CHLORINE IN COAL - AN XAFS SPECTROSCOPIC INVESTIGATION

K-edge XAFS spectroscopy has been used to examine directly the occurre nce of chlorine in a variety of coals worldwide. Chlorine XAFS spectra were also obtained for Illinois No. 6 coal before and after aqueous l eaching and conventional coal cleaning and during low-temperature (<35 0-degrees-C) slow pyrolysis under helium, and for coals treated with c hlorinated reagents. The chlorine XANES spectra for coals of rank high er than subbituminous are closely similar, regardless of chlorine cont ent, rank and geographic origin, and indicate that there is but one ma jor, universal mode of occurrence of chlorine in coal: chloride anions in moisture anchored to the surface of micropores in coal macerals by organic ionic complexes, such as quaternary amine groups and alkali c arboxyl complexes. However, except in an Australian brown coal with 60 % moisture, the chloride anions are not in true aqueous solution, beca use the interaction between the maceral surface and the chloride anion is relatively strong. No evidence was gained for any organic chlorine in any coal. Crystalline sodium chloride was observed in minor amount s in only a few coals. Moreover, it appears that the observation of Na Cl and other inorganic chlorides in coals is an artefact due to precip itation from the major chlorine form upon release of moisture from the coal during sample size reduction and subsequent storage. Preliminary bromine XAFS data for two US bituminous coals indicate that bromine i s found in coal in a mode of occurrence closely similar to that of chl orine.