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 si mulating drainage water flowing from abandoned mines was studied. A three-d imensional cathode was suitable for this purpose. Use of graphite felt elec trodes in deoxygenated solution reduced the copper concentration in the sol ution 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 increas e the pH of the solution to values greater than or equal to 10 to suppress the parasitic hydrogen evolution reaction. At these conditions, the zinc co ncentration 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 ide ntical conditions, a comparable current efficiency was achieved, but the ou tlet concentration of heavy metal ions increased to 22.1 mg/dm(3).