Multiprocess catalyzed Cu-EDTA decomplexation by non-thermal plasma coupled with Fe/C microelectrolysis: Reaction process and mechanisms

Abstract Decomplexation is an effective approach and key step for heavy metal–organic complex removal because conventional chemical precipitation is ineffective. In this study, a novel strategy of coupling discharge plasma and iron internal microelectrolysis (“plasma + iron”) was developed for decomplexation of Cu-ethylenediaminetetraacetic acid (Cu-EDTA). There were distinct synergistic effects on Cu-EDTA decomplexation in the “plasma + iron” system, resulting from Fenton reaction, Fe(III) displacement, and flocculation. Cu-EDTA decomplexation efficiency and energy efficiency were 1.53 and 2.31 times as those in single plasma system. Iron powder accelerated H2O2 decomposition and ·OH formation, especially ·OH production on the surface of iron, which mitigated the negative effects of radical quenchers. Moreover, co-precipitation with polymeric iron further promoted the removal of Cu ions released. Some small organic acids, amides, amines, alcohols, and NO3– were identified as a result of the effective Cu-EDTA decomplexation by the “plasma + iron” strategy. The synergetic decomplexation pathways of Cu-EDTA were then further proposed.