Mechanism and efficiency of Cu-EDTA wastewater treatment and Cu recovery by cation exchange membrane electrolysis reactor

Cu complexes with ethylenediaminetetraacetic acid (EDTA), which is commonly found in metal plating industrial wastewater and pose a serious threat to the environment and human health due to their high toxicity and low biodegradability. Cu-ethylenediaminetetraacetic acid (Cu-EDTA) has strong stability in water and is hard to remove by classical chemical precipitation technology. In this study, the treatment of Cu-EDTA wastewater using a cation exchange membrane electrolysis reactor (CMER) under redox, oxidizing and reducing electrolysis conditions were investigated. The results indicate that the main effect on Cu-EDTA decomplexation and Cu removal was reduction reaction at the cathode, followed by electrodeposition of Cu (0) at the cathode. The removal of total Cu from the solution could reach 97.3% after electrolysis for 480min. Electron paramagnetic resonance (EPR) and free radical quenching experiments confirmed that the •OH generated by electrolysis has a slightly contribution to the decomplexation of Cu-EDTA, while mainly playing an oxidative removal role for organic matter. Meanwhile, the Cu recovery energy efficiency of the reducing electrolysis system was 2.56g kWh-1, which was higher than that of the oxidizing electrolysis system (0.22g kWh-1) and generally higher than those previously reported in the literature This method can cost-effectively treat industrial wastewater containing Cu-EDTA and recover Cu from the wastewater.