Self-catalytic Fenton-like reactions stimulated synergistic Cu-EDTA decomplexation and Cu recovery by glow plasma electrolysis

Abstract

• Multiprocess stimulated Cu-EDTA decomplexation by plasma electrolysis was realized. • Cu-EDTA decomplexation was mainly triggered by •OH. • Sequence breakages of functional groups in Cu-EDTA were confirmed by 2D-COS. • Self-catalytic Fenton-like reactions were induced by Cu-based byproducts and H 2 O 2 . • Released Cu 2+ was simultaneously reduced to Cu + /Cu 0 by •H and e aq - on cathode. Heavy metal–organic complexes have potential threats to organisms in water environment and human health, and it is a big challenge to remove them by traditional chemical precipitation. In this study, a glow discharge plasma (GDP) system coupling oxidation and reduction processes was established to decompose heavy metal–organic complex, taking Cu-ethylenediaminetetraacetic acid (Cu-EDTA) as a model. Approximately 87% of Cu-EDTA decomplexation and 64% of Cu recovery were achieved after 90 min of GDP treatment. Cu-EDTA decomplexation was mainly triggered by oxidation by •OH in the GDP system, leading to successive breakage of Cu–O > C-O > C-N > OH > C = O based on two-dimensional correlation spectroscopy analysis. Self-catalytic Fenton-like reactions were induced by Cu-based byproducts and H 2 O 2 , further promoting Cu-EDTA decomplexation. The released Cu 2+ was simultaneously reduced to Cu + /Cu 0 by •H and e aq - on the cathode surface. The technique exhibited great performance for Cu-EDTA decomplexation in water environment, as well as for other heavy metal complexes. This study disclosed the underlying mechanisms of synchronous Cu-EDTA decomplexation and Cu recovery in the GDP system, providing a prospective technique for heavy metal complex control.