Process for electrolytic production of ultra-pure zinc or zinc compounds from zinc primary and secondary raw materials

Abstract

The process comprises the following stages: a) leaching; b) solid-liquid separation; c) neutralization of the aqueous solution; d) solid-liquid separation of the zinc-rich solution; e) zinc extraction; f) purification of the organic solvent from the extraction stage; g) stripping the ionic zinc loaded in the organic solvent; h) recovering the zinc contained in the aqueous acid solution from the stripping. The following barriers to impurities have been established: gentle leaching; alkaline pulp treatment; treatment of a small stream of aqueous solution, collected before and / or after the zinc extraction at step e); high selectivity of the dissolved zinc extraction; treatment of the zinc loaded in the organic solvent; cleaning treatment of the zinc-laden organic solvent, with an ultra-pure acid solution; partial bleeding and treatment of the stripped organic solvent; bleed of small stream of the final product producing loop, which will be recycled to the organic loop.

Description

OBJECT AND FIELD OF THE INVENTION[0001] This invention relates to an improved process to produce zinc or its compounds, all of them ultra-pure, by a hydrometallurgical process starting from zinc primary and / or secondary raw materials through a new combination of purification loops incorporating barriers to impurities.[0002] These barriers, according to the invention, consist of the combination of treatments that restrict the production or transport of impurities from the raw materials or from the outside to the product and / or permit their removal through successive depletions, and / or check the presence of impurities in the product, and / or prevent recontamination.STATE OF THE ART[0003] Several patented processes exist concerning the hydrometallurgical treatment of zinc primary and / or secondary raw materials. These processes, operating by employing appropriate means, are targeted towards the production of electrolytic zinc or zinc compounds. The ultimate objective of these processes i...

AI Technical Summary

Benefits of technology

[0012] Another object of this process is to permit the production of ultra-pure zinc in metal form by electrowinning or in the form of chemical compounds, e.g. zinc salts through a crystallization process, which permits recovering almost all the zinc contained in the raw material in gentle conditions.

Problems solved by technology

However, impurity concentration levels low enough to achieve extreme quality electrowinning are not achieved.

This implies the production of zinc which is not ultra-pure, unless other difficult and / or expensive additional stages are applied.

This process has several drawbacks: the range of raw materials considered for the feed is exclusively restricted to secondary materials and, despite the presence of purification stages, both for the aqueous stream and the organic stream, the purity of the zinc produced is considered insufficient for some specific end-users and would be worth improving.

However, due to the possible use of the zinc produced, and in the absence of suitable organic washing before the zinc stripping, the zinc-rich aqueous solution originating in the stripping does not produce high-purity zinc.

Nevertheless, in this process, the solvent extraction does not contain a purification stage and, consequently, the organic solvent is not capable of producing high-purity zinc.

On the basis of said documents, it is demonstrated that the different processes referred to cannot produce extremely pure zinc, or zinc compounds, as they are essentially focussed on the raw material and are not sufficiently aimed towards the purification stages.

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