The relation of interface electron transfer and PMS activation by the H-bonding interaction between composite metal and MCM-48 during sulfamethazine ozonation

Co-Ce as the dominant active sites immobilized MCM-48 (Co-Ce/MCM-48) was fabricated via H-bonding by the hydrothermal and incipient wetness co-impregnation method. The incorporation of Co-Ce/MCM-48 (67.2%) provided higher mineralization of sulfamethazine (SMT) than Co/MCM-48 (62.2%) and Ce/MCM-48 (39.4%) in O-3/peroxymonosulfate (O-3/PMS) system at 90 min reaction time. The catalytic efficiency could be further improved owing to enhanced PMS decomposition rate when initial pH increased to 9.4. The electron transfer capacity in Co-Ce/MCM-48/O-3/PMS was improved according to in-situ electrochemical tests. In situ-Raman characterization implied that PMS was bonded to the Co center dot center dot center dot HO-Si-O-Si-OH center dot center dot center dot Ce to generate the Ce-OH center dot center dot center dot HSO5- and Co-OH center dot center dot center dot HSO5- complexes, which was decomposed by O-3 and one-electron transfer reaction into reactive oxygen species (ROSs). LC-MS analysis indicated that the breakage of N-S bond, SO2 extrusion and -CH3 oxidation on rings were the major degradation pathway during SMT degradation. To uncover the relationship of interface electron transfer with Co-Ce/MCM-48 and PMS activation by O-3, electron paramagnetic resonance (EPR) spectra was recorded to investigate the variation of ROSs in different processes. Simultaneous PMS reduction and oxidation over the solid-liquid-gas interface occurred for the generation of free and non-free radicals in Co-Ce/MCM-48/O-3/PMS process.