The behavior of ozone on different iron oxides surface sites in water

A transformation process of ozone on different iron oxides suspensions, including α-Fe₂O₃, α-FeOOH, Fe₃O₄, was carried out using FTIR of adsorbed pyridine, ATR-FTIR and electron paramagnetic resonance (EPR) spectra with isotope ¹⁸O₃. It was verified that on the surface isolated hydroxyl groups and the surface hydroxyl groups without acid sites of these iron oxides, ozone was electrostatically adsorbed and did not interact with the surface of these oxides, stably existed as ozone molecule. In contrast, ozone could replace the surface hydroxyl groups on Lewis acid sites of oxides, and directly interacted with the surface metal ions, decomposing into reactive oxygen species (ROS) and initiating the surface metal redox. The results indicate that Lewis acid sites were active center while the electronic cycle of the Fe²⁺/Fe³⁺ is advantageous to promote ozone decomposition into O₂^•- and ^•OH radicals. The mechanism of catalytic ozonation in different surface acid sites of iron oxides aqueous suspension was proposed on the basis of all experimental information.