Effective removal of the heavy metal-organic complex Cu-EDTA from water by catalytic persulfate oxidation: Performance and mechanisms

It is difficult to remove heavy metal-organic complexes from water by chemical precipitation because of the strong complexation ability between heavy metal ions and organics. In this study, the removal of the Cu-ethylenediaminetetraacetic acid (Cu-EDTA) complex using autocatalytic persulfate (PS) oxidation was investigated. The Cu-EDTA removal efficiency reached up to 96.57% after 90 min of treatment by PS oxidation. A higher PS concentration favored Cu-EDTA removal; An increase in the initial concentration of Cu-EDTA benefited PS activation, and a greater removal performance was obtained at a lower Cu-EDTA initial concentration (0.1 mmol L-1). Excessive Cu2+ accelerated Cu-EDTA removal, while superfluous EDTA suppressed it. Relatively lower initial solution pH value favored Cu-EDTA removal. SO4 center dot-, center dot OH, and O-1(2) displayed significant roles in the Cu-EDTA removal process, as they destroyed the chelating sites of the Cu(II) and EDTA molecules; finally small molecular organic acids, alcohols, and NO3- were produced. The released Cu(II) existed in the precipitates in the forms of Cu-based carbonates, Cu-based hydroxides, and copper oxide. A possible decomposition pathway of Cu-EDTA was proposed. Overall, multipathway activation of PS induced by heavy metal complexes could be an effective technique for the removal of the heavy metal complexes.

Automated summary

In this study, removal of the Cu-ethylenediaminetetraacetic acid (Cu-EDTA) complex using autocatalytic persulfate (PS) oxidation was investigated, with a removal efficiency of 96.57% achieved after 90 min of treatment. Factors such as PS concentration, initial concentration of Cu-EDTA, and solution pH value were found to influence the removal performance. This study demonstrated the potential of multipathway activation of PS induced by heavy metal complexes for effective removal of heavy metal complexes.