Patent EA-004600-B1 (EA)
Title: Process for electrolytic production of highly pure zinc or zinc compounds from primary and secondary zinc raw material
Inventor: MARTIN SAN LORENZO DANIEL
IPC: C22B19/00
Filed: 2000-12-01
Abstract: 1. A process for the continuous production of a top purity electrolytic zinc or zinc compounds of high purity, starting from zinc containing raw materials to be extracted by a hydro-metallurgical treatment which comprises the following steps: a) leaching said raw material by an acidic aqueous solution in order to dissolve the zinc, b) optionally, depending upon the raw material, if the leaching residue have any valuable component, a solid/liquid separation would be included after leaching, c) neutralizing the aqueous solution or pulp, or the zinc containing solution when the raw material in liquid form, d) solid/liquid separating of the zinc rich aqueous solution from the solids, e) extracting the zinc contained in the pregnant aqueous solution by an organic acidic solvent, f) purifying the zinc rich loaded organic solvent coming from the extraction step e), g) stripping the ionic zinc from the zinc loaded organic solvent by an acidic solution, h) recovering the zinc from the zinc containing acidic aqueous solution coming out the stripping stage by electrowinning and/or crystallization and/or precipitation, characterized in that: for solid raw material case, the acid leaching of the raw material, according to step a) is conducted in "n" leaching zones, arranged in a cascade mode, "n" being at least equal to 2, the neutralization of the zinc rich aqueous solution produced in the leaching step, according to step c), is conducted in "p" zones arranged in a cascade mode, "p" being at least equal to 2, the purification (scrubbing / washing) treatment of the zinc loaded organic solvent, according to step f), is conducted in "q" physical and/or "r" chemical purification (successive) zone(s), organic and aqueous streams operating in counter current mode, "r" + "q" being at least equal to 1, and in that, eventually, a small flow of the aqueous phase from the leaching, neutralization, extraction steps, is treated, in order to adjust the water and/or alkaline elements balance and/or increase the zinc recovery, and to control the building up of dissolved impurities. 2. A process according to claim 1, characterized in that the to-be-extracted zinc containing raw materials are solid, whether primary raw materials or secondary materials, and contain from 3 to 80 % by weight of zinc, the zinc to be extracted being itself in the chemical form of oxides and/or salts and/or metal. 3. A process according to claim 1, characterized in that the raw materials are in the form of zinc impure aqueous solutions, with other cations and anions in several proportions. 4. Process according to any of the claims 1 and 2, characterized in that the acid leaching according to step a) is conducted preferably in a number "n" of cascade zones with n comprised between 2 to 8. 5. Process according to any of the claims 1 to 4, characterized in that the leaching aqueous acid solution contains at least one mineral acid. 6. Process according to claims 5, characterized in that the leaching aqueous solution contains a mixture of acids. 7. Process according to any of the claims 1 to 6, characterized in that the considered acids are chosen in the group constituted by sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid. 8. Process according to any of the claims 1 to 7, characterized in that the total aqueous acid leaching solution, including the acid make-up, contains between 0.1 g/l and 5 mol/l of equivalent (H<+>). 9. Process according to claim 1 to 8, characterized in that the pH of the aqueous media resulting in leaching is between 0 and 3 at the end of the leaching steps. 10. Process according to any of the claims 1 to 9, characterized in that the leaching is conducted over a residence time of 0.5 to 7 hours, and preferably over a residence time between 0.5 and 2 hours. 11. Process according to any of the claims 1 to 10, characterized in that the leaching is conducted at a temperature at most equal to 95 degree C and preferably conducted at a temperature comprised between 45 degree C and 65 degree C. 12. Process according to any of the claims 1 to 11, characterized in that the neutralization according to step c), of the aqueous solution originating from the leaching, is conducted preferably in a number "p" of cascade zones of neutralization, comprised preferably between 3 and 8. 13. Process according to claim 12, characterized in that the pH of the aqueous media resulting from the leaching is between 3 and 5 at the end of the neutralization steps. 14. Process according to claims 12 and 13, characterized in that the temperature of the aqueous media during the neutralization steps is at most equal to 95 degree C and preferably comprised between 45 degree C and 65 degree C. 15. Process according to any of the claims 12 to 14, characterized in that neutralization is conducted over a residence time of 0.5 to 7 hours, and preferably over a residence time between 1 and 4 hours. 16. Process according to claims 1 to 15 characterized in that a part of the zinc rich neutralized liquid solution or and raffinate is treated by means of an alkali reagent, in order to adjust the water and / or alkaline element balance and increase the zinc recovery and control the building up of dissolved impurities. 17. Process according to claims 16 characterized in that the part of the zinc rich neutralized liquid solution or and raffinate represents at most 25 % of the volume of said solution, and preferentially, 3 % to 15 % in volume. 18. Process according to any of the claims 1 to 17, characterized in that the extraction of the zinc contained in the zinc rich neutralized aqueous solution is conducted my means of an organic acid solvent, (in solution in kerosene) chosen in the group constituted by alkyl phosphoric acids, alkyl phosphonic acids, alkyl phosphinic acids. 19. Process according to claim 18, characterized in that the organic acid solvent is preferentially chosen in the group constituted by di-(2-ethylhexyl) phosphoric acid, di-2 ethylhexil phosphonic acid and di-(2,4,4 trimethylpentyl) phosphinic acid. 20. Process according to the claims 18 and 19, characterized in that the ratio between the phases, organic solvent phase and the aqueous solution liquor, (ratio described as O/A) is comprised between 0.5 and 6 and preferentially between 1 and 3. 21. Process according to any of the claims 1 to 20, characterized in that the zinc loaded organic solvent is subjected to a physical and chemical counter current purification (scrubbing washing) treatment conducted in a plurality of "q" physical and/or "r" chemical (successive) zone(s), ("r" + "q" being at least equal to 1), the number "q" of such physical purification treatment (scrubbing) zones being preferentially comprised between 1 and 4 and the number "r" of such chemical purification treatment (washing) zones being preferentially comprised between 1 and 4. 22. Process according to claim 21, characterized in that the physical treatment comprises the washing with an acidified water solution of the zinc loaded organic solvent from extraction in an organic/aqueous rate between 5 and 50. 23. Process according to claim 21, characterized in that the chemical purification treatment is conducted by mean of an aqueous zinc acid solution containing from 10 g/l to 100 g/l of zinc and from 0.1 to 1 g/L of equivalent (H<+>). 24. Process according to claim 1 to 23, characterized in that a bleed of the organic flow originating from step g), is sent to the regeneration stage, for treatment with a hydrochloric acid solution with acidity between 2 to 10 mol/l, and recycled.