Equilibrium removal, isotherm and kinetic studies of chromium (VI) adsorption onto biopolymers from aqueous solution: A comparative study

Abstract

In the present study biopolymers were used as adsorbents to treat Cr (VI) ions from the aqueous solutions. Chitin prepared using sea shells (CS) and commercially available chitin (CC) was used for the adsorption studies on Chromium VI removal from the synthetic waste water. Chitin was extracted from sea shells by two step procedure and was characterized for the composition, functional groups, surface morphology and the yield. Sorption tests were done at room temperature by varying the metrics like initial metal ion concentration, contact time, pH, and adsorbent dosage. The optimized parameters were: pH 2, 50 ppm Cr (VI) concentration, and 4 g/L of adsorbent dosage and contact time of 60 min. Isotherm and kinetic studies were carried out, the sorption capacities of CS and CC for Langmuir isotherm were 9.52 and 5.62 mg/g and that of the Freundlich isotherm was 0.542 and 3.68 mg/g. The intensity of adsorption was better for CS than CC suggesting the feasibility of adsorption. Both CC and CS exhibited better rate constant for a pseudo II order model which suggests that pseudo II order model best described the Cr (VI) adsorption kinetics on biopolymers.