Reduction of Nitrate in Secondary Effluent of Wastewater Treatment Plants by Fe0 Reductant and Pd–Cu/Graphene Catalyst

Nitrate reduction has attracted considerable attention from wastewater in wastewater management because total nitrogen (TN), in which nitrate (NO3 −) is dominant in the effluent of most wastewater treatment plants, cannot meet the requirement of Chinese wastewater discharge standard (<15 mg/L). In this study, the novel graphene–supported palladium–copper catalyst (Pd–Cu/graphene) with Fe0 reductant was investigated in the advanced treatment of nitrate. Series of specific operational conditions (such as mass ratio of Pd:Cu, catalyst amounts, reaction time, and pH of solution) were optimized for nitrate reduction in the artificial solution, and then, the selected optimal conditions were further applied for investigating the nitrate elimination of real effluent of a wastewater treatment plant in Beijing, China. Results indicated that 82 % of nitrate removal and 66 % of N2 selectivity could be obtained under the optimum condition: 5 g/L Fe0, 3:1 mass ratio (Pd:Cu), 4 g/L catalyst, 2 h reaction time, and pH 5.1. Finally, the nitrate catalytic reduction mechanism was also analyzed and interpreted.