Process for selective extraction of contaminant elements from mixtures of electrolytes in solution

A process for the removal of one or more contaminant elements, said contaminant elements including at least one of arsenic, antimony, and bismuth and being selected from the group consisting of arsenic, antimony, bismuth, iron, and mixtures thereof, from electrolyte solutions of at least one primary metal and the contaminant element or elements, said process comprising the steps of:

• (a) mixing an aqueous mineral-acidic electrolyte solution of primary and contaminant elementor elements with a sparingly water soluble organic solvent phase containing dissolved hydroxamic acid molecules according to the general formula I:
• ##STR6## wherein R.sup.1 represents a straight chain or branched saturated or unsaturated acyclic monovalent aliphatic hydrocarbon moiety containing from 6 to 22 carbon atoms, or a totally or partially cyclic saturated or unsaturated, including totally or partly aryl, hydrocarbon moiety having from 5 to 19 carbon atoms;
• said mixing being for a sufficient time to cause transfer of at least part of the contaminant element content from the electrolyte solution to the organic solvent phase, so as to produce an organic phase enriched in contaminant element content;
• (b) separating the mixed phases from step (a);
• (c) mixing the separated enriched organic liquid phase from step (b) with an aqueous extractant liquid phase, said extractant liquid phase consisting essentially of water and sufficient acid or base to give a pH effective for extraction, said mixing being continued for a sufficient time at a sufficient temperature and at a sufficient pH and temperature to cause transfer of at least part of the contaminantelement content from the organic liquid phase to the aqueous extractant liquid phase, so as to produce an intermediately enriched organic liquid phase having a content of contaminant element lower than at the end of step (b) but higher than at the beginning of step (a) and an aqueous extractant phase enriched in contaminant element content;
• (d) separating the enriched aqueous extractant phase from the intermediately enriched organic liquid phase present at the end of step (c);
• and
• (e) mixing the intermediately enriched organic liquid phase from step (d) with a source of sulfide ions so as to precipitate at least part of the contaminant element content thereof as solid sulfides and produce a depleted organic liquid phase.