A Preliminary Study of Spherical Surface-Modified Carbon Materials for Potential Application in La³⁺ (Ac³⁺) and Bi³⁺...

Separation of high-activity ²¹³Bi from ²²⁵Ac for targeted alpha therapy is challenging due to the instability of existing sorbents. Surface-modified carbon materials have shown promise for use in inverse ²²⁵Ac/²¹³Bi generators. However, previously reported materials with irregular shapes may limit their applications in column separations. In contrast, spherical particles are expected to be more suitable for column chromatography compared to irregular powders as they can ensure uniform flow patterns, lower pressure drop, and effective packing. To address this limitation, a method was developed for the synthesis of spherical carbon beads via the carbonization of cellulose beads. Subsequently, surface modification on the spherical carbon beads was performed via sulfonation or oxidation of the carbon beads. Batch sorption experiments were conducted to assess their selective sorption toward Bi³⁺ over La³⁺ (as a surrogate of Ac³⁺) by varying the concentrations of HNO₃ and NaNO₃. It was found that the selective sorption of Bi³⁺ onto spherical surface-modified carbon beads could be achieved by adjusting the concentrations of HNO₃ and NaNO₃. Furthermore, the sorption capacity of Bi³⁺ decreased as the concentration of HCl increased due to the formation of bichloride complexes and the H⁺ competition. This implies that Bi³⁺ can be effectively eluted from the spherical surface-modified carbon beads when using HCl as the eluate. Consequently, spherical surface-modified carbon beads show potential as alternative adsorbents for inverse ²²⁵Ac/²¹³Bi generators.