Ni(0) formation on carbon felt cathode triggers redox synergetic degradation of Ni-EDTA during electrochemical treatment for Ni-plating wastewater

Ni organic complexes are widely used in industrial production, posing severe threats to the natural environment and human health. In this work, we found that Ni (0) formed by the decomplexation and reduction of typical Ni organic complexes (Ni-EDTA) on the surface of carbon felt cathode. The formed Ni(0) as a catalytic site generates atomic hydrogen (H•) with strong reductive reactivity via electron transfer. H• not only accelerates the oxygen activation to form H₂O₂ on carbon felt cathode, but also reacts with H₂O₂ to generate strong oxidative hydroxyl radicals (HO•) and singlet oxygen (¹O₂). Under the attack of multiple active species, 95.5 % of Ni-EDTA is removed, and the removal efficiencies of total organic carbon (TOC) and dissolved Ni reach 43.8 % and 77.1 % after 120 min of electrolysis at -2.0 V (vs. Ag/AgCl). The redox synergistic reaction, initiated by the formation of Ni(0) on the carbon felt cathode, demonstrates excellent stability in treating real Ni plating wastewater. This approach eliminates the need for additional chemical reagents and prevents the release of heavy metals. Our findings offer a novel strategy for leveraging the self-transformation of Ni organic complexes to generate various active species for electrochemical treatment of Ni plating wastewater.