Langmuir isotherm model. The synthesized adsorbent showed the maximum adsorption capacity for BR18 and Cu2+ was found to be 250.81 and 344.82 mg g-1, respectively. The pseudo-second-order model was best fitted for kinetic studies [103].

2.3. Electrocoagulation The grouping of flotation, electrochemistry, and coagulation is known as electrocoagulation (EC), which is an alternative emergent technique toward heavy metal removal. In the EC technique, the succeeding development of bigger particles and accumulation of particles achieved through the advantage of flocculation/coagulation in which the system is destabilized by the neutralization of the repulsive forces amongst particles which results in the separation of toxicants. In EC there is no need to add external chemical coagulants because through applying electric current over the electrodes for the electrolytic oxidation of a sacrificial anode electrode the metal coagulants and polyelectrolytes or salts are produced in situ [104, 105]. There is a need to add up to three chemicals and pH change in some chemical coagulation procedures for reaching the greatest recitals, which brands chemical coagulation as a labor-intensive and expensive technique [106]. Characteristically, because of their low price, non-toxicity, high valence, and availability, EC electrodes are made of iron and aluminum metals [107, 108]. Though Gilhotra et al. reported that the EC procedure was utilized to remove arsenic successfully by utilizing stainless steel electrodes [109]. The aluminum electrodes were used in EC to remove zinc reported by Chen et al. The outcomes proved that the disturbance in the speed of coagulant formation and manufacture of Al3+ ions by alteration in current density the

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EC energy consumption and removal efficiency of zinc was affected. They performed the adsorption experiment with a wide-ranging initial zinc concentration of 50-2000 ppm in the EC technique. From the results, they concluded that after given some pre-treatments, the utilization of EC as a final treatment step is more favorable, which achieve advanced removal efficiencies at subordinate concentrations. In the EC technique, at the cathode, the electrochemical reactions occur through reduction of Zn2+ besides the precipitation by aluminum hydroxide, which similarly shows a vital role [110]. Doggaz et al. reported a similar EC process for the operative separation of iron from wastewater [111]. In continuation of the environmental research to treat wastewater making up the concentration of inorganic salts and toxicants, Xua et al. reported Fe0-electrocoagulation (Fe0-EC) for the removal of Cd2+ from wastewater thru examination of the effect of SO42− and Cl−. This study shows that the Fe0-electrocoagulation (Fe0-EC) were explored through assessing the alteration of Fe mineral. It was concluded from the experimental results that the property of Fe minerals handles the removal of Cd2+ from wastewater. From the results of co-ion studies on the adsorption efficiency, it was concluded that the attendance of SO42− exhibited the greatest adsorption for Cd2+ than the chloride green rust (GRCl) because of the generation of sulfate green rust (GRSO4) which was found in the mixture SO42− and Cl− solutions. This adsorption occurs because Fe2+– Fe3+ GRs (layered double hydroxides, LDHs) displayed a weaker affinity for monovalent Cl− than divalent SO42−. The negatively charged Fe flocs were generated in wastewater because of a high concentration of inorganic anions. Augmented the concentration of Cl− improved the ratio of Fe3+/Fe2+ in Fe flocs and endorsed the oxidation of Fe2+ to Fe3+ by chlorine-containing oxidants and subordinately owing to the increase of pH the Fe mineral magnetite (Fe3O4) was formed. So, by the process of adsorption i.e., coprecipitation and coagulation, the removal of Cd2+ ions increased in the presence of GRSO4 intermediate and then through using oxygen from the air, the produced GRSO4 was progressively altered into lepidocrocite (γ– FeOOH). Various parameters were optimized to check the adsorption efficiency, for example, initial Cd2+ concentration (C°), current density (j),

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regulating the ratio of SO42− and Cl− (RC:S), temperature (T°), and initial pH (pHi). Under the best parameters, the synthesized Fe°-EC showed the removal efficiency of 99.5% for Cd2+ ions and the equilibrium was reached in 10 min at temperature 40°C and pH 7–9 [112]. In the EC technique, an electrocoagulation reactor comprising triple aluminum tubes reported by Al Jaberi et al. for the removal of lead and it was built concentric, putting cathode electrode in between the tubes of the anode electrode. Various optimizing parameters are checked on the adsorption process i.e., initial lead concentration (10-300) ppm, electric current (0.2 - 2.6) Amps, the mixing speed of the neutral solution (150 rpm) and the electrolysis time (2-30) min. In this work, the lead ions are removed on the electrocoagulation reactor, which is an autocatalytic reactor and improved the kinetics of the adsorption process [113]. Xu et al. reported that in iron–electrocoagulation processes, the redox conditions governed the formation of functional products, which is an extraordinary parameter. They studied the removal of cadmium from wastewater on a newly synthesized rotating disc electrocoagulation system (RDEC) supported through sodium sulfite. The redox atmosphere is altered and regulated with sodium sulfite and rotate speed, respectively. First, various optimizing parameters such as current density (j), initial Cd2+ concentration (C0), electrode distance (d), rotate speed (n), initial pH (pHi), and Na2SO3 dosage (CS) in RDEC (Rotating disc electrocoagulation system) process are assessed by an iron disc as sacrificial electrodes. Outcomes show that electrode distance and rotate speed display a reverse, while effect current density, Na2SO3 dosage, and initial pH have a positive effect on Cd2+ removal. The upsurge removal efficiency of Cd2+ may be ascribed to the formation of Fe2+ – Fe3+ layered double hydroxides (LDHs) at high Na2SO3 dosage or low rotate speed. Thus, it was concluded that owing to oxygenfree solution environment, and it is found to be a vital intermediate for the removal of cadmium. In conclusion, to investigate the interactional influences, Response Surface Methodology (RSM) is performed amongst Na2SO3 dosage, rotate speed, and current density, and the experiment based on a single factor experimental result. The actual energy consumption (EEC)

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was found to be 2.98 kWh m-3, and removal efficiency was 98.11% for Cd2+ ions at the optimum operating conditions [114].

CONCLUSION A critical examination of adsorbents, Carbon nanotubes, electrochemical methods, electrocoagulation in this chapter demonstrates the all the mentioned innovative method have been utilized for the mitigation of heavy metal, inorganic, anions, organic and biological pathogens. Synthesized adsorbents have the tendency to remove the toxic ions even at the minimum concentration at different variable factors like pH, temperature, adsorbent dose, etc. A lesser amount of adsorbent dose consumption makes the adsorbents economically viable. Additionally, is has been noticed the short time interval required by some composites like biomimetic SiO2@CS composite around 2 min. The higher adsorption up to 602 mg g-1 for mercury ions was reported by graphene oxide embedded calcium alginate. All diagnosed tremendous properties related to higher adsorption capacity, required low concentration, amount of dose, appropriate pH, fast removal during batch experiment contributed the goal of new generation methods at the pilot, and industrial-scale columns. Most early studies and current work have a dazzling future of new generation methods in wastewater treatment. This chapter will give an insight to the readers to put better effort to materialize economically, and workable water treatment technology to solve the globally biggest issue.

ACKNOWLEDGMENTS The authors gratefully acknowledge the support from the Ministry of Human Resource Development Department of Higher Education, Government of India under the scheme of Establishment of Centre of Excellence for Training and Research in Frontier Areas of Science and Technology (FAST), for providing the financial support to perform this

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study vide letter No, F. No. 5–5/201 4–TS.Vll. Dinesh Kumar is also thankful DST, New Delhi for financial support to this work (sanctioned vide project Sanction Order F. No. DST/TM/WTI/WIC/2K17/124(C).

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[66] Mahdavi, S., Jalali, M. and Afkhami, A. (2013). Heavy metals removal from aqueous solutions using TiO2, MgO, and Al2O3 nanoparticles. Chemical Engineering Communications, 200, 448-470. [67] Wang, H. Q., Yang, G. F., Li, Q. Y., Zhong, X. X., Wang, F .P., Li, Z. S. and Li, Y. H. (2011). Porous nano-MnO2: large scale synthesis via a facile quick-redox procedure and application in a supercapacitor. New Journal of Chemistry, 35, 469-475. [68] Chen, Y. H. and Li, F. A. (2010). Kinetic study on removal of copper (II) using goethite and hematite nano-photocatalysts. Journal of Colloid and Interface Science, 347, 277-281. [69] Mahdavian, A. R. and Mirrahimi, M. A. S. (2010). Efficient separation of heavy metal cations by anchoring polyacrylic acid on superparamagnetic magnetite nanoparticles through surface modification. Chemical engineering journal, 159, 264-271. [70] Hu, J., Chen, G. and Lo, I. M. (2005). Removal and recovery of Cr (VI) from wastewater by maghemite nanoparticles. Water research, 39, 4528-4536. [71] Wang, X., Cai, W., Lin, Y., Wang, G. and Liang, C. (2010). Mass production of micro/nanostructured porous ZnO plates and their strong structurally enhanced and selective adsorption performance for environmental remediation. Journal of Materials Chemistry, 20, 85828590. [72] Pakarinen, J., Koivula, R., Laatikainen, M., Laatikainen, K., Paatero, E. and Harjula, R. (2010). Nanoporous manganese oxides as environmental protective materials—Effect of Ca and Mg on metals sorption. Journal of hazardous materials, 180, 234-240. [73] Recillas, S., Colón, J., Casals, E., González, E., Puntes, V., Sánchez, A. and Font, X. (2010). Chromium VI adsorption on cerium oxide nanoparticles and morphology changes during the process. Journal of hazardous materials, 184, 425-431. [74] Hua, M., Zhang, S., Pan, B., Zhang, W., Lv, L. and Zhang, Q. (2012). Heavy metal removal from water/wastewater by nanosized metal oxides: a review. Journal of hazardous materials, 211, 317-331.

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[85] Efome, J. E., Rana, D., Matsuura, T. and Lan, C. Q. (2018). Metal– organic frameworks supported on nanofibers to remove heavy metals. Journal of Materials Chemistry A, 6, 4550-4555. [86] Farha, O. K., Eryazici, I., Jeong, N. C., Hauser, B. G., Wilmer, C. E., Sarjeant, A. A., Snurr, R. Q., Nguyen, S. T., Yazaydın, A. O. and Hupp, J. T. (2012). Metal–organic framework materials with ultrahigh surface areas: is the sky the limit? Journal of the American Chemical Society, 134, 15016-15021. [87] Kobielska, P. A., Howarth, A. J., Farha, O. K. and Nayak, S. (2018). Metal–organic frameworks for heavy metal removal from water. Coordination Chemistry Reviews, 358, 92-107. [88] Peng, Y., Huang, H., Zhang, Y., Kang, C., Chen, S., Song, L., Liu, D. and Zhong, C. (2018). A versatile MOF-based trap for heavy metal ion capture and dispersion. Nature communications, 9, 187. [89] Burtch, N. C., Jasuja, H. and Walton, K. S. (2014). Water stability and adsorption in metal–organic frameworks. Chemical reviews, 114, 10575-10612. [90] Kim, H., Yang, S., Rao, S. R., Narayanan, S., Kapustin, E. A., Furukawa, H., Umans, A. S., Yaghi, O. M. and Wang, E. N. (2017). Water harvesting from air with metal-organic frameworks powered by natural sunlight. Science, 356, 430-434. [91] Wang, C., Liu, X., Demir, N. K., Chen, J. P. and Li, K. (2016). Applications of water stable metal–organic frameworks. Chemical Society Reviews, 45, 5107-5134. [92] Li, J., Wang, X., Zhao, G., Chen, C., Chai, Z., Alsaedi, A., Hayat, T., and Wang, X. (2018). Metal–organic framework-based materials: superior adsorbents for the capture of toxic and radioactive metal ions. Chemical Society Reviews, 47, 2322-2356. [93] Mon, M., Bruno, R., Ferrando-Soria, J., Armentano, D. and Pardo, E. (2018). Metal–organic framework technologies for water remediation: towards a sustainable ecosystem. Journal of Materials Chemistry A, 6, 4912-4947. [94] Sun, D. T., Peng, L., Reeder, W. S., Moosavi, S. M., Tiana, D., Britt, D. K., Oveisi, E. and Queen, W. L. (2018). Rapid, selective heavy

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metal removal from water by a metal–organic framework/ polydopamine composite. ACS central science, 4, 349-356. [95] Li, X., Liu, Y., Wang, J., Gascon, J., Li, J. and Van der Bruggen, B. (2017). Metal–organic framework-based membranes for liquid separation. Chemical Society Reviews, 46, 7124-7144. [96] Qiu, S., Xue, M. and Zhu, G. (2014). Metal–organic framework membranes: from synthesis to separation application. Chemical Society Reviews, 43, 6116-6140. [97] Rao, Z., Feng, K., Tang, B. and Wu, P. (2017). Surface decoration of amino-functionalized metal–organic framework/graphene oxide composite onto polydopamine-coated membrane substrate for highly efficient heavy metal removal. ACS applied materials & interfaces, 9, 2594-2605. [98] Pournara, A., Margariti, A., Tarlas, G. D., Kourtellaris, A., Petkov, V., Kokkinos, C., Economou, A., Papaefstathiou, G. S. and Manos, M. J. (2019). A Ca2+ MOF combining highly efficient sorption and capability for voltammetric determination of heavy metal ions in aqueous media. Journal of Materials Chemistry A, 7, 15432-15443. [99] Lv, S. W., Liu, J. M., Li, C. Y., Zhao, N., Wang, Z. H. and Wang, S. (2019). A novel and universal metal-organic framework sensing platform for selective detection and efficient removal of heavy metal ions. Chemical Engineering Journal, 375, 122111. [100] Zhang, R., Liu, Y., An, Y., Wang, Z., Wang, P., Zheng, Z., Qin, X., Zhang, X., Dai, Y. and Huang, B. (2019). A water-stable triazinebased metal-organic framework as an efficient adsorbent of Pb (II) ions. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 560, 315-322. [101] Guo, J., Li, J. J. and Wang, C. C. (2019). Adsorptive removal of Cr (VI) from simulated wastewater in MOF BUC-17 ultrafine powder. Journal of Environmental Chemical Engineering, 7, 102909. [102] Najafi, M., Sadeghi Chevinli, A., Srivastava, V. and Sillanpää, M. (2019). Augmentation of neodymium ions removal from water using two lanthanides-based MOF: ameliorated efficiency by synergistic

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[111] Doggaz, A., Attour, A., Mostefa, M. L. P., Tlili, M. and Lapicque, F. (2018). Iron removal from waters by electrocoagulation: Investigations of the various physicochemical phenomena involved. Separation and Purification Technology, 203, 217-225. [112] Xu, L., Wu, D., Liu, W., Xu, X. and Cao, G. (2019). Comparative performance of green rusts generated in Fe0–electrocoagulation for Cd2+ removal from high salinity wastewater: Mechanisms and optimization. Journal of environmental management, 237, 495-503. [113] AlJaberi, Forat Yasir. (2018). Studies of autocatalytic electrocoagulation reactor for lead removal from simulated wastewater. Journal of environmental chemical engineering, 6, 60696078. [114] Xu, L., Cao, G., Xu, X., He, C., Wang, Y., Huang, Q. and Yang, M. (2018). Sulfite assisted rotating disc electrocoagulation on cadmium removal: parameter optimization and response surface methodology. Separation and Purification Technology, 195, 121-129.

