Reclaiming of lead in form of high purity lead compound from recovered electrode paste slime of dismissed lead batteries and/or of lead minerals

Abstract

An all-wet process for reclaiming the lead content of impure electrode paste or slime from discarded lead batteries and / or lead minerals, in form of high purity lead compound, comprises a) suspending the impure lead containing material in a lead sulphate dissolving aqueous solution of a salt belonging to the group composed of the acetates of sodium, potassium and ammonium; b) adding to the suspension sulphuric acid in an amount sufficient to convert all lead oxides to lead sulphate soluble in the acetate salt solution and slowly adding to the suspension either hydrogen peroxide or a sulphite or bubbling sulphurous anhydride through it, in a measure adapted to reduce any lead dioxide to lead oxide converted eventually to soluble lead sulphate by the sulphuric acid; c) separating a limpid acetate salt solution containing dissolved lead sulphate from a solid phase residue including all undissolved compounds and impurities; d) adding to the separated solution of lead sulphate either carbonate or hydroxide of the same cation of the acetate salt of the lead sulphate dissolving solution for precipitating highly pure lead carbonate / oxycarbonate or lead oxide or hydroxide, respectively, while forming sulphate of the cation, soluble in the acetate salt solution; and e) separating the precipitated high purity lead compound from the acetate salt solution now containing also sulphate of the same cation of the acetate salt. The acetate salt solution containing also sulphate of the same cation of the acetate salt separated from the precipitated compound of lead is re-cycled to step a) and the content of sulphate of the same cation in the solution is maintained below saturation limit by continuously or periodically cooling at least a portion of the solution separated from the precipitated lead compound to cause selective crystallization of sulphate salt of the same cation of the acetate salt and removing it as a by-product. Optionally, the separated solid phase comprising insoluble compounds of lead and / or undissolved concretions of lead compounds is treated in hot concentrated hydroxide of the same cation of the selected acetate salt and converting these compounds of lead and / or undissolved concretions of lead compounds to soluble plumbites, and the separated lead containing alkaline liquor may be added to the limpid acetate solution for precipitating all reclaimable lead in form of high purity lead oxide or hydroxide.

Description

FIELD OF THE INVENTION[0001]This disclosure relates to techniques for reclaiming high purity lead compound from impure mixtures, like recovered electrode paste slime of dismissed batteries or lead minerals.BACKGROUND OF THE INVENTION[0002]Departing from the long established processes for reclaiming valuable lead content from recovered electrode paste of dismissed lead batteries or lead minerals based on calcination, prior PCT patent application No. PCT / IT2008 / 000022, in the name of the present applicant, the content of which is herein incorporated by express reference, disclosed a novel process almost completely based on wet treatment of the recovered electrode paste or lead minerals capable of producing highly purified lead carbonate at high yield with much reduced burden of disposing of noxious residues and efficient use of reagents. Nevertheless, in order to use the reclaimed lead for making new battery paste, the lead carbonate has to be decomposed to lead oxide by heating the c...

AI Technical Summary

Benefits of technology

[0005]With the aim of reducing the lead reclaiming cost in terms of plant inventory of treatment vessels and related agitators, heaters and / or coolers, filters, overall treatment plant complexity, pumping and energy requirements, the applicant has found that an outstandingly effective simplification of the all wet lead reclaiming process flow is not only viable but even more efficient.

[0009]Precipitation of high purity lead compound from the clear lead sulphate solution may then by effected either by adding to the solution carbonate of the same cation of the acetate salt used for selectively dissolved lead sulphate for precipitating insoluble carbonate / oxycarbonate of lead, as contemplated in the process disclosed in said prior PCT patent application No. PCT / IT2008 / 000022, or, more preferably, according to an alternative embodiment, instead of a carbonate salt, to the clear solution of lead sulphate is added hydroxide of the same cation of the acetate salt used for selectively dissolved lead sulphate for causing precipitation of either oxide or hydroxide of lead, depending from the temperature of the precipitation bath, thus eliminating even the burden of eventually having to convert the reclaimed lead carbonate to lead oxide by heating the carbonate in an oven.

Problems solved by technology

Nevertheless, in order to use the reclaimed lead for making new battery paste, the lead carbonate has to be decomposed to lead oxide by heating the carbonate to about 400-450° C. This is expensive in terms of energy required.

Besides the energy required for eventually converting the carbonate to lead oxide, the acid leaching step of the impure starting material implies certain costs and treatment plant complexities.

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