Isotope fractionation during oxidation of tetravalent uranium by dissolved oxygen

Research output: Contribution to journalArticlepeer-review


We conducted laboratory experiments to investigate isotopic fractionations during oxidation of tetravalent uranium, U(IV), by dissolved oxygen. In hydrochloric acid media with the U(IV) dissolved, the δ238U value of the remaining U(IV) increased as the extent of oxidation increased. The δ238U value of the product U(VI) paralleled, but was offset to 1.1±0.2‰ lower than the remaining U(IV). In contrast, oxidation of solid U(IV) by dissolved oxygen in 20mM NaHCO3 solution at pH=9.4 caused only a weak fractionation (~0.1‰ to 0.3‰), with δ238U being higher in the dissolved U(VI) relative to the solid U(IV). We suggest that isotope fractionation during oxidation of solid U(IV) is inhibited by a "rind effect", where the surface layer of the solid U(IV) must be completely oxidized before the next layer is exposed to oxidant. The necessity of complete conversion of each layer results in minimal isotopic effect. The weak shift in δ238U of U(VI) is attributed to adsorption of part of the product U(VI) to the solid U(IV) surfaces.

Original languageEnglish (US)
Pages (from-to)160-170
Number of pages11
JournalGeochimica et Cosmochimica Acta
StatePublished - Feb 1 2015

ASJC Scopus subject areas

  • Geochemistry and Petrology


Dive into the research topics of 'Isotope fractionation during oxidation of tetravalent uranium by dissolved oxygen'. Together they form a unique fingerprint.

Cite this