Sorption Characteristics of Hexavalent Chromium [Cr(VI)] onto Bone Char and Bio-char.

Abstract: The sorption characteristics of hexavalent chromium [Cr(VI)] onto bone char and bio-char were evaluated as a function of pH, initial Cr(VI) concentration, and dosages of bone char and bio-char. Batch tests were conducted by using synthetic wastewater in this study. The effects of various initial Cr(VI) concentrations between 5 mg/L and 1000 mg/L were evaluated using bone char as a sorbent. A Cr(VI) removal efficiency of 100 % was achieved at pH 1 with 2 g of bone char in 50 mL of solution at 3 hours of reaction time using initial Cr(VI) concentration of 10 mg/L. About 100 % of Cr(VI) was removed at pH 2 with initial Cr(VI) concentrations of 10 mg/L using 4 g of bio-char in 200 mL of solution at 5 hours of reaction time. The initial Cr(VI) concentrations were varied between 10 mg/L and 500 mg/L when bio-char was used as the sorbent. The maximum sorption capacities of bone char and bio-char were determined to 6.46 mg Cr(VI)/g, and 1.717 mg Cr(VI)/g, respectively. Equilibrium, kinetics, and isotherms of the sorption process were also investigated. The sorption kinetics of Cr(VI) onto bone char and bio-char followed the second order kinetic model suggesting that the sorption reaction rate depends on two parameters, which might be the sorbate concentration and sorbent dosage. The Langmuir isotherm model was the best one for the description of sorption of Cr(VI) onto bone char and bio-char.