基于HERFD-XAS/XES技术研究偕胺肟基与碳酸根对铀酰的竞争吸附机理

The interaction mechanism between amidoxime (AO) ligand and uranyl carbonate ion is one of the important issues for uranium extraction from seawater. Previous researches believe the chemical reaction involves decomplexation of uranyl carbonate ion to uranyl ion, followed by complexation of uranyl ion with AO group. But recently some experts realize that the dissociation of uranyl carbonate ion is so highly endothermic that hinder the reaction. Exploring the complexation process between AO ligand and uranyl carbonate ion, can faver to develop effective adsorption group. In present proposal, two advanced techniques based on synchrotron radiation light source including High-energy-resolution fluorescence detected XAS (HERFD-XAS) and Hard X-ray emission spectroscopy (XES) combined with the first principles calculation will be employed to systematic study the complex structure of uranyl carbonate ion and the coordination mode between the functional ligands and uranyl ions. The electronic structure information of U-5f/6d and ligand atoms-2p will be obtained by qutantum chemistry calculation, to mainly analyze the binding strength and binding mode. Then the detailed chemical process will be examinated to exploring the competition mechanism between the amidoxime ligands and carbonate ions. The HERFD-XAS/XES technology with smaller width of the spectral features can also identify the close ligand atom in the periodic table, and thus superior to the conventional X-ray absorption fine structure technology. The proposal first attempt to use the advanced HERFD-XAS/XES technology in the actinide materials in domestic.

偕胺肟基团（AO）与碳酸铀酰离子的相互作用机理是目前海水提铀研究中的关键科学问题。很长时间内研究者均认为碳酸铀酰离子先自发解离然后与AO发生配位，然而近来有确凿证据表明碳酸根的解离是强吸热反应以致难以进行，因此亟需阐明AO配体与碳酸根的竞争机理为提铀材料的设计提供思路和依据。拟申请课题将利用基于同步辐射的高能量分辨荧光探测吸收谱学（HERFD-XAS）和硬X射线发射谱学（XES）并结合第一性原理计算系统地获取碳酸铀酰离子、AO/铀酰离子配合物的稳定结构以及U-5f/6d轨道与配体2p轨道的成键性质和强度等信息，重点分析配合方式与结合能力，进而通过设计中间构型探索反应路径，建立AO与碳酸根的竞争吸附模型。相较于常规XAS方法，HERFD-XAS与XES方法具有谱峰展宽小且可分辨C、N、O原子的特点，对于上述研究有极强的针对性。本课题的实施对于这两种技术在锕系材料的研究应用中有重要的探索作用。

偕胺肟基团（AO）与碳酸铀酰离子的相互作用机理是目前海水提铀研究中的关键科学问题。很长时间内研究者均认为碳酸铀酰离子先自发解离然后与AO发生配位，然而近来有确凿证据表明碳酸根的解离是强吸热反应以致难以进行，因此亟需阐明AO配体与碳酸根的竞争机理为提铀材料的设计提供思路和依据。在本项目的资助下，我们研究了偕胺肟配体与铀酰的络合构型，以及添加碳酸根离子后偕胺肟配体与碳酸根配体的竞争作用机制。我们发现偕胺肟配体是直接取代碳酸根的位置参与配位，支持阳离子型的吸附剂设计，同时U 5f/6d与配体（N、O）2p之间的共价作用在铀酰提取过程中起着重要的作用。在项目资助下，我们也发展了基于XANES直接获取铀酰配合物局域结构的分析方法，该方法特别适合于低铀浓度体系的结构研究。