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dc.contributor.advisorPurcell, W.
dc.contributor.advisorNel, J. T.
dc.contributor.authorKoko, Fanie
dc.date.accessioned2018-05-28T09:45:57Z
dc.date.available2018-05-28T09:45:57Z
dc.date.issued2013-06
dc.identifier.urihttp://hdl.handle.net/11660/8349
dc.description.abstractEnglish: Tantalum and niobium occur in nature in the form of minerals such as tantalite and columbite. Recent advances in technology have increased the demand for these elements and their chemical compounds. Tantalum is extensively used in the electronics industry, especially in cell phones and laptops while niobium is used mainly in the production of super metal alloys for the use in the construction industry. The presence of U and Th in these Nb/Ta containing minerals (NORMs) however complicates the beneficiation process of the minerals immensely. Regulatory constraints on the quantity of material that can be handled at one time, processing equipment, transportation and waste disposal of these materials put more strain on the processing of these minerals. This strain adds a financial burden on the total beneficiation value chain when U and Th are present. The overall aim of this study was to investigate the selective removal of U and Th from these minerals prior to their complete dissolution in order to increase the safety of processing and/or transportation procedures. The methods included acid leaching (time and temperature variation), anion precipitation and ion exchange chromatography. The results obtained from these studies indicated varying degrees of success. The acid leaching study involved the use of sulphuric acid, phosphoric acid, hydrochloric acid, nitric acid, perchloric acid and aqua regia, of which the first three of these acids proved to be the most effective in the removal of the majority of U and Th from the mineral. Analytical results obtained for while using concentrated sulphuric acid as reagent indicated that an increased amount of radioactive material was removed from the mineral. The Th content removed from the mineral ore increased from 68.82% at 50°C to approximately 100% at 100°C after 3 hours of leaching in both cases. Additionally, the U content in the filtrate increased from 64.37% at 100°C to 81.27% at 150°C and finally to 90.08% at 200°C. Phosphoric acid was less effective in the removal of uranium and thorium at 50°C while an increase in temperature to 150 °C resulted in 85.10 and 98.77 % of U and Th respectively being removed after 3 hours. On the other hand, hydrochloric acid exhibited the same trend as sulphuric and phosphoric acid with an increasing amount of U and Th present in the filtrate as time and temperature were increased. At 90°C and 3 hours of leaching, hydrochloric acid succeeded in removing 51.53 and 91.09% of U and Th respectively. The main disadvantage of the use of these concentrated acids as leaching reagents at elevated temperatures and extended times, is the simultaneous removal of Ta and Nb from the mineral. Analytical results indicated that 9.70 and 29.11% of Ta and Nb respectively were dissolved at 150°C after 3 hours using sulphuric acid. The use of sulphuric acid as reagent, a temperature of 50°C and 2 hours leaching time were selected as the most suitable conditions for the subsequent beneficiation process as a compromise between the maximum U and Th removal and the minimum amount of Ta and Nb removed from the NORMs. The selective removal of the radioactive elements using anion precipitation and ion exchange was also investigated. The selective precipitation using several different anions indicated that sulphate (SO42-) was the most successful anion in the selective removal of U and Th from the mineral solution compared with all of the acids investigated. The sulphate resulted in the precipitation of 5.11 % of the total U precipitated along with 82.58 % of the Th, 80.13 % of the Nb and 99.21 % of the Ta. The ion exchange chromatography method, however, was unsuccessful in the separation of uranium and thorium from the tantalum and niobium as there was no selectivity in retention and/or elution of these elements. The final step in this study was to investigate the possible beneficiation of the tantalite ore by combining the acid leaching with the magnetic removal and microwave dissolution of the mineral. The mineral sample which was investigated possessed minute magnetic properties and small amounts of Ta and Nb (1.79 and 1.69 % respectively) together were removed together with Fe by magnetic separation. The acid leaching resulted in consistent but lower U and Th removal. Interestingly, the microwave digestion preferentially removed U, Th and Nb, as indicated by their presence in the filtrate, leaving the precipitate with significantly more Ta. The ratio of niobium to tantalum changed from 1:1 in the initial mineral sample to 3:1 and 1:2 in the filtrate and the precipitate respectively. The final insoluble mineral contained 0.13 % Th (initially 0.50 %), 1.33 % U (initially 3.07 %), 12.18 % Nb (initially 28.1 %) and 21.41 % Ta (initially 27.71 %). The filtrate, on the other hand, contained 0.14 % and 0.98 % of thorium and uranium as well as 13.00 % niobium and 3.99 % tantalum.en_ZA
