Study of leaching of a 2M-Zirconolite (Ca0,83Ce0,17ZrTi1,66Al0.34O7) in acidic and basic media

Abstract

Zirconolite is a mineral intended for actinides elements confinement and is known for its good chemical durability. In this work, 2M-zirconolite, with the chemical formula: Ca0,83Ce0,17ZrTi1,66Al0.34O7 have been synthesized at 1400 o C by the metallurgical route at a laboratory scale. This stoechiometry corresponds to a CeO2 loading of 8.61 m.%. Ce is employed as an actinide surrogate. The effect of both pH and temperature on the chemical durability of this mineral has been studied. Phase identification and micrography observations have been done by X-ray diffraction, scanning electronic microscopy, and Fourrier transform infra-red spectroscopy. The end-product has a monophasic structure of 2M-zirconolite. Its density is about 4.013 g/cm3 , and its relative density is of 96 %TD. It has a microhardeness of 370 MPa. The Ce behavior in leaching media of extreme pH values: acidic medium (pH = 2) and basic medium (pH = 12), at 23 o C and 70 o C, shows that the Ce dissolution speeds are faster at 70 o C compared with those obtained at 23 o C. The 2M-zirconolite matrice presently studied appears to have a good chemical durability