Ravindra Kumar Gautam

CHAPTER 1:Contamination of Heavy Metals in Aquatic Media: Transport, Toxicity and Technologies for Remediation

The presence of pollutants in aqueous solution, particularly from hazardous heavy metals and metalloids, is an important environmental and social problem. As many of these elements are stable they are bio-accumulative, and assessment of their safe limits is very difficult in the ecosystem. Few metals, such as Fe, Zn, Cu, Co, Cr, Mn and Ni, are required for biological metabolism in trace amounts; however, their higher dose may cause toxic effects. Others, such as Pb, Hg, Cd and As, are not suitable for biological functions and are positively toxic. Toxicity of these elements is of considerable concern worldwide because of their environmental burden. During the past few decades scientists have been developing cheap and environmentally friendly technologies for the treatment of wastewater generated at the household and up to the industrial scale. In this regard, methods like ion-exchange, membrane filtration, catalysts including photocatalysts and photocatalysis, microbe-assisted phytobioremediation and adsorption over low-cost biosorbents and nanomaterials have been developed and demonstrated to be successful. Because of the demand for water to feed the growing population and the needs for industrial processing, the separation and purification of generated wastewater by adsorption phenomena is gaining major relevance. Adsorption over biomass-derived biosorbents has provided the capability to treat wastewater on a large scale. Several low-cost biosorbents have been synthesized and successfully applied to remove toxic metals and metalloids from wastewater. Nanomaterials and their analogues, such as magnetic nanosorbents and layered double hydroxides, have been the focus for the development of novel materials with high surface area and low-cost synthesis to develop new generation super-adsorbents. In this introductory chapter a comprehensive appraisal over the transport, toxicity and development of removal technologies is given along with their merits and demerits.

Degradation of Di- Through Hepta-Chlorobiphenyls in Clophen Oil Using Microorganisms Isolated from Long Term PCBs Contaminated Soil.

Present work describes microbial degradation of selected polychlorinated biphenyls (PCBs) congeners in Clophen oil which is used as transformer oil and contains high concentration of PCBs. Indigenous PCBs degrading bacteria were isolated from Clophen oil contaminated soil using enrichment culture technique. A 15xa0days study was carried out to assess the biodegradation potential of two bacterial cultures and their consortium for Clophen oil with a final PCBs concentration of 100xa0mgxa0kg−1. The degradation capability of the individual bacterium and the consortium towards the varying range of PCBs congeners (di- through hepta-chlorobiphenyls) was determined using GCMS. Also, dehydrogenase enzyme was estimated to assess the microbial activity. Maximum degradation was observed in treatment containing consortium that resulted in up to 97xa0% degradation of PCB-44 which is a tetra chlorinated biphenyl whereas, hexa chlorinated biphenyl congener (PCB-153) was degraded up to 90xa0% by the consortium. This indicates that the degradation capability of microbial consortium was significantly higher than that of individual cultures. Furthermore, the results suggest that for degradation of lower as well as higher chlorinated PCB congeners; a microbial consortium is required rather than individual cultures.

Advanced Nanomaterials for Wastewater Remediation

Dye-consuming industries, especially textile industries, are among the prime consumers of water, by which a huge proportion of the aquatic environment has been compromised due to the discharge of dyes, which are, most often, persistent and toxic. Conventional physicochemical processes cannot completely remove dyes from water and wastewater due to their complex structures. Nowadays, electrooxidation (EO) processes are proposed for the degradation of synthetic dyes. Employing electrons as the major reagent, EO processes are well known for being among clean processes. The advantages of electrochemical processes (ECPs) include environmental compatibility, versatility, amenability of automation, and high energy efficiency. These processes are classified into two main categories. First, direct EO, in which hydroxyl radicals are produced on the anode surface. The hydroxyl radical generated is a powerful oxidant that degrades dye structure. Second, indirect EO, where either oxygenor chlorine-based oxidizing agents are electrochemically produced in the solution. Indirect EO is also divided into two processes, involving the production of an oxidizing agent (H2O2) at the cathode and the generation of active chlorine species at the anode. The electrogenerated H2O2 in the presence of a transitional metal (Fe2+) can produce the hydroxyl radicals in a process called electro-Fenton. This chapter presents (1) direct EO theory, principles, and various studies of dye degradation by direct EO; (2) applications of indirect EO in different conditions; and (3) advances and challenges of electrochemical oxidation in colored wastewater treatment.

