Continuous Chromatography with Reactions for the Purification of Rare Earth Elements

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1403854WangPurdue UniversityThe project aims to develop new efficient and economical methods to produce compounds of rare earth elements (REEs), such as neodymium, Nd, praseodymium, Pr, and samarium, Sm. Such elements are widely used in many high-tech products, such as petroleum refining catalysts, phosphors in color television and flat panel displays, permanent magnets, and rechargeable batteries. They are in short supply in the US and need to be imported from China, which produces over 95% of the world's REE supply and plans to restrict exports. It is important for the US industry and national security to develop environmentally sustainable methods to increase domestic REE supply, while minimizing production costs. The objective of this proposed project is to understand the fundamental concepts and generate the new data required to develop efficient continuous chromatography with reactions to replace the current extraction-based purification processes for REEs production. Systematic design and scale-up methods based on intrinsic adsorption and mass transfer parameters and dimensionless groups will be developed. The Standing Wave Design methods for continuous isocratic-elution systems without reactions will be extended to continuous systems with reactions. The design methods will be verified with rate model simulations and experimental data from three REEs (Pr, Nd, and Sm). The two purification methods (step-wise elution and displacement) will be integrated with capture chromatography in an efficient continuous process. A new six-zone continuous chromatography unit will be designed, built, and tested for the separation of Pr, Nd, and Sm. Both ligand-assisted stepwise elution and displacement chromatography will be tested using this new equipment. Both purification methods will be evaluated and compared with batch chromatography and tandem SMB for productivity, solvent usage, and separation costs. The results will have a major impact on managing the life cycles of REEs, while minimizing purification costs, solvent usage, waste production, and environmental impact. The design methods and the simulation tools developed in this project can be used to develop efficient continuous chromatography processes with reactions to produce other high-purity chemicals with high yield from complex mixtures.The project will involve graduate and undergraduate students, and will lead to improved teaching materials. The results potentially will be used by industry for REE production and by other researchers for similar or different separations. The results will have a major impact on the production costs of fine chemicals, biochemicals, foods, and pharmaceuticals, which have multibillion dollar annual sales. The project will also impact teaching of separations and help transfer this new technology to industry.