GEO-CM:A systematic investigation of sorption mechanisms of light REEs on iron oxides: roles of mineral morphology, crystallinity, and surface sites

稀土元素（ree）是许多前沿技术的关键材料，这些技术是清洁能源运输、能源生产和储存、通信和计算的基础。由于美国国内缺乏足够的稀土产量，稀土的供应尤其令人担忧。高风化环境中稀土元素的富集为未来勘探提供了良好的机会。然而，对于稀土元素在次生矿物(如粘土和铁/铝（水）氧化物（岩石风化的常见产物）中富集的基本地球化学控制，特别是稀土元素如何与矿物表面结合和从矿物表面动员的机制，我们的理解存在重大知识空白。该项目旨在获得稀土与氧化矿物相互作用的基础科学知识，这是通过岩石风化准确预测稀土矿床的发生和形成所必需的，并可能为提取这些关键材料的新方法提供信息。同样重要的是，从高中到研究生的多层次学生的直接参与和培训，以吸引潜在的下一代科学家进入STEM学科。氧化矿物学对稀土吸附机制的影响可能在风化环境中控制稀土的命运中起重要作用，但对其了解甚少。本项目将利用氧化铁作为模型系统揭示这些以前未被认识到的因素。总体目标是阐明矿物结构、结晶度、形态和界面结构动力学如何影响矿物质-水界面的稀土吸附反应。轻稀土将被用作探测元素，并将在氧化铁颗粒和赤铁矿单晶上采用一系列综合的实验室湿化学实验和基于同步加速器的x射线技术来完成研究目标。该研究将深入了解在岩石风化过程中控制这些关键元素沉积形成的基本地球化学过程。该奖项反映了美国国家科学基金会的法定使命，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。

Rare-earth elements (REEs) are critical materials to many leading-edge technologies that underlie clean energy transportation, energy generation and storage, communication, and computing. The availability of REEs is of special concern due to the lack of adequate U.S. domestic production. REEs enrichment in minerals in highly weathered environments represents a promising opportunity for future exploration. However, major knowledge gaps exist in our understanding of the fundamental geochemical controls on REEs accumulation in secondary minerals like clays and iron/aluminum (hydr)oxides (common products of rock weathering), especially the mechanisms of how REEs bind to and are mobilized from mineral surfaces. This project seeks to obtain the foundational scientific knowledge on REEs interactions with oxide minerals, which is required to accurately predict the occurrence and formation of REEs deposits via rock weathering and could be informative in new ways to extract these critical materials. Of equal importance will be the direct involvement and training of students at multiple levels from high school to graduate students to attract the potential next generation of scientists into STEM disciplines.The effects of oxide mineralogy on the sorption mechanisms of REEs could play important roles in controlling REE fate in weathering environments but are poorly understood. This project will reveal these previously unrecognized factors using iron oxides as the model system. The overall goal is to elucidate how mineral structure, crystallinity, morphology, and interfacial structure dynamics could affect REEs sorption reactions at mineral-water interfaces. Light REEs will be used as the probing elements and an integrated series of laboratory wet chemistry experiments and synchrotron-based X-ray techniques will be employed on both iron oxide particles and hematite single crystals to accomplish the research objectives. The proposed study will obtain insight into fundamental geochemical processes controlling the formation of these critical element deposits during rock weathering processes.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.