BIOGRAPHICAL SKETCHES Rekha Sharma Affiliation: Banasthali Vidyapith Education: MSc, PhD Research and Professional Experience: 4.5 years Professional Appointments: Assistant Professor in Banasthali Vidyapith Publications from the Last 3 Years: 4 research papers and 6 book chapters.

Sapna Affiliation: Banasthali Vidyapith Education: MSc, PhD

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Research and Professional Experience: 4 years Professional Appointments: Research Scholar Publications from the Last 3 Years: 1 research papers and 6 book chapters.

Dinesh Kumar Affiliation: Central University of Gujarat, Gandhinagar Education: MSc, PhD Research and Professional Experience: 17 years Professional Appointments: Associate Professor Publications from the Last 3 Years: 25

In: Drinking Water Editor: Cécile Marcil

ISBN: 978-1-53618-070-1 © 2020 Nova Science Publishers, Inc.

Chapter 2

WATER TREATMENT METHODS FOR DETOXIFICATION OF METAL IONS: STATE-OF-THE-ART, FUTURE SCENARIO AND CHALLENGES Kritika S. Sharma1, Rekha Sharma2, PhD and Dinesh Kumar1,, PhD 1

School of Chemical Sciences, Central University of Gujarat, Gandhinagar, India 2 Department of Chemistry, Banasthali Vidyapith, Rajasthan, India

ABSTRACT Approximately two million people die annually because of contaminated drinking water and unsafe sanitation practices. The generation of heavy metal ions is one of the prominent causes of water pollution. Heavy metals such as lead, mercury, chromium, and arsenic exist naturally, but anthropogenic activities cause contamination in water. The World Health Organization (WHO) reports that approximately 1 billion people across the world don’t have an approach to clean drinking water. This count is presumed to eventually increase with increasing population 

Corresponding Author’s E-mail: [email protected].

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Kritika S. Sharma, Rekha Sharma and Dinesh Kumar i.e., 7.7 billion (2019) from 7.5 billion (2018), energy requirement and climate change. There are many commercially available methods to detoxify water from heavy metals, while they are liable to rejection because of: less efficient, expensive, generate hazardous toxic waste and energyconsuming. This chapter will explore some advanced treatment methods, which are in use like metal-organic frameworks (MOFs), UV irradiation, etc. Some traditional techniques are still in use like adsorption, reverse osmosis, electrodialysis and so on. Although they serve the purpose, either cannot address these problems quickly, economically, long-term stability or high performance despite development on the technical side. The challenge is to provide solutions which are a universal or single solution, inexpensive, has ease of implementation, cent percent efficiency, and domestic use. The functional integration of different technologies or treatments may solve the current water hazards. Impending water shortage will lead to detoxifying the water, which is now considered undrinkable. This chapter will emphasize the newest easy process, inadequacy, hurdles, and prospects of drinking water treatment.

Keywords: detoxification, heavy metals, metal-organic frameworks, ubiquitous solution

1. INTRODUCTION Water covers 70% of the Earth, out of which only approximately 2.5% is freshwater. But, 2.1% out of 2.5% freshwater is unreachable by the human, as it is trapped in: glaciers, atmosphere and in massive depth of earth surface [1]. Thus, only 0.4% of fresh drinkable water is available for 7.7 billion people (2019) [1]. Figure 1 illustrates the distribution of water on Earth. Thus, because of increasing population and water pollution, there is an alarming situation in the drinking water crisis across the world. There are many sources of water pollution. Out of all the sources, contamination of drinking water with metal ions is severe global distress. Metals like lead, mercury, arsenic, chromium and so on occur in nature, but man-made industrial activities such as mining and printing cause metal ion contamination in water [2]. The notable characteristics of these metal ions are bioaccumulation propensity, non-biodegradability because of these, they are highly toxic even at a less concentration [3]. These pollutants have

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various adverse health effects in humans, ranging from losing listening and vision power to fatal diseases such as kidney impairment and cancer [4]. Because of the consumption of contaminated water and unsound sanitation practice, around two million people die per year. Thus, metal ions in water are dangerous for mankind and require treatment [5]. This chapter will explore conventional and advanced treatment methods. The limitations of conventional decontamination methods are lengthy or expensive or possess operative hurdles or all [6, 7, 8]. Thus, there is an urgent need to find new alternatives to traditional or conventional methods used to treat water. Water crises will lead to the treatment and utilization of water sources, which are now observed as hazardous if consumed by humans [8]. Implementing nanotechnology has a broad scope in water treatment technologies, as much research studies have shown favorable results. Nanotechnology is considered as a costly method. However, the nanotechnology-based techniques were not only inexpensive but also highly efficient than traditional treatment methods was found in a study [9]. Nanotechnology-based treatment methods may be immensely vital in severe water treatment solutions for a new and a trace amount of pollutants [9]. The challenge is to find a single solution to all water pollutants with high efficiency and cost-effectiveness. The combination of various treatment methods may be a unique solution. However, much research on this idea is still not performed. The idea of developing a universal or single solution which is costeffective, has ease of implementation, 100% efficiency, and can be used domestically paves the way for more research on alternatives that can be used in future. Thus if these aspects achieved in the future, they will further provide a wide spectrum of implementation of next generation water treatment methods on large scale. This chapter will deliberate on the Stateof-the-Art, challenges, and future scenario for detoxification of metal ions in an aqueous environment.

Figure 1. Distribution of water on Earth.

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2. STATE-OF-THE-ART OF WATER TREATMENT METHODS Herein, the most modern treatment methods for water treatment will be discussed. Water treatment comprises multi-step processes, as shown in Figure 2. Industrial and municipal water treatments consist of primary, secondary, and tertiary processes to get safe water. The primary treatment process is another or introductory process applied before any treatment method applied to the purification of water. It comprises many methods such as sedimentation, centrifugation and so on, out of which microfiltration and chemical precipitation are used. For detoxification of metal ions from water; the secondary process is generally applied for organic contaminant removal and is not discussed here as per the interest of the topic. Tertiary processes are more refined methods used at an end or final stage to get safe water. Out of several tertiary processes used electrochemical precipitation, adsorption, membrane-based technologies are used for detoxification of metal ions from water. Primary, secondary, and tertiary processes comprise several methods; however, here, we will only discuss methods for detoxification of metal ions in water as per the interest of the topic.

Figure 2. Multi-step water treatment process.

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2.1. Primary Process 2.1.1. Microfiltration Microfiltration, with large pore size 100-1000 nm, is a membrane filtration technology, which is based on the polymer or ceramic membrane. It removes and filters some heavy metal ions, bacteria, microorganisms bigger than micro-pollutants and viruses, total dissolved solids (TDS), and algae [10], however, the efficiency of metal ions removal is not high. Thus, after this primary treatment process, this water can be further treated in tertiary purification processes such as ion-exchange and adsorption and so on for more efficient detoxification of metal ions from water [11]. 2.1.2. Chemical Precipitation In this treatment, pH alteration of heavy metal ions and treatment methods with chemical reagents such as sulfides, hydroxides, etc. leads to an insoluble particle generation. These insoluble particles are separated via sedimentation. Chemical precipitation is being used on a large scale in the industrial treatment process for heavy metal ion removal. This process is comparatively simple and is a cost-efficient and smooth operation characteristic, which makes it helpful over other techniques [12]. However, it has a big disadvantage of a compulsory requirement of post-treatment as heavy metal ion amount does not reach the safe discharge range. Other disadvantages are secondary contamination, massive sludge production, and thus, the sludge discard process becomes mandatory [11].

2.2. Tertiary Process 2.2.1. Electrochemical Precipitation Formation of a thin layer of metal ions can get the elemental state of metal on a surface of the cathode using electrochemical methods [13]. This process is eco-friendly, simple, and requires relatively lesser labor and energy requirements. This process can also remove chemical oxygen

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demand from polluted water. But, the effectivity of heavy metal ions removal is relatively less than tertiary treatment processes.

2.2.2. Adsorption In the adsorption process, a substance (adsorbate) adheres to the adsorbent surface because of the mass transfer process [14]. Similarly, this concept is used in the water treatment process. The contaminants are removed by stimulating adsorption on the adsorbent [15]. This treatment process is popular, efficient, and cost-effective for heavy metal ion removal [26]. It has several advantages, such as effective removal, the chance of adsorbent regeneration and tunable: operation and design. Nanoparticles (NPs) have a large surface-to-volume ratio, thus making them favorable for adsorption because it is a surface-based phenomenon [17]. Carbon, zeolite, and metal-based nanoadsorbents are different classes of adsorbent mostly used. Other than these adsorbents, bioadsorbents are a new emerging class of adsorbents with potential use. 2.2.2.1. Carbon-Based Nanoadsorbents For heavy metal ion treatment, carbon-based nanoadsorbents is being massively used. Nowadays most commercially used carbon-based adsorbent is activated carbon (AC) [14]. Activated carbon has many advantages of higher: surface area, porous structure, surface reaction affinity. Thus it is effective and used for inorganic and organic contaminant removal from water [18, 19]. Other emerging nanoadsorbents like graphene, carbon nanotubes (CNTs) have also shown effectiveness in water treatment. Carbon nanotubes show relatively more removal of heavy metal than AC. Thus, researchers have shifted from AC to CNTs in the last decennary [20, 21]. Carbon nanotubes are further characterized into two major allotropes: single and multi-walled carbon nanotubes. These two allotropes show efficiency in removing heavy metal ions such as cadmium, cobalt, chromium, copper, mercury, lead, europium, manganese, nickel, thorium, and arsenic. The mechanism of heavy metal adsorption on CNTs is complicated and is assigned to the chemical interaction, electrostatic attraction, and sorption precipitation [21].

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2.2.2.2. Metal-Based Nanoadsorbents Efficient and cost-effective heavy metal ion removal is shown by nano metal oxides of iron, magnesium, cerium, and zinc, etc. The heavy metal ion removal mechanism is attributed to the oxygen present in the metal oxidesheavy metal ions complex formation in a water sample [22, 23]. Nowadays, the metal oxide has attracted much attention because of its favorable characteristics such as higher surface/ volume ratio, mechanical sturdiness, and easy regeneration. These characteristics lead to higher reactivity with heavy metal ions [24, 25]. For removal of arsenic from water samples, the most extensively used metal-based material is granular ferric hydroxide. 2.2.2.3. Zeolite Based Nanoadsorbents The crystalline hydrated aluminosilicate materials with uniform-sized pores are called zeolites. Zeolite based nanoadsorbents have been used for heavy metal ion treatment [26-28]. Characteristics such as ion-exchange, adsorption, and catalysis make zeolite-based nanoadsorbents favorable for industrial use [29]. They are classified as nanomaterials because of their 0.41 nm pore size. However, their particle size lies in a range of 1-10 mm [14]. The most widely used natural zeolite is Clinoptilolite. Synthetic zeolite X106 and zeolite 4A105 are also reported. Sprynskyy et al. used natural zeolites to remove multi-metal ions such as cadmium, lead, copper, and nickel [26] simultaneously. The sorption occurred over three different steps of fast adsorption on the external surface of clinoptilolite microcrystal by the ion-exchange mechanism. They concluded that the sorption happened via reversal step and scattering. Further authors observed that ion-exchange adsorption is dependent on pH significantly. The detrimental effect on adsorption was observed at a lower pH, and it may be due to H+ ions competition [26]. Zeolite exchangers were examined by comparison of the natural zeolite Clinoptilolite and the synthetic zeolites NaPl to effectively remove metal ions [30, 31]. Synthetic or changed zeolites showed significantly upgraded exchange capacity than the natural zeolites. 2.2.2.4. Bioadsorbents Bioadsorbtion technique is used for the binding of a metal ion with itself to separate metal ion pollutants from water. This method is even more

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efficient at less metal ion concentration, like ion-exchange methods [22]. Several adsorbents have also been derived from a waste of seafood, agriculture, cellulose, etc. These adsorbents are eco-friendly, inexpensive and thus are seen as potential alternatives to treat heavy metal ions [32, 33].

