Search for: All records

One of the major challenges in processing rare earth element (REE) materials arises with the large amounts of radioactive thorium (Th) that are often found within REE minerals, encouraging enhanced metal separation procedures. We report here a study aimed at developing improved systems for REE processing with the goal of efficient extraction of Th(IV) from acidic solution. A tripodal ligand, TRPN-CMPO-Ph, was prepared that utilizes carbamoylmethylphosphine oxide (CMPO) chelators tethered to a tris(3-aminopropyl)amine (TRPN) capping scaffold. The ligand and its metal complexes were characterized using elemental analysis, NMR, FT-IR, mass spectrometry, and luminescence spectroscopy. Using a liquid-liquid metal extraction protocol, TRPN-CMPO-Ph selectively extracts Th(IV) at an efficiency of 79% from a mixture of Th(IV), UO22+, and all rare earth metal cations (except Pm) dissolved in nitric acid into an organic solvent. Thorium(IV) extraction selectivity is maintained upon extracting from a mixture that approximates a typical monazite leach solution containing several relevant lanthanide ions, including two ions at higher concentration relative to Th(IV). Comparative studies with a tris(2-aminoethyl)amine (TREN) capped derivative are presented and support the need for the larger TRPN capping scaffold in achieving Th(IV) extraction selectivity.