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dc.contributor.advisorPurcell, W.
dc.contributor.advisorNel, J. T.
dc.contributor.authorNete, Motlalepula
dc.date.accessioned2015-09-16T10:09:21Z
dc.date.available2015-09-16T10:09:21Z
dc.date.copyright2013-05
dc.date.issued2013-05
dc.date.submitted2013-05
dc.identifier.urihttp://hdl.handle.net/11660/1228
dc.description.abstractEnglish: The aim of this project was to investigate the possible dissolution, separation and purification of tantalum and niobium in synthetic ((Ta/Nb)F5 and (Ta/Nb)2O5) and natural (tantalite minerals) compounds using eco-friendly reagents which are easy to handle as well as having benefits such as economical and scalable properties. The possible separation of Ta or Nb was investigated using the pentafluoride compounds due to their solubility in a wide variety of solvents and their possible formation from the NH4F•HF flux fusion. Selective precipitation of the two metals was initially investigated with different chelating or precipitating agents and good separations were obtained using p-phenylenediamine as reagent. The experimental parameters which were investigated include the influence of concentration and the pH effects on metal recovery. Niobium recoveries in excess of 80% with only 4% tantalum were obtained in the precipitate with the separation factor of 100(9) using a 50% mixture of NbF5 and TaF5. The quantitative determination of Nb and Ta content in the supernatant solution using ICP-OES indicated that more than 95% of the initial tantalum complex remained in solution. The presence of the pentoxides in the tantalite minerals prompted the investigation into the separation of the metals in a synthetic mixture. It involved the dissolution and subsequent separation of Nb and Ta using a variety of fluxing agents and solvent extraction, selective precipitation and ion exchange techniques. The dissolution of a 50% of Nb2O5 and Ta2O5 was investigated with Na2HPO4/NaH2PO4•H2O mixture, KF, NaF and NH4F•HF as fluxes in a flux fusion digestion technique. NH4F•HF was found to be highly successful in the dissolution of the pentoxide mixture with recoveries of 100.4(9)% and 100(1)% for Nb and Ta respectively. In addition, only the NH4F•HF fusion dissolution was found to support the subsequent separation techniques. The application of the selective precipitation on the NH4F•HF digestion solutions indicated 23(5) and 73(3)% precipitation of Nb and Ta respectively. The separation of Nb and Ta using solvent extraction technique indicated that Ta is selectively extracted into the methyl isobutyl ketone (MIKB) with recoveries of 101(1)% and 0.6(5)% for Ta and Nb. The distribution ratio of tantalum (D(Ta)) was found to increase with an increase in H2SO4 concentration and was determined as 3.46 at [H2SO4] = 4.0 M. The separation on the strongly basic Amberlite IRA-900 and a weak basic Dowex Marathon anion exchange columns using HCl as an eluent indicate unfeasible separations with recoveries of 91.7 to 96.1% Nb and 52.4 to 73.4% Ta. The dissolution and separation methods that were successfully developed and evaluated using the synthetic (Ta/Nb)2O5 mixture were then evaluated on the two tantalite mineral samples. The NH4F•HF fusion dissolution was successfully applied on the tantalite ore samples and experimental conditions such as the fusion temperature and flux concentration effects were investigated to optimise the procedure. Excellent recoveries of 100.3(5) and 100.0(9)% were obtained for Nb and Ta in Sample A and 96.4(3) and 101.3(4)% for Nb and Ta in Sample C. The application of the selective precipitation, solvent extraction and ion exchange separations produced results similar to the separation of Nb and Ta in the pentoxide mixture. Different solvents were evaluated for the selective extraction of Ta and a pure tantalum compound was isolated using methyl isoamyl ketone (MIAK). The magnetic removal of some of the impurities and the H2SO4 leaching of the NORM’s preceded the dissolution of the rest of the minerals. TiO2 and Fe2O3 (57.4(9) and 65(2)%) were removed in the magnetic separation step and 60.77(1)% ThO2 and 62.4(1)% U3O8 were separated in the H2SO4 leaching method. Tantalum was selectively extracted into the MIAK after its dissolution using NH4F•HF with D(Ta) of 6.21 at 4.0 M H2SO4. Niobium was extracted from the mineral matrix using the weak Dowex Marathon wba anion exchanger using HCl as an eluent. Nb2O5 and Ta2O5 of 96% purity were obtained after precipitation with ammonia.en_ZA
