Use of electrodialysis for the regeneration of acid solutions

摘要

To produce dark grey to black covering layers of uniform colour shade on shaped articles consisting of zinc-copper-titanium alloys, an acid solution of 60 to 95 % by volume of water, 5 to 40 % by volume of nitric acid and 2.5 to 10 % by volume of sulphuric acid is used. For regeneration of this acid solution, the electrodialysis process is used, in which the acid solution is passed through a dialysis cell (2) bounded by perm-selective membranes (3-4) and arranged between a pair of electrodes (5, 6). IMAGE