Self-Driven UV/Periodate Process for Cu-EDTA Decomplexation and In Situ Copper Recovery

Stable copper-ethylenediaminetetraacetic acid (Cu-EDTA) poses significant challenges for simultaneous ligand degradation and metal recovery. A self-driven ultraviolet/periodate (UV/PI) process that enables efficient decomplexation of Cu-EDTA coupled with in situ copper recovery was developed. This process achieved 94.50% decomplexation and 68.94% copper recovery via precipitation within 90 min without pH adjustment. Mechanistic investigations revealed that the UV/PI process generates reactive iodine species (IO₃^•) and singlet oxygen (¹O₂), and Cu(I)/Cu(II)/Cu(III) redox cycling, driving stepwise decarboxylation of EDTA and Cu²⁺ release. Consequently, proton consumption during PI activation and IO₃^- formation induces a gradual pH increase to ∼7.5, triggering the precipitation of released Cu²⁺. This intrinsic coupling of oxidative decomplexation and pH-driven precipitation enables a self-sustained pathway for simultaneous ligand removal and Cu recovery. While the electrical energy per order (EEO) is comparable to that of UV/H₂O₂, the UV/PI process exhibits markedly lower energy consumption per mass of copper recovered than other UV/oxidant processes. Moreover, the UV/PI process further exhibits strong resistance to water matrix interference, effective performance in real electroplating wastewater, and broad applicability toward various heavy metal complexes. This study provides a mechanistically informed and environmentally benign strategy for the treatment of metal-EDTA-containing wastewater.