2.2.3. Membrane-Based Technologies Water treatment membrane-based technologies have further subdivided into different classes: reverse osmosis ultrafiltration, nanofiltration, electrodialysis, and nanohybrid membranes. 2.2.3.1. Reverse Osmosis It is the most widely used desalination technique across the globe. Thus, it is also known as reverse seawater osmosis (SWRO). It is most useful for the removal of several ions except As(III) from water. It is being used in paper industries, dairy, pulp, food, and power plants, and so forth. A semipermeable membrane is used for the separation of ions by RO from water by exerting hydrostatic pressure in opposition to osmotic pressure. The osmotic pressure settles the threshold of hydrostatic pressure. The waterloving characteristics of RO membranes augment the transport of water [34]. However, the significant disadvantages of RO are losses of treated water, more energy requirements, and expensive. Also, RO requires post-treatment and readjustment because of a non-selective way to remove ions. 2.2.3.2. Ultrafiltration Ultrafiltration (UF) has a membrane pore size that lies in a range of 10100 nm. It is used widely for the removal of bacteria, natural organic colloids, viruses, and color pigments [35]. It has a favorable characteristic of less energy requirement than reverse osmosis (RO). However, its membrane pore size is greater than hydrated metal ions. Thus, these metal ions easily go across UF membranes. This leads to unsatisfactory metal ion rejection. To deal with this undesirable result, the surfactants are exteriorly added to water, which leads to the generation of micellar-enhanced ultrafiltration (MEUF). This improves the heavy metal ion rejection to ≥99% [36].

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2.2.3.3. Nanofiltration Nanofiltration (NF) membranes are used to treat contaminants 99.8% of these ions from a 1 ppm sample. Also, composite characteristics are well kept in real water samples of the river and spiked seawater with a minimal quantity of lead. Thus, extraordinary selectivity is shown by this composite. Selectivity was also constant in the presence of interferential ions like sodium ions, humic acid in high concentrations [6]. MOF-polymer composite, FeBTC/PDA showed excellent selectivity and extraction rate for a massive amount of lead and mercury. Also, this composite by advancing the reduction of tiny quantities of lead ions can make seawater drinkable in 1 minute. These noticeable characteristics are obtained by adding porosity externally to a nonporous polymer-MOF template. The advantage of a nanoporous window of the template is that it prevents draining of hydrophilic polymer into the water, thus promoting consistent performance, simple separation, and cycling. This nanoporous window also prevents the damage of the composite by preventing the organic interferents dispersal in a composite. This FeBTC/PDA composite

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showed more performance, inexpensive separation, simple tunability, renewability, and extended stability. Thus, potential results are shown by this composite, and it may be used in domestic and water technologies in a water shortage situation. The wise selection of MOF-polymer units may lead to selective removal of a broad range of trace pollutants in water and air. Further study and tuning of the characteristics of the FeBTC/PDA composite will pave the way for its various unexplored applications [6].

3.2. Cathodic Hydrogen Peroxide Generation and UV Photolysis Adsorption on oxides of iron for removing trace toxic elements is an economical and potent technique. However, a generation of iron precipitates is restricted in natural water resources at a comparatively low concentration of iron. This is because of the existence of metal-complexing ligands linked with natural organic matter (NOM). Thus, this situation arises the need to add iron, and this makes the procedure complex as it leads to more quantities of solids to be discarded. Although usually generation of an iron precipitate is blocked because of the existence of metal complexing ligand linked with NOM. A device composed of a cathodic cell generated H2O2 by UV illumination to reduce NOM colloid stability and metal-complexing ability in groundwater was developed. UV illumination changed NOM and converted approximately six μm of iron oxides into precipitated form. This led to the removal of 0.5-1 μm of copper, lead, and arsenic by adsorption on iron oxides. After treatment, consistent changes in NOM with the loss of iron-complexing carboxylate ligands were observed [8].

3.3. Photocatalytic Converter Porphyrin (PP) dye-sensitized nanohybrids or nanomaterials possess a new absorption band that corresponds to the solar irradiance spectrum. This property makes the nanohybrid favorable for photocatalysis use. Here we have infused protoporphyrin IX with copper(II) ions and sensitized porous

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TiO2 microspheres (approximately 1.5 mm in diameter) to generate a functional nanohybrid for application in visible light photocatalysis. In water, Cr6+ is carcinogenic, thus a dangerous heavy metal pollutant. However, Cr3+ is not a toxic and vital nutrient for life forms. In the water on UV light illumination, nanohybrid reduces Cr6+ to Cr3+. The favorable impact of the Cu ion infusion into the sensitizing PP dye is noticeable from the effectiveness in the photocatalytic reduction in the presence of water dissolved metal ions (Cr3+ and Fe3+) is demonstrated. During photocatalytic reduction, nanohybrid with the absence of Cu(II) experience other metal ion intrusion [49]. (Cu)PP–TiO2 nanohybrids demonstrates effective recyclability, increased photostability, and photocatalytic activity than PP–TiO2. Also, PP–TiO2 demonstrates a notable decrease in photocatalytic activity because of the existence of Cr3+ and Fe3+ in potable water. However, negligible decrease in photocatalytic activity is shown by (Cu)PP–TiO2. Further, in this study, a model for the real world or practical use was developed. In this context, the (Cu)PP–TiO2 nanohybrid fabricated on a stainless-steel mesh shows effective Cr6+ reduction. The (Cu) PP–TiO2 photocatalyst acts as a detoxifying agent to reduce Cr6+ to Cr3+. The stainless-steel mesh serves as a filter to eliminate dispersed matter, such as an insoluble photo-reduced product. Thus, there is a two-fold cleaning action by the model developed. Thus, to tackle chromium pollutants in water, this unique prototype or model may serve as a potential device in future [49].

3.4. Graphene-Based Microbots A graphene oxide microbots (GOx-microbots) for treatment of lead (heavy metal) through an adsorption process was developed. These microbots are self-propelling, and it seizes, transplants remove and recuperates for recycling. These microbots comprise many layers of platinum, graphene oxide and nickel, and each layer provides divergent functions, as shown in Figure 3. Motile GOx-microbots is tenfold effective than non-motile microbots. GOx-microbots cleanse water by a decreasing

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level of lead from 1000 to 50 ppb in 1 hour. The microbots can be recycled and used again after the chemical removal of Pb from the microbots surface.

Figure 3. Diagrammatic representation of GOx-microbots.

Microbots can be removed and recovered quickly by magnets. In a microfluidic system under the magnetic influence, the microbots removal and recovery was proved. The GOx-microbots may be used as an advanced device for the eradication of Pb because of its effective eradication and probability of Pb recovery and reusability. Thus, more functions such as sensing, drug delivery, and so forth of graphene-based nanomaterials can be explored in future research [5].

4. FUTURE OUTLOOK In 21st centenary with the increase in population and water pollution and climate variation, there is an urgent need for new water treatment methods for secure drinking water. To supply safe drinking water in sufficient volume by improvement in terms of cost-efficiency and sturdy materials is the requirement of water industries. With an increment in water demand, more

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firm health guidelines and emerging pollutants, the traditional methods show inefficiency for supplying secure water. There is a need for inexpensive and sturdy treatment methods that can not only provide safe drinking water. In future modifications of nanotechnology treatment methods to conventional methods will pave the way for advancement in drinking water treatment processes. Nanotechnology water treatment methods have advantages such as inexpensive, non-dependency on colossal infrastructure and fulfill several functions. Also, the NPs can be used for catalysis, adsorption for oxidative degradation, and removal of virulent pollutants from water. The vast potential to remove organic contaminants is shown by the integration of membrane technology with NPs. To remove metallic contaminants such as Cd, Cu, As, Zn, Hg, and Cr from water, several minerals, agriculture waste, and clay have been used continuously for a long time. Today, nanostructured materials and nanoparticles are considered a significant substitution for traditional adsorbent materials. There is a need for further research in inherent characteristics, mechanisms, and commercialization of nanotechnology-based and other alternative water treatment methods [50]. Nanotechnology is seen as a new opportunity to be explored by researchers. However, much knowledge of this field is still unrevealed because of its originality. Thus, in future nanotechnology treatment methods will be implemented on a massive scale because of its advantages over conventional or traditional water treatment methods. Metal nanoparticles (MNPs) are thus appropriate for the expulsion of many heavy metals such as arsenic. Less toxicity and elevated efficiency for the removal of heavy metal from potable or drinking water is shown by MNPs. Disinfection via MNPs is less expensive, handy than alternative disinfection treatments. Thus, MNP applications in water treatment have a full scope [51].

5. CHALLENGES In this chapter, we have discussed current widely used water treatment methods for metal ion treatment in water. Several aspects of treatment

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methods such as efficiency implementation, advantages, disadvanatges, etc. are discussed. A single treatment method that can perform treatment of all current pollutants is still not found because of the limitations or disadvantages of each method, as shown in Table 1. This gap can be used as a stepping stone for future research. A solution for this idea of single or ubiquitous treatment may combine the developed methods which may challenge in terms of commercialization feasibility. Also, it is also noticeable that not even a single treatment technique with cent percent efficiency under real world samples is yet to be developed. Improvement on the technical side is very rapid. However, improvement in aspects of cost-effectiveness, efficiency, and commercialization feasibility is at a much lower rate than technical development or improvement. The causes for such a difference in the rate of development of these aspects are also various and divergent [11]. Table 1. Widely used treatment methods and their limitations/disadvantages Treatment methods Microfiltration Chemical Precipitation

Electrochemical Precipitation Adsorption and Ion Exchange

Reverse osmosis

Ultrafiltration

Electrodialysis

Limitations/disadvantages Large pore size, less efficiency in the removal of metal ions, requires further treatment. secondary contamination, massive sludge production, and thus, the sludge discard process becomes mandatory, less efficiency in removal of metal ions, requires further treatment. less efficiency in removal of metal ions Efficiency limit is thermodynamically forbidden by the equilibrium nature of the process between bound and unbound ions on a physical adsorption/exchange surface. In ion exchange: the nominal 100% efficiency is impeded by defects present on real membranes, which lead to a small, yet not negligible leakage and highly ion-specific [52]. significant losses of treated water, more energy requirements, expensive, requires post-treatment and readjustment because of a non-selective way to remove ions. membrane pore size is greater than hydrated metal ions. Thus, these metal ions easily go across UF membranes. This leads to unsatisfactory metal ion rejection. Electricity driven process

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Although Nanotechnology-based technique is seen as potential alternatives to conventional methods used for treatment of water. The challenge is to thoroughly study its environment toxicity and effects on human health. In fact, gold standards for assessing the toxicity of nanomaterials are still relatively scarce at present times. Hence, comprehensive evaluation of the potential toxicity of nanomaterials is an urgent need to enable and secure the full use of nanomaterials in real water treatment applications [53, 54]. Well developed and widely used techniques like RO, electrodialysis and nanofilteration have major challenges such as high capital and operating costs [55]. And solution for these challenges should be found out for more efficient treatment methods that can be used in future. However, in spite of the above attempts to discuss the different methods used for treatment, it is important to notice that water treatment is a extremely important and complicated problem. The treatment process is complicated and challenging due to the use of different highly specific treatment processes with different water pollutants. Thus, hierarchy arrangement of different process is not fair, as all the process remains highly specific to the different varieties of pollutants, and no single treatment process provide a ubiquitous or universal solution to all current contaminants in water.

ACKNOWLEDGMENTS Dinesh Kumar and Kritika S. Sharma are thankful DST, New Delhi for financial support to this work (sanctioned vide project Sanction Order F. No. DST/TM/WTI/WIC/2K17/124(C).

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[55] Greenlee, L. F., Lawler, D. F., Freeman, B. D., Marrot, B., and Philippe, M. “Author’s Personal Copy Reverse Osmosis Desalination: Water Sources, Technology, and Today’s Challenges.” https://doi.org/ 10.1016/j.watres.2009.03.010.

BIOGRAPHICAL SKETCHES Kritika S. Sharma Affiliation: Central University of Gujarat, Gandhinagar 382030 Education: MSc Research and Professional Experience: 01 years Professional Appointments: Research Scholar Publications from the Last 3 Years: 5 book chapters

Rekha Sharma Affiliation: Banasthali Vidyapith Education: MSc, PhD Research and Professional Experience: 4.5 years Professional Appointments: Assistant Professor in Banasthali Vidyapith Publications from the Last 3 Years: 4 research papers and 6 book chapters.

Water Treatment Methods for Detoxification of Metal Ions Dinesh Kumar Affiliation: Central University of Gujarat, Gandhinagar 382030 Education: MSc, PhD Research and Professional Experience: 17 years Professional Appointments: Associate Professor Publications from the Last 3 Years: 25

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In: Drinking Water Editor: Cécile Marcil

ISBN: 978-1-53618-070-1 © 2020 Nova Science Publishers, Inc.

Chapter 3

A RAPID, NANOPOROUS ZEOLITE BASED APPROACH FOR REMOVAL OF BIOCHANIN A IN POTABLE WATER DESTINED FOR DISTRIBUTION Pawandeep Singh1, Vivek Sharma2 and Moushumi Ghosh1,* 1

Department of Biotechnology, Thapar Institute of Engineering and Technology, Patiala, India 2 School of Life and Basic Science, Jaipur National University, Jaipur

ABSTRACT The presence of Endocrine disrupting chemicals or EDCs in water poses a serious threat to human health and several food production systems. Apart from EDCs of synthetic origin, phytoestrogens which are plant derived have received little attention in terms of affordable interventions in potable water destined for distribution. This study reports a simple effective intervention for Biochanin A in influent water using ZSM-5, a Nano porous crystalline zeolite. The adsorbent ZSM-5 was prepared in laboratory and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer– *

Corresponding Author’s E-mail: [email protected].

