Gallium and germanium static and kinetic sorption and desorption studies on cerium dioxide nanoparticles

Abstract Positron-emitting 68 Ga has become an integral part of nuclear medicine. It is a radionuclide obtained from 68 Ge/ 68 Ga radionuclide generators. Apart from other qualities, it is a feature that have caused its growing popularity in medical practice. Nevertheless, the increasing demand for 68 Ga supply results in the need of new and improved separation systems to obtain it. Hydrous oxides such as titanium or zirconium dioxide are usually the preferred separation materials, but other oxidic materials are under study. Thorough testing of the sorption behaviour is often overlooked in these studies, though it is indispensable for the applicability and suitability assessment. This work is focused on the sorption behaviour description of cerium dioxide prepared by calcination of ceric nitrate. Both batch and kinetic sorption experiments were conducted. Such a thorough study has never been carried out for this material. In batch experiments, the optimal conditions for separation of 68 Ga and 68 Ge were found. Kinetic experimental data were used for mathematical modelling. Six kinetic models derived from various rate-controlling processes were used and their applicability was demonstrated. The diffusion in an inert layer is the rate-controlling process of both gallium and germanium sorption and desorption. This model description of sorption kinetics will further enable us to optimise the sorption and desorption processes numerically. Thus far, it was found out that the prepared cerium dioxide can quantitatively adsorb germanium in very short time of 10 min from 1mM hydrochloric acid and the most convenient medium for 68 Ge and 68 Ga separation is 0.1 M hydrochloric acid.