Heterogeneous photocatalyst-driven persulfate activation process under visible light irradiation: From basic catalyst design principles to novel enhancement strategies

Recently, light-driven persulfate-based advanced oxidation processes (AOPs) employing heterogeneous catalysts to generate sulfate radicals (SO4 center dot-) from persulfates [peroxydisulfate (PDS, S2O82-) and peroxymonosulfate (PMS, HSO5-)] have been extensively investigated in the field of water remediation, to remove organic contaminants. This article aims to provide a comprehensive review of visible light-driven heterogeneous catalysis of persulfate activation, including the reaction mechanisms involved and the various types of heterogeneous catalysts utilized in organic contaminant removal, with particular focus on strategies for its enhancement. In the present review, we summarize three strategies for improving the visible light/persulfate/heterogeneous catalyst system, including photocatalyst design, photoelectricity coupling, and indirect activation mediated by homogeneous Fe (III) or Cu(II). This review highlights the advances in the photo-activation of persulfates for organic contaminant removal and also provides perspectives on the major challenges and opportunities involved.