Humic acid-based Fe/Ag bimetallic Fenton-like catalysts for efficient degradation of sulfadiazine in water.

Humic acid (HA) was a natural organic macromolecule, which was considered as an ideal carrier for Fenton-like catalysts due to the large number of active functional groups on its surface. For this reason, humic acid-based Fe/Ag bimetallic catalysts (Fe3O4/HA/Ag) were synthesized by introducing Fe and Ag to the humic acid carrier. The morphology and physicochemical properties of Fe3O4/HA/Ag was revealed by different characterization methods. In the optimized "Fe3O4/HA/Ag + H2O2" Fenton-like system, Fe3O4/HA/Ag can rapidly activate H2O2 and accelerate electron transfer. It was applied for sulfadiazine (SDZ) degradation and the removal efficiency reached nearly 100 %. After five cycle experiments, the degradation percentage was maintained at 88.7 %, showing excellent regeneration ability. In addition, Fe3O4/HA/Ag has good resistance to co-existing ions and different water matrices. The main active substances in the "Fe3O4/HA/Ag + H2O2" system were hydroxyl radicals (•OH), superoxide radicals (•O2-) and singlet oxygen (1O2), which supported by EPR and XPS analysis. This study provides a new way for the promotion of SDZ degradation through bimetallic co-catalytic activation of H2O2, which has significant potential for the treatment of antibiotic wastewater.