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Channel and column samples of the Herrin and Springfield coals, as well as roof shales, were collected from four underground coal mines in southern Illinois. Coal lithotypes (vitrain, bright banded coal, subbright banded coal, dull coal, and fusain) and mineral partings were hand-picked from the channel and column samples. Chemical, petrographic, and mineralogical studies of the samples indicate that the vitrain separates have the highest chlorine (CI; mean 0.52%) and lowest sodium (Na; mean 0.088%) and ash (mean 2.8% high-temperature ash) contents. Roof shale and mineral partings have the lowest CI content (mean 0.25%) and highest Na (mean 0.263%) and ash (mean 40.6% high-temperature ash) contents. The Cl/Na ratio of the lithotypes is significantly greater than that of NaCl, the dominant dissolved salt in the ground water associated with Illinois coals. Chlorine and Na in the coal samples studied are concentrated in vitrinite and mineral matter, respectively. Part of the Na and a small fraction of the Cl occur as dissolved NaCl in macropores and mesopores, mainly within the mineral matter and inertinite. The remaining Na is adsorbed on clay minerals. The zeta potential data obtained for the same lithotypes support the interpretation that the organically associated Cl in coal is adsorbed primarily on the micropore walls.

One set of lithotypes was leached with water at 27 °C and 93 °C, and with a 4.3 M NH4OH solution at 27 °C. The aqueous leachability of Cl increases from vitrain, through bright banded, subbright banded, and dull coal, to fusain. This is in the order of decreasing vitrinite content and, consequently, of decreasing micropore abundance in which most of the Cl is held. Thus, variable Cl leachabilities among the lithotypes may be related to their pore-size distributions.

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