CAREER: Enabling Efficient Separation of Rare-Earth Elements Using Liquid-Metal Bipolar Membranes

稀土材料是风力涡轮机和电动汽车的永磁电机等可再生能源技术的组成部分。尽管稀土材料在向低碳经济转型的过程中发挥着关键作用，但目前只有不到1%的稀土被回收利用。预计未来十年对稀土需求的增长将超过开采矿石的供应。开发高效、环保的稀土回收技术对未来清洁能源技术的部署至关重要。该项目的目标是开发一种有效的稀土元素分离方法，使用液态金属作为选择性屏障（即双极膜），当施加电压时，允许稀土元素而不是其他元素通过。本研究将验证液态金属与稀土元素之间的强化学相互作用将增强稀土元素通过双极膜的假设。如果成功，液态金属双极膜将提供一种通过在单个电化学电池中直接分离从报废产品中回收稀土材料的方法。通过减少与稀土开采和对能源密集型稀土分离技术的依赖相关的环境负担，这将广泛地造福社会。通过让学生参与对美国长期经济竞争力至关重要的领域，包括电化学储能、材料合成、能源关键材料分离和耐腐蚀涂层，将研究和教育结合起来。研究生和本科生的电化学知识将通过整合实践研究经验和目标课程的整体课程来培养。高中生和STEM教育工作者将通过“材料可持续性电化学”外展项目参与其中。该计划旨在将非专业人士引入电化学领域，培养对电化学及其在解决现实挑战中的作用的好奇心，并激励对STEM职业的追求。首席研究员的长期职业目标是通过开发节能分离和回收技术来实现材料的可持续性。为了实现这一目标，该项目研究了一种新的电化学方法来有效分离稀土元素，利用液态金属作为双极膜，允许独特的电化学反应和稀土元素在电场作用下通过液态金属双极膜的质量传递。该项目的研究目标是建立控制稀土电化学选择性和渗透性的液体-金属双极膜的基本热力学、界面和输运性质。该项目的成果将包括稀土的高度精确的热力学、界面和输运性质，这对于开发液态金属双极膜以及开发可靠的实验技术来测量它们至关重要。实验验证的性质将被整合到计算工具（溶液模型和第一性原理计算）的开发中，用于模拟原子键合、相平衡、界面动力学和原子扩散。这种方法将加速对稀土具有特殊选择性和渗透性的液态金属双极膜的设计，增强计算材料建模的预测能力，并推进当前对稀土的认识。在这个项目中开发的科学方法将作为发现优质材料的一般手段，更好地控制稀土以外的其他能源关键材料的化学选择性。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 materials are components of renewable energy technologies such as permanent magnet motors for wind turbines and electric vehicles. Despite the critical role of rare-earth materials in the transition to a low-carbon economy, less than 1% of the rare earths are currently recycled. The projected increase in demand for rare earths over the next decade will outpace supply from mined ore. The development of efficient and environmentally-friendly rare-earth recycling techniques is essential for future deployment of clean energy technologies. The goal of this project is to develop an efficient rare-earth element separation using liquid metals as a selective barrier (i.e., a bipolar membrane) that allows rare-earth elements, but not other elements, to pass through when a voltage is applied. This study will test the hypothesis that strong chemical interactions between liquid metals and rare-earth elements will enhance the passage of the rare-earth elements through the bipolar membrane. If successful, the liquid-metal bipolar membrane will provide a way to recycle rare-earth materials from end-of-life products through direct separation in a single electrochemical cell. This will broadly benefit society by reducing the environmental burden associated with rare-earth mining and reliance on energy-intensive rare-earth separation technology. Research and education are integrated by engaging students in fields essential to long-term U.S. economic competitiveness, including electrochemical energy storage, materials synthesis, separation of energy-critical materials, and corrosion-resistant coatings. Graduate and undergraduate students' knowledge of electrochemistry will be cultivated through a holistic curriculum that integrates hands-on research experience with targeted coursework. High school students and STEM educators will be engaged through the "Electrochemistry for Materials Sustainability" outreach program. The program aims to introduce non-experts to the field of electrochemistry, cultivating a curiosity about electrochemistry, its role in solving real-world challenges, and motivating the pursuit of STEM careers.The Principal Investigator's long-term career goal is to enable materials sustainability through the development of energy-efficient separation and recycling technologies. Toward this goal, this project investigates a new electrochemical approach for efficient separation of rare-earth elements, utilizing liquid metals as a bipolar membrane that allows for unique electrochemical reactions and mass transport of rare-earth elements across the liquid-metal bipolar membrane under an electric field. The research objectives for this project are to establish the fundamental thermodynamic, interfacial, and transport properties of a liquid-metal bipolar membrane that govern electrochemical selectivity and permeability for rare earths. The outcomes of the project will include highly accurate thermodynamic, interfacial, and transport properties of rare earths, essential for developing liquid-metal bipolar membranes, as well as development of reliable experimental techniques for their measurement. The experimentally-verified properties will be integrated into the development of computational tools (solution models and first-principles calculations) for simulating atomic bonding, phase equilibria, interfacial kinetics, and atomic diffusion. This approach will accelerate the design of liquid-metal bipolar membranes that possess an exceptional selectivity and permeability for rare earths, enhance the predictive capabilities of computational materials modeling, and advance the current knowledge of rare earths. The scientific approaches developed in this project will serve as a general means for the discovery of superior materials with better control over chemical selectivity for other energy-critical materials beyond rare earths.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.