Collaborative Research: ECO-CBET: Putting entropy to work: Leveraging the role of water organization in peptide binding events to selectively recover rare earths

稀土元素是风力涡轮机、电动汽车和智能手机的关键部件。美国100%的稀土元素都是从中国进口的，这些元素在中国的开采和提纯过程耗时耗力。美国在从煤炭工业废水、电子废物和化肥开采废物等废物流中回收稀土元素方面具有巨大潜力。该项目由凯斯西储大学、克莱姆森大学和宾夕法尼亚州立大学合作，将从磷石膏中回收有价值的稀土元素（La、Ce、Nd、Pr）。磷石膏是一种肥料开采废料，与放射性受损的水混合在一起。目前，磷石膏通过管道输送到开放的沟渠或池塘，并作为“堆”无限期储存。今天，仅在佛罗里达州，估计就有超过2亿吨的稀土元素被困在未处理的磷石膏废物中。由于放射性物质的挑战和分离单个元素的困难，这种稀土元素的来源目前尚未开发。此外，自1994年以来，磷石膏堆场已造成超过2亿加仑的污染水排放到佛罗里达州的含水层和地表水中，堆垛故障对环境构成了威胁。因此，该项目的愿景是发现新的分离机制、材料和工艺，从肥料工业的废物流中回收有价值的资源（稀土元素、肥料、清洁水），为可持续的国内稀土元素供应和可持续的农业部门铺平道路。这样做将使原本无法使用的废物流得以循环利用，并处理威胁当地供水的受损水域。同时，下一代工程师将接受培训，以解决食品-能源-水关系前沿的复杂环境工程问题。教育外展项目将通过社交媒体应用TikTok针对普通大众，并让当地高中生参与研究体验和指导项目。此外，将为以可持续性和水处理为重点的K-12外展活动制定互动活动。传统的膜分离机制依赖于大小和电荷的差异，由于它们的半径相似，形式电荷相同，因此不足以纯化单个稀土元素。本项目采用多级分离工艺：1)化学消解法从磷石膏中提取稀土元素，2)电渗析法从阴离子中分离并浓缩稀土元素，3)多肽功能化膜选择性分离稀土元素。本研究的一个关键技术目标是发现支撑肽离子选择性的机制，并利用这些机制来设计一类新的高选择性膜。多肽-离子络合的热力学将使用x射线吸收光谱、生物分子表征技术和多尺度建模进行研究。机器学习将用于基于热力学描述符预测新的肽结构。新发现的多肽将通过“点击”化学方法被纳入电纺丝膜中。将进行技术经济分析和生命周期评估，以量化拟议设计的环境和财务影响，并为该设计的迭代提供信息。从这项研究中产生的知识将广泛地使目前具有挑战性的膜和吸附材料领域的选择性分离成为可能。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 are critical components in wind turbines, electric vehicles, and smart phones. The United States imports 100% of its rare earth elements from China, where they are mined and purified through time- and energy-intensive processes. The United States has great potential to recycle rare earth elements from waste streams such as coal industry waters, electronic wastes, and fertilizer mining wastes. This project, a collaboration between Case Western Reserve University, Clemson University, and Pennsylvania State University-University Park, will recover valuable rare earth elements (La, Ce, Nd, Pr) from phosphogypsum—a fertilizer mining waste mixed with radioactive impaired water. Currently, phosphogypsum is piped to open ditches or ponds and stored indefinitely as “stacks”. Today, an estimated more than 200 million tons of rare earth elements are trapped in unprocessed phosphogypsum waste in Florida alone. This source of rare earth elements is presently untapped due to challenges associated with radioactive species and the difficulty of separating the individual elements. Further, stack failures post a threat to the environment as phosphogypsum sites have caused over 200 million gallons of contaminated water to be released to Florida aquifers and surface waters since 1994. Thus, the vision for this project is to discover new separation mechanisms, materials, and processes to recover valuable resources (rare earth elements, fertilizers, clean water) from waste streams of the fertilizer industry, paving the way for a sustainable domestic supply of rare earth elements and a sustainable agriculture sector. Doing so will enable the recycling of an otherwise unusable waste stream and treat impaired waters that threaten local water supplies. Simultaneously, the next generation of engineers will be trained to tackle complex environmental engineering problems at the forefront of the food-energy-water nexus. Educational outreach programs will target the general public using the social media app TikTok and engage local high school students in research experiences and mentoring programs. In addition, interactive activities for K-12 outreach events focused on sustainability and water treatment will be developed.Traditional membrane separation mechanisms rely on differences in size and charge which are insufficient to purify individual rare earth elements due to their similar radii and identical formal charge. This project pursues a multistage separation process in which rare earth elements are 1) extracted from phosphogypsum by chemical digestion, 2) separated from anions and concentrated by electrodialysis, and 3) selectively separated using peptide-functionalized membranes. A key technical goal of this research is to discover the mechanisms that underpin peptide-ion selectivity and leverage those mechanisms to design a new class of highly selective membranes. The thermodynamics of peptide-ion complexation will be studied using X-ray absorption spectroscopy, biomolecular characterization techniques, and multiscale modeling. Machine learning will be employed to predict new peptide structures based on thermodynamic descriptors. Newly discovered peptides will be incorporated into electrospun membranes using “click” chemistry. Techno-economic analysis and life cycle assessment will be performed to quantify the environmental and financial impacts the proposed design and inform iterations of this design. Knowledge generated from this research will broadly enable currently challenging selective separations across the fields of membranes and sorbent materials.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.