An exploration of benchtop X‐ray emission spectroscopy for precise characterization of the sulfur redox state in cementitious materials

The evolution of sulfur chemistry in cements is best known in the bailiwick of failure mechanisms via sulfate attack, but is equally important for its contributions to the reduction capacity of cementitious materials often used for immobilizing nuclear waste streams destined for long‐term storage, f...

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Bibliographic Details
Published in:X-ray spectrometry 2022-03, Vol.51 (2), p.151-162
Main Authors: Abramson, Jared E., Avalos, Nancy M., Bourchy, Agathe L. M., Saslow, Sarah A., Seidler, Gerald T.
Format: Article
Language:English
Subjects:
Acid digestion
cementitious material
Cements
Chemical Sciences
Chemistry
Colorimetry
Emission spectroscopy
Evolution
Failure mechanisms
Fluorescence
Heat treatment
Immobilization
Material chemistry
Oxidation
Radioactive wastes
Radioisotopes
Reducing agents
Sulfur
sulfur redox state
Titration
Valence
Waste management
Waste streams
X‐ray emission spectroscopy
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Summary:The evolution of sulfur chemistry in cements is best known in the bailiwick of failure mechanisms via sulfate attack, but is equally important for its contributions to the reduction capacity of cementitious materials often used for immobilizing nuclear waste streams destined for long‐term storage, for example, cementitious waste forms (CWF). The total reduction capacity of CWFs, encompassing contributions from both S and Fe reductants, and its implications toward radionuclide immobilization is most often studied by destructive wet chemistry methods requiring acid digestion in the presence of Ce(IV) and subsequent titration and colorimetric interpretation. Here, we investigate a similarly analytical but nondestructive alternative, benchtop high resolution wavelength‐dispersive X‐ray fluorescence spectroscopy, most commonly known as X‐ray emission spectroscopy (XES), for probing the bulk sulfur oxidation state distribution. We present here an initial investigation of S XES, including an improved experimental protocol for lab XES of inhomogeneous samples, both as a complement to the Ce(IV) test and for new scientific opportunities that it enables for observing changes in sulfur chemistry. We discuss future improvements and opportunities, including: (1) the practical challenges associated with coordinating XES and Ce(IV) liquid extraction for a more comprehensive perspective on reduction capacity and for a high‐precision evaluation of uncertainties in the Ce(IV) test; and (2) new opportunities, due to the nondestructive nature of XES, for controlled evolution studies aimed at elucidating specific chemical responses of CWFs exposed to invasive gas or liquid species or to accelerated aging by radiative dose or thermal treatment.
ISSN:0049-8246
1097-4539
DOI:10.1002/xrs.3276