Study on the sorption and desorption behavior of La and Bi by bis(2-ethylhexyl)phosphate modified activated carbon

The separation of 213 Bi from its parent radionuclide 225 Ac via radionuclide generators has proven to be a challenge due to the limited performance of the current sorbents. This study evaluated the separation performance of La 3+ (as a surrogate for 225 Ac) and Bi 3+ using bis(2-ethylhexyl)phosphate monofunctionalized activated carbon (HDEHP/AC). The potential applications of phosphate groups as active sites and the carbon structure as a sorbent support were confirmed and validated. Various factors, including pH values, salt concentration, halide ions, contact time, solid-to-liquid ratio, initial La 3+ /Bi 3+ concentration, and gamma irradiation were examined through batch sorption experiments in both single and binary systems. HDEHP/AC had a high sorption capacity for La 3+ via electrostatic attraction, with the sorption data fitting well to the pseudo-second-order kinetic equation and Langmuir model. The sorption performance of La 3+ on HDEHP/AC was minimally affected as the NaCl/NaI concentrations increased at pH = 2, whereas the sorption capacity for Bi 3+ decreased significantly. Additionally, selective desorption of La 3+ and Bi 3+ was achieved using HNO 3 and NaI solutions, respectively. These results backed up by a conceptual separation process point toward a potential use of these materials in a direct/inverse 225 Ac/ 213 Bi radionuclide generator. Further optimization of the material and separation process will be required to bring this class of promising materials into an actual generator for medical applications. The separation of 213 Bi from its parent radionuclide 225 Ac via radionuclide generators has proven to be a challenge due to the limited performance of the current sorbents.