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

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.