Trace Elements in West Virginia Coals
Trace Elements in West Virginia Coals
HAFNIUM (Hf)
Geologic Distribution: The chemistry of hafnium is very similar to that of zirconium, and as such Hf usually makes up 1-5% of most zirconium minerals, especially zircon (ZrSiO4) 1. Finkelman suggested that zircon was the site of most Hf in coal 2. Zircon is a common trace detrital mineral in coal and coal partings and its distribution (and Hf) should parallel that of ash in the coal. Average whole-coal Hf was 0.72 ppm. Hafnium correlated with ash yield, and the ash related elements thorium (Th), tantalum (Ta), chromium (Cr), scandium (Sc), lithium (Li), zirconium (Zr) and tin (Sn), and rare earth elements present in monazite, mainly cerium (Ce), lanthanum (La) and samarium (Sm). Coals of the upper Kanawha Formation and Allegheny Group contain the highest average hafnium contents with lower and variable Hf in other West Virginia coals.
Economic Impact: Hafnium is used in incandescent light bulb filaments as a scavenger or "getter" to absorb contaminant oxygen and nitrogen in the bulb vacuum and in nuclear reactor control rods used in nuclear submarines 1.
Environmental Impact: There are no known environmental hazards caused by Hafnium during coal mining or use 3.
References:
1. CRC Handbook
of Chemistry and Physics
2. Finkelman,
R.B., (1981)
3. Swaine,
D.J., (1990)
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