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Characterization of Mineralogical Changes of Chrysotile and its Thermal Decomposition by Heat Treatment

열처리에 따른 백석면의 광물학적 특성 변화와 열분해 과정 연구

Jeong, Hyeonyi;Moon, Wonjin;Roh, Yul
정현이;문원진;노열

  • Received : 2015.12.24
  • Accepted : 2016.03.28
  • Published : 2016.04.28

Abstract

Chrysotile is a 1:1 sheet silicate mineral belonging to serpentine group. It has been highlighted studies because of uses, shapes and structural characteristics of the fibrous chrysotile. However, it was designated as Class 1 carcinogen, so high attentions were being placed on detoxification studies of chrysotile. The objectives of this study were to investigate changes of mineralogical characteristics of chrysotile and to suggest detoxification mechanism of chrysotile by thermal decomposition. Samples for this study were obtained from LAB Chrysotile mine in Canada. The samples were heated in air in the range of 600 to $1,300^{\circ}C$. Changes of mineralogical characteristics such as crystal structure, shape, and chemical composition of the chrysotile fibers were examined by TG-DTA, XRD, FT-IR, TEM-EDS and SEM-EDS analyses. As a result of thermal decomposition, the fibrous chrysotile having hollow tube structure was dehydroxylated at $600-650^{\circ}C$ and transformed to disordered chrysotile by removal of OH at the octahedral sheet (MgOH) (Dehydroxylation 1). Upon increasing temperature, it was transformed to forsterite ($Mg_2SiO_4$) at $820^{\circ}C$ by rearrangement of Mg, Si and O (Dehydroxylation 2). In addition, crystal structure of forsterite had begun to transform at $800^{\circ}C$, and gradually grown 3-dimensionally to enstatite ($MgSiO_3$) by recrystallization after the heating above $1,100^{\circ}C$. And then finally transformed to spherical minerals. This study showed chrysotile structure was collapsed about $600-700^{\circ}C$ by dehydroxylation. And then the fibrous chrysotile was transformed to forsterite and enstatite, as non-hazardous minerals. Therefore, this study indicates heat treatment can be used to detoxification of chrysotile.

Keywords

chrysotile;thermal decomposition;dehydroxylation;detoxification;heat treatment

References

  1. Ball, M.C. and Taylor, H.F.W. (1963) An X-ray study of some reactions of chrysotile. Journal of Applied Chemistry, v.13, p.145-150.
  2. Brindley, G.W. and Hayami, R. (1965) Mechanism of formation of forsterite and enstatite from serpentine. Mineralogical Magazine, v.35, p.189-195. https://doi.org/10.1180/minmag.1965.035.269.21
  3. Edington, J.W. (1974) The operation and calibration of the electron microscope. Macmillan Education UK, 1-34.
  4. Hendry, N.W. (1965) The geology, occurrence, and major uses of asbestos, Annals of the New York Academy of Sciences, v.132, n.1, p.12-21. https://doi.org/10.1111/j.1749-6632.1965.tb41086.x
  5. Koshi, K., Hayashim, H. and Sakabe, H. (1969) Biological and mineralogical studies on serpentine minerals in heat treated state. Industrial Health, v.7, p.66-85. https://doi.org/10.2486/indhealth.7.66
  6. Marconi, A. (1983) Application of infrared spectroscopy in asbestos mineral analysis. Annali dell'Istituto Superiore di Sanita, v.19, n.4, p.629-638.
  7. Martin, C.J. (1977) The thermal decomposition of chrysotile. Mineralogical Magazine, v.41, p.453-459. https://doi.org/10.1180/minmag.1977.041.320.05
  8. Madejova, J. (2003) FTIR techniques in clay mineral studies. Vibrational Spectroscopy, v.31, n.1, p.1-10. https://doi.org/10.1016/S0924-2031(02)00065-6
  9. Page, N.J. and Park, M. (1968) Chemical differences among the serpentine ''Polymorphs''. American Mineralogist, v.53, p.201-215.
  10. Perkins, R.L. and Harvey, B.W. (1993) Method for the determination of asbestos in bulk building materials. Environmental Protection Agency, 600-R-93-116.
  11. Skinner, H., Catherine W., Ross, M. and Frondel, C. (1988) Asbestos and other fibrous materials; Mineralogy, Crystal Chemistry and Health Effects. Oxford Univ. Press, 1998, Oxford University Press, p.28-33.
  12. Virta, R.L. (2003) Asbestos: Geology, Mineralogy, Mining, and Uses. U.S. Department of the Interior U.S. Geological Survey, Open-File Report 02-149.
  13. Whittaker, E.J.W. (1953) The structure of chrysotile. Acta Crystallographica, v.6, p.747. https://doi.org/10.1107/S0365110X53002118
  14. Yada, K. (1967) Study of chrysotile asbestos by high resolution electron microscope. Acta Crystallographica, v.23, p.704-707. https://doi.org/10.1107/S0365110X67003524
  15. Yada, K. (1971) Study of microstructure of chrysotile asbestos by high resolution electron microscopy. Acta Crystallographica, v.A27, p.659-664.
  16. Yariv, S. and Heller-Kallai, L. (1975) The relationship between the IR spectra of serpentines and their structures. Clay and Clay Minerals, v.23, n.2, p.145-152. https://doi.org/10.1346/CCMN.1975.0230210

Acknowledgement

Supported by : 한국환경산업기술원