An investigation on the dissolution of synthetic brannerite (UTi2O6)

A number of different uranium minerals are processed in different regions of the world to produce the uranium that is used to generate electricity. The three main types of uranium minerals that are found at the worldʹs largest single uranium bearing ore body at Roxbury Downs, South Australia are uraninite (nominally UO2), coffinite [U(SiO4)1 − x(OH)4x], and brannerite [U(Ti, Fe)2O6]. Detailed knowledge of the influence of temperature, [H2SO4] and [Fe]/solution oxidation–reduction potential (ORP) on the dissolution of uraninite are well known, yet little information on the influence of the aforementioned on the dissolution of brannerite has been reported in the literature. In this study the influence of three key parameters on the rate of synthetic brannerite (UTi2O6) dissolution was investigated. The parameters that were investigated included temperature, [H2SO4] and [Fe(III)]. Of these parameters [H2SO4] and temperature were found to have the most significant effect on the rate/overall extent of UTi2O6 dissolution under the test conditions used. Tests conducted on synthetic brannerite residues combined with fresh synthetic brannerite showed that decreases in dissolution rates observed during the dissolution of synthetic brannerite were predominantly not due to decreasing brannerite slurry concentration. The significant decreases in dissolution observed were most likely due to one or more of the following: changes in surface composition/surface passivation, changes in surface morphology and/or changes in particle size.