X-ray Fluorescence Analysis of Feldspars and Silicate Glass: Effects of Melting Time on Fused Bead Consistency and Volatilisation

BELL, Anthony M. T., BACKHOUSE, Daniel J., DENG, Wei, EALES, James D., KILINC, Erhan, LOVE, Katrina, RAUTIYAL, Prince, RIGBY, Jessica C., STONE, Alex H., VAISHNAV, Shuchi, WIE-ADDO, Gloria and BINGHAM, Paul A. (2020). X-ray Fluorescence Analysis of Feldspars and Silicate Glass: Effects of Melting Time on Fused Bead Consistency and Volatilisation. Minerals, 10 (5), e442.

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Open Access URL: https://www.mdpi.com/2075-163X/10/5/442#abstract (Published version)
Link to published version:: https://doi.org/10.3390/min10050442
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    Abstract

    Reproducible preparation of lithium tetraborate fused beads for XRF analysis of glass and mineral samples is of paramount importance for analytical repeatability. However, as with all glass melting processes, losses due to volatilisation must be taken into account and their effects are not negligible. Here the effects of fused bead melting time have been studied for four Certified Reference Materials (CRM’s: three feldspars, one silicate glass), in terms of their effects on analytical variability and volatilisation losses arising from fused bead preparation. At melting temperatures of 1065 °C, and for feldspar samples, fused bead melting times shorter than approximately 25 min generally gave rise to a greater deviation of the XRF-analysed composition from the certified composition. This variation might be due to incomplete fusion and/or fused bead inhomogeneity but further research is needed. In contrast, the shortest fused bead melting time for the silicate glass CRM gave an XRF-analysed composition closer to the certified values than longer melting times. This may suggest a faster rate of glass-in-glass dissolution and homogenization during fused bead preparation. For all samples, longer melting times gave rise to greater volatilisation losses (including sulphates and halides) during fusion. This was demonstrated by a linear relationship between SO3 mass loss and time1/2, as predicted by a simple diffusion-based model. Iodine volatilisation displays a more complex relationship, suggestive of diffusion plus additional mechanisms. This conclusion may have implications for vitrification of iodine-bearing radioactive wastes. Our research demonstrates that the nature of the sample material impacts on the most appropriate fusion times. For feldspars no less than ~25 min and no more than ~60 min of fusion at 1065 °C, using Li2B4O7 as the fusion medium and in the context of feldspar samples and the automatic fusion equipment used here, strikes an acceptable (albeit non-ideal) balance between the competing factors of fused bead quality, analytical consistency and mitigating volatilisation losses. Conversely, for the silicate glass sample, shorter fusion times of less than ~30 min under the same conditions provided more accurate analyses whilst limiting volatile losses.

    Item Type: Article
    Additional Information: ** From MDPI via Jisc Publications Router ** Licence for this article: https://creativecommons.org/licenses/by/4.0/ **Journal IDs: eissn 2075-163X **History: published 15-05-2020; accepted 12-05-2020
    Uncontrolled Keywords: XRF, glasses, minerals, volatilisation, fused bead, melts
    Identification Number: https://doi.org/10.3390/min10050442
    Page Range: e442
    SWORD Depositor: Colin Knott
    Depositing User: Colin Knott
    Date Deposited: 18 May 2020 09:41
    Last Modified: 18 Jun 2020 19:59
    URI: http://shura.shu.ac.uk/id/eprint/26350

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