Removal of cadmium and hexavalent chromium from electroplating waste water using thiocarbamoyl chitosan

Thiocarbamoyl chitosan (TC-Chitosan) was prepared, characterized and evaluated for the removal of Cr(VI) and Cd(II) from electroplating waste effluents. TC-Chitosan was characterized by various spectral techniques like SEM, EDAX, BET and FTIR. It was observed that Cd(II) adsorption was maximum at alkaline pH (7.5) in contrast to acidic pH (2.0) for Cr(VI). Langmuir isotherm model fitted better compared to the Freundlich model indicating monolayer adsorption. Equilibrium studies revealed a maximum adsorption capacity of 666.7 mg/g for Cd(II) and 434.8 mg/g for Cr(VI). The sorption process was found to follow pseudo second order kinetics with a rate constant of 0.0498 and 0.028 g/mg/h for Cr(VI) and Cd(II) respectively. Thermodynamic parameters such as Delta S, Delta H and Delta G indicated the suitability of TC-Chitosan towards the removal of Cr(VI) and cadmium. Simultaneous removal of both Cr(VI) and Cd(II) were achieved and applied to the removal of these heavy metals from electroplating wastewater. (c) 2012 Elsevier Ltd. All rights reserved.