Distribution characteristics of minerals and elements in chromite ore processing residue

Abstract

In this paper, environmental scanning electron microscopy (ESEM) is applied to characterizing the mineral and element distribution of chromite ore processing residue (COPR). The test results show that Cr-bearing brownmillerite occurs in the rim of COPR particle, while hydroandradite with Cr(VI) in its structure presents inside the COPR particle. Periclase and calcite occur in the interstitial area. Element analyses show that Ca, Fe and Al are distributed throughout the COPR particle, and Mg exists mostly in the interstitial area or on the particle surface. A lower content of Cr is evenly distributed in the COPR particle, while slightly higher concentration of Cr occurs inside the particle. It is suggested that it will take a relatively longer time for Cr to migrate out of COPR, especially for hexavalent chromium, so the leaching time and the particle size may be two important factors to affect the release of Cr(VI).

Keywords

chromium / chromite ore processing residue / scanning electron microscopy / mineralogy / element distribution

References

[1] Gu C., Dan Z., Wang Ruiqi. Investigation on pollution of chromic slag to local soil[J]. Mining Safety and Environmental Protection, 2005, 326, 18-20.

[2] Zhang S., Lin Y., Hua X., et al. The facing problems and countermeasures of Chinese contaminated cite management[J]. Environmental Science and Management, 2007, 326, 5-7.

[3] Broadway A., Cave M. R., Wragg J., et al. Determination of the bioaccessibility of chromium in Glasgow soil and the implications for human health risk assessment[J]. Science of the Total Environment, 2010, 4092, 267-277.

[4] Chrysochoou M., Dermatas D., Grubb D. G., et al. Importance of mineralogy in the geoenvironmental characterization and treatment of chromite ore processing residue[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2010, 1363, 510-521.

[5] Chrysochoou M., Moon D. H., Fakra S., et al. Use of micro X-ray absorption spectroscopy and diffraction to delineate Cr(VI) speciation in COPR[J]. Global Nest Journal, 2009, 113, 318-324.

[6] Chrysochoou M., Dermatas D. Application of the Rietveld method to assess chromium(VI) speciation in chromate ore processing residue[J]. Journal of Hazardous Materials, 2007, 1412, 370-377.

[7] Chrysochoou M., Fakra S. C., Marcus M. A., et al. Microstructural analyses of Cr(VI) speciation in chromite ore processing residue (COPR)[J]. Environmental Science and Technology, 2009, 4314, 5461-5466.

[8] Hillier S., Lumsdon D. G., Brydson R., et al. Hydrogarnet: A host phase for Cr(VI) in chromite ore processing residue (COPR) and other high pH wastes[J]. Environmental Science and Technology, 2007, 416, 1921-1927.

[9] Elzinga E. J., Cirmo A. Application of sequential extractions and X-ray absorption spectroscopy to determine the speciation of chromium in Northern New Jersey marsh soils developed in chromite ore processing residue (COPR)[J]. Journal of Hazardous Materials, 2010, 1831–3, 145-154.

[10] Chrysochoou M., Dermatas D. Evaluation of ettringite and hydrocalumite formation for heavy metal immobilization: Literature review and experimental study[J]. Journal of Hazardous Materials, 2006, 1361, 20-33.

[11] Tinjum J. M. Mineralogical Properties of Chromium Ore Processing Residue and Chemical Remediation Strategies[D]. 2006, Wisconsin, USA: The University of Wisconsin-Madison.

[12] Moon D. H., Dermatas D., Sanchez A. M., et al. Assessment of brownmillerite and periclase hydration in chromite ore processing residue at elevated temperature[J]. Geotechnical Special Publication, 2008, 177, 375-382.

[13] Xiao Kai, Li Guocheng. Mineralogical characterization of chromite ore processing residue[C]. In: 2011 International Conference on Electric Technology and Civil Engineering. Lushan, China, 2011.

[14] Hillier S., Roe M. J., Geelhoed J. S., et al. Role of quantitative mineralogical analysis in the investigation of sites contaminated by chromite ore processing residue[J]. Science of the Total Environment, 2003, 3081–3, 195-210.

[15] Redhammer G. J., Tippelt G., Roth G., et al. Structural variations in the brownmillerite series Ca₂(Fe_2−xAl_x)O₅: Singlecrystal X-ray diffraction at 25 °C and high-temperature Xray powder diffraction (25 °C⩽T⩽1 000 °C)[J]. American Mineralogist, 2004, 892/3, 405-420.