Friday, April 1, 2016

Distribution of Germanium in Gondwana coals of Jharkhand state, India.



Distribution of Germanium in Gondwana coals of Jharkhand state, India.

                                               

By
Dr. Nitish Priyadarshi
Geologist
Email: nitish.priyadarshi@gmail.com

Introduction:

Coal is the most important fossil fuel resources in India. Coal is composed of those elements generally considered to be organic ( C,H,O and N) along with significant quantities of ‘inorganic’ elements as an extremely heterogeneous constituents. These inorganic elements are associated primarily with individual mineral phases in the coal, and commonly termed as “mineral matter”. Mineral matters, including major, minor and trace elements composed a significant proportion of coal and germanium is also one of them.  

There has been a great interest in germanium in coal as source of germanium for semi-conductor materials. The presence of germanium in coal was established by Goldschmidt (1930) using the optical and X-ray spectroscopic methods. There is a general agreement that organically bound germanium is common in most coals. The overall range for most coals of the world is around 0.5 – 50 ppm (parts per million) , with a mean of about 6 ppm  germanium.

Germanium has no known biological function and in view of present knowledge of Ge compounds ‘no environmental nor human health hazards are apparent’ (Furst,1987).

Development of germanium transistors by the electronics industry in 1948 increased demand for the metal and created almost a worldwide interest in coal as a possible new source of germanium. Although most of the production of germanium was from by-products of smelting zinc ore, small quantities were known to occur in coal.

The following generalizations represent an adequate summary of the various aspects of germanium occurrence in coal (Fisher,1960).

  1. Coals with a high- vitrain (woody coal) content are much higher in germanium than coal with low-vitrain content.
  2. Low- ash coals are richer in germanium than coals with high-ash content.
  3. Geologically older coals usually have a lower germanium content than more recent coals.
  4. Germanium is believed to be associated with the organic matter and not the mineral matter in coal.
  5. Germanium is usually concentrated in the top or bottom few inches of coal beds.

Goldschmidt (1950) in his pioneering work indicated that germanium is 1600 times more concentrated in ashes of certain coals than in average rocks. Stadnichenko et. al (1953) in their studies on the germanium content in American coals have observed that the highest concentrations of germanium are found in the coal logs and pieces of woody coals occurring as isolated pieces in the sediments.

Source of trace elements in coal:

The trace elements in coal accumulate through the following natural processes ( Swaine, 1962).

  1. The elements absorbed by the plants from the soil or crust (concentrated mainly in biogenic ash).
  2. The elements associated with the mineral matter (sediments) brought into the basin concomitantly with the vegetal matter through the natural transporting (concentrate in terrigenous ash).
  3. Metals contributed by the surface as well as underground circulating waters during the primary stage of coal formation. Most of these trace elements form organometallic complexes in coal.
  4. Trace elements together with mineral matter deposited in the coal microstructure and deformational passages in the coal seams through surface as well as underground circulating waters.
  5. Trace elements deposited through the hydrothermal solutions during the igneous activity in and around coal basins.

The present study:

Data of germanium in Jharkhand coals were collected from different workers. Spectrographic analysis was done by researchers to analyse the amount of germanium present in coals.


Distribution of Germanium in Jharkhand coals. ( Mukherjee et.al 1982)

  1. Ramgarh coalfield: 5-30 ppm (parts per million)
  2. Argada Seam, South Karanpura coalfield: 0-5 ppm.
  3. Kargali seam, East Bokaro coalfield: 0-5 ppm.
  4. Mahuda seam, Marulidih colliery, Jharia coalfield : 0-5 ppm.
  5. Rajmahal coalfield, Hura North block: 0-15 ppm.


Conclusion:

The element germanium is characteristically low in Gondwana coals of Jharkhand (0-5 ppm) except that of Ramgarh coalfield where concentration varies from 5-30 ppm.

Reference:

Fisher, F.L. (1960) Germanium, mineral facts and problems, Bull 585, U.S. Bureau of mines Washington.

Furst, A. (1987) Biological testing of germanium. Toxicol. Ind. Health, 3 , 167-204

Goldschmidt, V.M. (1930) The presence of germanium in coals and products, Nachr. Ges. Wiss. Goettingen, Math-Phys. Kl., Fachgruppe,3, 398-401.

Goldschmidt, V.M. (1950) Occurrence of rare elements in coal ashes. Progress in coal science London.

Mukherjee, K.N., Raja Rao, C.S., Chowdhury, A.N., Pal, J.C., and Das, M. (1982) Trace elements studies in the major tertiary and gondwana coalfields of India. Bulletins of the Geological survey of India, series-A Economic Geology, no. 49.

Stadnichenko, T., Murata, K.J., Zubovic, P., and Hufschmidt, E.L. ( 1953) Concentration of germanium in the ash of American coals, a progress report. US Geol. Surv. Circ., No.272, 34 pp.

Swaine, D.J. (1962) Trace elements in coal, II. Origin mode of occurrence and economic importance. C.S.I.R. Div. Coal Res. Tech. Commun.

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