Another opportunity to accelerate ozonation reactions is to use heterogeneous or homogeneous catalysts. Several metal oxides and metal ions (Fe2O3, Al2O3–Me, MnO2, Ru/CeO2, TiO2–Me, Fe2+, Fe3+, Mn2+, etc.) have led to a significant acceleration in the decomposition of the target compound.
Advanced oxidation of chlorobenzenes in wastewater as well as in model solutions using iron and manganese ions as heterogeneous catalysts has concluded that the reduction of total organic carbon (TOC) and chemical oxygen demand (COD) from wastewater was more efficient with the ozone/catalyst system than oxidation with ozone at high pH values.
The O3/Mn(II) and O3/Fe(II) systems have found to be more effective in the removal of organochloride compounds than the O3/Fe(III) and O3/high pH systems.Catalytic ozonation of succinic acid is a must as it is barely oxidized by ozone alone. Ru/CeO2 can be used as a catalyst in this case.
Catalytic ozonation process using Al2O3, TiO2 in its anatase form, and clay as the support for metal catalysts; have worked well with compounds like Salicylic acid showing complete removal.
O3/TiO2 system is preferable in terms of process efficiency in TOC reduction when oxalic acid is the main compound to be removed. Ozone–Granulated Activated Carbon systems (O3/GAC) make a special case of catalytic ozonation. Quite well-known is the combined system O3/GAC for biorefractory compounds (for example, pesticides) destruction where the GAC’s bed life is prolonged due to the ozonated water. Using the GAC as a catalyst for free radical formation in ozonated water is getting popular.