As one of advanced oxidation processes(AOPs), catalytic ozonation has recently gained significant attention in the field of wastewater treatment. Heterogeneous catalytic ozonation have notable advantages of strong oxidation, less ozone dosage and especially its potentially greater effectiveness in the mineralization of organic matter. New catalysts have been studied world widely, but the reaction process and mechanisms are much more complicated. The efficiency of catalytic ozonation process depends to a great extent on the catalyst and its surface properties. On the surface active sites of catalyst,pollutants adsorbed form surface complexes or ozone decomposes to various reactive oxygen species such as surface atomic oxygen (^*O), surface peroxide (O₂^·-), hydroxyl radical (·OH). Thus the main mechanisms of heterogeneous catalytic ozonation are reviewed, including radical mechanism, oxygen vacancies theory, surface atomic oxygen mechanism, surface complexes theory and direct ozonation mechanism. The hydroxyl groups on the surface of catalyst are mainly catalytic active centers. The catalytic reaction mechanisms by hydroxyl groups are introduced in this paper. Surface properties of the catalysts determine the properties of the surface active sites and its amount, which play a key role in ozone decomposition. The structure and morphology, the specially surface area, the catalytic performance as well as reaction mechanisms of modified catalysts are reviewed. The future development of heterogeneous catalysts are also discussed to provide a theoretical reference of heterogeneous catalytic ozonation.

Contents
1 Introduction
2 Mechanism of heterogeneous catalytic ozonation
2.1 Radical mechanism
2.2 Oxygen vacancies mechanism
2.3 Surface atomic oxygen mechanism
2.4 Surface complexes mechanism
2.5 Direct ozonation mechanism
3 Catalytic reaction mechanisms by hydroxyl groups on the surface of catalyst
4 Heterogeneous catalytic ozonation mechanism after modification of the catalysts
4.1 Catalytic performance of modified catalysts
4.2 Reaction mechanism of modified catalysts
5 Conclusion and outlook