Nitrate reduction to nitrogen in wastewater using mesoporous carbon encapsulated Pd-Cu nanoparticles combined with...

The conversion of NO₃^--N to N₂ is of great significance for zero discharge of industrial wastewater. Pd-Cu hydrogenation catalysis has high application prospects for the reduction of NO₃^--N to N₂, but the existing form of Pd-Cu, the Pd-Cu mass ratio and the H₂ evolution rate can affect the coverage of active hydrogen (*H) on the surface of Pd, thereby affecting N₂ selectivity. In this work, mesoporous carbon (MC) is used as support to disperse Pd-Cu catalyst and is applied in an in-situ electrocatalytic H₂ evolution system for NO₃^--N removal. The Pd-Cu particles with the average size of 6 nm are uniformly encapsulated in the mesopores of MC. Electrochemical in-situ H₂ evolution can not only reduce the amount of H₂ used, but the H₂ bubbles can also be efficiently dispersed when PPy coated nickel foam (PPy/NF) is used as cathode. Moreover, the mesoporous structure of MC can further split H₂ bubbles, reducing the coverage of *H on Pd. The highest 77% N₂ selectivity and a relatively faster NO₃^--N removal rate constant (0.10362 min^-1) can be achieved under the optimal conditions, which is superior to most reported Pd-Cu catalytic systems. The prepared catalyst is further applied to the denitrification of actual deplating wastewater. NO₃^--N with the initial concentration of 650 mg L^-1 can be completely removed after 180 min of treatment, and the TN removal can be maintained at 72%.