dc.description.abstractAfrikaans: In die natuur kom die elemente tantaal en niobium in minerale soos tantaliet en kolumbiet voor en het die vraag na hierdie twee elemente in die afgelope paar jaar skerp toegeneem as gevolg van die gebruik daarvan in verbeterde tegnologiese produkte. Tantaal word veral gebruik in die vervaardiging van selfone en skootrekenaars terwyl die vernaamste gebruik van niobium in die konstruksiebedryf is waar dit in die vervaardiging van super metaal allooie gebruik word. Die teenwoordigheid van U en Th in hierdie Nb/Ta bevattende minerale bemoeilik egter die veredeling van hierdie minerale geweldig. Wetgewing beperk byvoorbeeld die hoeveelheid materiaal wat op 'n gegewe moment hanteer mag word, tipe verwerkingstoerusting, die vervoer daarvan asook afvalverwydering. Bogenoemde maatreëls plaas geweldige finansiële druk op die waarde-ketting vir die verwerking en veredeling van hierdie minerale indien U en Th teenwoordig is. Die oorhoofse doel van hierdie studie was die bestudering van die moontlike selektiewe verwydering van U en Th uit hierdie minerale voordat die volledige vertering uitgevoer word. Die metodes wat ondersoek is, het onder andere suur-Ioging (funksie van tyd en temperatuur), anioon-presipitasie en ioonuitruilingschromatografie ingesluit. Die resultate wat uit die suur-Ioging studie verkry is, het wisselende grade van sukses in die verwydering van die radioaktiewe elemente aangetoon. Tydens die studie is swaelsuur, fosforsuur, soutsuur, salpetersuur, perchloorsuur en aqua regia as logingsreagense ondersoek en die analitiese resultate het duidelik getoon dat die eerste drie sure in bogenoemde reeks die suksesvolste was in die verwydering van die meeste van die U en Th uit die mineraal. Resultate wat verkry is met die gebruik van gekonsentreerde swaelsuur as logingsreagens het In duidelik 'n toename in die verwydering van radio-aktiewe elemente met In toename in tyd en temperatuur aangetoon. Die Th-inhoud in die filtraat het vanaf 68.82% by 50°C tot sowat 100% by 100°C toegeneem. Daarbenewens het die U-inhoud in die filtraat vanaf 64.37% by 100°C tot 81.27% by 150°C verhoog en uiteindelik tot 90.08% by 200°C. Fosforsuur was duidelik ondoeltreffend in die verwydering van U en Th by 50°C, maar met 'n temperatuur toename na 150°C is 85.10 en 98.77% van U en Th na 3 ure uit die mineraal verwyder. Die kwantitatiewe analises het ook duidelik getoon dat soutsuur dieselfde tendens as swaelsuur en fosforsuur volg met 51.53 en 91.09% van U en Th wat by 90°C en 3 uur verwyder is. Die nadeel van die gebruik van hierdie gekonsentreerde sure as logingsreagense by verhoogde hoë temperature en verlengde tye is die ongewenste verwydering van Ta en Nb van uit die mineraal. So byvoorbeeld loog swawelsuur 9.70 en 29.11% Ta en Nb by 150°C na 3 ure uit die erts. As kompromie, met doel die maksimum verwydering van die radio-aktiewe elemente en die minimum Nb en Ta verwydering, is swaelsuur as logingsreagens by 50°C en 2 ure vir die verdere mineraalveredelingstudie gebruik. Die selektiewe verwydering van die radio-aktiewe elemente met behulp van die anioonneerslag en ioonuitruiling is ook ondersoek. Die selektiewe presipitering met die verskillende anione het aangetoon dat SO42- die mees suksesvolle anioon in die selektiewe verwydering van U en Th is. Eksperimentele resultate het verder aangetoon dat 5.11% van die U saam met Th (82.58%), Nb (80.13% ) en Ta (99.21%) deur die byvoeging van swawelsuur gepresipiteer word. Ioonuitruiling was egter onsuksesvol in die skeiding van die U en Th van Ta en Nb of enige ander onsuiwerhede wat in die mineraal-oplossing voorgekom het. Die finale stap in hierdie studie was 'n ondersoek na die moontlike stapsgewyse veredeling van die tantaliet-erts deur van deur eerstens van magnetiese verwydering van onsuiwerhede, daarna die suurlogingstap en laastens van mikrogolf-vertering gebruik te maak. Klein hoeveelhede Ta en Nb (1.79 en 1.69% onderskeidelik) is saam met die yster in die magnetiese skeidingsproses verwyder. Die daaropvolgende suurloging het tot konstante, maar effens laer hoeveelhede U en Th verwydering gelei, terwyl die mikrogolfvertering bykomende hoeveelhede van U, Th asook groot hoeveelhede Nb uit die mineraalopgelos het. Die finale van Nb:Ta verhouding het na 'n 3:1 en 1:2 in die filtraat en die neerslag vanaf die 1:1 verhouding na hierdie stap verander. Die oorblywende, onopgeloste mineraal bevat 0.13% Th (aanvanklik 0.50%) en 1.33% U (aanvanklik 3.07), 12.18% Nb (aanvanklik 28,1%) en 21.41% Ta (aanvanklik 27.71 %) Ta. Daarenteen bevat die filtraat 0.14% Th, 0.98% U, 13.00% Nb asook 3.99% Ta.en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectRadioactiveen_ZA
dc.subjectTantalite Aen_ZA
dc.subjectDigestionen_ZA
dc.subjectLeachingen_ZA
dc.subjectBeneficiationen_ZA
dc.subjectDissolutionen_ZA
dc.subjectSeparationen_ZA
dc.subjectPrecipitationen_ZA
dc.subjectRecoveryen_ZA
dc.subjectRegulationsen_ZA
dc.subjectFluxen_ZA
dc.subjectNiobiumen_ZA
dc.subjectDissertation (M.Sc. (Chemistry))--University of the Free State, 2013en_ZA
dc.titleNiobium and tantalum beneficiation from tantalite oreen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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