Benefication,Decompostion and Separation of Niobium and tantalum From Ethiopian Kenicha Pegmatite Ore

Abstract

The aim of this dissertation was to examine various beneficiation, leachingand extraction approaches for tantalum and niobium from the Ethiopian Kenticha pegmatite ore. The Kenticha rare-earth element pegmatite, an internationally imperative tantalite spring in the Neoproterozoic rocks of the Adola greenstone belt, of Southern Ethiopia, is normally called a Kenticha pegmatite field. Three zones have been identified for the Kenticha pegmatite in previous studies: the granitic, the Spodumene-free, and Spodumene-bearing zones. The beneficiation methods for Ethiopian Kenticha pegmatite-Spodumene ores have been assessed through mineralogical and quantitative analyses with X-ray Diffraction (XRD) and Energy Dispersive X-ray Fluorescence (EDXRF). The upper zone deposit of Kenticha pegmatite-Spodumene deposit contains up to 58.7 weight%, more tantalite than the inner zone. XRD analysis revealed that the upper zone is dominated by manganocolumbite (tantalite) while the inner zone is predominantly tantalite-Mn. Repeated cleaning and beneficiation of the upper zone ore resulted in concentrate compositions of 57.34 weight% of Ta2O5, and 5.41 weight% of Nb2O5. Washing the tantalite concentrates using 1 volume% KOH, and 1 M H2SO4 leads to the complete removal of thorium and radioactive uranium oxides from the concentrate at a time. The findings of this study suggest that the beneficiation and alkaline washing of Kenticha pegmatite-Spodumene ore produces a high-grade export quality tantalite concentrate with negligible radioactive oxides. Afterwards, acid and alkaline leaching agents were used to decompose Kenticha tantalite ore. The decompositions of tantalite ore were carried out using HF-to-H2SO4 and KOH. The different factors that would affect the decomposition product and residue, such as fusion time, ratio of concentration, particle size of the ore and mass of KOH towards the retained mass of the residues in the fusion and digestion media were investigated. The residues were analyzed by EDXRF, FT-IR, and XRD. The EDXRF analysis showed that the percent composition of Nb2O5 was less than Ta2O5 in both the residues obtained using 6 N HF: 2 N H2SO4 and 10 g KOH as decomposition agents. 14.20 weight% Ta2O5 was obtained in the residue using alkaline fusion has, followed by water leaching, while only 0.23weight% Ta2O5 was obtained using the acidic decomposition step. The XRD diffraction patterns indicated that the residue from the primary chemical fusion method shown similarity with crystalline patterns of KTaO3. No KNbO3 phase was observed in the residues obtained using both decomposition approaches. Finally, the dissolution of Kenticha tantalite ore in KOH fusion and the hydro leaching systemwas studied at 400 0C for one hour reaction time. From the dissolved solution, niobium and tantalum were extracted from the neutralized alkaline dissolved and hydrolyzed solution with a new greener process, i.e., EMIC/AlCl3 media, as the ionic liquid extractant. The new process, using selective stripping, precipitation and calculations resulted in a highly crystalline 99.84 weight% pure Nb2O5 and amorphous 90.81 weight% Ta2O5. The compositions of the dissolved metal ions and solids were analyzed by ICP-OES, EDXRF, XRD, and FT-IR.