Enhanced mineralization of oxalate by heterogeneous peroxone: The interfacial reaction on the core-shell CeOx@SiO2

The mesoporous core-shell CeOx@SiO2 was synthesized and characterized by XRD, pyridine-FTIR, BET, SEM, TEM and XPS. CeOx@SiO2 was the hollow nanosphere with high surface area of 1291.4 m2 g−1, which benefited for mass transfer of reactants. CeOx@SiO2 exhibited the excellent catalytic activity for oxidizing oxalic acid (OA) in O3/H2O2/CeOx@SiO2. The greatest OA mineralization (91.2%) was achieved at pH = 3.2 in O3/H2O2/CeOx@SiO2, which was 5.5 times higher than that in peroxone (O3/H2O2, 15.9%). Influence of pH, HSO3−, PO43− and detection of ozone and H2O2 concentration were conducted to explore the mechanism. The interface reaction played vital role for OA removal in O3/H2O2/CeOx@SiO2 process. Protonated surface hydroxyl groups (Ce-OH2+) was the active sites, where OA, O3 and H2O2 were chemi-absorbed. The peroxide-like species (≡(Ce(IV)-O2H2)) formed by the complex of H2O2 with active sites were the important intermediates, which initiated ozone decomposition into hydroxyl radical (·OH) and led to the high OA mineralization. Moreover, Lewis acid sites and electron transfer effect of Ce(III)/Ce(IV) also accounted for the high catalytic activity of CeOx@SiO2. In addition, CeOx@SiO2 maintained stable structure and catalytic activity in three cycles.