PURPOSE: To deposit copper on a cathode and to separate and recover cond. hydrochloric acid with good efficiency, by introducing mineral acid into the anode chamber partitioned by a cation exchange membrane and an aq. soln. of concd, hydrochloric acid contg. negatively charged copper ions into a cathode chamber, respectively, and electrolyzing the same.

CONSTITUTION: An electrolytic cell is partitioned by a cation exchange membrane consisting of a polymer contg, sulfonate groups, etc. mixedly with carboxy late groups, etc. About 10W30% hydrochloric acid is introduced into the anode chamber and an aq. soln. of concd. hydrochloric acid contg. copper ions discharged after washing a steel material such as stainless steel contg. copper is introduced into the cathode chamber, respectively. The content of the copper ions in the above-mentioned aq. soln. of concd. hydrochloric acid contg. copper ions is preferably 50W0.1g/l and the concn. of the aq. soln. of concd. hydrochloric acid is 10W35%. The soln. is electrolyzed at 0.2W50A/dm2 current density with copper, iron, stainless steel, carbon, etc. as the cathode and platinum, etc. as the anode in the electrolytic cell, whereby copper is deposited on the cathode and is separated and recovered; at the same time, the concd. hydrochloric acid that can be cyclically used for washing is recovered as the resulted product of the cathode chamber.