Catalytic reduction of nitrate in secondary effluent of wastewater treatment plants by Fe-0 and Pd-Cu/gamma-Al2O3

摘要

Total nitrogen, in which NO3- is dominant in the effluent of most wastewater treatment plants, cannot meet the requirements of the Chinese wastewater discharge standard (<15 mg/L), making nitrate (NO3-) elimination attract considerable attention. In this study, reductant iron (Fe-0) and gamma-Al2O3 supported palladium-copper bimetallic catalysts (Pd-Cu/gamma-Al2O3) were innovatively used for the chemical catalytic reduction of nitrate in wastewater. A 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 secondary effluent of a wastewater treatment plant in Beijing, China. Results indicated that a better catalytic performance (74% of nitrate removal and 62% of N-2 selectivity) could be obtained under the optimal condition: 5 g/L Fe-0, 3: 1 mass ratio (Pd: Cu), 4 g/L catalyst, 2 h reaction time and pH 5.1. It is noteworthy to point out that nitrogen gas (N-2) predominated in the byproducts without another system to treat ammonium and nitrite. Therefore, the chemical catalytic reduction combining Fe-0 with Pd-Cu/gamma-Al2O3 could be regarded as a better alternative for nitrate removal in wastewater treatment.