A kinetic model of ti(IV)-catalyzed H2O2/O3 process in aqueous solution

Oxygen vacancies and Lewis sites activating O3/H2O2 at wide pH range via surface electron transfer over CeOx@SiO2 for nitrobenzene mineralization

The low efficiency of peroxone (O₃/H₂O₂) at acidic and neutral pH restrained its application in water purification. To overcome this shortcoming, CeO_X@SiO₂ with large surface area, abundant surface oxygen vacancies (V_o), Lewis sites (L sites) and high Ce(III)/Ce(IV) ratio were synthesized to change the traditional electron transfer pathway between O₃ and H₂O₂. V_o was facile in absorbing H₂O₂ to form V_o-H₂O₂ and L sites were capable of absorbing O₃ to form L-O₃. The electron at V_o could be donated to V_o-H₂O₂ and generate V_o-HO₂^-, which then effectively triggered the decomposition of L-O₃ at CeO_X@SiO₂'s interface and O₃ in bulk solution. The electron transfer at the solid-liquid interface with the help of Ce³⁺/Ce⁴⁺ redox cycle and V_o was pH independent and different from the traditional electron transfer of peroxone reaction. Nitrobenzene (NB) mineralization was promoted to 92.5% in CeO_X@SiO₂-peroxone, but only 63.8% TOC was removed in tradition peroxone process. Moreover, CeO_X@SiO₂-peroxone had a wide pH application range. NB's degradation in CeO_X@SiO₂-peroxone process followed the co-oxidation mechanism of superoxide free (•O₂^-) and hydroxyl radical (•OH). The finding of this study could broaden the popularization of peroxone in water treatment and provided a strategy for catalyst design.