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.