Application of Electron Emission Spectroscopy to Characterize Sulfur Bonds in Coal

Electron binding energies of minerals typically found in coal were measured by the induced electron emission method. The shift in binding energies for Fe and S atoms were correlated with different chemical environments. The iron 2p_3/2 electron in pyrrhotite (Fe_1−xS) is bound by 3.8 eV more than the Fe 2p_3/2 electron in pyrite (FeS₂), whereas the 2p sulfur electron is shifted by 0.8 eV. Chemical shift data for minerals and organic sulfides were determined and correlated with structure variations. Subsequently, multiple sulfur signals observed on raw coals were correlated with this IEE data. Thus, we have demonstrated that the modes of occurrence of sulfur (pyritic, sulfate, organic) can be determined on raw coal; this represents the first spectroscopic technique capable of performing this characterization.