Comparison of Raman and mid-infrared spectroscopy for quantification of nitric acid in PUREX-relevant mixtures
McFarlan, Catriona and Nordon, Alison and Sarsfield, Mark and Taylor, Robin and Chen, Hongyan (2023) Comparison of Raman and mid-infrared spectroscopy for quantification of nitric acid in PUREX-relevant mixtures. Progress in Nuclear Energy, 165. 104898. ISSN 0149-1970 (https://doi.org/10.1016/j.pnucene.2023.104898)
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Abstract
During the plutonium uranium reduction extraction (PUREX) process, nitric acid facilitates the extraction of actinides from the aqueous phase into the organic phase by forming neutral, organic soluble complexes with tri-n-butyl phosphate (TBP). The concentration of nitric acid is generally measured by titration; however, titration is a time-consuming method that generates significant volumes of additional waste. Optical spectroscopic techniques can be used to perform fast, automated measurements off-line or on-line, without generating any waste. In this work, the effectiveness of Raman and mid-infrared (MIR) spectroscopy has been compared for the first time as an alternative to titration for the quantification of nitric acid in PUREX-relevant mixtures. Samples of 0 – 12 M nitric acid in the aqueous phase and 0 – 1.10 M nitric acid in the organic phase (TBP/odourless kerosene (OK)-H2O-HNO3 model system) were analysed and partial least squares (PLS) regression models were built to predict nitric acid concentration. MIR spectra required less pre-processing than Raman spectra and more accurate predictions of nitric acid concentration were obtained for MIR spectroscopy than for Raman spectroscopy, with root mean square error of prediction (RMSEP) values of 0.099 M versus 0.148 M obtained for the aqueous phase and root mean square error of cross validation (RMSECV) values of 0.006 M versus 0.013 M obtained for the organic phase. To investigate the ability to predict nitric acid concentration in the presence of uranyl nitrate, samples containing uranium (0 – 100 g/L) and nitric acid (0.15 – 0.64 M) in the organic phase (U-TBP/OK-H2O-HNO3 model system) were analysed by Raman and MIR spectroscopy. The RMSECV was 0.027 M and 0.066 M for MIR and Raman spectroscopy, respectively; these values are higher than those obtained in the absence of uranyl nitrate owing to differences in the experimental approaches employed. Therefore, the results obtained demonstrate that MIR or Raman spectroscopy could be used to measure the concentration of nitric acid in the organic and aqueous phases in the PUREX process.
ORCID iDs
McFarlan, Catriona ORCID: https://orcid.org/0000-0003-1571-7533, Nordon, Alison ORCID: https://orcid.org/0000-0001-6553-8993, Sarsfield, Mark, Taylor, Robin and Chen, Hongyan;-
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Item type: Article ID code: 86805 Dates: DateEvent30 November 2023Published26 September 2023Published Online7 September 2023AcceptedSubjects: Science > Physics > Nuclear and particle physics. Atomic energy. Radioactivity Department: Faculty of Science > Pure and Applied Chemistry
Technology and Innovation Centre > Continuous Manufacturing and Crystallisation (CMAC)
Strategic Research Themes > Advanced Manufacturing and Materials
Strategic Research Themes > Measurement Science and Enabling TechnologiesDepositing user: Pure Administrator Date deposited: 29 Sep 2023 11:01 Last modified: 28 Sep 2024 14:14 URI: https://strathprints.strath.ac.uk/id/eprint/86805