Degradation and ion exchange mechanisms in metatorbernite-type (Cu(UO2)2(XO4)2.8H2O, X=As, P) minerals; implications for remediation of radiochemical

偏云母矿型(Cu(UO2)2(XO4)2.8H2O, X=As, P)矿物的降解和离子交换机制；

• 批准号: 2244202
• 金额: --
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2244202
• 关键词: Degradation; ion; exchange; mechanisms; metatorbernite

This project aims to understand the structure, stability and degradation mechanisms of metatorbernite type minerals. Metatorbernite (Cu(UO2)2(PO4)2 8H2O), and its arsenate analogue metazeunerite (Cu(UO2)2(AsO4)2 8H2O), are common secondary uranium minerals that result from the alteration of uranium ore (uraninite). Both minerals are considered significant hosts for uranium in natural and anthropogenically contaminated environments. Understanding the stability of these mineral phases is therefore essential in the development of retention and remediation strategies aimed to prevent the (re)release of toxic elements into the environment.Metatorbernite and metazeunerite are layered minerals, comprised of uranyl phosphate/arsenate sheets with hydrated interlayers containing water coordinated copper(II) ions. A complete solid solution exists between the two end member phases: Cu(UO2)2(PO4)2-x(AsO4)x 8H2O, 0x2. Through a series of leaching experiments we have found that the stability of the solid solution is composition dependent, with As-rich phases exhibiting a lower stability, particularly with respect to U-leaching. To understand the reason(s) for this composition-based stability, we have begun an in-depth investigation into the mineral structure. Dominant X-ray scattering exhibited by uranium and arsenic has meant that previous studies have been unable to experimentally locate the position of hydrogen atoms within the crystal lattice using X-ray techniques alone. Our analysis includes a combination of synchrotron powder X-ray diffraction, single crystal X-ray diffraction, neutron powder diffraction, infrared spectroscopy, and computational methods. Our work aims to present a new structural model for the metatorbernite metazeunerite solid solution, and apply this knowledge to the observed stability differences.

本项目旨在了解变斑铜矿类矿物的结构、稳定性和降解机制。变铀云母（Cu（UO 2）2（PO 4）2·8H 2 O）及其砷酸盐类似物变铀云母（Cu（UO 2）2（AsO 4）2·8H 2 O）是铀矿石（晶质铀矿）蚀变过程中常见的次生铀矿物。这两种矿物都被认为是天然和污染环境中铀的重要宿主。了解这些矿物相的稳定性，因此是必不可少的保留和补救策略的发展，旨在防止（再）释放到environment.Metatorbernite和metzeunerite的有毒元素是层状矿物，由磷酸铀酰/砷酸盐片与含水夹层含有水协调铜（II）离子。在两个端元相之间存在完全固溶体：Cu（UO 2）2（PO 4）2-x（AsO 4）x 8H 2 O，0x 2。通过一系列的浸出实验，我们已经发现，固溶体的稳定性是组成依赖性的，与富As相表现出较低的稳定性，特别是相对于U-浸出。为了了解这种基于成分的稳定性的原因，我们已经开始深入研究矿物结构。铀和砷所表现出的主要X射线散射意味着以前的研究无法单独使用X射线技术在晶格中实验定位氢原子的位置。我们的分析包括同步加速器粉末X射线衍射，单晶X射线衍射，中子粉末衍射，红外光谱和计算方法的组合。我们的工作旨在提出一个新的结构模型的变斑铜矿变沸石固溶体，并将此知识应用到观察到的稳定性差异。