Demineralization of coal by stepwise bioleaching: a comparative study of three Indian coals by fourier transform infra red and X-ray diffraction techniques

  • D. K. Sharma
  • G. Wadhwa


A method was devised for the removal of deleterious minerals and metals from high ash-containing Indian coals. A selective enriched mixed culture developed for this purpose was used for stepwise aerobic bioleaching of two high ash Indian bituminous coals (Topa coal and Godavari coal) and Neyveli lignite. The process of bioleaching resulted in the removal of more than 50% of the mineral matter in five repeated steps and thus produced relatively demineralized, clean coal. Various parameters were optimized for bioleaching in order to maximize the removal of mineral matter. Based on the above studies a two-step pilot experiment was conducted under optimum conditions. The results obtained indicated removal of 75% of the mineral matter from one of the coals. The changes in mineral matter composition of these coals were evaluated using Fourier Transform Infra Red (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. The results indicated a decrease in the intensity of many peaks when seen in combination with the amount of mineral matter removed from the bioleached coals. The mechanism of the bioleaching process is discussed and many uses of the clean coal produced are suggested.

Key words

Bioleaching demineralization FTIR mineral matter X-ray diffraction 


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  1. Acharya, B.S. 1992 Quantitative determination of minerals in Indian coals by X-ray diffraction.FUEL 71, 346–348.CrossRefGoogle Scholar
  2. Erlich, H. L. 1986 What types of microorganisms are effective in bileaching, bioaccumulation of metals, ore benefication and desulfurization of fossil fuels: query.Biotechnology and Bioengineering Symposium 16, 227–237.Google Scholar
  3. Farmer, V.C. 1987 The infrared spectra of minerals. London: Mineralogical Society.Google Scholar
  4. Fass, R. 1994 Metal leaching from coal fly ash. CA 2084-714, 07.12.92-CA-084714 (15.08.93) 07.12.92 as 92CA-084714.93- 352322/45.Google Scholar
  5. Glick, A.C. & Davies, A. 1987 Variability of inorganic elemental contents of U.S. coals including results of cluster analysis.Organic Geochemistry 11, 331.CrossRefGoogle Scholar
  6. Hutchins, S.R., Davidson, M.S., Brierley, J.A. & Brierley, CL. 1986 Microorganisms in reclamation of metals.Annual Review of Microbiology 40, 311–36.CrossRefGoogle Scholar
  7. Israel-elec. 1993 Extraction of metals from coal fly ash. CA 2063-687: 20.03.92-CA 063687 (21.09.93) 20.03.92 as 063687. 93-395807/50.Google Scholar
  8. Krishna, C.R. & Francis, A.J. 1988 Microbial treatment of coal and its effects on ash fusion properties. Paper presented at International Symposium on Chemistry of Microbial Coal Conversion and Bioprocessing of Coal. American Chemical Society Meeting, Los Angeles.Google Scholar
  9. Morgan, M.E., Jenkins, R.G. & Walker, P.L. Jr. 1981 Inorganic constituents of the American lignites.FUEL 60, 189–193.CrossRefGoogle Scholar
  10. Nyquist, R.A. & Kagel, R.O. 1971Infrared spectra of inorganic compounds, New York: Academic Press.Google Scholar
  11. Ogunsola, O.I. & Lam, W.W. 1993 Mineralogical composition of Nigerian coals.Fuel Science and Technology International 11, 1319–1329.Google Scholar
  12. Olson, G.J. & Kelly, R.M. 1986 Microbiological metal transformations: biotechnological applications and potential.Biotechnology Progress 2, 1–15.CrossRefGoogle Scholar
  13. Sharma, D.K. & Gihar, S. 1991 Chemical cleaning of low grade coals through alkali-acid leaching employing mild conditions under ambient pressure conditions.Fuel 70, 663–665.CrossRefGoogle Scholar
  14. Sharma, D.K. & Mishra, S. 1989 Successive extractive disintegration of coal under atmospheric pressure conditions.Energy and Fuels 3, 641–646.CrossRefGoogle Scholar
  15. Sharma, D.K. & Singh, S.K. 1995 Stepwise coal conversion.Fuel Science and Technology International 13, 1185–1192.Google Scholar
  16. Sharma, P. & Verma, A. 1991 Microbial reclamation of metals from ores and industrial waste waters.Indian Journal of Microbiology 31, 1–26.Google Scholar
  17. Shelef G. 1992 Microbial leaching of metals from oxides. CA 2043-245 : 24.05.91-CA-043245 (26.11.91) 24.05.91 as 043245. 92-057255/08.Google Scholar
  18. Srivastava, R.D., Campbell, I.M. & Blaustein, B.D. 1989 Coal bioprocessing: a research-needs assessment.Chemical Engineering Progress 85, 45–53.Google Scholar

Copyright information

© Rapid Science Publishers 1997

Authors and Affiliations

  • D. K. Sharma
    • 1
  • G. Wadhwa
    • 1
  1. 1.Fuels and Biofuels Engineering LaboratoryCentre for Energy Studies, Indian Institute of TechnologyNew DelhiIndia

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