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Pawandeep Singh, Vivek Sharma and Moushumi Ghosh Emmett–Teller (BET) adsorption and Fourier transform infrared (FTIR) spectroscopy. ZSM-5 was nonporous with a surface area of 653 m2 g-1. The effect of different parameters such as contact time, adsorbent dose and initial solute concentration for removal of Biochanin A by ZSM-5 was evaluated. The equilibrium data for the adsorption of Biochanin A on ZSM-5 was tested in Langmuir and Freundlich adsorption models. Results indicated that Langmuir isotherm model fitted well to equilibrium data in contrast to Freundlich isotherm model. Complete removal of Biochanin A using ZSM-5 in water indicated the possibility of application in drinking water.

Keywords: phytoestrogens, ZSM-5, removal, drinking water, safety, Biochanin A

1. INTRODUCTION The application of appropriate methods for the development, management and use of water resources contributes to availability and safety of water (WHO1989) for sustainable food production (Jime´nez 2005). Intensive agricultural practices and waste disposal systems release a number of contaminants into surface water. Therefore, the quality of influent water prior to conventional treatment for consumption varies in terms of constituents many of which escape usual treatment processes. A number of studies in the past decade have addressed the issue of human exposure and risk of phytoestrogens through water. Regulatory norms for these, however, exist in few countries (e.g., Japan). Besides, the effect of sub lethal consequences for androgenic, estrogenic and anti-androgenic contaminants of these compounds has largely been ignored. Phytoestrogens are naturally occurring plant compounds that are structurally or functionally similar to mammalian estrogens and their active metabolites. Among them lignans, isoflavones, flavonoids and coumestains form a major class (Wang et al., 2002, Patisaul & Jeffron. 2010, Knight & Eden. 1996). Many isoflavones have the ability to inhibit cell proliferation and growth. Moreover it is found that phytoestrogens interfere with organizational role of estrogens in developing brain and reproductive system

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(Crain et al. 2008). Manipulation in estrogen level during critical development phases such as gestation and early infancy leads to adverse health outcomes including malformations in the ovary, uterus, mammary gland and prostate, early puberty, reduced fertility, disrupted brain organization, and reproductive tract cancers (Gorski 1963, Lindzey & Korac1997). Presence of phytoestrogens in lakes and other water bodies have a significant effect of skewed sex ratio in fishes resulting gross decline in productivity. To date several reports have clearly indicated the potential loss of fish productivity upon exposure to phytoestrogens and synthetic endocrine disruptors. It is imperative that apart from other features the presence of phytoestrogens in water used for drinking purposes should be minimal to ensure safety. The occurrence of phytoesterogens in surface water varies widely depending upon their sources. Few strategies however exist or have been advocated for this purpose. Zeolite, a microporous, crystalline solid has a well defined structure of which framework is composed of silicon, Aluminum and oxygen (Ohlin et. al., 2013, Tavolaro & Drioli 1999). Presence of uniform micropores render zeolites unique and responsible of characteristics separating molecules based on their sizes, shape and polarity (Davis M. 2002). Nanocrystalline zeolites have emerged as promising adsorbent materials as they have higher surface areas and reduced diffusion path lengths relative to conventional micrometer-sized zeolites (Song et al. 2004, Lindmark & Hedlund. 2010) and have been used safely for water purification. The application of zeolites especially nanocrystalline zeolites may prove to be useful in rapid removal of phytoestrogens in water destined for distribution. The economy and simplicity for such adsorptive removal using nanozeolites can help enable practicability of this approach to regulate phytoestrogen contents in potable water. The purpose of this study was therefore development and applicability of nanocrystalline zeolites with an aim of removing the phytoesterogen, Biochnain A from potable water. The main parameters considered were contact time, adsorbent dose and initial adsorbate concentration. The data was fitted in various adsorption models to elucidate the adsorption mechanism and a final validation for determining real time removal was attempted. We envisaged that a simple affordable

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process may help assure safety of influent water through removal of phytoestrogens effectively, thereby assuring safety to consumers.

2. METHODS 2.1. Synthesis of Zeolite (ZSM) and Its Characterization The synthesis of nanoporous zeolite ZSM-5 was carried out by the method proposed by Darzi et al. (2013). Tetraethylorthosilicate and Aluminum Isopropoxide were used as a silica and aluminum sources and TPAOH (Tetrapropylammonium hydroxide) was used as structure directing agent (SDA) respectively. In the synthesis reaction, add 0.24 g of aluminum isopropoxide in 17.7 mL solution of TPAOH (1 M) with stirring, followed by successive addition of NaOH (0.0071 g) and double distilled water (22.8 mL). In the above mixture, add 15.87 mL of Tetraethylorthosilicate (TEOS) and stirred at ambient temperature (ca. 25°C) for 24 h. Thereafter, the synthesized gel was stirred under reflux at 100°C for 48 h. The crystals so obtained were centrifuged, washed several times with distilled water and dried at 90°C overnight. The synthesized nano porous zeolite was calcinated in an electrical furnace at 550°C for 5 h to remove of organic template. Crystal size and crystalline phase purity (Gursesa et al. 2006) of the synthesized sample was determined by X-ray powder diffractometer (XPERT-PRO). The XRD pattern for ZSM-5 was recorded by X-ray diffractometer (Xpert Pro MPD, DY3190) at 35.4 kV and 28 mA. The scanning range of 2h was set between 2° and 60° with a scan rate of 0.05 degree/second. Energy Dispersive X ray spectroscopy (EDX) were recorded on INCAx- act (Oxford instruments) and employed to study the elemental composition of nano crystals. Fourier transform infrared spectroscopy was recorded at room temperature using FT-IR spectrometer (Aligent resolution Pro, Cary 660). Scanning electron microscope (JEOL JSM-6100) was employed to study the size and morphology of obtained nano porous crystals (Harlick & Tezel. 2003); the specific surface area of ZSM-5 was determined by Nitrogen adsorption-desorption isotherm (BET-Brunauer-Emmett-

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Teller) analysis (Kaur, 2015). Analysis of Biochanin A following adsorption studies was performed by UV-VIS spectrophotometer (Shimadzu UV1800).

2.2. Coating of ZSM-5 on PVDF Membrane ZSM-5 corresponding to concentrations ranging from 0.01 - 0.6 g/L were weighed and added in 5 mM phosphate buffer having pH 7.4. This suspension was ultrasonicated for 30 min. PVDF (Polyvinylidene fluoride) filter was then placed in filter assembly connected with vacuum pump(Millipore, model no X15522050) and suspension was passed through the filter assembly for three times. The coated filter membranes were placed in an oven preset at 80ºC for 1.5 hours.

2.3. Adsorption Studies Adsorption studies were carried out using zeolite coated membrane filter. Different concentrations of Biochanin A (20, 40, 60, 80, 100 µg/L) and ZSM-5 (0.01, 0.05, 0.1, 0.2, 0.4, 0.6 g/L) was used for adsorption studies. The standard solution of Biochanin A was passed through zeolite coated membrane filter and at different time intervals residual concentration of Biochanin A was determined with a 1.0 cm light path quartz cells using UV-VIS spectrophotometer at a maximum wavelength of 258 nm. All experiments were performed in duplicates, and only the mean values are reported. The maximum deviation observed was less than 5%. The removal efficiency of BiochaninA was calculated according to the following equation: %R = C0-CF × 100 C0

(1)

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Where C0 and CF (micrograms per liter) are the initial and final concentration of element, respectively. The adsorption capacity qe after equilibrium (micrograms per gram) was calculated by the following mass balance relationship: qe = (C0-Ce) × V W

(2)

Where, Co and Ce (micrograms per liter) are the initial and equilibrium liquid–solid phase concentrations of element, respectively, V is the volume of the solution (milliliters) and W is the mass of adsorbate (grams). The sorption data for optimized contact time and Biochanin A concentration was fitted to isotherm equation using MATLAB (Foo & Hameed. 2010). The goodness of fit was determined based on coefficient of determination (R2) and rigorous error functions (Ho. 2004).

Figure 1. XRD pattern of nanoporous ZSM-5.

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3. RESULTS AND DISCUSSION 3.1. Characterization of ZSM-5 and Membrane Coated ZSM-5 The XRD pattern of powdered ZSM -5 is depicted in Figure 1. The peaks observed at 20 = 7.9°, 8.9°, 23.2°, 24.5° indicates the purity of ZSM-5 nanoporous zeolite obtained in comparison to references obtained from the literature (Darji et al. 2013). Field Emission Scanning Electron Microscope (FE-SEM) images of ZSM-5 nanoporous zeolite (Figure 2) indicated the formation of spherical nano sized particles of average diameter of less than 100 nm. Figure 3 depicts the FT-IR spectra of synthesized ZSM-5. The formation of SiO4 tetrahedron units were confirmed from the bands located at 790, 1080-1200 cm-1 characteristic of SiO4 (Darji et al. 2013). The external asymmetric stretching vibration near 1,219 cm-1 may be attributed to the presence of structures containing four chains of four-member rings of zeolite structure. The band near 833 cm-1 is assigned to the symmetric stretching of external linkages and the one near 542 cm-1 is attributed to a structuresensitive vibration caused by the double four-member rings of the external linkages (Li & Armor. 2012).

Figure 2. Fe-SEM images of nanoporous ZSM-5.

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Figure 3. FTIR spectra of nanoporous ZSM-5.

Energy-dispersive X-ray spectroscopy (EDX) technique provides useful information about the presence of elements and their composition in the synthesized zeolites. The EDX spectrum of ZSM-5 nanoporous zeolite is illustrated in Figure 4. The elemental distribution comprises maximal proportions of oxygen; aluminum and silicon are in the synthesized ZSM-5 (Table 1), the silicon rich nature, it is evident from the above data that silicon contributes 45.03% by weight. Moreover aluminum and oxygen are also present in ZSM-5 in line with those reported by Darzi et al. (2013). The Scanning Electron Micrographs (Figure 5) depicts formation of few zeolite layers over the surface of surface of membrane and a homogenous distribution of ZSM-5 layers on membrane surface. The N2 adsorption/desorption isotherms at 77 K and pore sizes distribution of ZSM5 (results not shown) indicated characteristics of nano porous material. The specific surface area was found to be 653m2 g-1. A high surface area has been suggested to be an important parameter for effective adsorption. Table 1. Elemental composition of synthesized ZSM-5 Elements Oxygen Aluminium Silicon Total

Weight percentage 53.79 1.00 45.03 100.00

Atomic percentage 67.29 0.74 31.97 100.00

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Figure 4. EDX spectra of nanoporous ZSM-5.

Figure 5. Scanning Electron Microscope (SEM) images of uncoated membrane (a) and ZSM-5 coated membrane.

3.2. Adsorption Studies 3.2.1. Effect of Initial Concentration and Time on Biochanin A Removal Effect of initial concentrations on Biochanin A removal by ZSM-5 coated filter membrane was studied using different concentration ranging from 20µg/L to 100µg/L and adsorbent dose 0.6 g/L. The removal of different concentration of Biochanin A increased with time and attained maximum value at about 20 min, thereafter the values

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remained constant (Figure 6). At lower initial concentration of 20µg/L almost 50% removal was observed in first 5 min in contrast to 40% removal at the concentration of 100 µg/L. Thus, Biochanin A removal was dependent on contact time and its initial concentrations. Table 4 depicts the adsorption kinetics of Biochanin A; during the early stages of adsorption, the rapid removal of Biochanin A was observed which, in turn, attains constant value for longer contact time with negligible effect on the rate of adsorption of Biochanin A (Zhang & Wang. 2015). Hence, the equilibrium time of 20mins was used for Biochanin A removal on ZSM-5 coated membrane. Iryani et al. (2017) reported a similar observation during adsorption of Congo Red dye using ZSM-5. An increase in adsorption rate was observed during the first stage which slows down with the approach of equilibrium stage Equilibrium sorption time depends upon several parameters include agitation rate in liquid phase, physical properties of the adsorbent such as surface charge density, porosity and surface area, amount of adsorbent, properties of the adsorbate to be removed, initial concentration of adsorbate and the presence of other molecules that may compete with the adsorbate molecule of interest for the active sites (Say et al. 2003). The mechanism of solute transfer to the solid includes diffusion through the fluid film around the adsorbent particle and diffusion through the pores to the internal adsorption sites. In the initial stages of Biochanin A adsorption, the concentration gradient between the film and the available pore sites is large, resulting in faster rate of adsorption. However, in later stages of Biochanin A removal, rate of adsorption decreases due to slow pore diffusion of solute in the bulk of adsorbent. At low concentration, the ratio of available surface to the initial Biochanin A concentration is larger, so the removal observed is greater in comparison to higher concentrations, where the available surface area to initial Biochanin A ratio is low; this explains the reason for lower Biochanin A removal. Few studies have carried out adsorptive removal of Biochanin A and Table 3 summarizes the maximum efficiency of adsorbents reported. In comparison to activated carbon which shows good removal efficiencies, ZSM-5 does not require prior activation and therefore can be a better option.

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Figure 6. Effect of contact time and initial Biochanin A concentration on adsorption by ZSM-5 coated membrane filters.

