Abstract: The present invention relates to a method for manufacturing zinc hydrometallurgically from zinc-containing starting materials. The method comprises one or more leaching stages, one or more solution purifying stages and one or more electrowinning stages for recovering metallic zinc from the leaching solution obtained. The method is operating with a closed solution circuit. A predetermined part volume of the solution obtained in the electrowinning stage or stages is withdrawn and concentrated by evaporation so as to precipitate any magnesium and manganese present in the part volume in the form of metal salt crystals. The precipitated crystal mass is separated from the residual liquid phase. The liquid phase in this manner purified with respect to magnesium and manganese can be recycled to the leaching process or utilized for some other purpose.

Abstract: A method of recovering copper and nickel from sulphidic minerals containing copper, nickel and iron comprises the steps of roasting the mineral, preferably to provide magnetite; sulphating, for example with sulphuric acid, sulphur trioxide, metal sulphate and/or sulphur dioxide together with oxygen; and a subsequent leaching of the sulphated material and recovery of copper from the leaching solution, for example by electrolysis. All or part of the leaching solution with its nickel content is recycled to the roasting stage, and the nickel content is removed in the form of nickel oxide together with the leaching residue, from which nickel can be recovered.

Abstract: The invention is a method for working-up shale while recovering metals therefrom and the sulphur content thereof. The method comprises crushing the shale and leaching and roasting the shale. The sulphur content is oxidized and converted into sulphuric acid, concentrated sulphur dioxide or sulphur. The leaching operation is effected with sulphuric acid. The leached metals are recovered in a manner known per se and the residual solution is passed to the roasting stage.

Abstract: A method for recovering copper and/or other non-ferrous metals from sulphidic raw material by roasting the material to a substantially sulphur-free state and then in a separate furnace sulphatize the roasted material into a form of a readily soluble sulphate and/or basic sulphate and then leaching the sulphatized material with an aqueous sulphuric acid solution. Copper and/or other non-ferrous metals are recovered from the spent leaching solution. The leaching solution is after said recovering recirculated to the leaching stage and to the roasting stage.