dc.description.abstractAfrikaans: Die doel van hierdie ondersoek was om die moontlike vertering, skeiding en suiwering van tantaal en niobium in sintetiese ((Ta/Nb)F5, (Ta/Nb)2O5) en tantaliet minerale te ondersoek deur van omgewingsvriendelike reagense te gebruik wat addisioneel voordele soos goedkoper prosesse, opskaling asook makliker hantering insluit. Die moontlike skeiding van Ta of Nb is ondersoek deur gebruik te maak van die pentafluoriedverbindings as gevolg van hul oplosbaarheid in 'n wye verskeidenheid van oplosmiddels en die moontlike vorming van dié betrokke verbindings met ʼn NH4F•HF soutsmeting. Selektiewe neerslag van die twee metale is aanvanklik met verskillende kelaatvormende of presipiterende agente ondersoek. Goeie skeidings is met fenileendiamien as reagens verkry. Die eksperimentele parameters wat ondersoek is, sluit onder andere die invloed van konsentrasie en pH op element herwinning in. Niobium herwinning van meer as 80% is verkry en met slegs 4% tantaal in die presipitaat teenwoordig. ʼn Skeidingsfaktor van 100(9) vir die 1:1 mengsel van NbF5 en TaF5 is bereken. Die kwantitatiewe bepaling van Nb en Ta-inhoud in die filtraat met behulp van IGP-OES het aangedui dat meer as 95% van die aanvanklike tantaalkompleks in oplossing bly. Die teenwoordigheid van die pentoksied in die tantaliet minerale het aanleiding gegee tot die ondersoek na die skeiding van die metale in 'n sintetiese mengsel. Dit het die ontbinding en daaropvolgende skeiding van Nb en Ta met behulp van verskillende smeltmiddels en ekstraktiewe oplosmiddels, selektiewe neerslag en ioonuitruiling tegnieke behels. Die soutsmeltingsvertering van 'n 1:1 Nb2O5 en Ta2O5 mengsel is gevolglik met ʼn Na2HPO4/NaH2PO4•H2O mengsel, KF, NaF en NH4F•HF ondersoek. NH4F•HF is hoogs suksesvol bevind in die ontbinding van die pentoksied mengsel met herwinning van 100.4(9)% en 100(1)% vir Nb en Ta onderskeidelik. Daarbenewens het slegs die NH4F•HF soutsmelting die daaropvolgende skeidingstegnieke ondersteun. Die toepassing van die selektiewe neerslagvorming op die NH4F•HF verteringsoplossings 247 het 23(5) en 73(3)% neerslagvorming van Nb en Ta onderskeidelik aangedui. Die skeiding van Nb en Ta met behulp van oplosmiddel-ekstraksie tegnieke het aangedui dat Ta selektief in metiel-isobutielketoon (MIKB) geïsoleer kan word, met herwinnings van 101(1)% en 0.6(5)% vir Ta en Nb onderskeidelik. Resultate het getoon dat die verspreidingsverhouding van tantaal (D(Ta)) direk afhanklik van H2SO4 konsentrasie is en is as 3.46 by [H2SO4] = 4 M bepaal. Die skeiding van die twee metale met behulp van die sterk basiese Amberlite IRA-900 en swak basiese Dowex Marathon anioonuitruilkolomme en met HCl as 'n elueermiddel, was oneffektief met die gesamentlik herwinning van 91.7 tot 96.1% Nb en 52.4 tot 73.4% Ta. Die ontbindings en skeidings metodes wat suksesvol op die sintetiese (Ta/Nb)2O5 mengsel ontwikkel en geëvalueer is, is vervolgens op twee tantaliet bevattende minerale geëvalueer. Die NH4F•HF soutsmeltingsvertering is suksesvol op die tantaliet erts monsters toegepas en eksperimentele kondisies soos die smelt-temperatuur en soutkonsentrasie-effekte is ondersoek om sodoende die prosedure te optimaliseer. Uitstekende herwinning van 100.3(5) en 100.0(9)% vir Nb en Ta is in een monster verkry en 96.4(3) en 101.3(4)% vir Nb en Ta in 'n ander monster is verkry. Die toepassing van die selektiewe presipitasie, oplosmiddel-ekstraksie, en ioonuitruiling het resultate soortgelyk van die skeiding van Nb en Ta in die sintetiese pentoksiedmengsel verkry. Verskillende oplosmiddels is vir die selektiewe ekstraksie van Ta geëvalueer en 'n suiwer tantaalverbinding is met metiel-iso-amielketoon (MIAK) geïsoleer. Die magnetiese verwydering van sommige van die onsuiwerhede en die H2SO4 loging van die radio-aktiewe element het die totale vertering van die res van die mineraalmonsters voorafgegaan. TiO2 en Fe2O3 (57.4(9) en 65(2)%) is in die magnetiese skeidingstap verwyder terwyl 60.77(1)% ThO2 en 62.4(1)% U3O8 in die H2SO4 uitloging metode geskei is. Tantaal is selektief, ná die vertering met die gebruik van NH4F•HF, met behulp van MIAK geëkstraheer en die ekstraksie-verhouding (D(Ta)) is as 6.21 in 4.0 M H2SO4 bepaal. Niobium is daarna met hulp van die swak Dowex Marathon ioonuitruiler en HCl as 'n elueermiddel as produk geïsoleer. Nb2O5 en Ta2O5 met 96% suiwerheid is na neerslagvorming met ammoniak verkry.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectNiobiumen_ZA
dc.subjectTantalumen_ZA
dc.subjectTantalite samplesen_ZA
dc.subjectQuantitative analysisen_ZA
dc.subjectBeneficiationen_ZA
dc.subjectDissolutionen_ZA
dc.subjectSeparationen_ZA
dc.subjectPurificationen_ZA
dc.subjectRecoveryen_ZA
dc.subjectQualitative analysisen_ZA
dc.subjectNiobium compounds -- Synthesisen_ZA
dc.subjectNiobium compounds -- Analysisen_ZA
dc.subjectThesis (Ph.D. (Chemistry))--University of the Free State, 2013en_ZA
dc.subjectQualitative analysisen_ZA
dc.titleSeparation and purification of niobium and tantalum from synthetic and natural compoundsen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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