process for removal of acidity from cathodic elektrotauchlackier - baedern by electrodialysis.

摘要

In acid removal from cathodic electro-dip lacquering baths, employing ultrafiltration, the novelty is that the ultrafiltrate is further processed by (a) passage through the chambers K1 of an electrodialysis cell ZA having the characteristic sequence (K2-M1-K1-M1)n (M1 = anion exchange membranes; n = 1 to 500), while an aq. base is passed through the chambers K2; (b) passage through the chambers K1 of an electrodialysis cell ZB having the characteristic sequence (K2-M1-K1-M2)n (M1 = anion exchange membranes; M2 = bipolar membranes), while water or an electrolyte (pref. the acid to be sepd. and/or a salt of this acid) is passed through the chambers K2; or (c) passage through the chambers K1 of an electrodialysis cell ZC having the characteristic sequence (K3-M1-K1-M1-K2-M2)n (M1 = anion exchange membranes; M2 = cation exchange membranes), while an aq. base is passed through the chambers K2 and water or an electrolyte (pref. the acid to be sepd. and/or a salt of this acid) is passed through the chambers K3. Electrodialysis is carried out at up to 100 mA/sq.cm. current density, the requisite electric field being applied by two electrodes at the ends of the cell (ZA, ZB or ZC).