Self-catalytic decomplexation of Cu-TEPA and simultaneous recovery of Cu by an electrochemical ozone production system using heterojunction Ni-Sb-SnO₂ anode

Heavy metal complexes from the industrial wastewater induce risks for the humans and ecosystems, yet are valuable metal resources. For energy saving and emission reduction goals, the simultaneous decomplexation and recovery of metal resources is the ideal disposal of wastewater with heavy metal complexes. Herein, a self-catalytic decomplexation scheme is developed via an electrochemical ozone production (EOP) system to achieve efficient decomplexation and Cu recovery. The EOP system could achieve 94.36% decomplexation of Cu-TEPA, which is a typical complex in catalyst industrial wastewater, and 86.52% recovery of Cu within 60 min at a current density of 10 mA/cm². The O₃ and ^•OH generated at the anode would first attack Cu-TEPA to produce Cu-organic nitrogen intermediates, which further catalyze O₃ to generate ^•OH, thus self-enhancing the decomposition process in the EOP system. The released Cu²⁺ was gradually reduced to Cu⁺ and finally deposited as Cu₂O and Cu to the stainless steel cathode. The technological feasibility was confirmed with other Cu-complexes such as Cu-EDTA and Cu-citrate, and the actual Cu-TEPA-containing industrial wastewater. The results provide new insights regarding the application of EOP in the simultaneous treatment of heavy metal complex wastewater and resource recovery.