Difficult to separation
It is difficult to separate and extract single pure tombarthite elements from the mixed tombarthite by decomposing the tombarthite ore.One of the reason is that the physical properties and chemical properties of lanthanides is very similar; the other reason is the occurrence of impurity elements in tombarthite minerals, such as thorium, uranium and niobium, tantalum, titanium, zirconium, iron, calcium, silica, fluorine, phosphorus, lead, etc. Therefor the separation process of tombarthite elements is more complex.
Methods of tombarthite separation mainly include chemical separation process, ion exchange resin chromatography and solvent extraction. Chemical separation is divided into fractional step method and oxidation-reduction method.The fractional step method is the oldest and most classic method to separate the tombarthite elements. Fractional step method includes two steps: fractional precipitation, fractional crystallization,but now it has been replaced by extraction and ion exchange resin chromatography.Currently,Chinese have hundreds of production of single tombarthite products.A single tombarthite oxides can reach 95% ~ 99.99% and the purity of individual products can reach 99.999% (Y2O3).