| 【Objective】The study aimed to explore the optimal conditions for adsorption of Cr by bagasse biochar
and reveal the underlying mechanisms.【Method】Under the preservation of N2, three types of bagasse biochar were
prepared with the temperature precisely controlled at 350, 450 and 550 ℃ , respectively. The changes in morphology of
bagasse before and after carbonization were compared by using scanning electron microscope（SEM）. The effects of
preparation temperature, dosage of biochar, initial concentration of Cr and reaction time on the adsorption of Cr（Ⅲ）
and Cr（Ⅵ）were investigated.【Result】The porosity of bagasse biochar expanded with the increase in preparation
temperature. Bagasse biochar prepared at low temperature exhibited good efficiency for Cr（Ⅵ）removal, when the mass
concentration of Cr（Ⅵ）and carbon dosage were 50 mg/L and 15 g/L, the maximum amount of adsorbed Cr（Ⅵ）by
bagasse biochar prepared at 350 ℃ was 5.703 mg/g after reaction for 7 d, with the removal rate of 92.39%. The bagasse biochar prepared at high temperature showed optimal efficiency for Cr（Ⅲ ）removal rate. When the mass concentration
of Cr（Ⅵ ）and carbon dosage were 75 mg/L and 10 g/L, the maximum amount of adsorbed Cr（Ⅵ ）by bagasse biochar
prepared at 550 ℃ was 9.158 mg/g after reaction for 7 d, with the removal rate of 97.06%. The adsorption isotherm of Cr
obeyed the Langmuir model, and the kinetics curves of Cr（Ⅵ）and Cr（Ⅲ）fitted the pseudo-first-order kinetic model
and pseudo-second-order kinetic model, respectively.【Conclusion】The efficiency of Cr（Ⅲ）and Cr（Ⅵ）removal was
largely dependent on the temperature for biochar preparation. Based on the results above, the biochar prepared at 350 ℃
showed optimal efficiency for Cr（Ⅵ）adsorption, and 550 ℃ for Cr（Ⅲ）adsorption. |