Table 2. Isotherm parameters of Langmuir and Freundlich isotherm models for Biochanin A adsorption onto ZSM-5 coated membrane Name Langmuir

Equation qe = QmKaCe/1 + KaCe

Freundlich

qe = KfCe1/n

Constant Qm = 95.38 Ka = 0.09073 Kf = 0.06317 N = 0.02275

R-square 0.9931 0.7841

Table 3. Comparison of maximum adsorptive capacities of Biochanin A (qe) of various reported adsorbates Qe (mg/g) reported for Biochanin A adsorption 6.54

Adsorbate

Reference

Granular Activated carbon

0.04

Biopolymer from starch degrading bacterial isolate from the environment Na A zeolite ZSM-5 nanozeolite

Kaur, K (2015) Adsorptive Removal and regeneration study of Biochanin A. MSc thesis, ThaparUniversity, Patiala, INDIA Sehgal, S (2013) Surface Assimilation of phytoesterogens by microbial polymers. MSc thesis, Thapar University, Patiala, INDIA Goyal et al. (2015) Current study

2.20 5.80

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3.2.2. Effect of Adsorbent Dose, Initial Concentration, pH and Temperature on Biochanin A Removal The influence of adsorbent amount varying from 0.01- 0.6 g/L onto the Biochanin A adsorption at different initial concentration (20µg/L to 100µg/L) is depicted in Figure 7. As observed from the figure, the Biochanin A removal at lower initial concentration reaches almost 70% as dose increased from 0.01 to 0.6 g/L. With increase in initial concentrations from 20µg/L to 100µg/L the removal percentage decreases from 70 to 50%. This decrease in Biochanin A removal can be explained by the fact that adsorbent molecules i.e., ZSM 5 posess a limited number of active sites, which is saturated above a certain concentration (Sharoff & Vaidya. 2011). Increase of the initial Biochanin A concentration results in a decrease in the initial rate of external diffusion and increase in the intra particle diffusion. The increase in Biochanin A removal with the adsorbent dose can be attributed to increased surface area and the sorption sites. A pH of 6 was found to be most favorable for maximal adsorption since higher concentrations resulted in insignificant adsorption. This can be explained by considering that an increase in pH over 6, leads to higher pHPZC(point of zero charge) on the adsorbent i.e., net negative charge; since Biochanin A has the same charge, adsorption is not favored. A temperature of 25°C was noted for maximal adsorption of Biochanin A. Increasing temperature decreased the adsorptive capacity. The adsorption spectra characterized by pi-pi *transition exhibits a red shift and a total adsorption intensity with decreasing temperature when hydrogen bonds are formed between solute and solvent molecules (Mitsuo, 1960) and explains the observations. These results were similar to those reported by Aziz et. al., (2017) where ZSM -5 was effectively used to adsorb VOCs. 3.2.3. Adsorption Isotherms Different adsorption mechanisms and interactions between adsorbent and adsorbate molecules are described using adsorption isotherm (Gupta & Kundu, 2006). The authors reported that the distribution of adsorbed molecules between solid and liquid phase occurred when the adsorption process reaches equilibrium state. Equilibrium studies are useful to obtain

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the adsorption capacity of ZSM-5 for Biochanin A removal. The equilibrium data for the adsorption of Biochanin A using ZSM-5 fit into various isotherm models which results in a suitable model that describes the interaction between adsorbent and adsorbate molecules and adsorption mechanism. In the present study, two equilibrium models were analyzed to investigate the most appropriate adsorption isotherm for Biochanin A removal using ZSM-5. Langmuir Isotherm The Langmuir equation is based on the assumption that maximum adsorption corresponds to a saturated monolayer of solute on specific homogenous sites of the adsorbent surface containing a finite number of identical sites. The energy of the adsorption is constant, and there is no transmigration of the adsorbate in the plane of the surface (Dada et. al., 2012). The non-linear equation of Langmuir isotherm model can be expressed in the following non-linear form: qe= QmKaCe/1 + KaCe

(3)

Figure 7. Effect of initial Biochanin A concentration and adsorbent dose on Biochanin A removal percentage.

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Where qe = amount of Biochanin A adsorbed per gram of adsorbent at equilibrium, Qm = maximum monolayer coverage capacity (µg/g), Ka = Langmuir isotherm constant, Ce = equilibrium concentration of adsorbate (µg/L). The results obtained from Langmuir isotherm are shown in Table 2. The high value of correlation coefficient i.e., R2 = 0.9931 indicate the best fitted model for this equilibrium data. This high value indicates a good agreement between isotherm parameters and experimental values confirms the monolayer adsorption of Biochanin A onto ZSM-5 surface shows the homogenous nature of ZSM-5 coated membrane i.e., each molecule of ZSM5 has equal adsorption activation energy. The essential characteristics of Langmuir isotherm and adsorption favorability can be expressed in terms of dimensionless constant called the separation factor or equilibrium parameter (RL), which is defined by the following equation (Kadirvelu et al. 2001): RL = 1/1 + KaCo

(4)

Where Ka is the Langmuir constant and Co is the initial concentration of Biochanin A with different concentration as mentioned from (20–100 µg/L). The value of RL is found in the range of (0.099 – 0.355) i.e., (0 < RL < 1) which confirms the favorable adsorption process for Biochanin A removal using ZSM 5 coated membrane under conditions used in this study. Freundlich Isotherm This isotherm is commonly used to describe the non-ideal and reversible adsorption which is not restricted to the formation of monolayer. The empirical model is applied for multilayer adsorption, with non-uniform distribution of adsorption heat and affinities over heterogeneous surface (Foo & Hameed, 2010). The non linear equation proposed by Freundlich is as follows: qe = KfCe1/n

(5)

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Figure 8. Langmuir and Freundlich isotherm models fitted in experimental adsorption data.

Where Kf = Freundlich isotherm constant (µg/g), 1/n = adsorption intensity, Ce = equilibrium concentration of adsorbate (µg/L), qe = amount of Biochanin A absorbed per gram of adsorbent at equilibrium. The constant “n” gives an indication of how favorable the adsorption processes are. The slope 1/n is a measure of adsorption intensity or surface heterogeneity that represents the deviation from linearity of adsorption as follows: if the value of 1/n = 1, the adsorption is linear, 1/n < 1, the adsorption process is chemical, if 1/n > 1, the adsorption is a favorable physical process and adsorption is cooperative (Crini et al. 2007). The results obtained from Freundlich isotherm are shown in Figure 8. The correlation coefficient, R2 = 0.7841, for Freundlich model shows that experimental data does not fit in this isotherm in comparison to Langmuir adsorption model. In real time surface water, significant (removal of Biochanin A was observed with 0.6g/L of ZSM-5 (Table 5). These results indicated that apart from effectively removing Biochanin A, interfering substances had possibly little effect on the process itself and therefore can be applied practically. The adsorption kinetics studied by evaluating the pseudo first-order and second-order adsorption rate models indicated that the pseudo second order model could describe the process better (results not

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shown). The adsorptive process was also endothermic. Similar results have been indicated by Goyal et al., (2016). Overall, the ZSM-5 synthesized in the present study could remove Biochanin A effectively from water destined for supply. We are currently evaluating the possibility of Vitellogenin as a biomarker for evaluating EDC levels especially in surface water at various locations, to study phytoestrogen impacted water. This should afford a possibility of application of ZSM-5 and subsequent monitoring to ensure safety of water as an additional treatment in influent water mandated for public distribution. Table 4. Effect of contact time on removal of Biochanin A by ZSM-5 Time (minutes) 0 5 10 15 20 25 30 40 50 60 70

Biochanin A removal (%) 0 50% 55% 58% 60% 63 66% 68% 69.5% 70% 75.2%

Table 5. Removal of Biochanin A from randomly sampled influent water (6 domestic water treatment locations) with ZSM-5 coated membrane. ZSM-5 was used at a dosage of 0.6g/L. ND = below detection threshold. Figures in parenthesis indicate mean + S.D (n = 3) Concentration of Biochanin A (µg/mL) in six randomly smpled water samples. 30 12 20 6 19 22

Residual concentration of Biochanin A (µg/mL) after ZSM-5 filtration 1.3 ± 0.02 ND 1.2 ± 0.04 ND ND ND

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CONCLUSION Overall, in this study Biochanin A, a prevalent phytoestrogen in influent water mandated for treatment and distribution could be effectively removed using nanoporous zeolite ZSM-5 synthesized in this study. Levels of phytoestrogens are usually not analyzed in either influent water or finished water. In view of the large variability of surface water especially in India, the phytoestrogen contamination of influent water from various sources (occurring from agricultural operations, wood processing industries, soya industries and others) assumes relevance. The removal of Biochanin A was a function of on the quantity of adsorbent, time and initial concentration of adsorbate. The removal of Biochanin A increased with time and maximum value of 70% at about 20 min at ambient temperature. Furthermore, almost 70% removal of Biochanin A occurred at lower initial concentration (20 µg/L) as the dose increased from 0.01 to 0.6 g/L. The equilibrium adsorption data were tested using Langmuir and Freundlich Isotherm model and data fitted well in Langmuir isotherm model which indicates the monolayer adsorption of Biochanin A onto ZSM-5 coated filter membrane. Given the actual concentration of Biochanin A as observed from analysis of surface water samples (Table 3), a near complete removal can be expected (within the MOE or Margin for exposure set forth for endocrine disruptors in drinking water, USEPA) prior to supply . Therefore safety of influent water following treatment resulting from potential estrogenic activities of Biochanin A is evident. In addition, the applicability of this method for water reuse especially for aquaculture and other purposes should also be possible.

ACKNOWLEDGMENTS The authors wish to acknowledge CSIR, Govt of India, for funding a part of this work.

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REFERENCES Aziz, A., Kim, M., Kim, S. & Kim, K. S. (2017). Adsorption and Kinetic Studies of Volatile Organic Compounds (VOCs) on Seed Assisted Template Free ZSM-5 Zeolite in Air Journal of Nanotechnology & Advanced Materials, 5(1), 1-9. Crain, D. A., Janssen, S. J., Edwards, T. M., Heindel, J., Ho, S. M., Hunt, P., Iguchi, T., Juul, A., McLachlan, J. A., Schwartz, J., Skakkebaek, N., Soto, A. M., Swan, S., Walker, C., Woodruff, T. K., Woodruff, T. J., Giudice, L. C. & Guillette, L. J. Jr. (2008). Female reproductive disorders: the roles of endocrine-disrupting compounds and developmental timing. Fertility and Sterility., 90, 911–940. Crini, G., Peindy, H. N. F., Gimbert, F. & Robert, C. (2007). Removal of Basic Green (Malachite Green) from aqueous solutions by adsorption using cyclodextrin-based adsorbent: kinetic and equilibrium studies. Separation and Purification Technology, 53, 97–110. Dada, A. O., Olalekin, A. P., Olatunya, A. M. & Dada, O. (2012). Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm studies of equilibrium sorption of Zn2+ up to phosphoric acids modified rice husk. IOSR journal of Applied Chemistry, 3, 38-45. Darzi, S. K. H. N., Maybodi, A. S. & Ghobakhluo, M. (2013). Synthesis and characterization of modified ZSM-5 nanozeolite and their applications in adsorption of Acridine Orange dye from aqueous solution. Journal of Porous Materials, 20, 909–916. Davis, M. Ordered porous materials for emerging applications. Nature 417, 813–821 (2002). Foo, K. Y. & Hameed, B. H. (2010). Insights into the modeling of adsorption isotherm systems. Chemical Engineering Journal., 156, 2-10. Gorski, R. A. (1963). Modification of ovulatory mechanisms by postnatal administration of estrogen to the rat. Journal of physiology., 205, 842– 844. Gursesa, A., Dogarc, C., Yalcina, M., Acikyildiza, M., Bayraka, R. & Karacab, S. (2006). The adsorption kinetics of the cationic dye, methylene blue, onto clay. Journal of hazardous material, 131, 217-228.

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Harlick, P. J. E. & Tezel, F. H. (2003). Adsorption of Carbon Dioxide, Methane and Nitrogen: Pure and Binary Mixture Adsorption for ZSM5 with SiO2/Al2O3 Ratio of 280. Separation and Purification Technology, 33, 199−210. Ho, Y. S. (2004). Selection of optimum sorption isotherm. Carbon, 42, 2115–2116. Iryani, A., Ilmi, M. & Hartanto, D. (2017). Adsorption study of Congo Red Dye With ZSM-5 directly synthesized from bangka kaolin without organic template Malyasian Journal of Fundamental and Applied Sciences, 13(4), 832-839. Knight, D. C. & Eden, J. A. (1996). A review of the clinical effects of phytoestrogens. Obstetrics and Gynecology, 87, 897-904. Kundu, S. & Gupta, A. K. (2006). Arsenic adsorption onto iron oxide-coated cement (IOCC): regression analysis of equilibrium data with several isotherm models and their optimization, Chemical Engineering Journal, 122, 93–106. Li, Y. & Armor, J. N. (2012). Nano-crystalline sieves: potential applications. Applied Catalysis B., 2, 239. Lindmark, J. & Hedlund, J. (2010). Modification of MFI Membranes with Amine Groups for Enhanced CO2 Selectivity. Journal of Material chemistry, 20, 2219−2225. Lindzey, J. & Korach, K. S. (1997). Developmental and physiological effects of estrogen receptor gene disruption in mice. Trends in Endocrinology and Metabolism, 8, 137–145. Ohlin, L. Bazin, P. Thibault, S. K. Hedlund, J. Grahn, M. Adsorption of CO2, CH4, and H2O in Zeolite ZSM-5 Studied Using In Situ ATRFTIR Spectroscopy. The Journal of Physical Chemistry C, 117(33), 16972-16982. Patisaul, H. B. & Jefferson, W. (2010). The pros and cons of phytoestrogens. Frontiers in neuroendocrinology, 4(31), 400-419. Say, R., Yilmaz, N. & Denizli, A. (2003). Biosorption of cadmium, lead, mercury, and arsenic ions by the fungus Penicillium purpurogenum. Separation and Purification Technology, 38(9), 2039–2053.

