Efficient separation of radium from natural thorium using a mesoporous silica-supported composite resin with sulfonic acid groups for the acquisition of targeted α-nuclides 212Pb

212Pb serves as one of the most important nuclides for targeted alpha therapy (TAT), with good potential in the treatment of malignant tumors. However, medical and clinical applications are seriously limited by its extremely short supply, which strongly depends on the acquisition of its parent nuclides such as 228Ra or 224Ra. To address this issue, we conducted a systematic investigation on the separation of trace radium from natural thorium using the ion exchange chromatography method, and a novel porous silica-based composite resin functionalized with sulfonic acid groups was prepared, characterized, and employed. Experimental results showed that the silica-supported resin was successfully prepared with the sulfonic acid groups, and possessed small particle size, mesoporous pore structure and large specific surface area. The resin exhibited high selectivity toward thorium compared with barium, and the separation factor reached 123 at low acidity and at low temperature. The resin demonstrated a fast adsorption speed and an excellent separation performance, and the adsorption mechanism was confirmed based on the ion exchange between the sodium carried and the target cations. On the basis, column experiments were further conducted and finally the separation of trace radium from thorium was realized using a small column filled with about 1.0 g resin. The chemical recovery of radium reached 97 %, and the decontamination factor for thorium exceeded 40,000. This work verifies the feasibility of directly extracting 228Ra and 224Ra from natural thorium using the sulfonic acid group functionalized materials in the dilute nitric acid solution, and presents an excellent material and systematic experimental data on the separation activities, rendering this study particularly significant.