Method of processing residues from the hydrometallurgical production of zinc

A process of treating residues from the hydrometallurgical production of zinc, comprising the steps of:

• (a) electrolytically producing zinc comprising leaching a zinc containing material with a hot sulfuric acid to obtain a zinc sulfate solution, purifying the zinc sulfate solution by precipitating out iron and electrolyzing the purified solution resulting in a zinc deposition and a spent cell acid,
• (b) leaching copper containing residue from a hydrometallurgical production of zinc with spent cell acid from step (a) at a temperature from 50.degree. to 100.degree. C. to obtain a concentration of free acid between 10 and 100 g/l at the end of the leaching,
• (c) separating undissolved matter from the suspension to obtain solution;
• (d) feeding the separated matter to the hot acid leaching in step (a),
• (e) precipitating copper by an addition of fine-grained iron metal to the solution obtained in step (c),
• (f) separating the precipitated copper to leave a liquid phase, and
• (g) feeding the liquid phase obtained in step (f) to step (a) prior to the precipitation of iron.