J.T. Nel

Primary beneficiation of tantalite using magnetic separation and acid leaching

Primary beneficiation was successfully performed prior to dissolution of manganotantalite (sample A) and ferrotantalite (sample C) samples obtained from two different mines in the Naquissupa area, Mozambique. Magnetic separation removed the majority of iron and titanium, whereas H2SO4 leaching removed a large portion of thorium and uranium in these samples. Analytical results indicated that 64.14wt% and 72.04wt% of the total Fe and Ti, respectively, and ∼2wt% each of Nb2O5 and Ta2O5 were removed from sample C (ferrotantalite) using the magnetic separation method, whereas only 9.64wt% and 8.66wt% of total Fe2O3 and TiO2, respectively, and ∼2wt% each of Nb2O5 and Ta2O5 were removed from sample A (manganotantalite). A temperature of 50°C and a leaching time of 3 h in the presence of concentrated H2SO4 were observed to be the most appropriate leaching conditions for removal of radioactive elements from the tantalite ores. The results obtained for sample A under these conditions indicated that 64.14wt% U3O8 and 60.77wt% ThO2 were leached into the acidic solution, along with 4.45wt% and 0.99wt% of Nb2O5 and Ta2O5, respectively.

Analysis of Non-Conducting Tantalite Minerals by Glow Discharge Optical Emission Spectrometry

Capabilities of the radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) for analysis of Ta2O5/Nb2O5 and tantalum and niobium in electrically non-conducting geological samples were investigated. The metal pentoxides (Ta2O5 and Nb2O5) and the tantalite mineral powders were mixed with a thermally conductive copper powder in ratios of up to 1:10 sample:copper and pressed into a disc sample for glow discharge sputtering. Studies were carried out to determine and optimize all the parameters affecting the analyses by the RF-GD-OES technique. This included the determination of the ability of the methodology to generate usable analytical curves for the target elements. Good calibration curves which were used for analyses of Ta and Nb in the tantalite minerals were obtained at optimized experimental conditions. Respective tantalum and niobium recoveries were in the order of 99.78–104.91% and 98.34–102.03% from the mineral analyses.

The beneficiation of CaF 2 to produce fluorocarbons and hf by means of hightemperature plasma processes

Fluorspar (CaF2) is the most important source for the manufacturing of F-compounds, e.g. HF and F2, and derived products like fluorocarbons. South Africa has the second largest reserve base of fluorspar in the world, and is the third largest global supplier. However, it exports the bulk of its fluorspar unbeneficiated and only about 5 % is beneficiated locally, mainly at Necsa for the production of HF, via the conventional sulphuric acid digestion process. Hightemperature plasma processes offer a unique method to access the F-values contained in CaF2.

A thermal non-transfer arc V-type torch plasma

Conventional linear DC plasma torches are known to have a relative long tail flame wherein a high temperature chemical reaction can be performed or where the plasma can act as a heat transfer medium. Introducing solid particles into these plasma torches generally destabilizes the plasma and may cause extensive erosion on the anode, thus shortening the torch operational time significantly. In this torch the solid particles are exposed to the arc temperature and not only the tail flame temperature. This torch enables one to introduce solid particles in very close proximity of the plasma arc and if the particle velocity is optimized, the particles may even penetrate the arc. This paper presents the design and typical operating parameters of a V-type plasma system, and discuses the advantages and disadvantages of such a system.