Thermal Desorption of Molybdenum (VI)-Oxide from Loaded Metal Oxide Ion Exchangers

Abstract

A new procedure for the final purification of "Mo, generated for medical use by the reaction J3S U(nth,f)"Mo, has been developed. It consists in the sorption of molybdate species on metal oxide ion exchangers from nitric acid medium followed by a thermal desorption of the volatile molybdenum (Vl)-oxide from the adsorber matrix by applying temperatures up to 1250°C. This method could efficiently substitute the existing final purification of "Mo, which is currently performed by sublimation of Mo03 from the residue of an evaporated "Mo-concentrate -a labour intensive and time consuming operation. The investigations presented in this paper describe the thermal desorption of molybdenum(VI)-oxide species from Mo-loaded A1¡03 and SnO¡ ion exchangers. The influence of temperature, sublimation time, Moloading, carrier gas atmosphere and grain size of the oxide particles on the sublimation yields has been determined.The assumption that water vapour present in the carrier gas applied during the volatilization would lead to a drastic increase in the sublimation yields was confirmed for both oxides. The release of molybdenum (Vl)-oxide from the porous A1203 exchanger was found to be in good agreement with the bulk diffusion mechanism based on FlCK's law. Sn02 exchanger demonstrated a distinct superiority for practical applications. Heated up to 1250°C in presence of an 02 /H20-carrier gas, this less porous oxide permits quantitative Mo-yields within 30 minutes. Sublimation experiments with other fission products retained on the SnOj exchanger resulted in the following decontamination factors: 1.5 for Te, 40 for Ru and > 100 for Sn and Zr.

Production Techniques of Fission Molybdenum-99

“…These aspects initiated a research program to simplify this process. The basic idea was to find a suitable metal oxide which is able to adsorb the molybdenum quantitatively from aqueous solutions and which permits a thermal desorption of the molybdenum-(IV)-oxide by applying high temperatures [14].…”