The catalyst Ru/TiZrO4 was applied in the degradation of Isophorone by catalytic wet air oxidation. Mathematical models for the effects of reaction conditions on the Isophorone degradation by catalytic wet air oxidation were developed using a response surface methodology. A model was obtained for each response with multiple regression analysis and then was refined. Analysis of variance revealed that the models developed were adequate. The validity of the models was also verified by experimental data. Analysis of response surface showed that total organic carbon removal and Isophorone conversion were significantly affected (P <= 0.01) by reaction time, temperature and their interactions, and affected (P <= 0.05) by the square of reaction time. The point of zero charge of Ru/TiZrO4 catalyst was about 1.72. The total organic carbon removal and Isophorone conversion had a great association with the zeta potential of Ru/TiZrO4 catalyst. Finally, the degradation pathway of Isophorone in catalytic wet air oxidation was proposed. Within 410 h, the total organic carbon removal remained above 95%, indicating that the Ru/TiZrO4 catalyst had a good stability. (c) 2012 Elsevier B.V. All rights reserved.