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

•A heterogeneous Fenton catalyst derived from contaminated biomass was proposed.•The deep removal of THX was achieved in a short time using optimal BHFC-600.•Rising metal contents in biomass promote the performance of derived catalysts.•h+, OH, and O2– served as the main reactive species for THX degradation.•The preparation of functional catalysts from contaminated biomass is promising.