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Song, W., Justice, R. E., Jones, C. A., Grassian, V. H. & Larsen, S. C. (2004). Synthesis, Characterization, and Adsorption Properties of Nanocrystalline ZSM-5. Langmuir, 20, 8301-8306. Tavolaro, A. & Drioli, E. (1999). Zeolite Membranes. Advanced Materials., 11, 975−996. Wang, C. C., Prasain, J. K. & Barnes, S. (2002). Review of the methods used in the determination of phytoestrogens. Journal of Chromatography B, 777, 3-28. Zhang, X. & Wang, X. (2015). Adsorption and Desorption of Nickel (II) Ions from Aqueous Solution by a Lignocellulose/Montmorillonite Nanocomposite. Plos one, 2 (10), doi:10.1371/journal.pone.0117077.

In: Drinking Water Editor: Cécile Marcil

ISBN: 978-1-53618-070-1 © 2020 Nova Science Publishers, Inc.

Chapter 4

THE ROLE OF SPHINGOMONAS PAUCIMOBILIS IN INTERGENERIC CO-AGGREGATION AND MIXED BIOFILM FORMATION WITH WATER BORNE PATHOGENIC BACTERIA IN THE DISTRIBUTED DRINKING WATER SYSTEM: IMPLICATIONS OF PUBLIC HEALTH RISK Parul Gulati and Moushumi Ghosh* Department of Biotechnology, Thapar Institute of Engineering and Technology, Patiala, India

ABSTRACT Sphingomonas a resident microorganism, is often encountered in the drinking water systems (DWDS). Its capability of growth over a range of temperatures, tolerance to chlorination and antimicrobial resistance patterns have recently raised health concerns. Several physiological aspects, for instance role of co-aggregation and biofilm formation *

Corresponding Author’s E-mail: [email protected].

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Parul Gulati and Moushumi Ghosh especially with water borne pathogens by Sphingomonas remains largely unknown and deserve attention. In this study, a Sphingomonas paucimobilis strain isolated from Indian drinking water system was evaluated for its ability to co-aggregate and form mixed biofilms with Salmonella typhimurium, Shigella flexneri, Escherichia coli O57:H7. Strong co-aggregation of Sphingomonas with the waterborne pathogens Escherichia coli O157:H7 ATCC 32150, Shigella flexneri 2a and Salmonella typhimurium ATCC 25315 was observed by qualitative and quantitative methods with individual pathogens as well with a cocktail of the above three water borne pathogens. Highest aggregation index was observed with Shigella flexneri 2a followed by Salmonella typhimurium and Escherichia coli O157:H7. The aggregation with Escherichia coli O157:H7 could not be reversed by heat, protease and sugars (lactose and galactose). The results of this study have a strong implication on risk of mixed biofilms of these water borne pathogens in DWDS which may have re-grown or introduced (either through leakage or faulty treatment processes) and eventually develop into biofilms with pre existing Sphingomonas. An effective, non invasive treatment strategy preferably aimed in disrupting signalling molecules of Sphingomonas may be of value, for assuring safety of drinking water.

Keywords: co-aggregation, adhesin, biofilms, sphingomonas, protease

INTRODUCTION The microbial ecology of water distribution systems has been an area of continued research, driven by the necessity to design innovative and effective control strategies for ensuring safe and high-quality drinking water. Existing results of microbial ecology of drinking water distribution systems indicate that pathogen resistance is greatly affected by the biodiversity of community and interspecies relationships. Biofilms have assumed considerable significance in this regard and biofilm formation and adhesion of bacteria on different surfaces and the EPS production by biofilm forming microbes have been well studied in general (Flemming et al., 2007; Furuhata et al., 2008; Simoes et al., 2007a; Skillman et al., 1998; Tsuneda et al., 2003). Sphingomonas has been a recent focus for study on account of its ubiquitous presence in water, persistence under low nutrient conditions and potentially pathogenic features highlighting the concern in the presence of these

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bacteria in drinking water distribution system. The biological safety issues which are caused by Sphingomonas in the distribution systems stem from their persistence and ability to secrete exopolysaccharides as major components of biofilm (Johnsen et al., 2000). Bereschenko et al. (2010) demonstrated that Sphingomonads were responsible for initial biofilm formation. Aggregation has been established as one of the essential steps towards biofilm formation and it depends on a range of interactions such as synergistic, antagonistic, mutualistic, competitive, and commensalism interactions (Simoes et al., 2007b). Bacterial co-aggregation is essential for the development of multispecies biofilm communities’ i.e., the adherence of different bacterial species to each other. Furthermore, co-aggregation is a significant phenomenon that facilitates interaction among different bacterial species in the biofilm (Foster et al., 2004; Rickard et al., 2003a). The interactions may occur between protein adhesins and polysaccharide receptors (Kline et al. 2009; Kolenbrander et al., 2006) or between proteinaceous adhesin-receptors (Daep et al., 2008). Therefore coaggregation of Sphingomonas with waterborne pathogens may assume significance in view of development of multispecies biofilms of potential concern. Few studies, however have systematically analyzed aggregation, co-aggregation and biofilm formation by Sphingomonas sp. isolated from drinking water (Buswell et al., 1997; Simoes et al., 2007a,b; Simoes et al., 2008; Yu et al., 2010) In an earlier study, we isolated a Sphingomonas sp. from public drinking water system and characterized its biofilm formation (Gulati and Ghosh, 2017); simulation studies indicated that this strain was able to form biofilms on various plumbing materials used in drinking water systems. The objective of the present study was to further characterize the aggregation and co-aggregation behavior with water borne pathogens of this Sphingomonas strain. We envisaged that investigations of these interactions will help shed light on the role of Sphingomonas in formation of mixed species biofilms and enable designing of effective treatment strategies for safe drinking water.

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MATERIAL AND METHODS Bacterial Strains and Culture Conditions Drinking water samples were collected from twenty different municipal sites and one hundred and forty isolates were screened by growing on Sphingomonas- specific growth medium (Yim et al., 2010) at 30ºC and 120 rpm for 24 hours. One isolate with demonstrable biofilm forming ability was selected for further studies. 16S sequence of the isolate was submitted in genbank database as Sphingomonas paucimobilis strain MG6. The standard strain of Sphingomonas terrae MTCC 7766 was used in parallel for the sake of comparison. The following water borne pathogens were used in coaggregation studies: Escherichia coli O157:H7 ATCC 32150, Shigella flexneri 2a and Salmonella typhimurium ATCC 25315. Prior to experiments, cultures were revived, grown on BHI agar thrice, individual colonies were inoculated in BHI (Brain Heart Infusion Broth, Himedia, India) broth and processed as described above.

Mixed Biofilm Profile by S. Paucimobilis MG6 The mixed biofilm of S. paucimobilis MG6 and S. terrae 7766 with water borne pathogens was formed by Crystal violet assay with modifications of Merritt et al. (2005). Standardized suspension of mid-log phase bacterial cultures were dispensed in each well of the polystyrene plates and incubated at 30°C. The unbound cells were removed by inverting the micro titer plate and vigorous tapping followed by rinsing the wells with phosphate buffer (pH 7.2). The adherent cells were stained with 200µl of 1% (w/v) crystal violet solution for 5 minutes. The wells were washed with deionized water extensively and the plates were allowed to dry. Following washing, 200µl of 30% (v/v) acetic acid was added to each well for 15 minutes; 100µl aliquots were then transferred to fresh micro titer plate and the absorbance measured at 585 nm. The variation from control S. paucimobilis MG6 was further confirmed by SEM.

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Aggregation Assay Both S. terrae MTCC 7766 and S. paucimobilis MG6 were further explored for their aggregation property. Fifty ml of the strains were harvested in their growth phases at 7000 *g for 5 minutes at 4ºC. After washing it twice in Phosphate Buffered Saline (PBS), the cells were resuspended in PBS and OD600 was adjusted to 1.0. The adjusted stock was used for aggregation analysis.

Visual Aggregation Assay The degree of auto- and co-aggregation was determined qualitatively by the scoring method of Cisar et al. (1979). To determine auto aggregation, both the strains were transferred to different test tubes, while in the case of co-aggregation, the cultures were mixed in pairs with each of the three pathogen, i.e., Escherichia coli O157:H7 ATCC 32150, Salmonella typhimurium ATCC 25315 and Shigella flexneri 2a. The pure and mixed cultures in pairs were vortexed for 30 sec and incubated at room temperature for 72 hours. The scoring range used is as follows: 0 represents no aggregation and turbid suspension; 1 represents small uniform aggregates in a turbid suspension; 2- easily visible aggregates in a turbid suspension; 3 clearly visible aggregates which settles leaving a clear supernatant; 4 - large flocs of aggregates that settle instantaneously (Cisar et al. 1979; Simoes et al. 2008).

Spectrophotometric Assay In order to quantitatively determine aggregation, test cultures in triplicates were prepared as described above for auto- and co-aggregation and incubated at room temperature. One hundred microlitre of the aqueous phase was transferred to microtitre plate and absorbance was recorded at 0,

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2, 4, 24, 48 and 72 hours. Percentage of aggregation was measured using the following formula: Percentage of Aggregation = [(A600 initial - A600 after incubation)/ A600 initial] *100

Aggregation Studies by Fluorescence Microscopy Cell aggregates were fixed in 10 ml of a 1% paraformaldehyde solution in 1X PBS for 2 hours at room temperature. The aggregates were mounted on a sterile glass slide and allowed to dry. Stained the slides with DAPI (4’,6’-Diamidino-2-phenylindole) and observed under epifluorescence microscope (Zeiss Axio Scope A1 Microscope, USA).

Coaggregation Reversal: Effect of Heat, Protease and Sugars To study the effect of heat treatment on the aggregation ability of Sphingomonas and the waterborne pathogens, both treated and untreated auto- and co-aggregating bacterial pairs were used for visual and spectrophotometric analysis. The bacterial cultures were incubated at 85ºC for 30 minutes for describing co-aggregation reversal by heat treatment (Kolenbrander et al., 1985). The method described by Rickard et al. (2003b) and Simoes et al. (2008) was used to understand the protease sensitivity of the aggregation. The protease type XVI from Streptomyces griseus (Himedia, India) was added at the final concentration of 2mg ml-1 and incubated at 30°C for 2 hours. After incubation, cells were harvested, washed twice and O.D. was adjusted to 1.0 at 600 nm. The untreated and treated strains were mixed in equal ratios. The experiment was carried out in triplicates (Ramalinganam et al. 2013). To study the effect of sugars on aggregation, filter-sterilized solutions of lactose and galactose were added to coaggregating partners to final concentrations of 50 mM to study the

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effect of sugars. Mixtures were vortexed and tested for coaggregation using the method of Rickard et al. (2003a).

RESULTS Mixed Biofilm Profile by Sphingomonas The sequence of the isolate has been deposited in GenBank database (Accession No KX594380). Both biomass quantity and microbial activity are the parameters mostly used to estimate the amount of biofilm (Characklis et al., 1990). The Crystal violet assay has been described as a rapid method for calculating cell biomass; maximum biofilm production occurred between 24 to 48 hours as the cells are in the late stationary phase before senescence phase starts. Cells in the stationary phase start synthesizing the EPS which facilitates the attachment of cells to the surface (Dunne 2002). Mixed biofilms (S. paucimobilis MG6/S. terrae 7766 + E. coli, S. flexneri 2a and S. typhimurium) exhibited variation than that observed in the controls and reached maturation with 65-70 hours by the kinetics (Figure 1). Scanning electron microscopy (SEM) was used to visualize the cell-surface of biofilm forming Sphingomonas with adhered pathogens on PVC coupons. Tight adherence of the biofilm cells with PVC was observed for S. paucimobilis with the cells being enmeshed in exopolysaccharides (Figure 2). Though S. terrae produced less exopolysaccharides, adherence was observed on PVC. The results suggested stable attachment of pathogen-S. paucimobilis bifilm on PVC matrix.

Visual Aggregation Assay Based on the scoring method, results of auto- and co-aggregation were analyzed. No aggregation of pure cultures as well as combinations after zero hour of incubation was observed. Hence the cultures were further incubated at room temperature. Aggregation was visible as turbid suspension after 24

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hours and clear supernatant with clear aggregates after 72 hours (Figure 3). Based on the visual observation, scores were provided following the scoring range used in literature (Cisar et al., 1979; Simoes et al., 2008).

Spectrophotometric Analysis The incubation time is an important requisite for determining the aggregation index of auto-aggregating bacteria as well as co-aggregating bacterial pairs as reported by Saravan et al. (2014). Therefore the aggregation index was determined for all the cases at 0, 2, 4, 24, 48 and 72 hours. Aggregation indices of S. terrae MTCC 7766 and S. paucimobilis MG6 were calculated to be 74.5% and 82.75% respectively after 72 hours of incubation (Figure 4). Aggregation index of Sphingomonas with Shigella flexneri 2a was found to be approx. 84.8% -highest when compared to other pathogens. 1.5

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A A+C+D+E B B+C+D+E Figure 2. Scanning electron Micrographs of mixed biofilms of (a) S. paucimobilis MG6 (b) S. terrae 7766, Figure Scanning electronisolate; Micrographs of mixed biofilms of (a) 7766; S. paucimobilis where,2.A=Sphingomonas B=Sphingomonas terrae MTCC C= Salmonella typhimurium ATCC MG6 (b) S. terrae 7766, where, A=Sphingomonas isolate; B=Sphingomonas terraebiofilms were developed 25315; D= Escherichia coli O157:H7 ATCC 32150; E= Shigella flexneri 2a. Mixed MTCC 7766; C= Salmonella typhimurium ATCC 25315; D= Escherichia coli on PVC coupons. O157:H7 ATCC 32150; E= Shigella flexneri 2a. Mixed biofilms were developed on PVC coupons.

