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

Synopsis: Novel strategy of coupling discharge plasma and iron internal microelectrolysis was developed for Cu-EDTA decomplexation. • Multiprocess catalyzed Cu-EDTA removal by plasma/ internal microelectrolysis is realized. • Distinct synergistic effects on Cu-EDTA decomplexation are obtained. • Contributions of reactive substances to Cu-EDTA decomplexation are analyzed. • Multiprocess induced by internal microelectrolysis promoted Cu-EDTA decomplexation. • Possible pathways of Cu-EDTA decomplexation in this system are proposed. 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 H 2 O 2 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 NO 3 – 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.