Review of hydrometallurgical recovery of zinc from industrial wastes

Zinc containing wastes, including zinc ash, dross, flue dusts, sludge, and residue, are produced by various chemical and metallurgical industries. These materials possess varying levels of impurities determined by their origins. The study evaluates hydrometallurgical processing as a flexible and effective method for treating these wastes, which allows for the control of impurities present. A suitable lixiviant, chosen based on the nature and composition of the secondaries, is employed to dissolve desired metals while leaving undesirable materials in the residue. The paper details various hydrometallurgical processes used for zinc recovery from these wastes, utilizing sulphuric acid, hydrochloric acid, ammoniacal solution, and sodium hydroxide as lixiviants. Subsequently, techniques such as precipitation, ion exchange, and solvent extraction are applied to purify the leach solution concerning dissolved impurities. The purified solution is then processed to obtain metal or salts via electrolysis or crystallization, highlighting an efficient approach to zinc recovery and addressing the challenges posed by hazardous waste disposal in the context of stricter environmental regulations.