Studies on the preparation of pure niobium oxide from pyrochlore concentrate

The applicability of acid leaching to the recovery of niobium oxide from pyrochlore concentrates has been investigated using hydrofluoric acid. Variables such as acid concentration, temperature, time of reaction, ratio of solid to acid, speed of agitation and particle size were correlated with recovery of niobium oxide. It is suggested that the process is diffusion-controlled. This is supported by the dependance of reaction rate on agitation speed and by the relatively low activation energy, δH=1,86kcal/mole. The optimum conditions for extracting niobium oxide from leach solution using either methylisobutyl ketone or n-tributylphosphoric acid were also studied. (orig.)