Abstract
Sulfate sulfur and pyritic sulfur in coals are widely analyzed by ISO method. However, it is not adequate for the analyses of many coal samples because of its time-consuming. Therefore, X-ray fluorescence is applied to the determinations of these two sulfur forms to develop the rapid analytical methods. Sulfate sulfur is extracted with dilute hydrochloric acid from coal, precipitated as barium sulfate and determined by measuring the sulfur Kα intensity of barium sulfate collected on membrane filter. Pyritic iron is extracted with dilute nitric acid from the residual coal after the extraction of sulfate sulfur, precipitated as hydroxide or carbamate and determined by measuring the iron Kα intensity of the precipitate collected on membrane filter. Pyritic sulfur is determined by calculating the amount of sulfur associated with pyritic iron. It is noteworthy that reagents of heavy metal compounds are never used for pyritic sulfur analysis by X-ray fluorescence. Accordingly any attention is not necessary to the treatment of toxic waste water containing heavy metal elements except barium.
Experiments were carried out with 23 coal samples of various ranks from lignite to anthracite by both X-ray fluorescence and ISO method. Any significant difference is not found between the two methods for both analytical results of sulfate sulfur and pyritic sulfur. The sensitivity limit of X-ray fluorescence method is lower than that of ISO method for each form of sulfur.
