Activation Of Gasifier Based Waste to Remove Heavy Metals from Wastewater

Abstract

India being a petroleum starved nation, the utilization of biomass based gasifier has increased tremendously because of easy availability of agricultural based biomass. (The ministry for Non- Conventional Energy Sources has assesses that nearly 500 million tons of biomass is generated every year from crop residue, bagasse, agro residue and forest sources. Out of this, only 170 million tons are used for power generation.) Under the National Biomass Gasifier Program in India 1,074 gasifier system have been installed in different states for various modes of applications including mechanical, electrical, thermal heating, and cooking besides village electrification. However, this route of generation of energy can leave large foot print on the environment because of significant quantity of solid waste generated. In this research an attempt has been made to prepare sorbent from gasifier based solid waste. Among various pollutants in drinking and wastewaters, inorganic species are major, and difficult to remove because of smaller size, low concentration and competition with nontoxic species. In this work, activated carbon has been prepared by chemical activation from gasifier based waste to study the effect of preparation variables and metal removal capacity. Characterizations were done for the observation of surface area, surface functional groups and its acidity. The Fourier transform infrared (FTIR) spectroscopy study has revealed that the functional groups (C=O, S=O,–OH) present on the sorbent surface. Application was tested through batch adsorption in single solutes solutions and fitting the equilibrium data to various equilibrium and kinetic models. Prepared carbons show very high adsorption capacities for borderline and soft metal ions like Lead(II), Cadmium(II), Chromium(VI) and As(V). The developed activated carbon is expected to be useful in removing borderline and soft metal ions as well as ionic or nonionic soft ligands of metalloids present in drinking and wastewaters. The adsorption parameters were estimated using both the Freundlich and Langmuir models. The experimental results indicated that the gasifier based waste can be used as a suitable sorbent and may easily replace activated carbon in wastewater treatment process. Max.% Removal efficiency achieved at optimized pH and single solute solution: lead II (96%), cadmium II (94%), chromiumVI (93%), arsenic V (88%).