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dc.contributor.advisorPurcell, W.
dc.contributor.advisorSnyders, E.
dc.contributor.authorNete, Motlalepula
dc.date.accessioned2018-07-31T09:02:52Z
dc.date.available2018-07-31T09:02:52Z
dc.date.issued2009-05
dc.identifier.urihttp://hdl.handle.net/11660/9048
dc.description.abstractEnglish: Qualitative and quantitative analyses of solid samples using a wet analytical technique, such as ICP-OES, are entirely dependent on the complete dissolution of the samples. Since 1866 niobium and tantalum samples have been successfully dissolved by hydrofluoric acid digestion. However, this method is not preferred in industry due to the dangerous nature of hydrofluoric acid as dissolution reagent. This study was aimed at finding alternative, economically viable and ecologically-friendly conversion methods for the dissolution of Nb metal, Nb2O5, NbF5 and three niobium containing minerals demarcated as Tantalite A, Tantalite B and Sample 1. Acid digestion of Nb and Nb2O5 on a hot plate was investigated with HNO3, HCl, H2SO4, H3PO4 and aqua regia. Both Nb and Nb2O5 dissolved to a greater extent in H2SO4 and H3PO4 (0.94% and 0.36% respectively) than in the other acids but the results were very inaccurate in all the acids. Good recoveries were obtained for NbF5 with recoveries of 95% and 93% from the dissolution of this sample in sulphuric acid and water respectively. Microwave-assisted acid digestion was also investigated with the same acids and high accuracy was obtained with recoveries of 99+% for Nb and Nb2O5 and 100% for NbF5 with H2SO4 digestion. Microwave-assisted digestion of the mineral samples produced 90+% Nb recoveries at digestion periods longer than that for the pure Nb samples. The calibration curves for all the elements showed good linearity as well as high precision (R2 ≥ 0.999) with low y-intercept values which indicated proper background corrections. Flux fusion digestion was investigated with different flux reagents for the dissolution of pure Nb2O5 and the mineral samples. Lithium tetraborate flux produced excellent results for niobium with recoveries of 98.56 to 109.59% Nb2O5 and other major and minor elements. The melt was dissolved in the mixture of H2SO4 and methanol to remove the excess of boron as the B(OMe)3 ester which otherwise resulted in the formation of an insoluble boric acid which coprecipitated with some of the analytes of interest. This dissolution method produced accurate results for pure Nb2O5 (102.76% Nb recovery) and for most of the analytes which were identified through the qualitative analysis in the mineral samples (98.56 to 109.59% Nb2O5, 100.58 to 108.57% Ta2O5, 101.03 to 103.29% TiO2 and 99.23 to 100.55% Fe2O3. Other analytes such as SiO2, ThO2 and WO3 showed lower accuracy with recoveries in the range 61.38 to 85.68%. Good linearity and precision was observed in the standard addition calibration curves for all the elements studied, which illustrates the reliability of the results. Semi-quantitative analyses of the solid mineral samples were done by means of XRF. The XRF results were in good agreement with the results obtained by fusion with Li2B4O7 and ICP-OES analysis. Finally, the mineral samples were qualitatively analysed by X-ray diffraction spectroscopy, Scintillometer, Microscope and a hand magnet to get positive identity of the test samples, mainly the sample demarcated as Sample 1. The XRD patterns for Tantalites A and B were identical and these minerals were radioactive but showed very little magnetic properties. Grains of euxenite, garnet, microlite, tourmaline, quartz, muscovite and manganotantalite were microscopically identified in both Tantalites A and B. From these tests, Tantalites A and B were identified as variations of manganotantalite with small amounts of microlite, euxenite, garnet, tourmaline and accessory of quartz and muscovite impurities. The XRD pattern of Sample 1 showed the presence of manganotantalite, garnet, quartz and muscovite. These minerals were also identified under the microscope. Different from the Tantalite minerals, Sample 1 showed no radioactivity but intense magnetic properties. Sample 1 was identified as a mixture of manganotantalite and garnet with quartz and muscovite impurities.en_ZA
