Purification of galvanic sewage from metals by electrodialysis

The electrodialysis process of solutions containing a salt mixture (Na2SO4 and ZnSO4, with concentrations of 0.05 N each) has been studied. The electric current density ranged from 5 to 25 mA/cm2. The solution was fed at a rate of 0.01 cm/s. The electromigration flux of zinc is approximately twice lower than that of sodium ions. The transport of hydrogen ions does not exceed 20% of the overall electric current, and it comes to pass as a zincateanion. The dependence of the electromigration transport of zinc ions vs. the electric current density has a maximum in the range 10–15 mA/cm2. In the presence of an ion-exchange fiber in the desalination chamber, the residual zinc concentration in the dialyzate does not exceed 2–3 mg/l.

The electrodialysis process of zinccontaining solution in the presence of a background electrolyte has been studied. The results are as follows: 1. The dependence of Zn2+ electromigrative transport reaches its maximum at i = 10–15 mA/cm2. 2. Up to 25 % of zinc is transferred across the anion-exchange membrane as its anionic form. 3. The presence of the ion-exchange filler in the desalination chamber leads to an increase in zinc electromigrative transport and a decrease in its concentration in the dialyzate. 4. The residual zinc concentration in the dialyzate decreases as the electric current density