PROCESS FOR PRODUCING A RAW MATERIAL SUITABLE FOR IRON PRODUCTION, FROM A PRECIPITATE FROM LECTROLYTIC ZINC PROCESS

A process for manufacturing a raw material suitable for iron production, from a precipitate derived from the electrolytic zinc process and mainly containing alkaline sulfates of iron, such as glockerite Fe4SO4(OH)10, ferrihydroxosulfate FeSO4OH, or jarosite A[Fe3(SO4)2(OH)6], in which A is an alkali metal, NH4, or H3O, and hydroxides, such as goethite FeOOH and ferrite (mainly zinc ferrite ZnFe2O4), and for recovering the valuable metals, such as zinc, copper, cadmium, etc., present in the precipitate, is disclosed in which a precipitate slurried in water or a mild sulfuric acid solution is treated hydrothermally at an elevated temperature so that the operation remains within the stability range of haematite Fe2O3 in the system Fe2O3-SO3-H2O, whereafter the haematite-containing solid suitable for iron production is separated from the solution containing valuable metals.