An Overview of Iron Precipitation in Hydrometallurgy

ABSTRACT Iron is commonly eliminated from hydrometallurgical process streams by oxidation to Fe3+, followed by hydrolysis–precipitation of a filterable iron compound. Current practice focusses on the precipitation of four species: iron hydroxide, the jarosites, FeO.OH and hematite. Although the precipitation of ferric hydroxide normally is avoided because of its poor filtration properties, the key role of Fe(OH)3 in the removal of the last traces of dissolved iron and in the elimination of objectionable impurities, such as germanium in zinc circuits, is discussed. The precipitation of jarosite–type compounds is widely used to reject iron and sulphate in a readily filterable form, and new applications of this technology are reviewed. The ability of jarosites to incorporate impurities such as silver or arsenic is discussed. The precipitation of α FeO.OH (goethite) in sulphate media requires that the concentration of Fe3+ be