Non-fluoride dissolution of tantalum and niobium oxides and their separation using ion exchange

- Phosphate dissolution of Ta and Nb compounds produced negatively charged species.
- Nb and Ta compounds were separated based on different adsorption properties.
- Complete elution of Nb was achieved with 8 M H3PO4 followed by Ta with 10 M H3PO4.
- Weak basic anion exchangers proofed more successful in the separation of Ta and Nb.

The study involved the separation of Ta and Nb in a phosphate matrix using ion exchange chromatography. Experimental variations included different types of Ta/Nb containing samples, types of resin, phosphoric acid concentration as eluent, flow rate and column dimensions. Experimental conditions were developed and refined using a pure 1:1 (Ta/Nb)2O5 synthetic mixture and the optimum conditions were then applied to a real tantalite mineral sample. Experimental results indicated the successful separation of the Ta and Nb in the synthetic sample using the weak basic Dowex Mathon and Dowex 66 free base resins. Almost complete recovery of Nb was achieved with 200 mL of 8 M H3PO4. It was found that Ta was more strongly absorbed but by using a stronger acid concentration of 10 M H3PO4, almost complete recovery was also obtained for Ta. Excellent elemental separation (α = 11.5) and recoveries were also obtained with tantalite mineral as sample under identical experimental conditions. Almost complete recoveries for both Nb and Ta were obtained after elution with 8.0 M and 10.0 M H3PO4 respectively. Apart from the complete separation of Ta and Nb, minor elements which are also present in tantalite like Fe, Mn and U could also be successfully separated and quantitatively recovered. However, the Nb fraction was contaminated with Ti because under these conditions these two elements are simultaneously eluted.The successful separation and recovery of both Ta and Nb from a phosphate matrix suggest a possible alternative to the conventional fluoride beneficiation methods. This method also has the potential of industrial applications.