NSF Award
2400992
This project is jointly funded by the Established Program to Stimulate Competitive Research (EPSCoR), and funds allocated to Clean Energy Technology Initiative investments. This Research Advanced by Interdisciplinary Science and Engineering (RAISE) award is made in response to Dear Colleague Letter 23-109, as part of the NSF-wide Clean Energy Technology initiative. Rare-earth elements (REEs) are essential components of emergent energy technologies that are key to the development of a sustainable energy future. Projections developed for REEs critical to the clean energy sector indicate that in the absence of efficient reuse pathways, demand is on target to outpace supply within the foreseeable future. Urban mining of REE-rich end-of-life products is a promising alternative to traditional energy-intensive mining of geological deposits. However, the costs and environmental impacts associated with re-separating and processing these materials are also substantial. This research targets an unexplored high-temperature pathway to REE recovery that may form the basis for new separation technologies with the potential to alleviate domestic supply risks and environmental concerns while enabling more circular manufacturing practices within the clean energy sector. Moreover, as clean energy technologies reduce carbon output due to hydrocarbon use, and as recycling of these metals also has a significantly lower carbon footprint than traditional mining, these efforts may further benefit society by reducing carbon emissions related to REE production and traditional energy strategies. This research will also promote awareness of critical minerals, their properties, and importance to clean energy technologies amongst the broader public through the development of an undergraduate and graduate curriculum and an interactive museum display.<br/><br/>With the recent discovery of high-temperature REE-sulfate liquids, and the growing demand for alternative REE extraction and separation technologies, there is an urgent need to assess the potential for high-temperature liquid-liquid phase equilibria to provide viable alternative routes to REE recovery from complex mixtures. Moreover, as these dense liquid phases are composed of only inorganic ionic species and water, the solutions in which they form also represent a unique class of high-temperature aqueous two-phase systems (ATPS) whose basic physical and chemical properties remain uncharacterized. This research aims to provide new insights into the physicochemical processes that promote the self-concentration of REEs within high-temperature ATPSs and to investigate the properties of the resulting REE-rich dense liquids that influence their formation kinetics, thermodynamic stabilities, and potential for recovery. The formation of REE-sulfate liquids will be observed in high-pressure optical cells over a range of temperatures, pressures, and solution compositions. Further characterization of the dense liquids by synchrotron-based X-ray techniques will provide information about the local structure and REE content of the sulfate liquids as they form, and structure modeling will be employed to generate atomistic models of the liquid phases that are consistent with the resulting datasets. The interfacial tension of the liquid-liquid interfaces will be measured by a droplet deformation method within a custom-made microfluidic device that will also facilitate separation of the dense and dilute liquid phases and the recovery of REEs.<br/><br/>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.
