Determination of iron and sulfur valence state in coal ashes by wavelength-dispersive X-ray fluorescence spectrometric technique

This paper describes the technique developed for X-ray fluorescence determination of sulfur and iron valence state in coal concentrates and ashes. The X-ray emission spectra of iron and sulfur were measured using the wavelength-dispersive X-ray fluorescence spectrometer. Samples were prepared as pressed powder pellets on a boric acid substrate. To estimate sulfur valence state SK beta' satellite was employed. Obtained data show that certified reference material ZUK-2 contains mainly sulfate sulfur and certified reference material KMM-1 contains mainly sulfide sulfur. Results of X-ray fluorescence analysis correspond to certified mineral composition and were proved by the results of certified gravimetric technique analysis. The ratio of divalent and total iron contents was measured using the ratios of FeK beta(5) line and FeK beta' satellite intensities to FeK beta(1,3) line intensity. The calibration plots were constructed using certified reference materials of coal concentrates and ashes. The FeO content was determined in CRMs SO-1 (Russia) and CTA-FFA (Poland) for the first time. The accuracy was estimated by comparison with certified titrimetric method results. Using the FeK beta(5) and FeK beta(1,3) lines intensities ratio allows to quantify ferrous iron.