Biosorption and desorption studies on chromium(VI) by novel biosorbents of raw rutin and rutin resin

Rutins are ubiquitous polyphenols of plants and the present work is the first study to investigate the utilization of raw rutin and rutin resin as novel biosorbents for removing the poisonous chromium(VI) from aqueous solution by a biosorption process. The biosorption studies were performed in batch mode under various parameters such as contact time, initial Cr(VI) concentration, initial pH, biosorbent dose and temperature. Langmuir and Freundlich isotherm models were found to fit the equilibrium data very well. Maximum biosorption capacities of raw rutin and rutin resin were 26.3 and 41.6 mg/g, respectively. By modeling the kinetic experimental data, the pseudo-second order prevailed over the pseudo-second order model. The thermodynamic characteristics of Cr(VI)-biosorption process onto the rutin biosorbents surface were estimated to be spontaneous and endothermic process. Desorption experiments were conducted for regenerating rutin resin which exhibited higher biosorption capacity after biosorption Cr(VI) using 0.1 N HNO3 and distilled water within 4 consecutive cycles. High recovery efficiency for desorbing Cr(VI) was attained with nitric acid until four cycles. Overall, the relatively low cost and high capabilities of raw rutin and rutin resin make them potentially attractive biosorbents for the removal of Cr(VI) from the aqueous solution.