MoS₂/rGO Heterojunction Modified Graphite Felt for Electrochemical Detoxification of High-Arsenic Fly Ash

Accumulating high-arsenic fly ash (HAFA) has become a severe environmental problem in China due to its highly harmful effect on human health and ecological equilibrium. A novel graphite felt (GF) electrode modified with M0S₂/rGO heterojunction was designed and successfully applied in detoxification of HAFA in this study. The autocatalysis mechanism of As oxidative dissolution of HAFA was revealed. MoS₂/rGO nano heterojunctions were synthesized by a facile hydrothermal method. Then the nano heterojunction/PTFE mixed emulsion was uniformly coated on GF. Finally, the modified GF after calcination was used as a cathode to detoxify HAFA in neutral electrolyte. The density of states, charge density differences, and O₂ adsorption energies of heterojunction and individual component were calculated by first-principles. The results showed that an ultrahigh yield of H₂O₂ was obtained by 2e^- oxygen reduction reaction (ORR), which benefited from efficient utilization of both dissolved oxygen in solution and gaseous oxygen. The formation of p-n heterojunction significantly improved electrical conductivity and oxygen adsorption capacity of the catalysts, resulting in a high 2e^- ORR current density of 8.43 mA/cm^-2. HAFA activated H₂O₂ to transform into a reactive oxygen species OH with higher oxidation potential, significantly improving oxidation dissolution efficiency of As and reducing energy consumption. This study provides an effective detoxification approach for As-bearing hazardous solid waste. 
* This work was supported by the City University of Hong Kong Strategic Research Grant (SRG) [Reference No. 7005105], a grant from Xilingol Vocational College [Reference No. Y69019L088]