Sulphur characterization in coal from X-ray absorption near edge spectroscopy

High resolution (less than or equal to 0.2 eV) S L-edge X-ray absorption near edge structure (XANES) spectra of several inorganic and organic sulphur model compounds are presented. The spectra were recorded in both total electron yield (TEY) and fluorescence yield (FY) modes. A qualitative interpretation is used to explain the origin of the fine features in the XANES spectra of certain model compounds. The XANES spectra of several coals such as the Rasa coal (Cretaceous, Yugoslavia), P-803 coal (Cretaceous, Canada) and fossilized Latex (Eocene, Germany) have also been recorded. Using the spectra of model compounds as fingerprints, several organic functional groups were identified in untreated coal. These include alkyl and aryl sulphides, alkyl and aryl disulphides, and heterocyclic sulphurs. Sulphonic acid and sulphate were observed for aerially oxidized coal. The S K-edge of several model compounds and coals were also recorded to compare with the L-edge. Advantages and drawbacks of the L-edge and K-edge techniques are described.