Pacific Northwest National Laboratory, Richland, Washington 99352, United States.
Environ Sci Technol. 2014 Jul 15;48(14):7766-73. doi: 10.1021/es500537g. Epub 2014 Jun 30.
A batch and cryogenic laser-induced time-resolved luminescence spectroscopy investigation of U(VI) adsorbed on quartz-chlorite mixtures with variable mass ratios have been performed under field-relevant uranium concentrations (5×10(-7) M and 5×10(-6) M) in pH 8.1 synthetic groundwater. The U(VI) adsorption Kd values steadily increased as the mass fraction of chlorite increased, indicating preferential sorption to chlorite. For all mineral mixtures, U(VI) adsorption Kd values were lower than that calculated from the assumption of component additivity possibly caused by surface modifications stemming from chlorite dissolution; The largest deviation occurred when the mass fractions of the two minerals were equal. U(VI) adsorbed on quartz and chlorite displayed characteristic individual luminescence spectra that were not affected by mineral mixing. The spectra of U(VI) adsorbed within the mixtures could be simulated by one surface U(VI) species on quartz and two on chlorite. The luminescence intensity decreased in a nonlinear manner as the adsorbed U(VI) concentration increased with increasing chlorite mass fraction-likely due to ill-defined luminescence quenching by both structural Fe/Cr in chlorite, and trace amounts of solubilized and reprecipitated Fe/Cr in the aqueous phase. However, the fractional spectral intensities of U(VI) adsorbed on quartz and chlorite followed the same trend of fractional adsorbed U(VI) concentration in each mineral phase with approximate linear correlations, offering a method to estimate of U(VI) concentration distribution between the mineral components with luminescence spectroscopy.
采用批量和低温激光诱导时间分辨发光光谱法，在野外相关的铀浓度（5×10（-7）M 和 5×10（-6）M）下，研究了在 pH8.1 合成地下水中，铀（VI）在石英-绿泥石混合物上的吸附，这些混合物的质量比可变。随着绿泥石质量分数的增加，U（VI）的吸附 Kd 值稳步增加，表明优先吸附到绿泥石上。对于所有的矿物混合物，U（VI）的吸附 Kd 值均低于假设各组分相加时的计算值，这可能是由于绿泥石溶解导致的表面修饰；当两种矿物的质量分数相同时，偏差最大。在石英和绿泥石上吸附的 U（VI）显示出特征的单独发光光谱，不受矿物混合的影响。混合物中吸附的 U（VI）的光谱可以通过石英上的一种表面 U（VI）物种和绿泥石上的两种来模拟。随着吸附的 U（VI）浓度的增加，发光强度以非线性方式降低，而绿泥石的质量分数增加，这可能是由于绿泥石中的结构 Fe/Cr 和水相中溶解和再沉淀的痕量 Fe/Cr 引起的发光猝灭。然而，吸附在石英和绿泥石上的 U（VI）的分光谱强度与每个矿物相中吸附的 U（VI）浓度的分数遵循相同的趋势，具有近似线性关系，这为利用发光光谱法估计 U（VI）在矿物组分之间的浓度分布提供了一种方法。
