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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) 2 O 5 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 H 3 PO 4 . It was found that Ta was more strongly absorbed but by using a stronger acid concentration of 10 M H 3 PO 4 , 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 H 3 PO 4 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. [ABSTRACT FROM AUTHOR]

A step-wise separation process for niobium and tantalum from tantalite by extraction and ion exchange was developed. A tantalite mineral was dissolved by a fusion technique using ammonium bifluoride as flux. Tantalum and niobium form stable anionic fluoride complexes in fluoride solutions. This fact was used to develop an analytical method to separate tantalum and niobium from other metals within the tantalite mineral and from each other. Tantalum was separated from the rest of the mineral matrix by solvent extraction using methyl isoamyl ketone. The analytical results indicated that 98.9(9)% Ta 2 O 5 was recovered from the organic portion while 101.6(3)% Nb 2 O 5 and the rest of the elements were recovered from the aqueous solution. Niobium was subsequently separated from the tantalite matrix by anion exchange technique using Dowex Marathon resin and HCl solution as a mobile solvent. The analytical results indicated Nb 2 O 5 recovery of 101(2)%. [ABSTRACT FROM AUTHOR]

Abstract: Tantalite ore from Mozambique was digested using molten ammonium bifluoride (NH4HF2) as an alternative to hydrofluoric acid. Niobium and tantalum were extracted from the water-leached filtrate using 1- and 2-octanol as extractants. The main process variables are time, temperature and the bifluoride-to-ore mass ratio, for the bifluoride treatment step, along with the sulphuric acid concentration of the aqueous filtrate, and the solvent-extraction contact time. The optimum parameters obtained for the bifluoride treatment were a reaction time of 3h, a reaction temperature of 250°C, and a tantalite-to-bifluoride mass ratio of 1:30. Under these conditions, up to 97.24% of Nb and 98.66% of Ta were recovered. Introduction of sulphuric acid (H2SO4) into the aqueous phase increases the extraction of Nb and Ta with octanol. It is shown that a 5M to 6M sulphuric acid concentration results in good extraction of tantalum. An acid concentration higher than 5M must be used for efficient extraction of niobium. A contact time of 10min between the feed solution and the solvent is required. McCabe–Thiele equilibrium diagrams constructed from the experimental data suggest that two and three extraction stages are sufficient for almost complete extraction of Ta and Nb respectively, at optimum extraction conditions. [Copyright &y& Elsevier]

Abstract: Tantalite–columbite with a combined Ta–Nb content of 33% was leached using 20M hydrofluoric acid. The acidity of the leach was adjusted with sulphuric acid and the tantalum–niobium content was extracted using methyl isobutyl ketone (MIBK) and trioctyl phosphine oxide (TOPO), with kerosene and xylene as diluents. Stripping and precipitation of the extracted species was performed using 30% V/V ammonia solution. Both tantalum and niobium were extracted to different extents, with greater degree of extraction observed for tantalum. The extraction of tantalum was found to be dependent on the concentration of sulphuric acid added. For systems involving TOPO as extractant, kerosene proved to be a better diluent than xylene. Synergism was observed with respect to tantalum extraction when 20g/l solution of TOPO in MIBK was used as the extractant. The number of extraction stages can be greatly reduced using a TOPO — MIBK blend in place of MIBK or TOPO only. [Copyright &y& Elsevier]