Magnetic separation of Red Sand to produce value

Abstract

The extraction of alumina from bauxite produces a high volume by-product which is stored in secure impoundments. In Western Australia, typically half of the by-product has a particle size in excess of 90 μm and can be called Red Sand. Alcoa World Alumina (Alcoa) has three Western Australian refineries and this coarse fraction represents a potential resource of up to 20,000 tonnes per day. This note documents investigations into processing Red Sand through standard mineralogical processes (Low Intensity Magnetic Separator – LIMS and Wet High Intensity Magnetic Separator – WHIMS), to produce various fractions that have a higher potential value than the total sand fraction. One product is high in iron oxides, typically about 40% as Fe. Another product has high silica content (ca 93% as SiO 2) and has potential use within concrete manufacture. A third fraction, comprised of a mixture of iron and silica, is suitable as general fill. Application of this technology has the potential to divert a large volume resource away from storage and into marketable commodities.