Developing the thermodynamic solid solution models for Th, U, REE phosphates needed to identify the formation conditions of Th, U-depleted REE ores

开发钍、铀、稀土元素磷酸盐的热力学固溶体模型，以确定贫钍、铀元素矿石的形成条件

• 批准号: 2149848
• 负责人: Xiaofeng Guo
• 金额: $ 42.57万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2149848&HistoricalAwards=false
• 关键词: Developing; thermodynamic; solid; solution; models

Rare earth elements (REE) are critical for the future of the U.S. economy, renewable energy, and national security. New technologies enhancing environmental sustainability, defense capability, and consumer products have sharply increased the demand for the REE. However, the supply of REE in the U.S. relies mostly on their import from foreign sources. Furthermore, many of the domestic deposits suffer from high concentrations of thorium (Th) and uranium (U) that contaminate the environment during mining. To deal with this issue, it is necessary to discover the conditions needed for economic concentrations of the REE to form in nature in the absence of Th or U; this requires understanding how Th and U mix with the REE in minerals and how such mixing can be avoided. This project will explore how Th and U mix with the REE in minerals through a combination of experiments and geological modeling. These results will make it possible to predict the natural environments in which Th- and U-poor REE minerals form and thereby provide geologists with the information they need to develop strategies to explore for and locate deposits of REE that can be economically and safely mined. This project also aims to educate high school, undergraduate, and graduate students in geochemistry, and prepare them for careers as scientists. The integrated education plan is committed to holding summer geochemistry schools for high school students, promoting geochemical education to student through visits to national laboratories and virtual lectures, and engaging students in the experimental and modeling methods that are used in the research project.The objective of this research proposal is to generate new knowledge enabling identification of the conditions under which Th and U-depleted REE phosphate ores can form. One of the major impediments to the recovery of REE from ores in the U.S. is the radioactivity generated during their processing and refining due to the presence of high concentrations of Th and U in the main REE ore minerals, monazite and xenotime. Thus, there is a strong need to find Th, U-depleted REE ores, which, in turn, depends on developing a better understanding of their formation conditions (e.g., temperature, pressure, oxygen fugacity, pH, etc.), particularly those for which the incorporation of Th and U into phosphate structures is minimal. Whereas the properties of the aqueous species of the REE, U, and Th are now reasonably well-known for the hydrothermal conditions of REE ore formation, there is almost no information on phosphate-based REE/U/Th solid solutions. A major challenge is to correctly account for thermodynamic non-ideality due to the mixing of Th and U with the REE, which is often incorrectly assumed to be ideal and thus can lead to inaccurate or false predictions. This project will establish accurate thermodynamic models describing the incorporation of Th and U in REE phosphates that are critically needed by geochemical modelers to predict the mobilization, fractionation, and deposition of REE/U/Th in hydrothermal systems. The knowledge obtained will enable the development of new exploration techniques permitting the identification and localization of Th- and U-depleted REE ores. The project also offers unique opportunities for students to receive the interdisciplinary education and training needed to become geochemists with broad mindsets and skillsets. This includes summer geochemistry schools for high school students and teachers to develop their interest in the geochemistry of the REE and other critical metals.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

稀土元素（REE）对美国经济、可再生能源和国家安全的未来至关重要。增强环境可持续性、防御能力和消费品的新技术大大增加了对稀土的需求。然而，美国的稀土供应主要依赖于从国外进口。此外，许多国内矿床都含有高浓度的钍（Th）和铀（U），在开采过程中会污染环境。为了解决这个问题，有必要发现在没有Th或U的情况下，在自然界中形成稀土元素经济浓度所需的条件;这需要了解Th和U如何与矿物中的稀土元素混合，以及如何避免这种混合。本项目将通过实验和地质模拟相结合的方法，探索钍、铀与矿物中稀土元素的混合方式。这些结果将使人们有可能预测自然环境中的Th-和U-贫稀土矿物的形成，从而提供地质学家的信息，他们需要制定战略，探索和定位的稀土矿床，可以经济和安全地开采。该项目还旨在教育高中生，本科生和研究生地球化学，并为他们作为科学家的职业生涯做好准备。综合教育计划致力于为高中生举办暑期地球化学学校，通过参观国家实验室和虚拟讲座，促进学生的地球化学教育，并让学生参与研究项目中使用的实验和建模方法。本研究提案的目的是产生新的知识，使Th和U-可形成贫化的稀土磷酸盐矿石。在美国，从矿石中回收稀土元素的主要障碍之一是由于主要稀土矿石矿物独居石和磷钇矿中存在高浓度的Th和U，在其加工和精炼过程中产生的放射性。因此，迫切需要找到Th、U贫化的REE矿石，这反过来又取决于更好地了解它们的形成条件（例如，温度、压力、氧逸度、pH等），特别是Th和U掺入磷酸盐结构中的量最少的那些。而稀土元素，U和Th的水溶液物种的属性，现在合理地众所周知的热液条件的稀土矿形成，几乎没有信息磷酸盐为基础的稀土/U/Th固溶体。一个主要的挑战是正确地解释由于Th和U与REE的混合而导致的热力学非理想性，这通常被错误地认为是理想的，从而可能导致不准确或错误的预测。该项目将建立精确的热力学模型，描述稀土磷酸盐中Th和U的掺入，这些稀土磷酸盐是地球化学建模者迫切需要的，以预测热液系统中REE/U/Th的活化、分馏和沉积。所获得的知识将使新的勘探技术的发展，允许识别和定位的Th和U贫化稀土矿石。该项目还为学生提供了独特的机会，接受成为具有广泛思维和技能的地球化学家所需的跨学科教育和培训。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Crystal Chemistry and Thermodynamics of HREE (Er, Yb) Mixing in a Xenotime Solid Solution

• DOI: 10.1021/acsearthspacechem.2c00052
• 发表时间: 2022-05
• 期刊: ACS Earth and Space Chemistry
• 影响因子: 3.4
• 作者: A. Strzelecki;Margaret E. Reece;Xiaodong Zhao;Wendy Yu;C. Benmore;Yang Ren;C. Alcorn;A. Migdisov;Hongwu Xu;Xiaofeng Guo

Uranium uptake by phosphate minerals at hydrothermal conditions

磷酸盐矿物在热液条件下对铀的吸收

• DOI: 10.1016/j.chemgeo.2023.121581
• 发表时间: 2023
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Jiménez-Arroyo, Ángel;Gabitov, Rinat;Migdisov, Artas;Lui, Juejing;Strzelecki, Andrew;Zhao, Xiaodong;Guo, Xiaofeng;Paul, Varun;Mlsna, Todd;Perez-Huerta, Alberto
• 通讯作者: Perez-Huerta, Alberto

Machine learning assisted phase and size-controlled synthesis of iron oxide particles

• DOI: 10.1016/j.cej.2023.145216
• 发表时间: 2023-03
• 期刊: Chemical Engineering Journal
• 影响因子: 15.1
• 作者: Juejing Liu;Zimeng Zhang;Xiaoxu Li;M. Zong;Yining Wang;Su Wang;Ping Chen;Zaoyan Wan;Yatong Zhao;Lili Liu;Yangang Liang;Wen Wang;Zhemin Wang;Shiren Wang;Xiaofeng Guo;Emily Saldanha;K. Rosso;Xin Zhang