Publisher: Chemical Society of Nigeria

Polycyclic Aromatic Hydrocarbons In Nigerian Coal Extracts

K. E. Ugwu, P. O. Ukoha
KEYWORDS: coal, gas chromatography, polycyclic aromatic hydrocarbons, solvents


Nine coal samples, consisting of bituminous and sub-bituminous coals, obtained from mines located in Ribadu and in Okobo (Nigeria) respectively were studied for the concentrations of some polycyclic aromatic hydrocarbons (PAHs) in the coals. The samples were extracted separately with acetone, dichloromethane (DCM) and n-hexane in a soxhlet extractor. These solvents have relatively low boiling points and readily available. The extraction ability of these solvents was evaluated on the basis of the amount of PAHs extracted from the samples. The PAHs in the extracts were determined using gas chromatography coupled with flame ionization detector (GC-FID). The results showed acetone extracted 535.31ppb of the target PAHs from the sub-bituminous coal and 961.89ppb of the target PAHs from the bituminous coal.  DCM extracted a total of 757.71ppb of the target PAHs in the sub-bituminous coal and 1243.03ppb of the target PAHs from the bituminous coal while n-hexane extracted 1690.95 ppb of the target PAHs from the sub-bituminous coal and 867.20ppb of the target PAHs from the bituminous coal. The solvents’ ability to extract different PAHs  in decreasing order was DCM>acetone>n-hexane. The quantity of PAHs extracted in decreasing order was DCM>acetone>n-hexane for bituminous coal, and n-hexane>DCM>acetone for the sub-bituminous coal. The extraction of any PAH varied on solvent basis and on the coal type. The solvents extracted more three-ring PAHs than other PAHs.

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