PROCESS FOR THE PRODUCTION OF ELECTROLYTIC ZINC OR HIGH PURITY ZINC SALTS FROM SECONDARY ZINC RAW- MATERIALS

摘要

ABSTRACTThe present invention relates to a process forthe production of either electrolytic zinc or high purityzinc salts from secondary zinc raw materials, comprising:leaching the raw material in a slightly acid aqueoussolution at controlled pH; separating the reaction mixtureinto a leaching liquor containing the leached zinc and asolid residue, which after suitable washing is discarded;directing the zinc-bearing liquor to a solvent extractionfacility where it is brought into contact with an organicsolution containing organic acids as cationic extractionreagents, by means of which, an ion exchange of zinc byhydrogen ions is achieved, resulting in a zinc loaded organicsolution and in an aqueous solution containing the stoichio-metric acidity to the extracted zinc; recycling the acidaqueous raffinate to the previous leaching step where it isused as the slightly acid aqueous solution to carry-out thezinc leaching from the raw material; sending the zinc organicextract to a stripping facility where it is brought intocontact with a strong acid solution of zinc sulphate, bymeans of which an ion exchange of zinc by hydrogen ions takesplace, thus producing a concentrated solution of zincsulphate and an organic solution free of zinc, containingthe stoichiometric acidity to the stripped zinc, which isrecycled back to the previous step to perform the zincextraction; directing the concentrated zinc sulphate aqueoussolution either to an electrowinning facility to produceelectrolytic zinc, or to a crystallization plant forthe production of pure zinc sulphate; recycling back tothe previous step of zinc stripping either the spentelectrolyte from the electrowinning facility or the motherliquors from the crystallization plant to form, aftersuitable sulphuric acid make-up, the strong acid solutionof zinc sulphate, by means of which zinc stripping fromthe organic extract is achieved.