Generator of Actinium-228 and a Study of the Sorption of Actinium by Carbon Nanomaterials
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rator of Actinium-228 and a Study of the Sorption of Actinium by Carbon Nanomaterials A. G. Kazakova,*, B. L. Garashchenkoa, R. Yu. Yakovleva, S. E. Vinokurova, S. N. Kalmykova,b, and B. F. Myasoedova,b,c a
Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia b Lomonosov Moscow State University, Moscow, 119991Russia c Interdepartmental Center for Analytical Studies in Physics, Chemistry, and Biology, Russian Academy of Sciences, Moscow, 117997 Russia *e-mail: [email protected] Received October 29, 2019; revised February 19, 2020; accepted February 20, 2020
Abstract—A method has been developed for isolation of 228Ac from aged samples of natural 232Th. Macroscopic amounts of the thorium bulk (20 g) were separated by its extraction by a solution of di(2-ethylhexyl)phosphoric acid in toluene from 4 M HNO3 solutions, with microamounts of 228Ra and 228Ac remaining in the aqueous phase. 228Ac was selectively extracted from the resulting solution by the method of extraction chromatography on a column with RE resin sorbent, and 228Ra quantitatively remained in the 4 M HNO3 eluate. 228Ac was washed out of the column with 0.05 M HNO3, it could be used as a radioisotope for research purposes. After the accumulation of the daughter 228Ac the solution of 228Ra in 4 M HNO3 was repeatedly passed through an identical column. The resulting 228Ac was used in the study to examine its sorption on commercial and modified carbon nanomaterials (CNMs) instead of the difficultly accessible 225Ac. It is shown that the application of CNMs as carriers of actinium isotopes for nuclear medicine purposes is promising. Keywords: actinium-228, radioisotope generators, extraction chromatography DOI: 10.1134/S1066362220050057
INTRODUCTION
the mother nuclide (T1/2 = 5.7 yrs) and the absence of long-lived daughter nuclide. The activity of 228Ra in the secular equilibrium with 232Th is about 1.6 kBq per gram of thorium nitrate. Therefore, with 228Ra isolated from gram amounts of thorium nitrate, 228Ac can be dayly extracted from the generator with activity sufficient for carrying out studies, including those performed in vivo (several and tens of kBq). Various ways to separate Th, Ra, and Ac are known from the literature [4–10]. 228Ra and 232Th are, as a rule, separated via coprecipitation of radium and its extraction in various systems [4, 5]. Actinium and radium are separated by ion-exchange chromatography [6, 7], extraction [8], selective sorption [9], and extraction chromatography [4, 6,10]. In these studies, small amounts of 232Th or trace amounts of 229Th have been used. At the same time, there is no published information about isolation of 228Ac from large amounts of 232Th (tens of grams).
The targeted alpha-therapy in nuclear medicine frequently uses the 225Ac that undergoes the fast alphadecays [1–3]. This isotope is obtained by different methods, including that in which thorium targets are irradiated with high-energy protons. However, this method does not find wide application because th
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