Catalytic degradation of ciprofloxacin by a visible-light-assisted peroxymonosulfate activation system: Performance and mechanism

• Published in: Water research (Oxford) Vol. 173; p. 115559
• Main Authors: Chen, Fei, Huang, Gui-Xiang, Yao, Fu-Bing, Yang, Qi, Zheng, Yu-Ming, Zhao, Quan-Bao, Yu, Han-Qing
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.04.2020
• Subjects: BiVO4; Catalysis; Catalytic degradation; Ciprofloxacin; decontamination; electron paramagnetic resonance spectroscopy; free radicals; Light; Mechanism; nanosheets; oxidants; oxidation; Peroxides; Peroxymonosulfate; pollution control; spectrometers; sulfates; toxicity; Visible light; water; Water treatment; Water treatment; Visible light; Peroxymonosulfate; Catalytic degradation; Mechanism; BiVO4; BiVO
• ISSN: 0043-1354; 1879-2448; 1879-2448
• DOI: 10.1016/j.watres.2020.115559

Peroxymonosulfate (PMS) is extensively used as an oxidant to develop the sulfate radical-based advanced oxidation processes in the decontamination of organic pollutants and various PMS activation methods have been explored. Visible-light-assisted PMS activation to construct a Fenton-like process has shown a great potential for pollution control. In our work, BiVO4 nanosheets were prepared using a hydrothermal process and used to activate PMS under visible light. A rapid degradation of ciprofloxacin (CIP) was achieved by dosing PMS (0.96 g/L), BiVO4 (0.32 g/L) under visible light with a reaction rate constant of 77.72-fold higher than that in the BiVO4/visible light process. The electron spin resonance and free radical quenching experiments indicate that reactive species of •O2−, h+, •OH and SO4•− all worked, where h+, •OH and SO4•− were found as the dominant contributors to the CIP degradation. The spectroscopic analyses further demonstrate that the photoinduced electrons were directly involved in the PMS activation process. The generated •O2− was partially utilized to activate PMS and more •OH was produced because of the chain reactions between SO4•− and H2O/OH−. In this process, PMS acted as an electron acceptor to transfer the photo-induced charges from the conduction band of BiVO4 and PMS was successfully activated to yield the high-powered oxidative species. From the degradation intermediates of CIP detected by a liquid-chromatography-mass spectrometer, the possible degradation pathways were proposed. The substantially decreased toxicity of CIP after the reaction was also observed. This work might provide new insights into the visible-light-assisted PMS activation mechanisms and is useful to construct environmentally-friendly catalytic processes for the efficient degradation of organic pollutants. [Display omitted] •PMS was effectively activated by BiVO4 nanosheets for water purification under visible light.•Separation of electron/hole pairs and generation of oxidative species were enhanced.•Visible-light-assisted PMS activation Fenton-like mechanism was elucidated.•High mineralization and low biotoxicity validated the application potential of the system.