Removal of Hexavalent Chromium from Aqueous Solutions Using Biopolymers

Abstract

Two biopolymers were prepared by reaction of chestnut and quebracho tannins with gelatin extracted from untanned hide wastes. Obtained biopolymers were evaluated as adsorbents for removing Cr(VI) from water using the batch equilibrium technique. Adsorption of Cr(VI) by gelatin–chestnut (GC) and gelatin–quebracho (GQ) biopolymers was investigated as a function of initial pH, adsorbent mass, contact time, and initial metal ion concentration. Maximum Cr(VI) uptake was obtained at pH 4 and the percentage of Cr(VI) adsorbed increased significantly by increasing the biopolymer mass. The contact times that were enough to reach equilibrium were 9 and 15 min using GC and GQ, respectively. The pseudo-second-order equation provided the best kinetic model for the biosorption process (R2=.9999 for GC and R2=.9916 for GQ). The intraparticle diffusion model was also investigated to describe the adsorption kinetics of Cr(VI) onto synthesised biopolymers. Langmuir and Freundlich isotherms were applied to describe the experimental equilibrium data obtained at 25±2°C. The process was well described by Langmuir isotherm and the maximum uptake values, Qmax, were 8.64 and 26.25 mg/g for dry GC and GQ biopolymers, respectively.