Role of interfacial electron transfer reactions on sulfamethoxazole degradation by reduced nontronite activating H2O2

It has been documented that organic contaminants can be degraded by hydroxyl radicals (•OH) produced by the activation of H 2 O 2 by Fe(II)-bearing clay. However, the interfacial electron transfer reactions between structural Fe(II) and H 2 O 2 for •OH generation and its effects on contaminant remediation are unclear. In this study, we first investigated the relation between •OH generation sites and sulfamethoxazole (SMX) degradation by activating H 2 O 2 using nontronite with different reduction extents. SMX (5.2–16.9 µmol/L) degradation first increased and then decreased with an increase in the reduction extent of nontronite from 22% to 62%, while the •OH production increased continually. Passivization treatment of edge sites and structural variation results revealed that interfacial electron transfer reactions between Fe(II) and H 2 O 2 occur at both the edge and basal plane. The enhancement on basal plane interfacial electron transfer reactions in a high reduction extent rNAu-2 leads to the enhancement on utilization efficiencies of structural Fe(II) and H 2 O 2 for •OH generation. However, the •OH produced at the basal planes is less efficient in oxidizing SMX than that of at edge sites. Oxidation of SMX could be sustainable in the H 2 O 2 /rNAu-2 system through chemically reduction. The results of this study show the importance role of •OH generation sites on antibiotic degradation and provide guidance and potential strategies for antibiotic degradation by Fe(II)-bearing clay minerals in H 2 O 2 -based treatments.