Efficiencies of electrolytic treatment of complexed metal solutions in a stirred cell having a membrane separator

Electrolytic recovery of metals such as Cu(II) and strong chelating agents such as EDTA (ethylenediaminetetraacetic acid) from their equimolar complexed solutions was investigated in a stirred cell having a membrane separator. The iridium oxide coated on titanium (IrO2/Ti) was used as the anode. Experiments were performed as a function of membrane-type (Neosepta CM-1 and CM-2), current density (18.5–185 A/m2), cathode material (Pt plate, Pt/Ti, Cu plate, stainless steel), initial catholyte pH (1–9) and initial Cu–EDTA chelate concentration (0.01–0.08 M), and initial anolyte NaNO3 concentration (0.1–0.8 M). An economically feasible current efficiency (>60%) and metal recovery (>95%) could be obtained if the Cu–EDTA chelate concentration was sufficiently high. Electrodeposition of other divalent metals including Pb, Hg, and Cd onto Pt/Ti cathode from their EDTA solutions was possible, but no apparent deposition of Co, Ni, Zn, and Mn was observed.