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.
|Effective start/end date
|8/15/21 → 7/31/25
- National Science Foundation: $438,056.00