Method of leaching zinc concentrate

A method of leaching a zinc concentrate in a hydrometallurgical production of zinc which comprises:

• (a) leaching a calcine, which is obtained by roasting a part of a zinc concentrate and which comprises zinc oxide, with a spent electrolyte containing free acid produced in an electrolytic extraction to thereby obtain a zinc sulfate solution;
• (b) repulping a neutral leach residue containing zinc ferrite which remains as an insoluble solid in step (a) and at least part of an iron residue produced in an iron oxidation, with a spent electrolyte to provide a pulp, and adding a zinc concentrate to the pulp to leach zinc sulfide contained in the zinc concentrate under atmospheric pressure and at a temperature of not lower than 90° C., but not higher than the boiling point of the zinc sulfate solution to obtain a zinc concentrate leach solution;
• and
• (c) adding an oxidizing agent to the zinc concentrate leach solution obtained in step (b) to oxidize ferrous ions contained in said zinc concentrate leach solution into ferric ions and adding calcine to the zinc concentrate leach solution as a neutralizer to recover iron, as an iron sediment, in the zinc concentrate leach solution, at least part of the iron being returned to step (b), with the remaining part of the iron being transferred to a subsequent residue treatment, while the neutralized leach solution is returned to step (a).