Determining individual mineral contributions to U(VI) adsorption in a contaminated aquifer sediment: A fluorescence spectroscopy study

Abstract

The adsorption and speciation of U(VI) was investigated on contaminated, fine grained sediment materials from the Hanford 300 area (SPP1 GWF) in simulated groundwater using cryogenic laser-induced U(VI) fluorescence spectroscopy combined with chemometric analysis. A series of reference minerals (montmorillonite, illite, Michigan chlorite, North Carolina chlorite, California clinochlore, quartz and synthetic 6-line ferrihydrite) was used for comparison that represents the mineralogical constituents of SPP1 GWF. Surface area-normalized K d values were measured at U(VI) concentrations of 5 Â 10 À7 and 5 Â 10 À6 mol L À1 that displayed the following affinity series: 6-line-ferrihydrite > North Carolina chlorite % California clinochlore > quartz % Michigan chlorite > illite > montmorillonite. Both time-resolved spectra and asynchronous twodimensional (2D) correlation analysis of SPP1 GWF at different delay times indicated that two major adsorbed U(VI) species were present in the sediment that resembled U(VI) adsorbed on quartz and phyllosilicates. Simulations of the normalized fluorescence spectra confirmed that the speciation of SPP1 GWF was best represented by a linear combination of U(VI) adsorbed on quartz (90%) and phyllosilicates (10%). However, the fluorescence quantum yield for U(VI) adsorbed on phyllosilicates was lower than quartz and, consequently, its fractional contribution to speciation may be underestimated. Spectral comparison with literature data suggested that U(VI) exist primarily as inner-sphere complexes with surface silanol groups on quartz and as surface U(VI) tricarbonate complexes on phyllosilicates. Published by Elsevier Ltd.

Characterizing particle‐scale equilibrium adsorption and kinetics of uranium(VI) desorption from U‐contaminated sediments

“…Quartz and plagioclase feldspar (compositions ranging from albite to Na‐anorthite) were the major (>25%) constituents, with moderate (5%–25%) amounts of pyroxene (augite, diopside, and/or pigeonite), and minor (<5%) quantities of illite, kaolinite, and smectite. Detailed analysis of clay mineralogy on the <2 µm fraction was not undertaken but has been reported to include smectite, muscovite, vermiculite, and chlorite [ Qafoku et al ., ; Wang et al ., ]. Extractable iron and manganese (determined by CBD) increased by a factor of three from the largest to smallest size fraction (Table ).…”

“…Extractable iron and manganese (determined by CBD) increased by a factor of three from the largest to smallest size fraction (Table ). Although present in low concentrations, phyllosilicates, as well as iron and manganese oxides, are likely adsorption sites for contaminant uranium [ Catalano et al ., ; Singer et al ., ; Stubbs et al ., ; Wang et al ., ].…”

“…Mobility and concentrations of U(VI) in deep vadose‐zone sediments from the 300‐Area are controlled by mass‐transfer rate‐limited adsorption/desorption reactions [ Bond et al ., ; Singer et al ., ; Wang et al ., ; Stoliker et al ., ]. Mass‐transfer limited uranium adsorption/desorption rates have been successfully described in the laboratory and field applications using a multirate SCM [ Liu et al ., ; Greskowiak et al ., ; Shang et al ., ]: where r U(VI) is the rate of U(VI) surface complex reactions, S is the sediment to solution ratio in the reactor (g L −1 ), q k is the concentration of surface complexed U(VI) on mass‐transfer site k (mol g −1 ), α k is the mass‐transfer rate constant for site k (h −1 ), Q k is the concentration of surface complexed U(VI) on mass‐transfer site k at adsorption equilibrium, and M is the total number of mass‐transfer sites for U(VI).…”

A luminescence line-narrowing spectroscopic study of the uranium(vi) interaction with cementitious materials and titanium dioxide

“…The spacing (Δ) between E and the first line of this series, S 1 , results in values for ν s in the ground state as follows: ν s = ∼870 cm −1 for the UO 2 2+ aquo ion 47,48 and 700 cm −1 < ν s < 800 cm −1 for uranium minerals (silicates, carbonates) and UO 2 2+ sorbed species. 26 in an ill-defined coordination environment (e.g. an amorphous matrix) are shown.…”

“…15 These studies revealed (1) ions occupy sites in amorphous host matrices or at the surface of solids. 15,21,26,27 In both cases the local coordination environment of the luminescing species is ill-defined resulting in a significant variation of the energies of states of the sorbed UO 2 2+ ions. Although the electronic transition line for each single sorbed UO 2 2+ ion may be sharp, the position of the electronic transition line and the spacings between the vibronic lines will vary among non-equivalent sorbed UO 2 2+ ions, which results in inhomogeneously broadened overall electronic and vibronic transition bands composed of all the sharp lines of each single sorbed UO 2 2+ ion.…”