Sorption of U(VI) at the TiO2-water interface: An in situ vibrational spectroscopic study
Sorption of U(VI) at the TiO2-water interface: An in situ vibrational spectroscopic study
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DOI：
10.1016/j.gca.2011.10.004
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发表时间：
2012-01-01
影响因子：
5
通讯作者：
Payne, Timothy E.
中科院分区：
文献类型：
--
作者：
Mueller, Katharina;Foerstendorf, Harald;Payne, Timothy E.
水-矿物界面吸附反应的分子尺度知识对于预测U（VI）在环境中的迁移过程是很重要的。在这项工作中，在原位衰减全反射傅里叶变换红外（ATR FT-IR）光谱被用于在一个全面的调查U（VI）到二氧化钛的吸附过程。原位ATR FT-IR技术的高灵敏度允许研究低微摩尔范围内的U（VI）浓度，这与大多数环境场景有关。一组高度纯化和良好的特征TiO 2相不同的起源，最稳定的多晶型物（金红石和金红石）的比例，在比表面积，等电点和粒度分布进行了研究。无论矿物相的组成，它表明，U（VI）形成类似的表面络合物，这是来自反对称拉伸模式nu（3）（UO 2），显示出一个特征性的转变，以较低的波数相比，相应的水溶液物种。快速扫描红外设备的可用性使得它可以进行时间分辨实验的吸附过程中的时间分辨率在亚分钟范围内。结果表明，在早期阶段的U（VI）的吸收，矿物相上的表面物种的形成，其特征在于由一个显着的红移吸收最大值被解释为一个bidendate内球复合物。长时间吸附后，红外光谱表明形成的第二个表面物种，显示出较小的位移相比，含水物种。这些研究结果进行了验证，通过一系列的光谱实验上进行的U（VI）饱和的表面，在不同的U（VI）浓度，pH值和在大气中衍生的碳酸盐的情况下。这项工作提供了新的分子的见解U（VI）在TiO 2上的吸附过程。原位红外光谱证实了表面络合的基本热力学思想。(C)2011爱思唯尔有限公司保留所有权利。
Molecular-scale knowledge of sorption reactions at the water-mineral interface is important for predicting U(VI) transport processes in the environment. In this work, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy was used in a comprehensive investigation of the sorption processes of U(VI) onto TiO2. The high sensitivity of the in situ ATR FT-IR technique allows the study of U(VI) concentrations down to the low micromolar range, which is relevant to most environmental scenarios. A set of highly purified and well characterized TiO2 phases differing in their origin, the ratio of the most stable polymorphs (anatase and rutile), in specific surface area, isoelectric points and in particle size distribution was investigated. Irrespective of the composition of the mineral phase, it was shown that U(VI) forms similar surface complexes, which was derived from the antisymmetric stretching mode nu(3)(UO2) showing a characteristic shift to lower wavenumbers compared to the respective aqueous species. The availability of a fast scanning IR device makes it feasible to perform time-resolved experiments of the sorption processes with a time resolution in the sub-minute range. It is shown that during the early stages of the U(VI) uptake, a surface species on the mineral phase is formed, characterized by a significantly red-shifted absorption maximum which is interpreted as a bidendate inner-sphere complex. After prolonged sorption, the IR spectra indicate the formation of a second surface species showing a smaller shift compared to the aqueous species. These findings were verified by a series of spectroscopic experiments performed on a U(VI)-saturated surface, at different U(VI) concentrations, pH values and in the absence of atmospheric-derived carbonate. This work provides new molecular insights into the sorption processes of U(VI) on TiO2. Basic thermodynamic ideas of surface complexation are substantiated by in situ infrared spectroscopy. (C) 2011 Elsevier Ltd. All rights reserved.