Uranium incorporation and reduction during Fe(II)-promoted transformations of U(VI)-sorbed iron oxyhydroxysulfates: Insights from U HERFD-XA

The study investigates the U-Fe interaction, crucial for understanding uranium's incorporation into iron (hydr)oxide minerals, impacting long-term soil retention. Using U HERFD-XANES at the U M4 edge, the proposal aims for molecular-level insights into U valence and the local environment. Experiments involved U(VI)-sorbed schwertmannite and jarosite, reacted with varying Fe(II) levels over 1 hour to 2 weeks in an anaerobic chamber (O2<0.5 ppm). Recent Fe EXAFS data show schwertmannite transformation to goethite and jarosite to lepidocrocite/goethite based on Fe(II) levels. U XANES spectra suggest U(V) predominance. U HERFD-XANES will clarify U incorporation in newly formed Fe(III) phases and assess U(IV) reduction in high Fe(II) samples. Insights into kinetics and mechanisms will enhance understanding of U(IV) reduction and repartitioning during schwertmannite and jarosite transformation.