Facile synthesis of platinum-loaded carbon nanosheets with high specific surface area for efficient CWAO of ammonia nitrogen: A low-cost alternative route for treating ammonia containing wastewater

Deep treatment is an important tool to solve the environmental pollution of ammonia-containing wastewater. Considering the stability and economy of industrial application, we propose a simple and economical synthesis strategy. The procedure is based on the carbonization of citrate at elevated temperatures to synthesize high specific surface area and pore-rich carbon nanoflowers, and carbon nanoflower-loaded Pt catalysts were constructed for the catalytic wet air oxidation (CWAO) of ammonia-containing wastewater. The results showed that the synergistic effect of Pt, edge carbon and carboxyl groups led to the increase of CWAO activity. During the reaction, Pt activated NH3 to put it in a high-energy state, and there was a positive synergistic effect between the oxygen-containing functional groups (carboxyl groups) on the surface of the porous carbon nanoflowers and the edge carbon exposed at the adjacent defect sites, which promoted the activation of O2 and the generation of reactive oxygen species. At 200 °C, the Pt1/PC catalysts showed high activity and hydrothermal stability for CWAO of NH3. The conversion of NH3 was 98.24 % within 4 h, and the selectivity of N2 was 100 %. The total nitrogen (TN) was reduced to below 15 mg‧L−1, which meets the Chinese emission standard for TN in petrochemical industry. Therefore, the novel catalyst proposed in this study effectively solved the problems of complicated catalyst synthesis steps and poor hydrothermal stability in ammonia CWAO studies. The catalyst has potential industrial applications for CWAO of ammonia-containing wastewater.