Abstract:A novel sludge biochar (KBC) was prepared by oxidation modification with KMnO4 for treating Cd(Ⅱ) in acid mine wastewater. The effects initial solution pH value, co-existing ions, dosage, adsorption time and pollutant concentration on the removal efficiency of Cd(Ⅱ) by modified biochar were investigated by batch adsorption tests, and the removal mechanism of Cd(Ⅱ) by modified biochar was explored by characterization techniques. The results show that the oxidation modification of KMnO4 increases the number of O-containing groups, the specific surface areas and the degree of graphitization in KBC. The batch adsorption tests show that the maximum adsorption of Cd(Ⅱ) by raw sludge biochar (BC) and KBC is 53.27 and 99.22 mg/g, respectively, under the optimum conditions including temperature of 25 ℃, dosage of 1 g/L, adsorption time of 300 min and pH value of 5.0. In addition, the concentration of NaCl has little effect on the adsorption of Cd(Ⅱ) by BC and KBC. After four replicate experiments, the removal efficiency of Cd(Ⅱ) by BC and KBC is 64.05% and 90.34%, respectively. Complexation of Cd(Ⅱ) with O-containing groups, Cd-π interactions, co-precipitation, and electrostatic interactions are the main mechanisms for Cd(Ⅱ) removal from aqueous solutions by BC and KBC. The oxidation modification of KMnO4 can effectively improve the treatment of Cd(Ⅱ) in acid mine wastewater by sludge biochar.