Mahesh Chandra Chattopadhyaya

Polymer functionalized nanocomposites for metals removal from water and wastewater: An overview.

Pollution by metal and metalloid ions is one of the most widespread environmental concerns. They are non-biodegradable, and, generally, present high water solubility facilitating their environmental mobilisation interacting with abiotic and biotic components such as adsorption onto natural colloids or even accumulation by living organisms, thus, threatening human health and ecosystems. Therefore, there is a high demand for effective removal treatments of heavy metals, making the application of adsorption materials such as polymer-functionalized nanocomposites (PFNCs), increasingly attractive. PFNCs retain the inherent remarkable surface properties of nanoparticles, while the polymeric support materials provide high stability and processability. These nanoparticle-matrix materials are of great interest for metals and metalloids removal thanks to the functional groups of the polymeric matrixes that provide specific bindings to target pollutants. This review discusses PFNCs synthesis, characterization and performance in adsorption processes as well as the potential environmental risks and perspectives.

Rapid scavenging of methylene blue dye from a liquid phase by adsorption on alumina nanoparticles

The adsorption behavior of methylene blue on as-synthesized alumina nanoparticles has been investigated. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), TG/DTA/DTG, X-ray diffractrometry and scanning electron microscopy. N2 adsorption–desorption measurements were carried out to analyze the porous structure and surface area of the adsorbent and results revealed that the adsorbent is mesoporous with a specific surface area of 76 m2 g−1. Batch experiments indicated that solution pH, initial dye concentration, contact time, temperature and the presence of ions had prominent impact on the dye removal process. The sorption kinetic data were found to be in accordance with pseudo-second order kinetics. The mechanistic interaction of the adsorbate–adsorbent system was also interpreted with the help of Weber–Morris model and the Boyd model and it was found that the adsorption process is controlled by a film diffusion mechanism. The investigation of adsorption isotherms suggested that the data fitted Langmuir isotherm model. The values the thermodynamic parameters for the process of removal were determined and the negative values change in free energy, ΔG0, indicated the spontaneous nature of the sorption process. A high desorption efficiency of 90.11% indicated a possible regeneration of the adsorbent. The adsorbent displayed almost the same adsorption capacity even after three cycles of regeneration bringing down the cost of treatment.

Biosorption of Heavy Metals: Recent Trends and Challenges

Water resources are of critical importance to both natural ecosystem and human developments. Increasing environmental pollution from industrial wastewater particularly in developing countries is of major concern. Heavy metal contamination exists in aqueous waste streams of many industries, such as metal-plating facilities, mining operations, tanneries, and pulp and paper. Some metals associated with these activities are cadmium, chromium, iron, nickel, lead, and mercury. Heavy metals are not biodegradable and tend to accumulate in living organisms causing diseases and disorders. Hence, there is a need to treat the wastewater containing toxic metals before they are discharged into the water bodies. Many physicochemical methods like coagulation, flocculation, ion exchange, membrane separation, and oxidation are available for the treatment of heavy metals. Major drawbacks of these methods are high sludge production, handling and disposal problems, high cost, technical constraints, etc. This necessitates cost-effective and environmentally sound techniques for treatment of wastewater containing heavy metals. During the beginning of twenty-first century, the increasing awareness and concern about the environment motivated research for new efficient technologies that would be capable of treating inexpensively wastewater polluted by toxic metals. This search brought biosorption to the foreground of scientific interest as a potential basis for the design of novel wastewater treatment processes. Several adsorbents are currently used which are by-products from agriculture and industries. Biosorption using low-cost adsorbents could be technically feasible and economically viable sustainable technology for the treatment of wastewater and industrial effluents.

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.

Enhanced adsorption of methylene blue on modified silica gel: equilibrium, kinetic, and thermodynamic studies

AbstractThe present work was undertaken to chemically modify silica gel (SG) with citric acid (CA) to enhance its adsorption power for methylene blue (MB) dye from aqueous solution. Citric acid-modified silica gel (CAMSG) was synthesized thermochemically and was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and elemental analysis. Influences of various parameters such as adsorbent dose, pH, initial dye concentration, contact time, and temperature on adsorption were studied. Equilibrium data were analyzed using Langmuir, Freundlich, and Temkin isotherm models. Kinetic studies show that the adsorption follows pseudo-second-order kinetics and intraparticle diffusion model. Negative values of Gibb’s free energy change (ΔG°) show that the adsorption was feasible and spontaneous in nature and the negative values of enthalpy change (ΔH°) confirm exothermic adsorption.

Adsorption Characteristics of Modified Wheat Husk for the Removal of a Toxic Dye, Methylene Blue, from Aqueous Solutions

Adsorption characteristics of modified wheat husk for the removal of a toxic cationic dye, methylene blue, from aqueous solutions have been investigated. The adsorbent, wheat husk, was characterized by Fourier transform infrared spectra (FTIR) and scanning electron microscopy (SEM) for its functional group and surface characteristics. The removal decreased by increasing temperature from 303 to 373 K. The removal was found to be pH dependent, and it decreased from 96.2 to 40.7% by varying the pH of the solution from 4.5 to 9.5. It was observed that 93.4% removal of methylene blue was achieved at an initial dye concentration of 13.37 × 10 −2 mol=L at 303 K. Equilibrium adsorption data for the removal of methylene blue were analyzed by Langmuir, Freundlich, and Tempkin isotherm models. Values of thermo- dynamic parameters viz ΔG°, ΔH°, and ΔS° were determined. The negative value of ΔH° confirmed the exothermic nature of removal of methylene blue by adsorption on modified wheat husk. DOI: 10.1061/(ASCE)HZ.2153-5515.0000191.

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.

Surface modification of silica gel for adsorptive removal of Ni2+ and Cd2+ from water

AbstractIn this study, surface of silica gel was functionalized with 1,2-ethylenediamine. The synthesized materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and elemental analysis. Batch adsorption studies were carried out to analyze the adsorption of nickel and cadmium ions from aqueous solutions. The factors influencing % adsorptive removal of Ni2+ and Cd2+ onto the silica gel and functionalized silica gel, such as initial pH value of the Ni2+ and Cd2+ ion solutions, adsorbent dose, initial Ni2+ and Cd2+ ion concentration, contact time, and temperature were investigated. Langmuir and Freundlich isotherm models were used to determine the isotherm parameters associated with the adsorption process. The monolayer adsorption capacity of ASG for Ni2+ and Cd2+ increased from 4.69 to 19.6 and 7.63 to 27 mg/g, respectively, after modification of activated silica gel (ASG) surface with 1,2-ethylenediamine. Kinetic data were analyzed considering pseudo-first-orde...

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.