Synthesis of Ce-doped magnetic biochar for effective Sb(V) removal: Performance and mechanism

A novel Ce-doped magnetic biochar was successfully synthesized by chemical co-precipitation (Ce/Fe _CP -BC) and solvothermal methods (Ce/Fe _ST -BC) for efficient Sb(V) adsorption. The Ce/Fe _CP -BC exhibited a high adsorption capacity of 25.0 mg/g, which was two times and one order of magnitude higher than that of Ce/Fe _ST -BC and un-doped BC, respectively. The excellent adsorption performance of Ce/Fe _CP -BC maintained over a wide pH range or in the presence of coexisting anions. The adsorption results indicated that co-precipitation method was superior to solvothermal method and Ce oxide was the main contribution to Sb(V) adsorption enhancement. The combined results of TEM, XRD, FTIR and XPS revealed that Ce atom was successfully doped into the Fe ₃ O ₄ structure and abundant hydroxyl groups were formed on the surface of Ce/Fe _CP -BC. The magnetic performance decreased after Ce doping, but Ce/Fe _CP -BC still showed good separation potential. Based on the results of batch experiments and physiochemical analyses, the underlying mechanisms controlling Sb(V) adsorption on Ce/Fe _CP -BC involved the inner-sphere surface complexation, hydrogen bonding, electrostatic attraction and ligand exchange. Among them, the ligand exchange and the formation of Ce–O–Sb complex were the main contributions to the significant Sb(V) adsorption increment on Ce/Fe _CP -BC. All the results implied that Ce/Fe _CP -BC could be used as a promising adsorbent for antimonate decontamination.