Study on the Hg⁰ removal characteristics and synergistic mechanism of iron-based modified biochar doped with multiple...

An iron-based composite adsorbent with biochar as the support was prepared by coprecipitation and the sol-gel method. Both single-iron-based modified biochar without doping with other metals and iron-based modified biochar doped with multiple metals (Ce, Cu, Co, Mn) were synthesised. The adsorption kinetics were analysed, and temperature-programmed desorption measurements were performed to reveal the inherent difference in mechanism between the oxidation and adsorption of Hg⁰ by the modified biochar and to elucidate the key mechanism of Hg⁰ removal. The results show that the removal of Hg⁰ by the modified biochar mainly includes adsorption and oxidation processes. The adsorption process is divided into two stages, external and internal mass transfer, both of which occur via multilayer adsorption. HgO and Hg-OM are the main forms of Hg⁰ present on the modified biochar surface. Doped metal oxides can play a synergistic role in enhancing the mercury removal performance of the modified biochar.