Kinetic and equilibrium study of chromium(VI) sorption on vernticompost

Chemistry Department, D. S. College. Aligarh-202 001, Uttar Pradesh, India

E-mail : drop1955@gmail.com

Manuscript received 30 December 2010, revised 06 May 2011, accepted 17 August 2011

The study concerns with the adsorption of Cr^VI under varying pH, contact time and also the effect of concentration of Cr^VI on vermicompost. The optimum pH and time of contact required for maximum adsorption was found to be 4 and 180 min respectively and adsorption decreased as pH rises above 4. Freundlich adsorption model was best fit for the adsorption data. The values of 1/n were less than unity implying a strong interaction between sorbent and metal ions. The kinetics of adsorption was found to follow the first order reversible reaction. The desorption rate constant was smaller than adsorption rate constant indicating a stable metal sorbent complex. The standard enthalpy changes (ΔHº ) showed the process is exothermic; the values of ΔGº support the inference that sorption process is spontaneous.