α-Zirconium(IV) Phosphate: Static Study of ²²⁵Ac Sorption in an Acidic Environment and Its Kinetic Sorption Study...

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 ²¹³Bi 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 ²²⁵Ac on the α-ZrP surface and its kinetics, while the kinetics of the sorption is studied using ^natEu as a non-radioactive homologue of ²²⁵Ac. 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 ²²⁵Ac sorption on the surface of α-ZrP can be described using a film diffusion model (FD). The equilibrium weight distribution coefficient D_w for ²²⁵Ac 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 ²²⁵Ac and in non-radioactive kinetic experiments with ^natEu, α-ZrP seems to be a very promising material for further construction of a ²²⁵Ac/²¹³Bi generator.