Chromite ore: X-ray fluorescence spectral analysis of Kβ and L-lines by WD-XRF

This work delves into the utility of chromium’s X-ray fluorescence (XRF) lines for the analysis of chromite ores, employing a wavelength-dispersive XRF spectrometer. The CrLα_1,2 and CrLβ₁ fluorescence lines, despite not involving electronic transitions from valence to K-core shell, offer substantial insights into the valence state of chromium. This study examines these relatively unexplored but potentially valuable lines and compares them with the CrKβ series fluorescence lines. Intriguingly, our investigation reveals striking differences in the L-line fluorescence spectra between metallic chromium (Cr(0)), chromite ores (Fe, Mg)Cr₂O₄, and K₂Cr₂O₇. Chemical shifts and peak shapes emerge as key discriminators, surpassing the sensitivity of the CrKβ_1,3 lines. Notably, the chemical shifts of L-lines are amplified, showcasing a clear trend: Cr(III) exhibits a larger shift than Cr(VI), mirroring the pattern observed in the Kβ-lines. The fluorescence peak shapes of Lα_1,2 and Lβ₁ for metallic chromium and chromite ores (both have unpaired 3d-electrons) are similar, whereas those of K₂Cr₂O₇ differ considerably in peak shape, indicating that unpaired 3d-electrons influence these peaks. A linear relationship was found between the area under the curve ratio for Lα_1,2 and Lβ₁ and the valence state of chromium.