Characterization of Chromite Ore Processing Residue

This paper summarizes the characteristics of chromite ore processing residue (COPR) in terms of their chemical compositions, phases, and recycling potential of iron and chromium through preliminary magnetic separation. COPR from nine hazardous waste sites in Hudson County, N.J., were analyzed using nondestructive instruments including environmental scanning electron microscope, x-ray diffraction spectrometer, and x-ray fluorescence spectrometer. The test results revealed that major phases of COPR were CaCO3, iron/chromium containing spinel, and SiO2. Concentrations of iron-containing phases, calculated as Fe2O3, ranged from 10 to 33% by weight. The COPR samples from nine sites can be divided into two groups, one with high concentration of iron oxide (20–33%) in a form of spinel having magnetic property, and another with low concentration of iron oxide (10–15%) without magnetic property. The manual/dry magnetic separation was able to concentrate iron and chromium oxides in COPR from the former group to 34.9–40.9 and 6.3–8.6%, respectively. The morphology of COPR from a sample containing high iron content revealed that COPR is mainly the remnant of chromite ore. The characteristics of COPR are different from those chromium-contaminated soils from other sources. The study will provide essential information for further remediation and recycling potential for COPR.