An advanced separation method for the acquisition of 212Pb/212Bi from natural thorium

Abstract

²¹²Pb/²¹²Bi hold significant potential for targeted cancer therapy; however, their supply remains severely limited. The extraction of ²¹²Pb/²¹²Bi from natural thorium is expected to fundamentally address this issue. This study proposes and verifies a new, efficient and low-cost method for separating ²¹²Pb/²¹²Bi from natural ²³²Th by investigating the separation behavior and mechanism of a silica-supported anion exchange resin (SiPyR-N4) toward multiple types of metal cations in hydrochloric solution. The experimental results demonstrated that SiPyR-N4 was successfully prepared with a uniform shape, porous structure, and containing quaternary amines. SiPyR-N4 showed extremely high selectivity for Pb²⁺ and Bi³⁺, but no affinity for Th⁴⁺, La³⁺, and Ba²⁺. The adsorption speed was more than six times as fast as traditional resins, providing significant advantages in the separation of short-lived nuclides. The hot separation experiment suggested that ²¹²Pb and ²¹²Bi were successfully isolated from natural ²³²Th by using natural thorium as the raw material, and the long-lived nuclides were removed completely. The selective separation mechanism was attributed to Pb²⁺ and Bi³⁺ forming anionic complexes in the hydrochloric acid medium, while Th⁴⁺, Ra²⁺, and Ac³⁺ did not form such complexes. Pb²⁺ and Bi³⁺ were bound to the active sites via chloride bridges, with [PbCl₃]⁻ and [BiCl₆]³⁻ serving as the main adsorbed species. This study is the first to report the direct and selective separation of ²¹²Pb and ²¹²Bi from ²³²Th decay chains using non-crown ether materials, and it provides an excellent material candidate for the separation of short-lived nuclides, showing significant application potential in the future.