Peroxymonosulfate activation by surface-modified bismuth vanadate for ciprofloxacin abatement under visible light: Insights into the generation of singlet oxygen

Lewis basic sites have been shown to induce singlet oxygen (O-1(2)) generation in metal-free catalysts while have yet to be elucidated in metal-containing bismuth vanadate (BiVO4). Herein, surface-modified BiVO4 photo-catalysts are developed and applied in peroxymonosulfate (PMS) activation for ciprofloxacin (CIP) abatement employing O-1(2) and photogenerated holes as the primary reactive species. The surface carbonyl moiety acts as Lewis basic sites to induce PMS hydrolysis under acidic conditions for O-1(2) generation. The occurrence of electron transfer from PMS to catalyst accounts for O-1(2) generation via PMS oxidation. Moreover, PMS as an electron acceptor kinetically accelerates charge separation, not only inducing SO4 center dot- and (OH)-O-center dot; generation but also allowing direct oxidation of CIP by efficiently separated holes. Accordingly, the optimal BVO-2/PMS/Vis system can completely degrade CIP in 9 min under visible light with a reaction rate of 0.4264 min(-1), far exceeding the BVO-2/PMS (0.0063 min(-1)) and BVO-2/Vis (0.0411 min(-1)) systems.