Abstract: A process of refining zinc oxide from roasted zinc sulphide bearing concentrates comprises leaching the concentrate in an aqueous sulphur dioxide solution under controlled conditions providing selective separation of zinc from other elements contained in the concentrate. The zinc bisulphite solution so obtained is separated from the remaining solids and is heat treated, preferably with steam, to precipitate zinc monosulphite crystals, possibly after first adding zinc dust to the solution to cement out residual copper and cadmium. The zinc monosulphite is then separated from the solution, possibly washed with water, and calcined to yield purified zinc oxide.

Abstract: The process for the electrochemical separation of metal mixtures and metal alloys comprises the steps of dissoloving the starting material in an electrolyte, substituting the metals dissolved in the electrolytic solution in succession in accordance with their electrochemical potential by electrochemically less noble metals in each case and depositing them. The electrolytic solution containing the dissolved metals is passed continuously through several cells, connected to each other, in which the electrolytic solution is brought into contact with said less noble metals. Several of the metals dissolved can be substituted simultaneously by one or more electrochemically less noble metals. Metals that are deposited simultaneously together are separated electrolytically from each other, and metals which have again gone into solution are again substituted outside the electrolysis cells by said less noble metals and deposited.