METHOD OF REGENERATING SOLUTION FROM BLACK CHROMATING OF ZINC COATS Russian patent published in 2013 - IPC C25D21/16 C02F1/46 C02F103/16 

FIELD: chemistry.

SUBSTANCE: method involves anodic treatment of a black chromating solution successively in an anode chamber and a middle chamber of a three-chamber electrolysis cell with anion-exchange and cation-exchange chambers, during which zinc ions are removed from the solution, trivalent chromium ions are oxidised to chromate and the solution is returned into the chromating bath. A catholyte based on sulphuric acid solution circulates between the cathode chamber of the three-chamber electrolysis cell, the cathode and anode chambers of the two-chamber electrolysis cell with an anion-exchange membrane, from where zinc and silver ions are separately extracted, wherein a powdered silver residue released on the cathode of the three-chamber electrolysis cell is removed from its surface, dissolved in nitric acid and returned into the chromating bath, and zinc released on the cathode of the two-chamber electrolysis cell is periodically removed from its surface.

EFFECT: method enables circulation of chromium and silver in a closed process cycle without any loss and formation of wastes.

1 dwg, 3 ex