A study of the ion-exchange behavior of Pb and Bi as homologs of elements 114 and 115, respectively, in aqueous and aqueous-methanol solutions of HNO3

Abstract

The ion-exchange behavior of Pb and Bi as homologs of elements 114 and 115, respectively, in aqueous and aqueous-methanol solutions of HNO 3 was studied. The distribution coefficients of Bi, Pb, Ra, and some actinides between the ion exchangers and HNO 3 solutions were determined in relation to the acid and methanol concentrations in the solution and to the kind of the ion exchanger. The distribution coefficients of Bi and other elements under consideration in sorption on the cation and anion exchangers from mixed aqueousmethanol HNO 3 solutions differ considerably. The optimum conditions were found for the isolation of carrierfree short-lived Pb and Bi isotopes and for their separation from actinides and other elements using the ion exchangers and aqueous-methanol HNO 3 solutions. The possibility of repeated isolation of short-lived Bi isotopes with their simultaneous separation from the long-lived parent radionuclides (Ac, Ra, Pb) on the cation exchanger (radioisotope generators) using mixed HNO 3 /CH 3 OH solution and of on-line preconcentration of these isotopes on the anion exchanger was demonstrated.The synthesis of superheavy elements (SHEs) with Z = 113-118, accomplished at the Flerov Laboratory of Nuclear Reactions (Dubna, Russia), is an experimental proof of the existence of the "islands of stability," hypothesized as early as the middle of the XX century. This success opens wide prospects for studying the chemistry of these elements [1].A study of the chemical properties of SHEs, determining their position in the periodic table, is one of priority problems of the modern radiochemistry. Data obtained in this field will expand our knowledge of the structure of atom electronic shells and will allow us to reveal relativistic effects associated with the electronic structure of heavy element atoms. Because of short lifetime of SHEs and low cross sections of their production in nuclear reactions, study of the chemistry of these elements is difficult and labor-consuming. For isolation of SHEs from irradiated targets, their chemical identification, and study of their behavior in various systems, specific methods and approaches are being developed using as examples their light homologs, as a rule, in the carrier-free state [2,3]. The most promising for studying the SHE chemistry in solutions are chromatographic methods allowing the speciation, complexation, oxidation state, and other chemical properties to be studied on high reliability level with ultrasmall amounts of elements.Previously we studied the ion-exchange behavior of Pb and Bi as homologs of elements 114 and 115, respectively, in solutions of hydrohalic acids and showed that, in dilute HCl and HBr solutions, these elements form strong neutral and anionic complexes sorbed by the anion exchanger [3][4][5][6][7]. This study deals with the ion-exchange behavior of carrier-free short-lived isotopes of Pb and Bi in aqueous and aqueous-methanol solutions of nitric acid and is aimed to examine the chemical forms and complexation of these isotopes in dilute HN...