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

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 (213)Bi 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 (225)Ac on the α-ZrP surface and its kinetics, while the kinetics of the sorption is studied using (nat)Eu as a non-radioactive homologue of (225)Ac. The sorption properties of α-ZrP were tested in an acidic environment (hydrochloric and nitric acid) using batch sorption experiments and characterized using equilibrium weight distribution coefficients D(w) (mL/g). The modeling of the experimental data shows that the kinetics of (225)Ac sorption on the surface of α-ZrP can be described using a film diffusion model (FD). The equilibrium weight distribution coefficient D(w) for (225)Ac 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 (225)Ac and in non-radioactive kinetic experiments with (nat)Eu, α-ZrP seems to be a very promising material for further construction of a (225)Ac/(213)Bi generator.