Process for the recovery of zinc from zinc-bearing raw materials

A process for the recovery of metal zinc or zinc-containing compounds from a raw material containing zinc, said process comprising:

• a) providing a solid or liquid zinc-bearing raw material containing at least 3 wt % of zinc;
• b) if the zinc-bearing raw material is solid, leaching said solid raw material with an acid aqueous solution having a pH between 0 and 4 to dissolve the zinc contained in the solid raw material, thus obtaining a pulp comprising a leached solution containing the dissolved zinc and a non-leached solid residue;
• wherein the ratio between the zinc weight contained in the solid raw material and the volume of the acid aqueous solution used in this leaching step is at least 20 kg zinc per m3 of acid aqueous solution;
• c) optionally, separating the non-leached solid residue from the leached solution containing the dissolved zinc;
• d) neutralizing the pulp obtained in step b), or the leached solution if step c) is carried out, or the zinc-bearing raw material when it is liquid, in the presence of a neutralizing agent, thus obtaining a neutralized zinc-rich solution containing solubilized zinc and a solid residue, and separating said zinc-rich solution from the solid residue;
• wherein when the zinc-bearing raw material is liquid, then it contains at least 40 g/L of zinc dissolved therein;
• e) solvent extraction of the solubilized zinc contained in the zinc-rich solution with an organic extractant, thus obtaining a zinc-loaded organic liquid phase and an aqueous raffinate containing impurities,
• wherein the weight ratio between quantities in the organic phase and aqueous phase (O/A ratio) ranges between 1.3 and 1.6, and wherein the temperature in this step ranges between 47 and 52° C.;
• f) purifying the zinc-loaded organic liquid phase by a method comprising washing and scrubbing said zinc-loaded organic liquid phase while maintaining the temperature between 47 and 52° C.;
• g) stripping the zinc loaded in the organic liquid phase with an acid aqueous solution, thus obtaining an acid aqueous solution containing zinc and an organic stream containing impurities;
• h) recovering the zinc contained in the acid aqueous solution obtained in step g) by a method selected from electrowinning, crystallization and precipitation, thus obtaining metal zinc or zinc-containing compounds and an acid aqueous solution.