Efficient Thorium/Barium Separation by Quaternary Ammonium Functionalized Silica Composite toward Sustainable Production of 212Pb for Targeted Alpha Therapy.

212Pb has become a critical parent isotope for 212Bi, which is an alpha-emitting radionuclide utilized in targeted alpha therapy (TAT) for oncology; however, its limited availability impedes broader clinical use. To tackle this significant challenge, this study focuses on a strategic approach to separate 228Th (a precursor to 212Pb) from its parent isotope 228Ra within the decay chain of naturally occurring 232Th. A novel porous silica composite, functionalized with quaternary ammonium groups through in situ polymerization (referred to as SiPVP-N4), was developed to efficiently achieve Th/Ba separation under highly acidic conditions. This material displays a unique spherical morphology with high porosity (25.4 nm pore size), rapid kinetics (achieving equilibrium within 30 min, which is six times faster than commercial resins), and exceptional selectivity for Th over Ba (with a separation factor SFTh/Ba of 1.6 × 103). The adsorption behavior aligns well with that of the Langmuir model, indicating a maximum adsorption capacity of 89.77 mg/g. Column experiments demonstrated 100% thorium recovery with high radiochemical purity under 9 M HNO3 adsorption conditions. Notably, SiPVP-N4 sustains over 95% capacity retention through five regeneration cycles, underscoring its potential for industrial application. This study establishes a robust platform for the production of medical isotopes, presenting a cost-effective alternative to traditional high-acid separation systems and contributing to the advancement of radiopharmaceutical development.