Theses and Dissertations Collection

Rare earth elements (REEs) are vital to energy-efficient modern technology and high-tech devices. Due to potential supply challenges for REEs, recycling these metals from post-consumer products, such as fluorescent lighting phosphors and neodymium iron boron magnets, has been proposed. Toward that end, liquid-liquid solvent extraction of various REEs was performed with tetrabutyl diglycolamide (TBDGA) in 1-octanol and 1-octanol modified carbon dioxide from chloride media. Hydrochloric acid, Cl-, TBDGA concentrations were varied, and the thermodynamics of the extraction of REEs with TBDGA in 1-octanol was explored. The extraction of REEs from phosphors and magnet materials using optimized conditions with TBDGA in 1-octanol was performed. Stripping the metal from the metal-loaded TBDGA in 1-¬octanol was investigated. HCl and an aqueous-soluble ligand, tetraethyl digylcolamide (TEDGA), were utilized for the back-extraction of the REEs into an aqueous phase. The concentrations of the HCl and the TEDGA were varied to determine if REEs could be selectively back-extracted and separated from one another.

Carbon dioxide is inert, has low cost, can be easily reused, and is readily available in a pure form. This means carbon dioxide is a better and “greener” diluent than traditional organic diluents for extraction. A system for extraction of REEs from chloride media with liquid carbon dioxide was optimized by varying mole percent 1-octanol, pressure, temperature, metal concentration, TBDGA concentration, chloride concentration and H+ concentration. The effect of water concentration on the extraction with TBDGA into 1¬-octanol modified CO2(l) was examined with UV-visible spectroscopy. Optimized CO2(l) extractions were performed on phosphor and magnet leachate solutions.