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Increasing demand of high-purity and radiopharmaceutical grade radionuclides leads to the research and development of new, fast, simple and cost-effective separation methods. The most frequently used separation methods in nuclear medicine are liquid-liquid extraction or chromatographic methods. For example, the radionuclide 223Ra for targeted alpha-particle therapy is exclusively gained from 227Ac/227Th/223Ra radionuclide system and the separation of 223Ra is usually performed by ion-exchange or extraction chromatography. Diglycolamide solid extractants were successfully used in case of extraction chromatography [1].
Diglycolamides, ligands forming strong complexes especially with trivalent ions, can find broad use in separation of various radionuclides in many branches of nuclear chemistry, such as reprocessing of used nuclear fuel, nuclear medicine, analytical chemistry or production of high-purity radionuclides.
Most of the diglycolamide solid extractants are based on impregnated silica or polymer matrix or a chromatographic paper. This study focuses on the synthesis of diglycolamides covalently bound to polyacrylonitrile (PAN) beads. It is presumed that the covalent bond with the matrix will eliminate the leakage of the extraction agent from the solid extractant matrix which is an issue in case of impregnated materials.
PAN beads were chosen as a convenient material for its physical, chemical and radiation endurance and its chemical structure [2]. The presence of nitrile groups in the molecule of polyacrylonitrile allows the formation of covalent bond with diglycolamide. The synthesis is based on partial surface reduction of nitrile groups of PAN beads to primary amine and subsequent solid-state synthesis of diglycolamide.
PAN beads were partially reduced using multiple systems such as complex metal hydrides metal hydrides with transition metal salts or hydrogen with homogeneous catalysts. Several samples of partially reduced PAN beads were prepared and characterised via FT-IR and NMR spectrometry. The content of amine groups in the prepared samples was determined using acid-base titration.
Subsequently, the best reduction systems were used for the preparation of precursors for solid state synthesis of diglycolamides that has been performed using amide formation via coupling agent. Prepared solid extractants were characterized by FT-IR and NMR spectrometry, scanning electron microscopy and measurement of specific surfaces, and tested by the basic sorption experiments.
[1] ALGETA AS. Isotope production method. Inventors: Jan R. KARLSON, Peer BØRRETZEN. European patent application. EP2564397 A1. 29.4.2011.
[2] ŠEBESTA, F. et al. Evaluation of Polyacrylonitrile (PAN) as a Binding Polymer for Absorbers Used to Treat Liquid Radioactive Wastes. SAND95-2729, 1995.
This work was supported by Ministry of the Interior of the Czech Republic, grant No.: VI20172020106 and the EU & Ministry of Education Youth and Sports of the Czech Republic, grant No.: CZ.02.1.01/0.0/0.0/15_003/0000464.
