Selective separation of Bi3+ from La3+/Ac3+ by sorption on sulfonated carbon materials for use in an inverse 225Ac/213Bi radionuclide generator: Batch and column tests

Abstract

213Bi-labeled radiopharmaceuticals for cancer treatment are receiving considerable interest. 213Bi must be separated from the parent radionuclide 225Ac in a radionuclide generator, but the choice of a suitable sorbent material with high chemical and radiolytic stability is challenging. Present work reports on the synthesis of sulfonated carbon materials (SCMs) prepared by carbonization of methyl cellulose at temperatures between 300 and 800 °C, followed by a sulfonation process. These SCMs were evaluated as sorbents in inverse 225Ac/213Bi generators. The sulfonated carbon material prepared at 500 °C (SCM-500) was selected as the most promising candidate sorbent based on its unique aromatic carbon structure, sufficient amount of oxygen-containing functional groups, and selective sorption performance towards La3+/Bi3+. In addition, various variables, including the acidity of the solutions, salt concentrations, and sorption time have been evaluated for separating Bi3+ from La3+ (as a surrogate of Ac3+) by performing batch sorption experiments. SCM-500 was found to exhibit a high sorption Bi3+ selectivity over La3+ at low pH or in the presence of a high concentration of NaNO3. The optimized conditions in a column tests with this sorbent demonstrated a high chemical 213Bi yield (94 ± 3%) with less than 0.04% 225Ac relative to the eluted 213Bi activity. These results indicate that SCM-500 is a promising material for use in an inverse 225Ac/213Bi radionuclide generator. Furthermore, a conceptual design of an inverse 225Ac/213Bi radionuclide for medical applications is suggested based on the separation properties of SCM-500 and AG MP-50.