Abstract: A method for the operation of electrolytic baths whereby a charged, dissociative metal cationic solute which dissolves in a solution such as treatment used for a metal surface acid-washing, is separated and migrated through the diaphragm of an ion-selective separatory membrane. The cathode chamber solution contains as the electrolyte maintaining the basic electrical conductivity, a salt containing ammonium and at least one of sodium or potassium ions as the cation, and a salt containing a chloric ion or both a chloric ion and a sulfuric ion, but no nitric ion, as the anions. Furthermore, as the regulator which maintains the alkalinity in response to the progress of the electrolysis process, the cathode chamber solution contains at least one of an ammonium salt, a carbonate or a carboxylate. By this, metal oxide particles or metal particles are separated and produced in the circulated cathode chamber solution.

Abstract: An apparatus and method for purifying metal ion-containing bath liquids used for metal surface cleaning. The method comprises circulating two kinds of bath liquids (11A, 11B) through a plurality of electrolytic cells (1), each composed of an anode (2) and a cathode (4) separated by two ion-selective permeable diaphragms (6, 7), in such a way as to introduce the bath liquid into the intermediate compartment (8), electrophoresing metal ions contained in the bath liquids (11A, 11B ) into the cathode compartment (5) of each electrolytic cell (1), simultaneously circulating the catholyte (14) through the cathode compartment (5) of the electrolytic cell (1), thereby forming and coagulating easily magnetizable metal particles and hardly magnetizable metal particles in the catholyte (14), and separating the coagulation using a magnetic separator (17).