Study on adsorption behavior of Acid Orange 10 onto modified wheat husk

AbstractThe present communication addresses the applicability of acid-modified wheat husk for the adsorptive removal of an anionic dye, Acid Orange 10 (AO-10) from aqueous solutions. The adsorbent was characterized by FTIR and SEM. The adsorption reached equilibrium within 30xa0min, and the percentage removal increased with contact time, adsorbent dosage, and ionic strength. Low pH condition enhances AO-10 sorption. The experimental data for kinetic study agrees with pseudo-second-order model. Detailed investigation of experimental kinetic data indicates that overall sorption rate is governed by film diffusion mechanism. The adsorption behavior followed a Freundlich adsorption isotherm with high correlation coefficient and low χ2 values. The maximum adsorption capacity was found to be 31.25xa0mg/g. The results of thermodynamic study demonstrated that the adsorption process was spontaneous and exothermic in nature. Desorption studies revealed that the adsorbent could be reused for two successive trials without...

Kinetics and Equilibrium Isotherm Modeling: Graphene-Based Nanomaterials for the Removal of Heavy Metals From Water

Monitoring and separating metal ions in water samples is a challenge to analysts and environmental engineers due to their toxicity and carcinogenicity on humans and animals. Various technologies such as membrane filtration, bioremediation, coagulation, precipitation, adsorption, and advanced oxidation processes have been utilized to decontaminate the heavy metals from aquatic systems. In recent years, separation technology supported on graphene-based nanostructure materials has received considerable attention. This chapter highlights the review of literature dealing with the application of graphene-based materials to the separation and preconcentration of metal ions and metalloids in water samples. The high surface area to volume ratio graphene or graphene oxide doped with inorganic and organic moieties have gained much attention. The graphene-based magnetic nanoparticles have been widely utilized for the removal of heavy metals from aqueous systems as they can be easily separated and regenerated with an external magnet. The magnetic extraction method is not only convenient, economical, and highly efficient but it also overcomes problems with conventional solid-phase extraction as the adsorbent–adsorbate system gains equilibrium within a shorter time as compared with conventional techniques. However, there is urgent need to conduct experiments regarding their use in column studies and on industrial scales.

Chapter 4 – Graphene-Based Nanocomposites as Nanosorbents

Continuous discharge of environmental pollutants into nearby water bodies has become a serious environmental problem due to the toxic behavior of pollutants on human beings and animals. Among various contaminants, heavy metals and dyes are the ubiquitous and versatile pollutants of aqueous streams because of their use and discharge during the processing of industrial products such as mining, metallurgy, metal finishing, battery industries, automobiles, textiles, wool processing, leather tanning, paints and varnishes, fertilizers, and sewage and domestic wastes. Adsorption system has been extensively applied to remove these contaminants before their discharge into the aquatic media. Graphene nanocomposites, composed of both inorganic and organic moieties, have recently been examined as promising platforms for detection and separation applications. This unique class of nanomaterials can retain not only beneficial features of both the inorganic and organic components but can also provide the ability to systematically tune the properties of hybrid materials through a combination of appropriate functional components. Graphene nanocomposites have received much attention due to their unique properties, such as their extremely small size, high surface-area-to-volume ratio, surface modifiability, multifunctionality, excellent conductivity, low-cost synthesis, and great biocompatibility. Graphene-based nanocomposites have proved their potential for the extraction and remediation of environmental pollutants from aquatic media. However, their use and application at the industrial scale is very limited and requires more research to be performed in this field, and efforts should also be taken to carry out studies with multipollutant systems in both batch column modes.

