THE RESEARCH WOULD GIVE A COST-EFFECTIVE TECHNIQUE FOR THE EXPLOITATION OF NATIVE DEPOSITS OF TANTALUM AND NIOBIUM OXIDES, TWO ELEMENTS WHICH HAVE A REMARKABLE IMPORTANCE IN PRESENT AND FUTURE HIGH TECHNOLOGY.
THESE ELEMENTS, IN FACT, ARE CLASSIFIED AS STRATEGIC AND CRITICAL MATERIALS, THAT IS DEFENSE RELATED, BECAUSE OF THEIR USE IN AERONAUTICS, ELECTRONICS, NUCLEAR ENERGY PRODUCTION AND TRANSPORTATION.
Physicochemical characterisation of ores, concentrates and tailings has been carried out for Echassieres, Penouta and Golpejas deposits in 2 European tin belts. Trials have been conducted to improve processing methods for ores and tailings, on pilot plant and laboratory scales, using physical and flotation techniques.
Experiments with a new reactor, with refrigerated walls for the condensation of volatile products, have shown concentration of tantalum and niobium in the residues. The mixtures of Penouta tantalocolumbite and carbon have been agglomerated with a chlorinated binding material. The use of these agglomerates in the new reactor leads to the formation of a residue containing almost pure compounds of the ditantalum (or diniobium) pentoxide type and chlorides of other elements in the condensates.
The research has been carried out into the use of advanced technology in the areas of high intensity magnetic separation, plasma processes, thermodynamic databanks, advanced hydrometallurgy processes and pyrometallurgy processes in order to explore a possible new process for mineral processing and the extraction of tantalum oxide (Ta2O5) and niobium oxide (Nb2O5). The research focused on kaolinized granite and altered pegmatite.
In Echassieres the main tantalum and niobium bearing minerals are microlite and tantalocolumbite. Concentrates of Golpejas and Penouta contain columbo tantalite. Up to 15% of the total tantalum and niobium content of these concentrates are present in the cassiterite as microinclusions and can not be recovered by the mineral processing. These elements are concentrated in the tin slag during the metallurgical processing of cassiterite.
The average tantalum and niobium oxides content of the Penouta tailing is about 3 times that of the original ore.
Using the classical magnetic separation, almost 100% of the columbo tantalite was recoverd.
Heat treatment after the classical magnetic, electrostatic and gravity separation increased the concentrate microlite content from 30% to greater or equal to 65%.
Chlorination of Golpejas and Penouta columbo tantalite permits the selective concentration of the major part of the tantalum compounds in the residue but chlorination of the Echassieres tantalo columbite was total and not selectivite.
Carbochlorination of Echassieres tantalo columbite between 600 and 900 C was selective while that of Golpejas and Penouta columbo tantalite was not.
For temperatures less than 700 C, selective chlorination of microlite was possible and high temperature carburation of columbo tantalite led to the formation of tantalum and niobium carbides. Treatment in the plasma furnace gave similar results.
THIS RESEARCH IS AIMED AT THE USE OF ADVANCED TECHNOLOGY IN THE AREAS OF HIGH INTENSITY MAGNETIC SEPARATION, PLASMA TECHNOLOGY, ADVANCED HYDROMETALLURGY AND PYROMETALLURGY PROCESS, IN ORDER TO EXPLORE A POSSIBLE NEW PROCESS FOR THE MINERAL PROCESSING AND THE EXTRACTION OF TA2O5 AND NB2O5. THIS RESEARCH WILL BE FOCUSED ON THE KORLINIZED GRANITE (ECHASSIERE, FRANCE AND THE JEGNATITIC GRANITE (GOLPEJAS AND PENOUNTE, SPAIN) AND THEIR BY-PRODUCTS.
THE RESEARCH WORK IS DIVIDED IN THE FOLLOWING STEPS:
-HIGH INTENSITY MAGNETIC SEPARATION, ELECTROSTATIC SEPARATION, GRAVITY SEPARATION
-HIGH TEMPERATURE TREATMENT USING PLASMA
-SYSTEMATIC STUDIES BY HYDROMETALLURGICAL AND PYROMETALLURGICAL TREATMENT.