One-stop rapid decomplexation and copper capture of Cu(II)-EDTA with nanoscale zero valent iron

Abstract

Heavy metal complexes widely exist in the industrial wastewater, imposing significant threat to public health. Conventional treatment of heavy metal complexes usually requires two-step procedures, including the advanced oxidation process for decomplexation and the subsequent precipitation to remove the released metal ions. Herein, we developed a one-stop technique for simultaneous Cu(II)-EDTA decomplexation and copper capture using nano zero-valent iron (nZVI). The dissolved Fe3+ from nZVI corrosion could rapidly complex with EDTA to destroy the Cu(II)-EDTA, while •O2- and •OH generated via the reaction of nZVI and molecular oxygen, would degrade the EDTA ligand. The liberated Cu2+ were subsequently reduced to metallic Cu or adsorbed by the iron hydroxides. Impressively, 99 % of Cu(II)-EDTA was removed within 10 min with the rate constant up to 0.49 min−1 and 70–90 % of Cu captured by nZVI. More importantly, this nZVI based one-stop technique was effective in an extremely broad pH range of 1–12 and could also realize the one-stop removal of Cu complexes from actual wastewater, producing effluent that stably meets the discharge standard of electroplating wastewater. This study provides a facile method to simultaneously destruct Cu(II)-EDTA and capture Cu, and also sheds light on the decomplexation mechanism of heavy metal wastewater.