The effects SIBX/C10 (or C12) TTC mixtures on flotation response of pyrite, gold and uranium from Anglogold Ashanti’s No 2 Gold Plant feed were investigated. In batch flotation tests where TTC was dosed from aged 1% wt stock solutions, synergism was shown to occur in gold flotation at 25 mole percent C12 TTC and in uranium flotation at a similar dosage of C10 TTC. With commercial C12 TTC, 8 mole percent recorded the highest uranium and gold recoveries. The SIBX/C12 TTC mixture had a greater effect on gold than on uranium. When C12 mercaptan replaced the TTC in SIBX mixtures, rates and recoveries decreased at all levels. Kinetics and recovery with a mixture of 92 mole percent SIBX and 8 mole percent commercial C12 TTC gave a better flotation activity than obtained with SIBX alone. A combination of SIBX and an aged 1% wt solution of TTC lost activity when compared to that of SIBX and commercial TTC. This was attributed to the hydrolysis of TTC. Micro-probe analysis, back-scattered electron images, and EDS analysis showed that all the uranium recovered in flotation concentrates was associated with either pyrite, galena or a carbonaceous material (karogen). This was attributed to the flotation of the uranium oxide minerals brannerite and uraninite. Conditioning at pH values between 1.9-3.7 improved kinetics of gold, sulphur and uranium collection, but sulphur and uranium final recoveries were lower and gold final recovery was higher than the standard. In the presence of 0.001M cyanide, equivalent to 70g/t copper sulphate failed to activate pyrite at both pH 5.5 and pH 7.2. At a similar molar dosage lead nitrate did activate pyrite at pH 5.5 but not at pH 7.2. / Dissertation (MEng(Metallurgical))--University of Pretoria, 2005. / Materials Science and Metallurgical Engineering / unrestricted

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A family of top-down statistical models describing energy consumption in the mining, milling, and refining of uranium are formulated. The purpose of the models is to estimate the energy-to-grade dependence for uranium extraction, while defining a minimum grade that can be feasibly mined and produced. The results serve as a basis for understanding the factors governing energy consumption in the production of U3O8. The models are applied to a considerably larger data set of operating mines than in any previous effort. In addition, the validity of the modeling approach is established by modeling energy for two other commodities, gold and copper, thereby showing it can be applied to other metals. Statistical measures of explanatory power show that the models the energy-to-grade relationship is well-described for both uranium and gold. For copper, there was insufficient data over a broad range of ore grades to obtain a model that passed statistical confidence measures. The results show that mining of lower-grade deposits of uranium is likely to be less energy-intensive than previous investigators concluded. It is shown that the uncertainty in the results is dominated by the contribution of the grade-independent component of energy consumption. / text

Th. 3e cycle--Phys. nucl.--Grenoble 1, 1978. N°: 18.

Made available in DSpace on 2014-10-09T12:52:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:12Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:52:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:12Z (GMT). No. of bitstreams: 0 / Neste trabalho foi estabelecido um procedimento para determinação da razão isotópica 238U/235U em amostras de UF6, utilizando-se um espectrômetro de massas quadrupolar com ionização por impacto eletrônico e detecção de íons por copo de Faraday ou multiplicador de elétrons. Para tanto, o espectrômetro foi otimizado, determinando-se os parâmetros para a fonte de íons que proporcionassem a maior intensidade de corrente iônica, mantendo o pico de forma arredondada, para a massa correspondente ao isótopo mais abundante; a resolução que reduzisse os efeitos não lineares e o número de ciclos analíticos que reduzisse a incerteza nos resultados. O processo de medição foi caracterizado quanto: aos efeitos de discriminação de massa, linearidade e efeito memória. A discriminação de massas mostrou ser linearmente dependente da pressão da amostra no tanque de expansão nas faixas de 0,15 a 0,30 mbar e de 0,30 a 0,40 mbar. O espectrômetro mostrou-se linear na medição de razões isotópicas entre 0,005 e 0,045. Os fatores de memória para a fonte de íons e para o sistema de introdução são, respectivamente, 1,000 ± 0,001 e 1,003 ± 0,003; o primeiro pode ser desprezado e o segundo eliminado por procedimentos de lavagem do sistema de introdução. O trabalho apresenta, em sua parte final, um roteiro para as análises de amostras de UF6 e a determinação das incertezas nos resultados. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

As a consequence of rising uranium prices an interest in Sweden’s U deposits has emerged. This raises the important question of the possible environmental impacts of U mining operations. One of the most significant and serious issues is the contamination of groundwater by U following mining activities. The processes of uranium release and subsequent transport in groundwater is closely tied to its aqueous chemistry i.e. aqueous speciation, adsorption to mineral surfaces and dissolved organic carbon (DOM). The chemical parameters exerting the most control over these processes are pH and redox potential. The redox potential plays a decisive role because it controls the solubility of uraninite, a common uranium mineral and ore in Sweden’s bedrock deposits. Thus, by gaining insight into how changing redox conditions affect uraninite solubility, assessments can be made in order to estimate the extent of uranium transport by groundwater. Therefore the effects of the redox po-tential on U mobility will be examined in this work by means of computer modeling in the geochemical software VISUAL MINTEQ 3.0. The composition of the water used for modeling resembled that of a typical bedrock groundwater of Northern Sweden in the areas above the highest coastline. The simulations were carried out under different redox potentials at different pH levels in the presence of ferrihydrite and DOM to include the effects of U adsorption. The results show that the redox potential at which the uraninite mineral dissolves varies depending on the pH of the groundwater. From pH 4.0 to 7.5 the redox potential at which uraninite oxidizes decreases from 240-250 mV to 50-60 mV. This means higher redox conditions are needed for the dissolution of uraninite at low pH. Additionally, it is further concluded that the adsorption of U to ferrihydrite and DOC is important at pH 5-8 and pH < 7 respectively, which therefore play an important role in controlling the mobility of U in the modeled groundwater.