Electrolytic treatment of copper-EDTA complexes in water: toward sustainable copper recovery and toxicity control

The decomplexation of Cu-EDTA system and Cu recovery in an aqueous medium by electrolysis were assessed. Unlike other works where electrochemical advanced oxidation processes are focused on degrading the ligand, this work also evaluated the in vitro cytotoxicity of samples before and after treatments. Analyses of copper recovery and complex degradation revealed that the higher the current density (between 1, 3 and 5 mA cm⁻²) the greater the decomplexation of Cu(EDTA)²⁻ and the higher the copper recovery. In contrast, at 10 and 25 mA cm⁻², both decomplexation and recovery decreased because hydrogen evolution competed with copper reduction. Electrochemical treatment at 5 mA cm⁻² for 180 min enabled the recovery of ~ 86% of copper as Cu_(s), with a uniform submicrometric grains morphology. In vitro cytotoxicity assays using HepG2 cells showed that EDTA complexed with Cu²⁺ was more toxic than free EDTA. The starting solution of 2.0 mM Cu(EDTA)²⁻ showed ~ 1.5% cell viability, which increased to at least 44% after the application of any of the tested current densities. Therefore, treatment at 5 mA cm⁻² promoted the complex breakdown, recovered much of the complexed copper, and reduced water toxicity to sub-toxic levels, with cell viability greater than 70%.