Catalytic wet-air oxidation processes: A review

Environmental catalysis usually refers to end-of-the-pipe treatment processes that reduce the emissions of hazardous pollutants. Abatement of pollutants in aqueous streams by means of heterogeneous catalysts is an example of such process. This paper reviews the developments in the field of catalytic wet-air oxidation (CWAO). Catalysts are reviewed first, followed by mechanistic speculations and kinetics that have been proposed for the CWAO process. The process is discussed more in detail only in those cases where it is already commercialised or at least foreseen to be in the near future. Particular attention was given to the heterogeneously catalyzed wet-air oxidation of real industrial wastewaters (such as Kraft bleach plant effluents) in batch and continuous-flow oxidation reactors. Finally, the considerable potential of the CWAO process to ultimately destroy organic pollutants in industrial effluents and detoxify them by using novel titania-supported Ru catalysts is presented.