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Figure 3. Visual aggregation assay of (a) Sphingomonas paucimobilis strain MG6 (b) Sphingomonas terrae MTCC 7766.

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Visualization of Aggregates by DAPI Direct staining by DAPI (4’,6-diamidino-2-phenylindole) is a method of choice, the DAPI molecules bind to DNA and fluoresce intensely. The enhancement in aggregation ability of S. paucimobilis MG6 in the presence of three pathogens could be clearly depicted by DAPI staining. Furthermore, a cocktail of all three pathogens used to co-aggregate with Sphingomonas indicated a similar result. In fact the aggregating pairs showed a higher level of interactions as compared to the visual aggregation test for these strains when observed by microscopy (Figure 5 and 6).

Nature of Interactions between Bacterial Strains The heat treated and untreated pure cultures did not aggregate either after zero hour of incubation or following 2 hours of incubation. Coaggregation between different combinations was significantly affected (p < 0.05) upon heat treatment with the exception of E.coli O157:H7, since aggregation index remained at 80% in both treated and untreated samples (Figure 7). Several E. coli O157:H7 surface proteins are thought to be important for adhesion and/or biofilm formation, therefore it is possible that the treatment processes failed to exert a substantial effect on binding. Coaggregation reversal by Lactose and galactose was not observed, suggesting possibilities with other sugars. The inhibition of aggregation of Sphingomonas with its aggregating partners might be due to surface protein like attachment (Figure 8s). Sphingomonas with its aggregating partner, E.coli O157:H7 showed no decrease in aggregation index. Treatment with sugars-lactose and galactose failed to revert co-aggregation (Figure 9 & 10)–. The differential behavior observed may be attributed to the enzyme type and concentration (Goldhar, 1995) important for affecting lectins during the treatment process, in addition to the nutritive media which modulates lectin production (GilboaGarber, 1988; Goldhar, 1995). However, further possibility of coaggregation reversal need also be examined with other sugars.

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Figure 8. Aggregation Index observed at different time intervals after protease treatment (a) S. paucimobilis MG6 and its various terrae 7766 and its various combinations combinations (b) S. terrae 7766 and its various combinations.

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DISCUSSION Previous studies have demonstrated that pathogens can be incorporated into heterotrophilic drinking water biofilms enhancing their persistence (Gião et al., 2008, 2009). It has also been suggested that for multi-species biofilms, it is very difficult to determine the positive or negative impact of different sessile microorganisms on pathogens, particularly the associations that occur within biofilms. Bacterial cells can interact within their own type or with other bacterial cells and facilitate the formation of biofilm. Aggregation has been well described for dental plaque isolates in complex media and aquatic species in potable water (Buswell et al., 1997; Kolenbrander and London, 1993; Rickard et al., 2003a). Cell to cell communication is requisite for initial colonization and therefore, biofilm formation. Both, autoaggregation and co-aggregation are significant in the process of communication. Autoaggregation in the biofilm boosts the adherence of genetically identical strains; these interactions are enhanced by increased hydrophobicity (Basson et al., 2008). Whereas, in co-aggregation genetically different bacteria adhere to each other via specific molecules (Rickard et al., 2003b). In the present study, we isolated and identified the Sphingomonas strain from municipal sites. This strain was chlorine resistant and could form biofilm in several plumbing materials commonly used in water distribution pipelines (unpublished observations). Detection of Shigella, Salmonella and E.coli O157:H7 from water samples of the Sphingomonas isolate prompted further exploration of the physiology of interactions of this isolate with water borne pathogenic bacteria. The aggregation, co-aggregation and biofilm formation by both the Sphingomonas sp. were evaluated. To the best of our knowledge, coaggregation of Sphingomonas with E.coli O157:H7, Shigella and Salmonella have not been reported. Our preliminary studies with the Sphingomonas have demonstrated the capability of this strain to produce EPS in line with earlier observations (Ashtaputre and Shah, 1995) and it also determines the immediate conditions of the life of biofilm cell (Flemming et al., 2007) by providing a variable gel matrix.

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Spectrophotometric analysis of aggregates indicated that with the increase in incubation time, percentage of aggregation increased. Also, coaggregation of Sphingomonas with different pathogens was higher as compared to autoaggregation of Sphingomonas. It was observed that coaggregation by bacteria promotes biofilm development by facilitating the attachment to the partner species, indicating the possibility of Sphingomonas to form biofilms with Shigella flexneri (Min and Rickard, 2009). This observation may be explained by the fact that aggregation depend on morphological features of bacteria such as size and density (Cisar et al., 1979) and require adequate incubation time prior to visualization. The results indicated both S. terrae and S. paucimobilis MG6 as floc formers. It was reported that visual aggregation testing is not an authentic method of measuring interactions between aggregating pairs (Buswell et al., 1997). Therefore, use of microscopic methods to investigate the potential aggregation between co-aggregating partners becomes inevitable beyond the screening test of the visual aggregation. DAPI staining was further used to investigate the role played by this bacterium in the co-aggregate formation. Autoaggregation has been proposed to be an important mechanism whereby a bacterial strain within a biofilm expressed polymers to enhance the integration of genetically identical strains. Autoaggregating strains of freshwater bacteria were found to be numerically dominant in freshwater biofilm communities; moreover, autoaggregation together with coaggregation has been shown to enhance the development of freshwater biofilms (Rickard et al., 2003a). Therefore, it was important to further investigate the co-aggregative abilities of Sphingomonas with waterborne pathogens. Previous studies reported that the formation of co-aggregates by bacteria is the result of specific lectin-carbohydrate interactions between aggregating partners (Cisar et al., 1979; Simoes et al., 2008). Protein molecules present on cell surface of one partner behaves like adhesin and the saccharide molecule present on other one behave like receptor (Rickard et al., 2000; Rickard et al., 2003a). The sensitivity of adhesin molecules to heat and protease has been suggested as evidence for presence of lectin-carbohydrate

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interactions occurring between aquatic bacteria as well as pathogens (Rickard et al., 2000; Rickard et al., 2003a). Co-aggregation by Sphingomonas natatoria have been shown to be important in promoting dual species biofims (Rickard et al., 2000) and the importance of surface proteins in mediating co-aggregation and biofilm development has been emphasized. The results of our study suggest the ability of Sphingomonas terrae and Sphingomonas paucimobilis MG6 to show aggregation and co-aggregate three water borne pathogens (albeit with variation) and role of surface proteins/lectins in according the interactions; both strains could form biofilms. The ability to co-aggregate supposedly confers protection of the Sphingomonas cells from directed shear forces and enables them to proceed to a multigeneric biofilm. Overall our results imply that mixed biofilms involving either or more of the pathogens with Sphingomonas could be of public health concern in drinking water distribution system and more effective treatment systems need to be developed in light of these observations.

CONCLUSION The present study demonstrated that Sphingomonas terrae MTCC 7766 and Sphingomonas paucimobilis MG6 isolated from Indian drinking water distribution system possessed abilities to form biofilm, aggregation. Coaggregation was observed with the water borne pathogens: Shigella flelneri, Salmonella typhimurium and E.Coli O157:H7; coaggregation reversal studies involving heat, protease treatment and sugars (lactose and galactose) indicated possibility of surface proteins or lectin to be in mediating the interaction; however conclusive evidence of interaction in case of E.coli O157:H7 could not be obtained. The results of this study provide valuable insights in the physiological behavior of Sphingononas specifically towards waterborne pathogens which could be important when designing interventions for water safety.

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BIOGRAPHICAL SKETCH Moushumi Ghosh Affiliation: Professor & Head, Department of Biotechnology, Thapar Institute of Engineering & Technology (TIET), Patiala, India Education: MSc (Biochemistry), PhD (Biotechnology), Banaras Hindu University, Varanasi, INDIA Research and Professional Experience: Over 16 years of research expertise in fundamental and translational aspects of microbial biopolymers

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and biofilms. Led, as principal investigator more than 10 research projects funded by national agencies (DST, WTI, UGC, CSIR) supervised 5 doctoral students and over 48 masters and M. Tech students. Developed novel microarray based detection methods for water borne bacterial and protozoan pathogens in collaboration with Heriot Watt University and University of Edinburgh, UK as bilateral INDO UKIERI project. Scientific contributions have been documented as policy and science based advocacy for sustainable water resources, in over 145 articles published in peer reviewed international journals, conferences, monographs, press and public media. Professional Appointments:     

  

July, 2019,Coordinator, TIET/TAU CoE for Food Security, Thapar Institute of Engineering & Technology, Patiala February 2017 –present; Head, Department of Biotechnology, Thapar Institute of Engineering & Technology, Patiala July 2015 –till date: Professor, Department of Biotechnology June 2010 – July 2015: Associate Professor, Dept of Biotechnology, Thapar University, Patiala June 2006 – June 2010: Assistant professor, Department of Biotechnology & Environmental Sciences, Thapar University, Patiala Jan 2002 – June 2006: Lecturer, Dept of Biotechnology & Env sciences, Thapar University, Patiala Jan 2001 – December 2002: Postdoctoral Scientist, GSF Research Centre for Environment and Health, Munich, Germany

Honors:  

Science and Technology Award for Research Excellence, EET CRS 2017; 11th June Bangalore. Advisor, Scientific Committee of American Academy of Sciences, Environmental Technology

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Overseas travel grant for scientific exchange, Department of Science & Technology, Govt of India (2016) UKIERI, Department of Science & Technology, Govt of India (2014) Noel Derr Gold medal: Sugar Technologist Association of India (2003) Junior and Senior Research fellowship: Ministry of Food and Civil supplies, Govt of India (1996-1999) GATE, Ministry of Human Resource Development, Govt of India (1996) Performance Excellence Award, TU (2006 -2015) Nominated Member, lifetime: Biotech Research Society of India, Association of Microbiologists of India (AMI), European Federation of Biosciences (FEBS), Organization of Women in Science, (OWSD), Trieste, Italy.

Publications from the Last 3 Years: Ghosh, M. (201). Lychee Juice and Pulp Extracts as Potential Components for Production of Extracellular Phosphate-Binding Biopolymer from Acinetobacter haemolyticus. In Lychee Disease Management, (pp. 181190). Springer Nature, Singapore. Ghosh, M. (2017). Microbial biopolymers as innovative, exploitable ‘green tools’ for sustainable treatment of water. Asia Pacific Technology Monitor, 34(3), 45-51. Gulati, P. & Ghosh, M. (2017). Biofilm forming ability of Sphingomonas paucimobilisSphingomonas paucimobilis isolated from community drinking water systems on plumbing materials used in water distribution. Journal of Water & Health., 15 (6), 942-946. Gulati, P., Singh, P., Chatterjee, A. K. & Ghosh, M. (2016). Monitoring of biofilm ageing in a Sphingomonas sp. strain from public drinking water sites through changes in capacitance. Environmental Technology, 30, 18

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Jain, S. & Ghosh, M. (2019). Effective removal of Bisphenol A from plastic waste leachates by microbial polymer impregnated with activated carbon International Journal of Environmental Science & Technology. DOI: 10.1007/s13762-019-02452-x. Kaur, T. & Ghosh, M. (2017). Characterization and toxicity of a phosphatebinding exobiopolymer produced by Acinetobacter haemolyticus MG606. Journal of Water & Health, 15, 103-111 Khaira, G. K. & Ghosh, M. (2016). Surface Engineered Green Polymers for Enhanced Water Decontamination. Environmental Science & Technology, 1, 143-153. Sharma, V., Kaur, T., Bridle, H. & Ghosh, M. (2017). Antimicrobial efficacy and safety of mucoadhesive exopolymer produced by Acinetobacter haemolyticus. International Journal of Biological Macromolecules, 94, 187-193.

