Application of a three-dimensional electrode to the electrochemical removal of copper and zinc ions from diluted solutions

Electrochemical removal of copper and zinc ions from synthetic solutions simulating drainage water flowing from abandoned mines was studied. A three-dimensional cathode was suitable for this purpose. Use of graphite felt electrodes in deoxygenated solution reduced the copper concentration in the solution from 150 to less than 0.05 mg/cubic decimeter (dm 3 ) with a current efficiency of 68%. For successful zinc removal, it was necessary to increase the pH of the solution to valuces ≥10 to suppress the parasitic hydrogen evolution reaction. At these conditions, the zinc concentration in the solution could be reduced from 200 to 1.1 mg/dm 3 with a current efficiency of 65%. Using a stainless steel wool cathode under identical conditions, a comparable current efficiency was achieved, but the outlet concentration of heavy metal ions increased to 22.1 mg/dm 3 .