Characterization of Adsorption Complexes at Water/Solid Interfaces

离子在水/固体氧化物和水/粘土界面上的分配在分子水平上知之甚少，但关于表面络合物的详细结构信息对于定量描述许多界面过程是必不可少的。这些过程在许多领域发挥着基础性作用，包括地球化学、海洋学和环境工程。拟议的工作将利用高强度、波长可调的同步辐射和X射线吸收光谱(XAS)、特别是扩展X射线吸收精细结构(EXAFS)和X射线近边缘吸收结构(XANES)，以获得最近邻居的直接、现场测量，以及在可能的情况下，近邻距离和身份，配位数，以及在有利的体系中，被吸附离子和固体表面阳离子之间的距离。这些信息将被用来帮助定义表面络合物的组成和结构，并区分吸附、吸附、沉淀和共沉淀。将研究10个体系：以Pb2+、Sr2+、Co2+、Cu2+、SeO4/2-和SeO3/2-为吸附体，以地质铁矿、γ-Al_2O_3、金红石和高岭石为吸附剂。拟议的研究将提供有关吸附络合物的详细组成和结构信息，并有机会比较几种方法获得的结果。它还将提供一个测试和改进当前吸附过程理论模型的机会。

The partitioning of ions at water/solid oxide and water/clay interfaces is poorly understood at the molecular level, yet detailed structural information about surface complexes is essential for quantitative description of many interfacial processes. These processes play fundamental roles in many fields, including geochemistry, oceanography, and environmental engineering. The proposed work will utilize high-intensity, wavelength-tunable synchrotran radiation and X-ray Absorption Spectroscopy (XAS), specifically Extended X-Ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES), to obtain direct, in-situ measurements of nearest- neighbor, and where possible, next-neighbor distances and identities, coordination numbers, and in favorable systems, distances between adsorbate ions and cations in the solid surface. This information will be used to assist in the definition of composition and structure of surface complexes and to distinguish among adsorption, absorption, precipitation, and coprecipitation. Ten systems will be studied: involving Pb2+, Sr2+, CO2+, Cu2+, SeO4/2-, and SeO3/2- as adsorbates, and geothite, gamma-Al2O3, rutile, and kaolinite as adsorbents. The proposed study will provide detailed compositional and structural information about adsorption complexes, and an opportunity to compare results obtained by several methods. It will also provide an opportunity to test and refine current theoretical models for adsorption processes.