Applications of Nanomaterials: A Novel Approach for Pollution Abatement in Industries

Book excerpt: The book “Applications of Nanomaterials: A Novel Approach for Pollution Abatement in Industries” highlights an in-depth research about applications of nanotechnology for dye decolouration and abatement of pollutants from industrial effluents and agriculture. The authors have emphasized the significance of synthesis of metallic nanoparticles and their applications in dye decolouration, biocidal activity, and pollution abatement. Wastewaters are producing gradually with rapid development in different type of industries such as textile, leather, pulp, and paper, printing, photographs, cosmetics, pharmaceuticals, commerce, hospitals, and health-care services. The industry use water as a principal medium for removing impurities, applying dyes, and finishing agents. Therefore, the main concern is the discharge of wastewater. Significant quantities of toxic and hazardous chemicals are being generated as an industrial waste. At present, there are thousands types of toxic chemicals commercially generated. Their virulence, firmness to natural disintegration and prolong accumulation in the environment are the cause of much concern to societies and regulatory authorities around the world. There are numerous methods for abatement of organic and inorganic compounds from the wastewater such as filtration, electrolysis, precipitation, ion exchange, coagulation, and adsorption processes. Most of these methods require high capital and recurring expenditure and consequently they are not suitable for small-scale industries. Besides, all the above-mentioned methods, photocatalysis is a highly effective and cheap process than the other methods. The search for novel technologies for the remediation and reduction of pollutants has attracted attention to adsorption phenomenon. The adsorption process involves a solid phase (biosorbent) and a liquid phase (solvent, normally water) containing dissolved species to be sorbed (sorbate, metal ions). As sorbent possess higher affinity for the sorbate species, the latter is attracted and attaches thereby different mechanisms. Metallic oxide nanoparticles are crystalline solids consisting of a metal cation and an oxide anion. Metals with high oxidation state forms oxides. Ionic metal oxides react with water to produce hydroxides. Transition metal oxides are compounds composed of oxygen atoms bound to transition metals. These are mainly used for their enhanced catalytic activity and semiconductor properties. Due to presence of superior physical and chemical properties, metal oxide nanoparticles express potential environmental remediation applications. When compared to bulk materials, they display novel properties that lead to the development of electronic and optoelectronic nano-devices with superior performance. It is well known that size and morphology are very important parameters in nanostructures. But there is limited information about the use of different nanoparticles as a photocatalytical removal of different pollutants from wastewater and in agriculture soils. Among the oxide nanoparticles, Titanium dioxide and zinc oxide and Iron oxide are the main compounds used in environment remediation study. Titanium Dioxide (TiO2), Zinc Oxide (ZnO) and Iron Oxide (FeO) nanoparticles are unique materials with band gap 3.2 eV, 3.37 eV, and 3.06 eV, correspondingly & wavelength of all three particles is above 400 nm. This means that UV light irradiation with a wavelength lower than 400 nm begins a photoreaction. The characteristic of TiO2, ZnO, FeO is the more powerful oxidative power of the VB holes than the reducibility of photo-induced electrons. Morphology, crystal structure, and elemental composition as characterization are important to understand nanoparticles based study. Widespread techniques used for morphological analysis are Transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM); Particle Size Analysis (PSA), Dynamic Light Scattering (DLS), etc. Chemical-based Techniques used are X-Ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible Spectroscopy (UV-Vis Spectroscopy), and Energy Dispersive X-Ray Spectroscopy (EDX). In the present era, thousands of dyes and pigments are produced in industries. A significant increase in the use of synthetic complex organic dyes as coloring material by textile industry has been presented. Comprehensively, synthetic dyestuffs are used in paper, textiles, printing industries, and dye houses. Estimation for the loss of color in waste stream during the manufacturing or processing operations of textile dyes indicates approximately 10 to 20% loss. Textile wastewater poses carcinogenic and genotoxic properties and affects the immune system and reproductive system. It is reported that most of the dyes and poisonous metals used in the color industries are stable to light and are non-biodegradable. In order to reduce the risk of environmental pollution from such waste, it is mandatory to treat them before discharging into the environment. Nanophotocatalyst can decompose most organic or inorganic substances in air or water by photocatalytic oxidation and reduce harmful inorganic substances in water. Current use of nanomaterials has been expanded in every fields of science including agriculture. Plants are very crucial to human and their surroundings but very few studies have been performed to assess the potentiality of nanoparticles in agriculture crops. It has been reported that use of micronutrient fertilizers in the form of NPs is a crucial way to release desired nutrients gradually and in a controlled way, which is fundamental to diminish the problems of fertilizer pollutions. It is because of that when materials are transformed to a nanoscale, which they revolutionize, their physical, chemical, and biological properties as well as catalytic properties and even more increase the chemical and biological activities. It is demonstrated that micronutrients in the form of NPs can be used in crop production to increase yield. Study on the effect of nanoparticles on the germination, growth and yield of crops is the need of an hour. Despite their great potential, the use of nanoparticles suffers certain restrictions under industrial process conditions like loss of nanoparticles, difficulty in separation and reuse of nanoparticles. To circumvent these limitations, several strategies for immobilization of nanocatalysts in polymer have been suggested. Nanoparticles immobilization appears to be an attractive approach to develop efficient catalyst with improved performances such as enhanced resistance to thermal and chemical inactivation, remarkable storage and operational stabilities, short response time and high reproducibility and reuse. Recently various immobilization materials like Ca-alginate beads, Chitosan, Polyvinyl Alcohol, Nanoporous Silica Gel, Polyacrylamide have been used for immobilization by researchers. Entrapment in Calcium alginate beads is of particular interest because of very mild and simple preparation conditions, non-toxicity, low cost and best performance. Indeed, Alginate is a natural anionic polysaccharide comprised of repetitive units of α-L-guluronic acid and β-D-mannuronic acid residues. Alginate chains are usually prepared by cross-linking of Guluronic acid with Mannuronic acid residues in the presence of divalent cations like Ca2+, Ba2+, Co2+. Therefore, in the present study an effort has been made on comparative investigations on synthesis, characterization of metallic nanoparticles and their applications in dye decolouration, biocidal activity, and abatement of pollutants from industrial effluents and agriculture. The present book would certainly be helpful to graduates, researchers, industrialists, practitioners and managers to use it as benchmark, concrete and conclusive remarks for dye decoloration as well as nutrients remediation of natural and anthropogenic industrial effluents using synthesized metallic nanoparticles at lab and industrial scales at regional, national and global scales.