dc.description.abstractAfrikaans: 'n Nat analitiese tegniek soos IGP-OES wat vir die kwantitatiewe en kwalitatiewe analises van vastestof monsters gebruik word, is afhanklik van die algehele oplossing van hierdie monsters. Sedert 1866 is niobium en tantaal monsters suksesvol deur waterstoffluoriedsuur-vertering, opgelos. Aangesien waterstoffluoriedsuur as oplossingmiddel gevaarlik en moeilik hanteerbaar is, word hierdie metode minder geredelik deur maatskappye en navorsers aangewend. Die doel van hierdie studie was om alternatiewe, ekonomies uitvoerbare en omgewingsvriendelike metodes vir die oplossing van niobiummetaal (Nb), niobium(v)oksied (Nb2O5), niobium(v)fluoried (NbF5) sowel as drie niobium bevattende minerale naamlik, "Tantaliet Naquissupa A", "Tantaliet Naquissupa B" en "Monster 1", te vind. Vertering van Nb-metaal en Nb2O5 op warmplaat-verhitting is met die volgende sure ondersoek: HNO3, HCl, H2SO4, H3PO4 en koningswater. Resultate het getoon dat beide Nb-metaal en Nb2O5 beter in H2SO4 en H3PO4 (0.94% en 0.36% onderskeidelik) as in die ander sure oplos, maar die resultate vir al die sure was baie onakkuraat. Goeie herwinnings met hierdie verteringsmetode is vir NbF5 verkry met opbrengste van 95% en 93% in swawelsuur en water onderskeidelik. Mikrogolf-geassisteerde suurverterings was ook met dieselfde sure ondersoek en hoë akkuraatheid met opbrengste van 99+% vir Nb-metaal en Nb2O5 en 100+% vir NbF5 is met H2SO4 vertering verkry. Mikrogolfgeassisteerde vertering van die mineraalmonsters het Nb opbrengste van 90+% vir langer verteringsperiodes gelewer. Die kalibrasie krommes van al die elemente wat ondersoek is, het goeie lineariteit (R2 ≥ 0.999), hoë mate van presisie (% herwinning) en klein y-afsnitte gehad wat op betroubare analitiese resultate dui. Vloeimiddelsmelting is met verskillende smeltmiddels vir die oplossing van suiwer Nb2O5 en ander mineraalmonsters ondersoek. Litiumtertraboraat as smeltmiddel het uitstekende opbrengste vir Nb (98.56 tot 109.59%) sowel as die ander hoofen newe elemente wat ondersoek is, gelewer. Die oormaat boor is met die byvoeging van metanol uit die smeltoplossing as die B(OMe)3 ester verwyder. Hierdie oplossingsmetode het akkurate resultate vir suiwer Nb2O5 (102.76% Nb herwinning) asook die meeste ander analiete in die ertsmonsters, gelewer, byvoorbeeld 98.56 tot 109.59% Nb2O5, 100.58 tot 108.57% Ta2O5,101.03 tot 103.29% TiO2 en 99.23 tot 100.55% Fe2O3. Ander onsuiwerhede soos SiO2, ThO2 en WO3 het laer vlakke van akkuraatheid getoon, met herwinningsvlakke in die omgewing van 61.38 tot 85.68%. Die betroubaarheid van die resultate wat met behulp van die standaard-addisie metode uitgevoer is, is deur kwaliteit eksperimentele data soos lineariteit en hoë herwinningsvlakke gekenmerk. Semi-kwantitatiewe analises vir die erts monsters is met behulp van XRF uitgevoer. Daar was goeie ooreenstemming tussen die XRF en ICP-OES (Li2B4O7 smelting) resultate. Die samestelling van die ertsmonsters was ook kwalitatief deur X-straal diffraksie spektroskopie en mikroskoop identifikasie gekarakteriseer. Die XRD spektra vir die Tantaliet A en B ertse is identies, beide toon onder andere radio-aktiewe eienskappe maar toon baie min magnetiese eienskappe. Brokstukke van euxeniet, graniet, mikroliet, toermalyn, kwarts, muskowiet en manganotantaliet is mikroskopies in beide Tantaliet A en B identifiseer. Vanaf hierdie toetse is Tantaliet A en B as variasies van manganotantaliet met klein hoeveelhede van mikroliet, euxeniet, granaat, toermalyn en bykomende kwarts en muskowiet onsuiwerhede gekarakteriseer. Die XRD spektrum van Monster 1 het ook die teenwoordigheid van manganotantaliet, granaat, kwarts en muskowiet getoon terwyl hierdie minerale ook onder 'n mikroskoop positief waargeneem is. Monster 1 het dan ook geen radioaktiewe eienskappe getoon nie maar wel intense magnetiese eienskappe. Monster 1 is dan ook met behulp van die mikroskoop as 'n mengsel van manganotantaliet, graniet met kwarts en muksowiet as onsuiwerhede identifiseer.en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectNiobiumen_ZA
dc.subjectTantaliteen_ZA
dc.subjectImpuritiesen_ZA
dc.subjectMicrowaveen_ZA
dc.subjectFusionen_ZA
dc.subjectDissolutionen_ZA
dc.subjectQualitativeen_ZA
dc.subjectQuantitativeen_ZA
dc.subjectAnalysisen_ZA
dc.subjectRecoveryen_ZA
dc.subjectNobium compounds -- Dissolutionen_ZA
dc.subjectTantalite -- Dissolutionen_ZA
dc.subjectSolution (Chemistry)en_ZA
dc.subjectDissertation (M.Sc. (Chemistry))--University of the Free State, 2009en_ZA
dc.titleDissolution and analytical characterization of Tantalite ore, niobium metal and other niobium compoundsen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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