α-Zirconium(IV) Phosphate: Static Study of 225Ac Sorption in an Acidic Environment and Its Kinetic Sorption Study Using natEu as a Model System for 225Ac

Zirconium phosphate (ZrP), especially its alpha allotropic modification, appears to be a very promising sorbent material for the sorption and separation of various radionuclides due to its properties such as an extremely high ion exchange capacity and good radiation stability. Actinium-225 and its daughter nuclide Bi-213 are alpha emitting radioisotopes of high interest for application in targeted alpha therapy of cancer. Thus, the main aim of this paper is to study the sorption of Ac-225 on the alpha-ZrP surface and its kinetics, while the kinetics of the sorption is studied using natEu as a non-radioactive homologue of Ac-225. The sorption properties of ff-ZrP were tested in an acidic environment (hydrochloric and nitric acid) using batch sorption experiments and characterized using equilibrium weight distribution coefficients Dw (mL/g). The modeling of the experimental data shows that the kinetics of Ac-225 sorption on the surface of ff-ZrP can be described using a film diffusion model (FD). The equilibrium weight distribution coefficient Dw for Ac-225 in both hydrochloric and nitric acid reached the highest values in the concentration range 5.0-7.5 mM (14,303 +/- 153 and 65,272 +/- 612 mL/g, respectively). Considering the results obtained in radioactive static sorption experiments with Ac-225 and in non-radioactive kinetic experiments with natEu, ff-ZrP seems to be a very promising material for further construction of a Ac-225/Bi-213 generator.