CHAPTER 4:Functionalized Magnetic Nanoparticles for Heavy Metals Removal from Aqueous Solutions

Worldwide contamination of aqueous environments is a severe problem. Heavy metals and metalloids such as mercury, lead, chromium, cadmium, copper, cobalt, zinc, manganese and arsenic are among the ubiquitous trace contaminants of aquatic ecosystem. These contaminations raise concerns, as small amounts of the heavy metals have been shown to be carcinogenic to humans and animals and can pose a risk to the aquatic biota. Hence, there is an urgent need to treat the wastewater containing heavy metals before they are discharged into the water bodies. Several wastewater treatment techniques such as ion exchange, precipitation, coagulation, membrane filtration, catalytic reduction and adsorption are available for the removal of heavy metals. All of these have their own advantages and limitations. The high operating costs, technical constraints and tedious design necessitate cost-effective and environmentally sound techniques for the treatment of wastewater containing heavy metals. Magnetic nanoparticles have received tremendous attention because of their small size, high surface area to volume ratio, surface modifiability, excellent magnetic properties, low-cost synthesis and great biocompatibility. Magnetic nanoparticles offer a new vista of separation and purification technology for heavy metals. The multifunctional magnetic nanoparticles have been successfully applied for the reduction of toxic metal ions up to the ppb level in waste treated water. This chapter highlights the potential application of magnetic nanoparticles for the removal of heavy metals from aqueous solutions.

CHAPTER 12:Heavy Metals in Tannery Wastewater and Sludge: Environmental Concerns and Future Challenges

Tannery wastewater is considered to be one of the most polluting effluents due to it containing a large variety of toxic heavy metals that range from chromium, cadmium, cobalt, lead, nickel, selenium to arsenic. As consequence of most tannery wastewater treatments, the tannery sludge that is produced contains considerable amounts of heavy metals, which are harmful to the environment and human health. Hence, tannery wastewater and sludge treatments have become a serious environmental issue. At present, the conventional options for sewage sludge disposal, such as fertilizers and soil amendment materials for the land and landfill, are widely applied. However, heavy metals in the tannery sludge often outweigh the soils heavy metal content, and the application of sludge can indeed increase the concentration of heavy metals in the agricultural soil and affect the crop production owing to uptake of the metals. Research on devising appropriate treatment technologies for tannery wastewaters has gone through various phases of development over the past decades following developments in processes related to the leather manufacturing industry. This chapter attempts to revise environmental concerns and future challenges related to the management of tannery wastewater and sludge.

Nanotechnology for Water Cleanup

Rapid industrialization, haphazard urbanization, and tremendous growth in population have discharged huge amounts of environmental contaminants into aquatic ecosystems such as ponds, lakes, rivers, and estuaries, affecting millions of people worldwide. Thus management of contaminants has become a major environmental issue. Nanotechnology plays a vital function in the remediation of pollutants from water and wastewater. During the recent few decades the scientific community is developing novel nanomaterials which can be efficiently utilized for water treatment. Nanoscale materials of mixed-metal oxides, such as magnetic nanomaterials, layered double hydroxides, metal organic frameworks, bimetallic nanoparticles, nanocatalysts, and graphene-based nanocomposites, have been widely developed and utilized for the separation and purification of hazardous pollutants from aqueous solutions because of their high surface area to volume ratio, high physicochemical stability, biocompatibility, and efficient regeneration of utilized nanoadsorbents. These nanomaterials have been widely used in the degradation, treatment, and remediation of aqueous environmental contaminants such as phenols, heavy metals, metalloids, anionic and cationic dyes, pharmaceuticals, and organic pollutants from wastewater before their discharge into the nearby water bodies. Nowadays, it has become a hot topic to develop novel nanoscale materials and evaluate their removal performance for environmental contaminants under varying experimental conditions. Adsorption–desorption of pollutants from aqueous media to the interface of nanoadsorbents has been evaluated as a crucial technique and has been modeled to get favorable optimization conditions by mathematical equations. A lot of attempts have been made to understand the removal of pollutants using kinetic rate equations. In this chapter, an overview on the recent advances made in the field of nanomaterials is presented.

Nanomaterials in the Environment: Sources, Fate, Transport, and Ecotoxicology

Nanotechnology deals with artificial structures as tiny as 1 billionth of a meter and was introduced into real life in the last 5xa0years. Recent applications of nanotechnology include the use of nanostructured materials in biomedicine, catalysts, electronics, space engineering, and environmental remediation. This chapter highlights the key concepts of nanotechnology to the layman’s community to introduce various state-of-the-art examples of current nanotechnology that were either created for use in biological systems or that can be utilized for biomedical and environmental applications, to provide recent updates on nanotoxicology to the living world, and to propose actions to tackle these challenges.