Method of recovering non-ferrous metals from sulphidic materials

In a method for recovering copper and/or other non-ferrous metals including precious metals, from iron-containing sulphidic raw material comprising copper and/or other non-ferrous metals, wherein the starting material is first subjected to a sulphatizing treatment so as to convert at least one of the non-ferrous metals into the form of a readily soluble sulphate and/or basic sulphate, whereafter said at least one non-ferrous metal in a leaching stage is leached out with an aqueous sulphuric acid solution, the major quantity of the leached metal or metals then being recovered from the leaching solution formed and wherein remaining non-ferrous metals in the leaching residue formed is optionally recovered by further process stages, the improvement which comprises carrying out the sulphatizing treatment process in two stages, the material being in a first stage roasted in a roasting furnace to a substantially sulphur-free state and then in a second stage the roasted material being treated in a separate reaction chamber by supplying sulphatizing agent thereto, the second stage treatment being effected under such conditions as to permit substantial forming of compounds comprising sulphates, basic sulphates or mixtures thereof of said at least one non-ferrous metal, feeding a first portion of the residual solution obtained subsequent to recovering non-ferrous metal content from the leaching solution to the leaching stage, the magnitude of said first portion being selected to effect said leaching and returning a second portion of said residual solution to the roasting furnace, where the sulphur content of said second portion of the solution is converted into sulphur dioxide and passed to the gases formed by the roasting.