Spectroscopic investigation of U(VI) sorption at the calcite-water interface

摘要: The interaction of U(VI) species with the calcite surface in pre-equilibrated suspensions at pH 7.4 and 8.3 P(CO2) = 10−3.5 bar was characterized situ using extended X-ray absorption spectroscopy (EXAFS) luminescence spectroscopies. Results indicate that uranyl triscarbonate-like adsorption complexes dominate solution concentrations <500 μM, whereas formation hydroxide carbonato precipitates is observed higher concentrations, consistent isotherm data aqueous speciation calculations. EXAFS weak splitting equatorial O shell complexes, which may are bound an inner-sphere fashion surface, although no Ca backscattering could be positively identified. presence least two change proportion loading. One species, dominating low-surface coverage, triscarbonate complex. A second loadings a spectrum intermediate between found lowest incorporated into bulk polycrystalline calcite. combined forming sites as loading increases, hydroxide/carbonato high concentrations. Consequently, multiple likely to exist during U(VI)-containing waters near-surface environment. Furthermore, complex sorption/desorption behavior kinetics associated differing stabilities sorbed calcite-containing materials.