The preparation of magnetite, goethite, hematite and maghemite of pigment quality from mill scale iron waste

Mill scale iron waste has been used to prepare some iron oxide pigments via specific precursors. Magnetite and goethite were precipitated from their respective precursors in aqueous media. Various red shades of hematite were prepared by the calcinations of the precipitated goethite at temperatures ranging from 600 to 900 °C. Maghemite was obtained by thermal treatment of magnetite at 200 °C. The iron oxides were characterized by Raman spectroscopy, X-ray diffraction (XRD), surface area determination and scanning electron microscopy (SEM). They are generally composed of very small particles (mainly <0.1 μm) with high surface area. These particle properties suggest that the above pigments (prepared from mill scale) will show high tinting strength, quality hiding power and good oil absorption. Oil absorption is a property of the pigment that is closely related to the ease of dispersion.