Abstract：Adsorption of Cr(VI) in aqueous solution by rape straw shell powder had been studied. The effects of initial Cr(VI) concentration, pH, absorbent dosage, and adsorption temperature on the adsorption of Cr(VI) ion by rape straw shell powder was investigated and optimized with the method of Box-Behnken Design. The models of isotherm, kinetics and thermodynamics were employed to assess the efficiency and study mechanism of action on the removal Cr(VI) in the aqueous solution by rape straw shell powder. The changes in the functional groups of rape straw shell powder formulations were identified by Fourier transform infrared spectra. The optimal conditions for the removal of Cr(VI) were found to be initial Cr(VI) concentration of 99.15mg/L, pH 1.01, adsorbent dosage of 2.90g/L and adsorption temperature of 35.70℃ during 1440min of adsorption. Under these conditions, the percentage of removal of Cr(VI) reached 91.97%. The equilibrium data were optimally illustrated by the Freundlich isotherm model, which represents an optimal and heterogeneous adsorption; The results from thermodynamic study indicated that the adsorption process was spontaneous and endothermic in nature under experimental conditions. It was found that a pseudo-second order kinetic model was the proper approach for determining the adsorption kinetics and ion exchange. The functional groups of rape straw shell powder, O—H, C—H, NH3+, N—H and C—O played a major role in adsorption of Cr(VI). The results revealed that rape straw shell powder is an effective adsorbent for removing Cr(VI) in water due to its high adsorption capacity, and pH is the key factor for affecting the efficiency for the removal of Cr(VI).
