Abstract
We report the application of laboratory based X-ray absorption spectroscopy to the speciation of Fe in iron phosphate glasses prepared by conventional and microwave melting. Analysis of the weak pre-edge features in Fe K-edge XANES data demonstrated glasses produced by microwave melting to have a higher fraction of reduced Fe2+ species, since microwave melts do not have sufficient time to equilibrate with the prevailing oxygen partial pressure, compared to counterparts produced by conventional melting. Furthermore, our laboratory XANES data are consistent with the formation of octahedral Fe2+ at the expense of tetrahedral Fe3+ species, with increasing Fe2+ content. These findings are consistent with the previous findings of our 57Fe Mossbauer study, synchrotron XANES data, and current understanding of the structure of iron phosphate glasses, and demonstrate the utility of laboratory based XANES for routine speciation of Fe in these and other materials.
Highlights
The baseline treatment option for intermediate level wastes in the UK is encapsulation in an ordinary portland cement matrix, combined with super-compaction, where appropriate
Analysis of the weak pre-edge features in Fe K-edge X-ray Absorption Near Edge Structure (XANES) data from a laboratory XAS spectrometer demonstrated microwave processed iron phosphate glasses to incorporate a higher fraction of Fe2+ species, compared to counterparts produced by conventional melting, consistent with our previous 57Fe Mossbauer spectroscopy study
Laboratory and synchrotron Fe K-edge XANES data from the same suite of glass materials were found to be in excellent agreement
Summary
The baseline treatment option for intermediate level wastes in the UK is encapsulation in an ordinary portland cement matrix, combined with super-compaction, where appropriate. X-ray absorption and 57Fe Mossbauer spectroscopy studies of iron phosphate glasses have demonstrated the Fe2+ / Fe ratio to be sensitive to melt composition and processing conditions (temperature, time and atmosphere) [16,17,18,19]. We demonstrated the first proof of concept Fe K-edge XANES speciation studies, using a commercially available laboratory X-ray spectrometer, from analysis of weak pre-edge features [30] This approach enables routine Fe speciation in materials with data acquisition times of only a few hours. Our preliminary results demonstrate that laboratory based Fe Kedge XANES has sufficient resolution and sensitivity to routinely determine Fe2+ / Fe ratio in iron phosphate glasses
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IOP Conference Series: Materials Science and Engineering
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
