Activation of HO, PMS, and PDS over anatase TiO-supported photocatalysts for efficient pollutant mineralization in water

Mineralization efficiency is a key performance descriptor for heterogeneous photocatalysts in the removal of organic pollutants from water. Although the use of radical promoters can enhance the mineralization process, their effectiveness is highly dependent on the nature of the reactive species generated and, in some cases, may even lead to reduced mineralization efficiency. In this work, a supported anatase-TiO 2 photocatalyst was used to investigate the mineralization of ortho-phenylphenol (OPP) under UVA irradiation in the presence of three radical promoters: H 2 O 2 , peroxymonosulfate (PMS), and peroxydisulfate (PDS). For this purpose, a core@shell SiO 2 @TiO 2 photocatalyst was synthesized and thoroughly characterized to relate its structural and surface properties to its ability to activate these radical promoters. Notably, photocatalytic experiments showed that OPP photodegradation and total organic carbon (TOC) removal were not directly correlated, indicating that fast pollutant degradation does not necessarily imply efficient mineralization. Accordingly, only PMS significantly improved OPP mineralization efficiency of bare SiO 2 @TiO 2 , achieving a conversion of ~95% within 2 h. Electron paramagnetic resonance (EPR) experiments revealed the main radicals generated in each system, providing mechanistic insights that were further corroborated by the differing reactivity of the visible-light-responsive ligand-to-metal charge-transfer (LMCT) complexes formed on the SiO 2 @TiO 2 photocatalyst surface. This study provides valuable guidelines for future research on the characterization and design of photocatalytic systems that utilize radical promoters.