A process for removing manganese and chloride ions from an aqueous acidic sulphate solution containing zinc, manganese and chloride ions without removing a substantial amount of zinc ions from the solution includes adjusting the free acidity of the solution if necessary to at least about 0.1 molar. The solution is then treated with ozone to oxidize manganese ions to manganese dioxide, and the ozone treatment is continued after the manganese concentration has fallen to a low level to oxidize chloride ions to chlorine gas. The precipitated manganese dioxide is removed from the solution.