Visible-light-driven photocatalytic activation of peroxymonosulfate by Cu(OH)PO for effective decontamination.

The advanced oxidation process (AOP) based on SO radicals draws an increasing interest in water and wastewater treatment. Producing SO radicals from the activation of peroxymonosulfate (PMS) by transition metal ions or oxides may be problematic due to high operational cost and potential secondary pollution caused by metal leaching. To address this challenge, the present study reports the efficient production of SO radicals through visible-light-driven photocatalytic activation (VL-PCA) of PMS by using Cu(OH)PO single crystal for enhanced degradation of a typical recalcitrant organic pollutant, i.e., 2,4-dichlorophenol (2,4-DCP). It took only 7 min to achieve almost 100% removal of 2,4-DCP in the Cu(OH)PO/PMS system under visible-light irradiation and pH-neutral condition. The 2,4-DCP degradation was positively correlated to the amount of Cu(OH)PO and PMS. Both OH and SO radicals were responsible for enhanced degradation performance, indicated by radical scavenger experiments and electron spin resonance (ESR) measurements. The Cu(OH)PO single crystal exhibited good cyclic stability and negligible metal leaching. According to density functional theory (DFT) calculations, the visible-light-driven transformation of two copper states between trigonal bipyramidal sites and octahedral sites in the crystal structure of Cu(OH)PO facilitates the generation of OH and SO radicals from the activation of PMS and cleavage of O-O bonds. This study provides the proof-in-concept demonstration of activation of PMS driven by visible light, making the SO radicals-based AOPs much easier, more economical and more sustainable in engineering applications for water and wastewater treatment.