INDEX A

B

activated carbon, 10, 15, 27, 43, 72, 108 activation energy, 76 active site, 5, 11, 72, 74 adhesin, 84, 85, 100 adhesion, 84, 93, 102, 105 adsorption, iv, v, vii, viii, ix, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 38, 41, 42, 43, 44, 48, 49, 51, 52, 54, 56, 57, 64, 65, 66, 67, 68, 70, 71, 72, 73, 74, 75, 76, 77, 79, 80, 81, 82 adsorption isotherms, 17 adsorption technologies, viii, 2 aggregation, ix, 83, 84, 85, 87, 88, 89, 90, 91, 93, 99, 100, 101, 102, 104 agriculture, 45, 51 aluminum oxide, 12, 13 aqueous solutions, 24, 25, 26, 30, 80 arsenic, viii, 2, 14, 19, 24, 31, 34, 37, 38, 43, 44, 48, 51, 81 atmosphere, 8, 21, 38 attachment, 89, 93, 100

bacteria, 3, 42, 45, 84, 90, 99, 100, 102, 103, 104, 105 bacterial cells, 99 bacterial strains, 104 bacterium, 100, 104, 105 bioaccumulation, vii, 1, 38 biochanin A, iv, v, vii, ix, 63, 64, 67, 68, 71, 72, 73, 74, 75, 76, 77, 78, 79 biodegradability, 38 biodiversity, 84 biofilms, iv, vii, ix, 84, 89, 91, 99, 100, 101, 102, 103, 104, 105, 106 biological samples, 28 biomass, 10, 89 biopolymers, 105, 107 Bisphenol A, 108 by-products, 14, 56

C cadmium, 6, 7, 8, 9, 10, 21, 26, 27, 28, 35, 43, 44, 81

110 calcium, 8, 22, 24 carbon, 4, 10, 27, 28, 43, 46, 73 carbon nanotubes, 10, 27, 28, 43 carcinogenic, vii, 1, 2, 49 carcinogenicity, 2 cellulose, 7, 10, 14, 26, 45 cerium, 14, 30, 44 challenges, 34, 39, 53 charge density, 72 chemical, viii, 2, 4, 5, 6, 7, 11, 19, 26, 35, 41, 42, 43, 46, 50, 77 chemical functionalization, 11 chemical interaction, 4, 6, 11, 43 chemical properties, 5 chemisorption, 10 chitosan, 5, 7, 8, 12, 25, 26 chlorination, viii, ix, 2, 83 chromium, viii, 8, 37, 38, 43, 49 co-aggregation, vi, ix, 83, 84, 85, 87, 88, 89, 93, 99, 100, 101 communities, 85, 100, 104 community, 84, 102, 103, 107 composites, 15, 22, 28, 31 composition, 9, 15, 66, 70, 105 compounds, 12, 64, 80 contact time, ix, 4, 8, 9, 18, 64, 65, 68, 72, 73, 78 contaminants, viii, 2, 11, 16, 43, 46, 51, 53, 64 contaminated water, 39 contamination, vii, viii, 1, 15, 25, 37, 38, 42, 52, 79 copper, 6, 7, 8, 9, 10, 30, 43, 44, 48 correlation coefficient, 76, 77 cost, vii, 1, 6, 13, 14, 16, 25, 31, 39, 42, 43, 44, 50, 52 crystal structure, 10, 13 crystalline, vii, ix, 12, 14, 18, 44, 63, 65, 66, 81 crystallization, 3 crystals, 18, 66 culture, 103, 104

Index D decontamination, 39 desorption, 7, 8, 66, 70 detection, 16, 17, 24, 33, 78, 106 detoxification, v, 23, 37, 38, 39, 41, 42, 54 developing brain, 64 diffusion, 11, 65, 72, 74 diseases, 3, 39, 103 disinfection, 12, 28, 51 dispersion, 13, 32 distribution, ix, 16, 38, 63, 65, 70, 74, 76, 78, 79, 84, 99, 101, 103, 105, 107 distribution function, 16 drinking water, iv, v, vi, vii, viii, ix, 1, 3, 14, 23, 25, 28, 37, 38, 47, 50, 51, 54, 64, 79, 83, 84, 86, 99, 101, 103, 104, 105, 107

E ecosystem, 2, 32 efficient, viii, 2, 3, 4, 16, 25, 26, 28, 29, 30, 31, 33, 38, 39, 42, 43, 44, 45, 46, 53 electric current, 19, 21 electrical resistance, 46 electrochemistry, 19 electrodes, 19, 21, 34 electrodialysis, viii, 3, 38, 45, 46, 52, 53, 58 electrolysis, 3, 21 electron, 66, 89, 91 electron microscopy, 89 electroplating, 29, 57 endocrine, 65, 79, 80 endothermic, 6, 9, 18, 78 energy, viii, 20, 21, 38, 42, 45, 52, 59, 75 energy consumption, 20, 21 environment, vii, 1, 15, 21, 23, 39, 53, 73, 104 environmental management, 25, 27, 29, 34, 35

Index equilibrium, ix, 4, 6, 12, 18, 21, 52, 64, 68, 72, 74, 76, 77, 79, 80, 81 equilibrium sorption, 80 estrogen, 65, 80, 81 evidence, 100, 101, 105 exopolysaccharides, 85, 89, 105

F fabrication, 13, 18 family physician, 25 filters, 31, 42, 73 filtration, viii, 2, 3, 42, 78 financial, 22, 53 financial support, 22, 53 flocculation, vii, viii, 2, 4, 19 food, ix, 14, 25, 45, 63, 64 food production, ix, 63, 64 formation, ix, 9, 12, 19, 21, 29, 44, 69, 70, 76, 83, 84, 90, 93, 99, 100, 102, 104 free energy, 13 freshwater, 38, 100, 104 FTIR, ix, 7, 8, 9, 10, 17, 18, 64, 70, 81 FTIR spectroscopy, 18

111 human exposure, 64 human health, ix, 53, 63 hybridization, 15, 103 hydrogen, 13, 74 hydrogen bonds, 74 hydrophilicity, 47 hydrophobicity, 99, 102 hydrothermal process, 10 hydroxide, 14, 20, 26, 31, 44, 66

I incubation time, 90, 100 industries, 45, 46, 50, 79 infrared spectroscopy, 66 integration, viii, 38, 51, 100 intervention, vii, ix, 63 ion-exchange, 3, 6, 12, 18, 42, 44, 45, 46 ions, 3, 6, 7, 8, 10, 11, 13, 14, 16, 17, 18, 19, 20, 21, 22, 28, 33, 38, 41, 42, 43, 44, 45, 46, 47, 48, 52, 81 IR spectra, 69 iron, 7, 12, 19, 20, 21, 28, 34, 44, 48, 81

K G groundwater, 48 growth, ix, 3, 64, 83, 86, 87, 104, 105

kidney, 39 kinetic model, 6 kinetic studies, 19 kinetics, 7, 9, 17, 21, 27, 34, 72, 77, 80, 89

H L hazardous materials, 28, 30, 31 health, ix, 3, 24, 39, 51, 65, 83, 103 health effects, 39 heavy metals, viii, 2, 4, 6, 7, 8, 10, 11, 15, 17, 18, 25, 26, 27, 28, 29, 30, 31, 32, 38, 47, 51, 55, 57, 58 human, ix, 3, 38, 53, 63, 64, 102 human body, 3

lactose, x, 84, 88, 93, 97, 101 landfill leachates, 3 layered double hydroxides, 20, 21 ligand, 15, 18, 48 light, 49, 67, 85, 101 liquid phase, 72, 74

Index

112 M magnetic composites, 28 magnetic materials, 15 manganese, 10, 12, 13, 25, 30, 31, 43 manufacturing, vii, 1, 12, 16 materials, 4, 12, 13, 14, 16, 24, 27, 29, 30, 31, 32, 33, 44, 50, 51, 65, 85, 99, 103, 105, 107 matrix, 6, 23, 29, 46, 99, 103 media, viii, 2, 33, 34, 93, 99, 106 membranes, 16, 23, 29, 31, 33, 45, 46, 47, 52, 54, 67, 102 mercury, viii, 8, 15, 22, 24, 28, 37, 38, 43, 47, 81 metal ion, vii, viii, 1, 5, 6, 8, 9, 10, 12, 14, 16, 17, 18, 24, 25, 26, 27, 28, 29, 31, 32, 33, 37, 38, 39, 41, 42, 43, 44, 45, 46, 49, 51, 52 metal oxides, 12, 13, 30, 44 metal-organic frameworks, viii, 14, 31, 32, 38 metals, viii, 2, 6, 12, 15, 19, 27, 30, 37 methemoglobinemia, 3 methodology, 35 methylene blue, 80 microorganism, ix, 83 microorganisms, 42, 99 microscope, 66, 88 microscopy, 93 microspheres, 6, 49 molecules, x, 46, 65, 72, 74, 84, 93, 99, 100 monolayer, 10, 75, 76, 79 morphology, 5, 8, 30, 66 municipal solid waste, 23

N nanomaterials, 10, 12, 44, 48, 50, 53 nanoparticles, 4, 8, 24, 25, 26, 30, 47, 51 nanostructured materials, 51

non-biodegradable, vii, 1 nucleic acid, 103 nutrient, 49, 84

O optimization, 34, 35, 81 organic matter, 48 osmotic pressure, 45 oxidation, 11, 19, 20, 25 oxide nanoparticles, 30 oxygen, 11, 14, 20, 21, 42, 44, 65, 70

P pathogens, ix, 22, 84, 85, 86, 88, 89, 90, 93, 94, 99, 100, 101, 106 pH, 4, 6, 8, 9, 13, 17, 18, 19, 20, 21, 22, 42, 44, 67, 74, 86 phosphate, 34, 67, 86, 108 physical properties, 72 physico-chemical parameters, 103 physicochemical properties, 7 physiology, 2, 80, 99 phytoestrogens, ix, 63, 64, 65, 79, 81, 82 pollutants, 3, 4, 9, 11, 29, 38, 39, 42, 44, 48, 49, 51, 52, 53 pollution, vii, viii, 1, 2, 23, 24, 27, 37, 38, 50 polymer, 15, 23, 42, 46, 47, 108 polymeric materials, 23 polymeric matrices, 46 polymerization, 47 polymers, 4, 14, 26, 73, 100 polysaccharide, 7, 26, 85 population, viii, 2, 37, 38, 50 porosity, 13, 14, 47, 72 porous materials, 80 precipitation, vii, viii, 2, 3, 11, 18, 20, 31, 41, 42, 43 preparation, iv, 27, 104

Index protease, x, 84, 88, 96, 100, 101 purification, viii, 2, 3, 41, 42 purity, 11, 66, 69

R reaction temperature, 4 reactions, 13, 20, 102 receptor, 81, 100, 102 recovery, 24, 25, 30, 46, 50 regeneration, 7, 14, 43, 44, 73 regression analysis, 81 rejection, viii, 16, 38, 45, 46, 52 remediation, 6, 12, 13, 14, 16, 23, 30, 32 removal, v, ix, 3, 5, 6, 7, 8, 9, 10, 13, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 41, 42, 43, 44, 45, 46, 47, 48, 50, 51, 52, 54, 55, 56, 57, 58, 63, 64, 65, 67, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 108 requirement, viii, 3, 38, 42, 45, 50 requirements, 42, 45, 52 researchers, 2, 11, 14, 43, 46, 51 resistance, ix, 83, 84, 105 reverse osmosis, viii, 3, 25, 38, 45, 102 room temperature, 8, 66, 87, 88, 89

S safety, x, 34, 64, 65, 66, 78, 79, 84, 85, 101, 108 scanning electron microscopy, ix, 63 science, 23, 26, 29, 31, 33, 53, 106 sedimentation, 3, 41, 42 selectivity, 15, 46, 47 sewage sludge, 6, 26 shortage, viii, 38, 48 solid phase, 28, 68 solution, viii, 6, 8, 9, 11, 17, 21, 26, 27, 28, 38, 39, 52, 53, 66, 67, 68, 80, 86, 88

113 sorption, 9, 11, 25, 30, 33, 43, 44, 68, 72, 74, 81 species, 3, 14, 85, 99, 100, 101, 103, 104, 105 specific surface, 13, 15, 66, 70 spectroscopy, ix, 64, 66, 70 sphingomonas, iv, vi, vii, ix, 83, 84, 86, 88, 89, 90, 91, 92, 93, 94, 95, 97, 98, 99, 100, 101, 102, 103, 104, 105, 107 stability, viii, 14, 15, 26, 32, 38, 48 structure, 6, 8, 11, 13, 15, 17, 18, 43, 65, 66, 69 superparamagnetic, 30 surface area, ix, 6, 11, 15, 18, 32, 43, 64, 65, 70, 72, 74 surface modification, 30 surface reaction, 11, 43 synthesis, 8, 11, 14, 26, 28, 29, 30, 33, 34, 66

T techniques, viii, 3, 5, 15, 18, 38, 39, 42, 53 technologies, vii, viii, 2, 25, 32, 38, 39, 41, 45, 48 temperature, 9, 18, 21, 22, 66, 74, 79 toxic effect, 3 toxic waste, viii, 38 toxicity, 2, 19, 25, 51, 53, 108 transmission electron microscopy, ix, 63 treatment, vii, viii, x, 1, 2, 3, 7, 10, 13, 16, 20, 22, 25, 27, 34, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 58, 64, 78, 79, 84, 85, 88, 93, 95, 96, 97, 98, 101, 107 treatment methods, vii, viii, 1, 38, 39, 41, 42, 50, 51, 52, 53

U ubiquitous solution, 38

Index

114 uniform, 12, 44, 65, 76, 87 UV irradiation, viii, 38 UV light, 49

W waste, vii, 1, 14, 24, 25, 27, 29, 45, 51, 57, 64, 108 waste disposal, 64 wastewater, viii, 2, 3, 4, 6, 7, 8, 9, 10, 13, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 27, 28, 29, 30, 31, 33, 34, 35, 54 water, vii, viii, ix, 1, 2, 4, 5, 8, 9, 10, 13, 14, 16, 17, 18, 22, 24, 25, 28, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 58, 63, 64, 65, 66, 77, 78, 79, 84, 86, 90, 99, 101, 102, 103, 105, 106, 107

water purification, 28, 65 water quality, viii, 2 water quality standards, viii, 2 water resources, 3, 48, 64, 106 water treatment, iv, v, vii, ix, 1, 2, 16, 22, 27, 34, 37, 38, 39, 41, 43, 45, 50, 51, 53, 55, 58, 59, 78

Z zeolite, iv, v, vii, ix, 4, 12, 29, 43, 44, 56, 57, 58, 59, 63, 65, 66, 67, 69, 70, 73, 79, 80, 81, 82 zinc, 3, 6, 8, 10, 14, 19, 24, 27, 44 zinc oxide, 14 ZSM-5, iv, vii, ix, 63, 64, 66, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 80, 81, 82