J. Osán, B. Török, S. Török and K. W. Jones
Study of the chemical state of toxic metals during the life cycle of fly ash using x-ray absorption near edge structure
X-Ray Spectrometry 26 (1997) 37-44


Abstract

The non-destructive X-Ray Absorption Near Edge Structure (XANES) method was applied for the quantitative determination of chromium and arsenic species in coal fly ash. In order to study the chemical state changes caused by deposition and sedimentation of the particles, land fill and river sediment samples obtained in the neighbourhood of power plants were also investigated. The measurements were carried out at the X26 beam line of the BNL National Synchrotron Light Source, in fluorescent mode. For achieving quantitative results on the ratio of close lying oxidation state forms, a nonlinear fitting model was developed to process the obtained XANES spectra. The features of the spectra such as the white line, the multiple scattering resonance peak and the absorption edge are modelled with analytical functions. The obtained results show that chromium is present mostly (> 95 %) as Cr(III) in fly ash and the chemical state remains the same after deposition and sedimentation. Arsenic is present in pentavalent form in fly ash and land fill samples, while the possible As(III) content of sediment samples is around 40 %.


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