Catalytic wet air oxidation (CWAO) is a powerful method to remove a broad range of contaminants in waste streams. In this process most organic compounds can be decomposed to CO₂ and other nontoxic substances. Ammonia elimination has been shown to be one of potential applications of CWAO in recent years. This thesis presents an experimental and fundamental study of heterogeneous catalysts for simultaneously oxidizing ammonia and organic compounds. _{2 2 3}...[ Read more ]

Catalytic wet air oxidation (CWAO) is a powerful method to remove a broad range of contaminants in waste streams. In this process most organic compounds can be decomposed to CO₂ and other nontoxic substances. Ammonia elimination has been shown to be one of potential applications of CWAO in recent years. This thesis presents an experimental and fundamental study of heterogeneous catalysts for simultaneously oxidizing ammonia and organic compounds.

Several transition metals (Cu, Co, Mo, Mn, Ru and Pt) supported on inert porous materials (activated carbon, TiO₂, AI₂O₃ and MCM-41) are applied in catalytic wet air oxidation of ammonia. Noble metal catalysts are more active than base metal catalysts. Activated carbon supported Pt catalysts are most effective in this process.

Optimum preparation conditions of activated carbon (AC) supported Platinum (Pt) catalysts are experimentally determined: calcination at 300 ℃ for 6 hours followed by reduction at 600 ℃ without any pretreatment of ready-made activated carbon support. The Pt/AC catalysts exhibit high activity of ammonia removal (>50%), high selectivity to N₂ (>98%), less pH sensitivity, etc. at the temperature of 200 ℃. Its application to highly polluted wastewater containing ammonia (up to 1500 ppm N) and phenol (up to 8000 mg/l COD) is successful.

Reaction mechanism and kinetics of catalytic wet air oxidation of ammonia are discussed. The oxidation process undergoes a fast reaction stage and then a slow reaction stage, which might be associated with a four-step over-oxidation mechanism. A first-order kinetic model with respect to ammonia is developed to characterize this process, and the kinetic parameters are determined.