Electromembrane extraction of Zn from Na-containing solutions using hybrid electrodialysis ion exchange method

Extraction of Zn2+ ions from solution containing Zn and Na sulphates in an electrodialysis cell, in which the desalination chamber was packed with ion-exchange resins, has been studied. The cation-exchanger KU-2 (Russia) and a mixture of the cation-exchanger KU-2 and the anion-exchanger AB-17 (Russia) were used during the experiments. With a mixed packing at lower than Limiting current densities, the current efficiency for Zn ions reached 90% and dropped to 60% when a current density two times higher than the limiting value was used. Removal of Zn from the solution containing Na ions was most effective when the cation-exchange resin KU-2 was in the cell. Coating this resin with a polyelectrolyte had two effects on the generation of Zn hydroxide in the desalination chamber, namely, increase the transport of Na ions to the concentration chamber and a rise in pH in the desalination chamber. During the investigation into electric attraction of Zn hydroxide to the cation-exchange resin the conditions for effective recovery of Zn as a precipitate were established. The hybrid electrodialysis ion-exchange method enabled the Zn ion concentration in the solution to be reduced almost 50- fold, that is from 1440 to 32 mg*I-1.