Ferromanganese oxide-functionalized TiO₂ for rapid catalytic ozonation of PPCPs through a coordinated oxidation...

Ferromanganese oxide (MFO_x) was first utilized to functionalize TiO₂ and an MFO_x@TiO₂ catalyst was developed for catalytic ozonation for rapid attack of pharmaceutical and personal care products (PPCPs) with adjusted reactive oxygen species (ROSs) composition and strengthened ROSs generation. Unlike Al₂O₃, which strongly relied on adsorption and was significantly influenced by MFO_x loading, synergistic catalytical effects of MFO_x and TiO₂ were observed, and optimal MFO_x doping of 2 wt% and MFO_x@TiO₂ dosage of 500 ppm were obtained for catalyzing ozonation. In ibuprofen (IBP) degradation, MFO_x@TiO₂-catalyzed ozonation (MFO_x@TiO₂/O₃) obtained 2.0-, 4.7- and 6.9-folds the k_obs of TiO₂/O₃, MFO_x/O₃ and bare ozonation (B/O₃). Stronger O₃ decomposition was observed by MFO_x@TiO₂ over bare TiO₂ with the participation of redox pairs Fe(II)/Fe(III) and Mn(II)/Mn(III)/Mn(IV) and increased surface oxygen vacancies (SOVs) from 9.8 % to 33.7 % was detected. The results revealed that Fe(II), Mn(II) and Mn(III) with low valance accelerated Ti(III) generation from Ti(VI), obtaining an unprecedented high Ti(III) composition occupying 35.3 % of the total Ti atoms. Ti(III) catalyzed the direct reduction of SOVs-O₂ to •O₂^-, and it accelerated the formation of Ti(VI)-OH and Ti(VI)-O which catalyzed O₃ decomposition into •O₂^-. •O₂^- was found to primarily initiate IBP degradation with nucleophilic addition and dominated over 66 % IBP removal. The enhanced •O₂^- generation further strengthened •OH and ¹O₂ production. MFO_x@TiO₂/O₃ obtained 17 %, 21 % and 30 % higher TOC removal over TiO₂/O₃, MFO_x/O₃ and B/O₃, respectively. Acute toxicity tests confirmed the effective toxicity control of organics by MFO_x@TiO₂/O₃ process (inhibition rate: 10.9 %). Degradation test of atenolol and sulfamethoxazole confirmed the catalytic effects of MFO_x@TiO₂. MFO_x@TiO₂ performed strong resistance to water matrix in application test and showed good stability and reusability. The study proposed an effective catalyst for strengthening the ozonation process on PPCPs degradation and provided an in-depth understanding of the mechanisms and characteristics of the MFO_x@TiO₂ catalyst and MFO_x@TiO₂/O₃ process.