Catalytic Oxidation of Ammonia over Cerium-Modified Copper Aluminium Zinc Mixed Oxides

Copper-containing mixed metal oxides are one of the most promising catalysts of selective catalytic oxidation of ammonia. These materials are characterized by high catalytic efficiency; however, process selectivity to dinitrogen is still an open challenge. The set of Cu-Zn-Al-O and Ce/Cu-Zn-Al-O mixed metal oxides were tested as catalysts of selective catalytic oxidation of ammonia. At the low-temperature range, from 250 °C up to 350 °C, materials show high catalytic activity and relatively high selectivity to dinitrogen. Samples with the highest Cu loading 12 and 15 mol.% of total cation content were found to be the most active materials. Additional sample modification by wet impregnation of cerium (8 wt.%) improves catalytic efficiency, especially N2 selectivity. The comparison of catalytic tests with results of physicochemical characterization allows connecting the catalysts efficiency with the form and distribution of CuO on the samples’ surface. The bulk-like well-developed phases were associated with sample activity, while the dispersed CuO phases with dinitrogen selectivity. Material characterization included phase composition analysis (X-ray powder diffraction, UV-Vis diffuse reflectance spectroscopy), determination of textural properties (low-temperature N2 sorption, scanning electron microscopy) and sample reducibility analysis (H2 temperature-programmed reduction).

Photocatalytic Treatment of Different Types of High−Concentration Ammonia Wastewater by Cu/TiO2 Film and its Mechanism Study

Photocatalytic oxidation of ammonia in wastewater has been abundantly investigated in lab − scale, but there are still many issues to be solved towards practical application. Herein, we have immobilized Cu/TiO2 photocatalyst on different solid substrates in order to practically utilize and recycle the photocatalyst during wastewater treatment, on the basis of exploring the effects of different influencing factors such as pH, temperature and salinity on the photocatalytic oxidation of ammonia in this work. The performance of Cu/TiO2 films was evaluated by circulated treatment of different types of wastewater including high salinity ammonia wastewater, copper − ammonia wastewater and liquid − ammonia mercerization wastewater. The characters of wastewater matrices significantly influence the performance for ammonia oxidation. Different from the slurry test of photocatalyst power that operated in a closed reactor, it is importantly found that oxygen in air plays significant role in photocatalytic oxidation of ammonia into dinitrogen in the aerobic oxidation process, when the Cu/TiO2 films were employed. The possible oxidation mechanism has been proposed to elucidate the ammonia oxidation process.