Review of hydrometallurgical recovery of zinc from industrial wastes

Zinc containing wastes/secondaries viz. zinc ash, dross, flue dusts, sludge, residue etc. are generated in various chemical and metallurgical industries. The materials contain different level of impurities depending on the source. The hydrometallurgical processing is effective and flexible for treating such materials as it can control the different level of impurities. Depending on the nature and composition of the secondaries, a suitable lixiviant could be selected to dissolve the desired metals leaving gangue in the residue. In the present paper, the hydrometallurgical processes have been described for the recovery of zinc from the secondaries using sulphuric acid, hydrochloric acid, ammoniacal solution and sodium hydroxide etc. as lixiviants. The leach solution thus obtained has been purified with respect to dissolved impurities using precipitation, ion exchange or solvent extraction method. The metal or salt is produced from the purified solution by electrolysis or crystallization.