INVESTIGATION OF SULFUR FORMS EXTRACTED FROM COAL BY PERCHLOROETHYLENE

The forms of sulfur present in a number of coals before and after extraction with perchloroethylene (PCE) at its boiling point (121 degrees C) for up to an hour have been examined by a combination of sulfur XAFS and Mossbauer spectroscopies and standard chemical methods. A hybrid forms-of-sulfur analysis was devised that included determinations of pyritic sulfur, elemental sulfur, organic sulfide, thiophene, oxidized organic sulfur forms, and sulfate. Of these forms of sulfur, only elemental sulfur was shown to be significantly extracted by PCE in the coals examined. Except for complications involving pyrite segregation during the extraction process in certain experiments, changes in all other sulfur forms with respect to the extraction were less than experimental uncertainties in the hybrid forms-of-sulfur analyses. Mossbauer and CCSEM data showed that pyrite and all other minerals in the examined coals are not significantly affected by the PCE extraction.