Sanjay K. Sharma

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.

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.

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.

Nano Based Photocatalytic Degradation of Pharmaceuticals

The removal of emerging contaminants from wastewater is urgently required and even more necessary for wastewater reuse. Since conventional WWTPs are not designed to treat water polluted with pharmaceuticals present at trace levels, the applied treatments are mostly ineffective in their removal. Therefore the use of more efficient processes for removing or improving the biodegradability of these compounds has become necessary. Among several advanced oxidation process, nano based photocatalytic processes represent a challenging alternative for pharmaceuticals removal due to its capacity to utilize the solar radiation as the light source, thus reducing significantly electric power required and therefore saving treatment costs and to operate without pH adjustment. This chapter is aimed at describing the state of the art in the heterogeneous photocatalytic degradation of pharmaceuticals using different nano particles (NPs).

Adsorptive behavior, isothermal studies and kinetic modeling involved in removal of divalent lead from aqueous solutions, using Carissa carandas and Syzygium aromaticum

Abstract This study is focused on the biosorption of lead(II) ion onto surface of Carissa carandas and Syzygium aromaticum biomass from aqueous solution. The operating parameters, pH of solution, biomass dosage, contact time, initial metal ion concentration, and temperature considerably affect the biosorption efficiency of Pb(II). Biosorbent C. carandas leaf powder showed higher sorption efficiency than that of biosorbent S. aromaticum powder under identical experimental conditions. It was observed that the lead(II) removal percentage was found highest of 95.11% for C. carandas and 91.04% for S. aromaticum at contact period of 180 min. Also, it was observed that the regression coefficient (R2 = 0.99) for the pseudo-second-order kinetic model is higher in comparison with the pseudo-first-order kinetic model and the calculated value of qe for the pseudo-second-order kinetic model is very close to the experimental value, which indicates that it fits well with the equilibrium data for Pb(II) sorption from aqueous solutions on biosorbents. Also, the adsorption of Pb(II) onto C. carandas was best described by the Freundlich isotherm model.

CHAPTER 5:Arsenic Contamination: An Overview

Arsenic (As) contamination, especially in groundwater, has been receiving increasing attention in recent years due to its adverse effects on human health and the environment. Its biogeochemical cycle involves several physico-chemical processes as well as biological mechanisms, in which microorganisms play a key role. The inorganic compounds arsenite [As(iii)] and arsenate [As(v)] are the most toxic and abundant species of arsenic in water. Depending on the environmental physico-chemical condition these compounds have a relatively high solubility and are readily transported through aqueous routes into the environment, transferred from soils to crops and accumulated in various food crops and aquatic plants, threating human health. According to recent studies rice may be the primary source of inorganic arsenic for human exposure. In this chapter sources, pathways and levels of arsenic are presented to address the problem of its contamination of the environment. Furthermore, the state-of-the-art treatment of arsenic-contaminated waters, including a variety of treatment technologies based on oxidation, coprecipitation, adsorption, ion exchange and membrane and bio-processes are reported. The efficiency and applicability/appropriateness of the technologies have been evaluated, with regard to influent arsenic concentration, differences in source water composition, production of toxic sludge, economical aspects and social acceptance.