Abstract:Biochar exhibits good adsorption capacity due to its highly developed pore structure, abundant surface functional groups and large number of surface charges. It has also attracted widespread attention due to the available raw materials and low cost. Applying wheat straw as biomass raw material to prepare a series of straw-derived biochars by modification with Fe(Ⅱ)/Fe(Ⅲ) iron compounds. Effect of different procedures of carbonization-impregnation at different temperatures on adsorption performance of modified biochars for Cr(Ⅵ) was investigated. The results show that the procedure of impregnation followed with carbonization is superior to that of carbonization followed with impregnation. The optimal temperature for carbonization is 450 ℃. Fe(Ⅲ) is beneficial to adsorption for Cr(Ⅵ), while Fe(Ⅱ) enhances the magnetism of biochars. For the biochar prepared with the procedure of impregnation by Fe(Ⅲ) followed with carbonization at 450 ℃, the removal rate of Cr(Ⅵ) reaches 99.99% under the conditions including initial concentration of Cr(Ⅵ) of 100 mg/L, biochar dosage of 0.1 g, pH value of the solution of 2, temperature of 30 ℃, and adsorption time of 21 h.