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 (O 3 /H 2 O 2 ) at acidic and neutral pH restrained its application in water purification . To overcome this shortcoming, CeO X @SiO 2 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 O 3 and H 2 O 2 . V o was facile in absorbing H 2 O 2 to form V o -H 2 O 2 and L sites were capable of absorbing O 3 to form L-O 3 . The electron at V o could be donated to V o -H 2 O 2 and generate V o -HO 2 − , which then effectively triggered the decomposition of L-O 3 at CeO X @SiO 2 ’s interface and O 3 in bulk solution. The electron transfer at the solid-liquid interface with the help of Ce 3+ /Ce 4+ 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 @SiO 2 -peroxone, but only 63.8% TOC was removed in tradition peroxone process. Moreover, CeO X @SiO 2 -peroxone had a wide pH application range. NB’s degradation in CeO X @SiO 2 -peroxone process followed the co-oxidation mechanism of superoxide free (•O 2 − ) 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.