Abstract: A process for distillation-crystallization of a zinc carbonate which is characterized in that a distillation column having a plurality of plates or trays is used for crystallizing basic zinc carbonate (2ZnCO.sub.3.3Zn(OH).sub.2 or ZnCO.sub.3.3Zn(OH).sub.2 H.sub.2 O) from a solution of basic zinc ammonium carbonate (Zn(NH.sub.3).sub.4 CO.sub.3); said solution is fed to an upper portion of the distillation column, while heating a bottom portion of the distillation column, to effect a distillation operation.

Abstract: A system for dissolution-purification of Zn-containing materials which comprises a dissolving means for dissolving the Zn-containing materials and an ion-exchanging means for separating heavy metal ions included in the solution resulting from the dissolving means. In these means, the liquid or slurry to be treated is subjected to the dissolution and ion-exchanging operation countercurrently and the treatment residue including impurities is separated from the liquid or slurry to be treated so as not to contaminate the liquid or slurry with impurities and to improve the solubility.