Synthesis and Characterisation of Nano-Biosorbents and Their Applications for Waste Water Treatment

Introduction

The major reason for the contamination of water is rapid urbanization and industrialization by the anthropogenic behaviour due to population explosion. (Khatri & Tyagi, 2015). For such a massive population there is need of more and more industries like metal plating (Venkateswaran, Vellaichamy, & Palanivelu, 2007), mining operations (Panayotova, 2016), surface finishing industry, tanneries (Qureshi, 2015), paper and pulp industries (Pöykiö, Nurmesniemi, & Keiski, 2007), color-alkali, fertilizer and pesticide industry (Marković, Radmanović, Đurović-Pejčev, Milinovic, & Kljajić, 2009), radiator manufacturing, smelting, energy and fuel production, aerospace and atomic energy installation, alloy industries, electroplating, and battery industries to fulfill their necessities (s. k. Das, Grewal, & Banerjee, 2011; Sato, Shimosato, & Klinman, 2018). Most of these industries produces heavy metals like zinc (Zn), copper (Cu), nickel (Ni), mercury (Hg), cadmium (Cd), lead (Pb), and chromium (Cr) (Jaishankar, Tseten, Anbalagan, Mathew, & Beeregowda, 2014) which leads to the water pollution. The continuous discharge of heavy metals into the water bodies has led to the abandon of several industries in various parts of the globe. The presence of these impurities in water results in an increased color, turbidity, chemical oxygen demand and several other parameters (Saritha, Srinivas, & Srikanth Vuppala, 2017). Therefore, there is an immediate requirement of cost effective, eco-friendly, efficient technique for the remediation of pollutants from such contaminated water. However, there are numerous conventional approaches for the remediation of pollutants from wastewater like precipitation (by precipitating down the heavy metals), coagulation (eliminates the heavy metals by forming a coagulation), membrane filtration (heavy metals are removed by using filters having specific pose size), ion exchange (eliminates heavy metals by exchanging ion), evaporation, absorption (heavy metals are eliminated by absorbing them), and adsorption (heavy metals are removed by adsorbing them on the surface of adsorbents) (Krishna, Kumar Chintalpudi, & Muddada, 2018). Out of which absorption is the most preferred techniques because of their simplicity of operation, handiness, less area requirement and tendency to work with diverse pollutants (Hanida, 2018). The absorption process is being applied in sensors, for the detection of gases and other molecules, in chromatography, in optical devices, in catalytic reactions, in industries, filters in wastewater treatment (Vanrolleghem & Lee, 2003). If the absorbents are recovered from the waste products of industries then it is more advantageous as it will not only reduce the cost of the absorbent and absorption mechanism but also minimize the pollution. Moreover, waste derived absorbents make the process economical and nonhazardous, as the absorbents are biodegradable. The absorbents obtained from the waste products have large number of functional groups on their surface, which further makes them more effective and efficient for the remediation of the pollutants (Güngen, Aydemir, Çoban, Düzenli, & Tasdemir, 2016); (Barakat, 2011). If the product is derived from the agricultural waste, then it has ketones, alcohols, carboxyl, carbonyl, aldehydes, amines, phenols, ethers and several other groups on their surface (Tojo & I. Fernandez, 2006). All these different groups have different mechanism of binding of pollutants and ultimately higher removal of pollutants from the wastewater at one go.