Highly Efficient Removal of Cadmium by Sulfur-Modified Biochar: Process and Mechanism

The problems of biochar such as low adsorption capacity and slow adsorption rate limit its application in removing cadmium from water. However, the modification for enhancing the efficiency and expanding the application of biochar is a good way. In this paper, sulfur-modified biochar (SBC) derived from bagasse was prepared by impregnation pyrolysis at 500 °C. Sulfur was successfully loaded on the surface of biochar by SEM–EDS analysis and the specific surface area of SBC could be significantly increased by BET analysis. Batch experiments showed that the cadmium removal efficiency by SBC could reach more than 90% within 10 min, and the maximum adsorption capacity of cadmium was 268.2 mg g −1 , which was 22.35 times as high as that of unmodified biochar. Ion exchange with Na + , surface precipitation (CdCO 3 and CdS), complexation with C-SH, S–O, and COOH, and electrostatic interaction were the main mechanisms by XRD, FT-IR, and XPS analysis.