Upcycling contaminated biomass into metal-supported heterogeneous catalyst for electro-Fenton degradation of thiamethoxam: Preparation, mechanisms, and implications

The safe disposal and resource utilization of heavy metal contaminated biomass has long posed a huge challenge. The direct preparation of heavy metal-contaminated straw into a biomass-derived multi-metal loading heterogeneous Fenton catalyst (BHFC) through pyrolysis for thiamethoxam (THX) degradation is a win–win strategy to address this problem. In this method, Fe, Mn, Cu, and Zn in contaminated biomass collected from mineral areas are released as active metals and loaded in the form of metal oxides on biomass pyrolysis biochar with a mesoporous structure. The presence of multiple metals accelerated the mutual redox, increased oxygen mobility, synergistically promoted the generation of hydroxyl radicals, and reached 100% THX degradation rate and 90% total organic carbon removal within 20 min using the optimum BHFC-600. The BHFC derived from biomass contaminated with different heavy metal contents showed differences in catalytic performance. The THX degradation rate of BHFC prepared from higher metal level biomass increased by 1.2-fold compared to the low level. Possible pathways and mechanisms of THX degradation was investigated using different methods, including density functional theory calculations. The degradation of THX can be mainly attributed to h⁺, [rad]OH, and [rad]O₂^– attacking the region with a high Fukui index. This study presents a promising strategy for preparing sustainable environmentally functional materials and provides new feasible ideas for the safe treatment of contaminated biomass.