Novel 3D Pd-Cu(OH)₂/CF cathode for rapid reduction of nitrate-N and simultaneous total nitrogen removal from...

Removal of NO₃^- is a challenging problem in wastewater treatment. Electrocatalysis shows a great potential to remove NO₃^- but selectively converting NO₃^- to N₂ is facing a low efficiency. Here, a novel 3D Pd-Cu(OH)₂/CF cathode based electrocatalytic (EC) system was proposed that can rapidly and selectively convert NO₃^- to NH₄⁺, and further convert to N₂ simultaneously. The special designs for the system include: Cu(OH)₂ nanowires were firstly grown on copper foam (CF) with excellent conductivity that features high specific surface area in enhancing NO₃^- absorption and conversion to NO₂^-. Then, palladium (Pd) with a superior photons activation capacity was doped on the Cu(OH)₂ nanowires to promote the reduction of NO₂^- to NH₄⁺. Then NH₄⁺ was quickly oxidized into N₂ by active chlorine. Finally, total nitrogen (TN) could easily be removed completely via above exhaustive cycle reactions. The 3D Pd-Cu(OH)₂/CF cathode exhibits a 98.8 % conversion of NO₃^- to NH₄⁺ in 45 min with the reported highest removal rate of 0.017 cm^-2 min^-1, which is 19.4 times higher than that of CF. The converted NH₄⁺ was finally exhaustively oxidized to N₂ with a 98.7 % of TN removal in 60 min.