Studies on Removal of Cd 2+ using Chitosan Coated Carbon Biosorbent from Wastewater

Abstract

Chitosan, a hydrophilic natural polymer produced by alkaline deacetylation of chitin, obtained mainly by extraction from shrimp and crab shells, is the most abundant biopolymer occurring in nature, after cellulose. It is composed of both glucosamine and acetylglucosamine as a monomer in the heteropolymeric network. It is characterized by a high content of nitrogen, present as amine groups capable of adsorbing the metal ions through several mechanisms – including chemical interactions, such as chelation, electrostatic interactions or ion exchange. In this study chitosan was coated on the carbon up to five coating. 5th coated carbon was characterised by FTIR, TGA, DSC and XRD. FTIR study shows broad band at 3456.25cm-1 was attributed to intermolecular hydrogen bonded N-H stretching, O-H starching and the strong polymeric association of chitosan coated carbon. TGA shows increase in thermal stability of the chitosan by coating on carbon. DSC shows single glass transition temperature (Tg) due to attractive molecular interaction shows the polymer miscibility and compatibility of both materials. XRD shows sample having amorphous nature and the percentage of crystallinity is 18.7%. After characterisation it was used for the adsorption study of Cd2+ from water by changing various parameters such as contact time, adsorbent dosage and pH. Optimum contact time was 300min with 71.5% removal of Cd2+, adsorbent dose was 5g with 72.5% removal and pH was 5.5 with 77% removal. Sorption data were analysed by Langmuir and Freundlich adsorption isotherm. Sorption data well fitted to Freundlich isotherm than the Langmuir isotherm. Sorption data were used for kinetics study and it follows Pseudo-second-order kinetics.