Removal of Cr(VI) from aqueous solution using modified pomegranate peel: Equilibrium and kinetic studies

Abstract

The present investigation deals with the utilization of modified pomegrenate peel (MPGP) and formaldehyde modified pomegrenate peel (FMPGP) as adsorbents for the removal of chromium Cr(VI) from aqueous solution. A series of experiments were conducted in a batch system to evaluate the effect of system variables. The effect of pH, initial Cr(VI) concentration, contact time, adsorbent dosage and temperature were considered. The optimal pH values of Cr(VI) removal by MPGP and FMPGP were 2.0 and 3.0 respectively. The time required for equilibrium was found to be about 100 minutes. The initial Cr(VI) concentration and adsorbent dosage was found to have large effect on the adsorption of Cr(VI). The maximum uptake capacities were 13.01 and 22.28 mg of Cr(VI) per gram of MPGP and FMPGP respectively. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. Kinetic studies showed that the adsorption followed a pseudo second order reaction due to the high correlation coefficient and the agreement between the experimental and calculated values of qe.The adsorption may follow intraparticle diffusion as well, due to the highest values of rate constants for the surface adsorption and intraparticle diffusion kinetic models, the higher values of rate constants are related to an improved bonding between Cr(VI) ions and adsorbent particle.The Dubinin-radushkevich, Freundlich and Tempkin models were the closest fit for the equilibrium data of MPGP and FMPGP.