ИСТИНА

Extraction chromatography is a technique that is ideally suited to the separation of radionuclides from a wide range of sample types. This technique combines the selectivity of liquid-liquid extraction with the ease of operation of column chromatography. α-emitters, such as 225Ac and 223Ra, may be produced from irradiated thorium. This radionuclides are used for nuclear medicine. When irradiating thorium with medium-energy protons (up to 141 MeV) a great number of spallation and fission product are formed. Radiochemical separation of actinides and rare earth elements is a very difficult task. For this aim we used extraction chromatography resins by TrisKem International company: TEVA (mixture of trioctyl and tridecyl methyl ammonium chloride as an extractant), DGA (N,N,N`,N`tetroctyldiglicolamide), LN (di(2-ethylhexyl)orthophosphoric acid) and TRU (octylphenyl-N,N-di-isobutyl carbomoylphosphine oxide). TEVA resin is proposed for sorption of Th. The distribution coefficient (k’) for Th(IV) increases with HNO3 concentration up to 400 in 6 M HNO3. The value of Th sorption capacity is 70 mg/g (manufacturer’s data), whereas the sorption of trivalent ions is negligible. DGA and LN resins have a steep dependence of k’ for trivalent ions on HNO3 concentration. k’ (DGA) reaches maximum in 6-7 M HNO3 solution and drops down to 1-2 in 10-2 M HNO3 solution. k’ (LN) demonstrates inverse acidity dependence [1,2]. We used these resins to adsorb actinium and rare earth elements from HNO3 solution of favorable acidity, while mono- and divalent ions (Cs+, Ra2+, Ba2+, Sr2+) as well as most of Ru, Zr, Nb, and others were washed out of the column. TRU resin displays a moderate k’ values ~102 for trivalent ions in the range of 1-5 M HNO3 [2]. Optimization of acidity and column length allowed us to separate actinium from lanthanides. Distribution coefficients of 225Ac on DGA, Ln, TRU – resins in nitric acids solutions with various concentrations were studied.