Abstract
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•Surface-modified bismuth vanadate is prepared for PMS activation under visible light.•CIP oxidation in BVO-2/PMS/Vis system is dominated by 1O2 and photogenerated holes.•Surface CO acts as Lewis base site to induce PMS hydrolysis in acidic condition.•The efficiently separated electrons can reduce PMS for SO4− and OH generation.
Lewis basic sites have been shown to induce singlet oxygen (1O2) generation in metal-free catalysts while have yet to be elucidated in metal-containing bismuth vanadate (BiVO4). Herein, surface-modified BiVO4 photocatalysts are developed and applied in peroxymonosulfate (PMS) activation for ciprofloxacin (CIP) abatement employing 1O2 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 1O2 generation. The occurrence of electron transfer from PMS to catalyst accounts for 1O2 generation via PMS oxidation. Moreover, PMS as an electron acceptor kinetically accelerates charge separation, not only inducing SO4− and OH 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.