Mineralogical characterization of chromium ore processing residue

Understanding the mineralogical characterization of chromium ore processing residue (COPR) is the basis of soil remediation which is polluted by chromium. Some techniques, such as X-ray fluorescence (XRF), X-ray diffraction technology (XRD) and environmental scanning electron microscopy (ESEM), were applied to identify the elemental composition, mineral composition and surface feature of COPR respectively. The result shows that the dominant elements of COPR are Ca, Fe, Mg, Al, Si and Cr in content order, which are evenly distributed throughout of COPR particles. The weight percentage of chromium is around 6%. COPR particles consist of brownmillerite, periclase, calcite, dolomite, hydroandradite, chromite and quartz. Trivalent chromium exists in brownmillerite and chromite. Hexavalent chromium possibly exists in hydroandradite. Particle size of COPR would not take effect on its mineral composition. Larger COPR particles are conglomerates of smaller particles, which suggests that chromium exists everywhere in COPR and it couldn´t exist in some particles of specific sizes.