Monitoring synchrotron X‐ray‐induced radiolysis effects on metal (Fe,W) ions in high‐temperature aqueous fluids |
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Authors: | Robert A. Mayanovic Alan J. Anderson Hingure A. N. Dharmagunawardhane Sakura Pascarelli Giuliana Aquilanti |
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Abstract: | Radiolysis‐induced effects on aqueous tungsten ions are observed to form a precipitate within seconds upon exposure to a synchrotron X‐ray micro‐beam in a WO3 + H2O system at 873 K and 200 MPa. In situ Fe K‐edge energy‐dispersive X‐ray absorption spectroscopy (ED‐XAS) measurements were made on Fe(II)Cl2 aqueous solutions to 773 K in order to study the kinetics of high‐temperature reactions of Fe2+ and Fe3+ ions with transient radiolysis species. The radiolytic reactions in a fluid sample within a hydrothermal diamond anvil cell result in oxidation of the Fe2+ ion at 573 K and reduction of Fe3+ at temperatures between 673 and 773 K and of the Fe2+ ion at 773 K. The edge‐energy drift evident in the ED‐XAS data directly reflects the kinetics of reactions resulting in oxidation and/or reduction of the Fe2+ and Fe3+ ions in the aqueous solutions at high temperatures. The oxidation and reduction trends are found to be highly consistent, making reliable determinations of reaction kinetics possible. |
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Keywords: | energy‐dispersive XAS radiolysis oxidation/reduction hydrothermal fluid |
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