Sulfamethoxazole degradation by Ni2+ doped Fe2O3 on a nickel foam in peroxymonosulfate assisting photoelectrochemical oxidation system: Performance, mechanism and degradation pathway

In this work, to promote the catalytic efficiency of Fe2O3 and achieve the facile retrieve and recycle from the solution, Ni2+ doped Fe2O3 in-situ growing on a nickel foam (NF) (Ni-Fe2O3/NF) was fabricated using NF as the Ni2+ internal doping source and the substrate support and used in the peroxymonosulfate (PMS) assisting visible-light photoelectrochemical oxidation (EC + Photo + catalyst + PMS) system for sulfamethoxazole (SMX) degradation. Benefiting from more Fe2+ and oxygen vacancies generation after Ni2+, and the enhanced electrical conductivity owing to NF substrate, the optimum Ni-Fe2O3/NF(II) exhibited excellent catalytic efficiency. 100% of SMX was removed in 10 min in the EC + Photo + Ni-Fe2O3/NF(II) + PMS system and the pseudo-first order kinetic constant (kobs) was 45.10 × 10-2 min−1, being about 9.80 folds of powder Fe2O3. Meantime, due to the employed loading method benefits in the Ni-Fe2O3 uniformly and steady loading on NF, Ni-Fe2O3/NF(II) demonstrated the excellent stability and recycle ability. Reactive oxygen species (ROSs) quenching and electron paramagnetic resonance evidenced that photo-induced hole (h+), hydroxy radical (•OH) and superoxide radical (•O2−) contributed to SMX degradation. And the SMX degradation pathways were deduced according to the determined degraded products and density functional theory (DFT) calculation. This study developed one convenient separation and recovery catalyst suitable for EC + Photo + catalyst + PMS system for efficient and environmentally friendly antibiotics removal in water.