Highly Efficient Extraction of 212 Pb/212Bi from the Decay Chain of 232Th-Based on Anion Exchange in Bromide Medium.

Although 212Pb and 212Bi have significant applications in targeted α-nuclide therapy for malignant tumors, their use is limited by the scarcity of 212Pb/212Bi resources. To address this bottleneck problem, an advanced strategy for selectively extracting 212Pb and 212Bi from the decay chain of 232Th is first proposed by using an efficient porous silica-supported anion exchanger in bromide medium. The selective adsorption mechanisms of the resin for Pb(II) and Bi(III) in bromide medium are first clarified through spectroscopic analyses and theoretical calculations. Using the novel method and exchanger, 2.07 MBq of 212 Pb is successfully separated from 232Th and its daughters, with a record-breaking chemical yield of 88.2% and an estimated radionuclide purity of over 99.9%. Mechanism analysis suggests that Pb(II) and Bi(III) can form anionic complexes in the HBr medium, with [PbBr3]- and [BiBr5]2- being the main species captured; while Th(IV), Ac(III) and Ra(II) mainly exist as cationic forms and thus can't be fixed. To date, this represents the first report of successfully extracting 212Pb/212Bi from 232Th and its daughters using anion exchanger in bromide medium, as well as the mechanism illustrations, which enables the supply of 212Pb/212Bi directly from the abundant natural thorium resource to be possible.