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Mineral Matter in Coal and the Environment |
11211
1 Laboratory for Geochemistry and Cosmochemistry, Department of Chemistry, University of Ni
, P.O. Box 91, 18000 Ni, FR Yugoslavia
2 Institute of Nuclear Sciences Vin
a, 11000 Beograd, FR Yugoslavia
The existence of vanadyl (VO2+)-non-porphyrins (P) in a thin band (enriched with vanadium) of the Western (W.) Kentucky (KY) No. 9 coal seam was shown by electron spin resonance (ESR). The ESR analysis indicates that VO2+-non-P are associated with the coal organic insoluble fraction. ESR parameters show that VO2+ ion is in an environment with approximately axial symmetry and chelated possibly by carboxylic/phenolic oxygen ligand donor atoms. These parameters are compared with those of VO2+-fulvic acid complexes and the model complexes with salicylic/phthalic acids reported by others. It is concluded that the vanadylation of W. KY No. 9 thin coal band occurred during its diagenetic (peat-forming) stage in the Pennsylvanian swamp. The extraordinary V enrichment of the top 15 cm, relative to the lower parts of the W. KY No. 9 coalbed is interpreted by a high V concentration of the past swamp water attained through a sudden and exceptional external supply. The predominant source of the metal was probably volcanic ash on the land that was weathered/leached of its vanadium. The association of V/Cr (together with their enrichment in the top of the seam) and Ni implies that the volcanic ash was derived from basalts. Abundant organic (humic) materials (with the high V enrichment factor) and low rate of deposition were the primary factors responsible for the high vanadium content of the coal. From the chemistry of VO2+, FeS2 and CrOH2+ it is deduced that the oxidation potential Eh and pH of the ancient peat interstitial water were approximately –0.2 to –0.3 V and 5–6, respectively.
