Method for recovering metal zinc from solid metallurgical wastes

A method for recovering metal zinc from a solid metallurgical waste comprising zinc and manganese, the method comprising:

• (a) bringing the solid metallurgical waste into contact with an aqueous leaching solution comprising chloride ions and ammonium ions to produce at least one leachate comprising zinc ions and manganese ions and at least one insoluble solid residue;
• (b) cementing the at least one leachate by adding metal zinc as a precipitating agent, to eliminate at least one metal other than zinc and manganese optionally present in the at least one leachate as ions and producing a purified leachate;
• (c) precipitating the manganese ions by oxidation with permanganate ions to form a precipitate comprising MnO2, and subsequently separating the precipitate;
• and
• (d) electrolyzing the purified leachate in an electrolytic cell, comprising a cathode and an anode immersed in the purified leachate, to deposit metal zinc on the cathode and producing at least one exhausted leachate,
• wherein the precipitating (c) is conducted in the bringing (a) or after the cementing (b) and before the electrolyzing (d), and
• wherein the precipitating (c) comprises:
• (i) dosing permanganate ions to the at least one leachate comprising zinc ions and manganese ions;
• (ii) measuring at least pH, redox potential, and optionally temperature of the at least one leachate;
• (iii) periodically calculating a precipitation redox potential value by a calibration curve which correlates the precipitation redox potential to at least pH values and optionally the at least one leachate temperature;
• and
• (iv) varying dosage of the permanganate ions so as to bring the redox potential value of the at least one leachate to the calculated precipitation redox potential value.