Proefschrift Universiteit van Amsterdam. / Met samenvatting in het Nederlands.

Please read the abstract in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2010. / Immunology / unrestricted

Niobium (Nb) and tantalum (Ta) are found in the same group (VB) of the periodic table of elements and therefore have similar chemical properties, which is the reason why they are difficult to separate. They are usually found together in various minerals of which the most important are columbite ((Fe, Mn, Mg)(Nb, Ta)2O6) and tantalite ((Fe, Mn)(Nb, Ta)2O6). Several methods have been used to separate Nb and Ta. Most methods use very high concentrations of hydrofluoric acid (HF) and sulphuric acid (H2SO4) as the aqueous phase, tributyl phosphate (TBP) as the extractant and methyl isobutyl ketone (MIBK) as the organic phase. High extraction can be achieved, but the reagents used are hazardous. With the increasing demand of both pure Ta and Nb, as well as stricter environmental requirements, a need exists to develop a more efficient and safer technique to separate Ta and Nb. In this project the focus was on the solvent extraction (SX) of Ta and Nb with the possible application in a membrane-based solvent extraction (MBSX) process. For this purpose, eight different extractants were investigated, namely the cation exchangers di-iso-octyl-phosphinic acid (PA) and di-(2-ethylhexyl)-phosphoric acid (D2EHPA), the neutral solvating extractant 2-thenoyl-trifluoro- acetone (TTA), and the anion exchangers Alamine 336, Aliquat 336, 1-octanol, 2-octanol and 3-octanol. The extractant to metal ratio was varied from 0.1:1 to 10:1, while cyclohexane was used as diluent and 3% v/v 1-octanol was used as modifier for the organic phase. In addition, four different acids, hydrochloric acid (HCl), nitric acid (HNO3), sulphuric (H2SO4) and perchloric acid (HClO4), were used at different concentrations to determine the best combination for extraction. First, fluoride salts of Ta and Nb (Ta(Nb)F5) were tested and the optimum results showed that the highest extraction was obtained with PA and D2EHPA, irrespective of the type of acid used. Similarly, irrespective of the acid used, extraction with PA and D2EHPA increased with increasing acid concentration, followed by Alamine 336, Aliquat 336 and then TTA and the octanols. Extraction values of 97% Ta at 15 mol/dm3 and 85% Nb between 12 and 15 mol/dm3 were obtained. Although extraction of both Ta and Nb was achieved with all the acids tested, only H2SO4 showed sufficient separation (log D = 3) of the two metals in the 0 to 2 mol/dm3 acid range and 15 mol/dm3 for PA and D2EHPA, respectively. Precipitation, probably due to hydrolysis of the metals, occurred in the absence of acid when using Alamine 336, Aliquat 336 and TTA. The octanols showed the least amount of extraction of Ta and Nb, irrespective of the acid investigated. The optimum extraction was achieved with an E/M ratio of 3:1 of PA and D2EHPA as the extractant and 10 mol/dm3 H2SO4 in the aqueous phase. The NH4Ta(Nb)F6 salt solution was investigated using the optimum conditions for maximum extraction obtained from the Ta(Nb)F5 experiments, i.e. 4 mol/dm3 H2SO4 with an E/M ratio above 3:1 for the extractant PA and 4 mol/dm3 H2SO4 with an E/M ratio of 20:1 for the extractant D2EHPA. Kinetic equilibrium for PA was reached after 10 minutes and for D2EHPA after 20 minutes. The highest extraction of Ta (100%) above 3 mol/dm3 H2SO4 and Nb (54%) at 8 mol/dm3 with the highest separation factor of 4.7 with PA was achieved, followed by the 100% extraction of Ta above 5 mol/dm3 and 40% Nb at 10 mol/dm3 with the highest separation factor of 4.9 in D2EHPA. Although the aim of this study was the extraction and separation of Ta and Nb, the recovery or back extraction of the metals from the organic phase, as well as the membrane-based solvent extraction (MBSX) was briefly investigated. From the preliminary results obtained it became apparent that further research into the different aspects, including the type of stripping agent used, stripping agent concentration, effect of Ta to Nb ratio and different sources of Ta and Nb is needed to obtain the optimum conditions for the MBSX process and the subsequent recovery of Ta and Nb. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2013.

Niobium (Nb) and tantalum (Ta) are found in the same group (VB) of the periodic table of elements and therefore have similar chemical properties, which is the reason why they are difficult to separate. They are usually found together in various minerals of which the most important are columbite ((Fe, Mn, Mg)(Nb, Ta)2O6) and tantalite ((Fe, Mn)(Nb, Ta)2O6). Several methods have been used to separate Nb and Ta. Most methods use very high concentrations of hydrofluoric acid (HF) and sulphuric acid (H2SO4) as the aqueous phase, tributyl phosphate (TBP) as the extractant and methyl isobutyl ketone (MIBK) as the organic phase. High extraction can be achieved, but the reagents used are hazardous. With the increasing demand of both pure Ta and Nb, as well as stricter environmental requirements, a need exists to develop a more efficient and safer technique to separate Ta and Nb. In this project the focus was on the solvent extraction (SX) of Ta and Nb with the possible application in a membrane-based solvent extraction (MBSX) process. For this purpose, eight different extractants were investigated, namely the cation exchangers di-iso-octyl-phosphinic acid (PA) and di-(2-ethylhexyl)-phosphoric acid (D2EHPA), the neutral solvating extractant 2-thenoyl-trifluoro- acetone (TTA), and the anion exchangers Alamine 336, Aliquat 336, 1-octanol, 2-octanol and 3-octanol. The extractant to metal ratio was varied from 0.1:1 to 10:1, while cyclohexane was used as diluent and 3% v/v 1-octanol was used as modifier for the organic phase. In addition, four different acids, hydrochloric acid (HCl), nitric acid (HNO3), sulphuric (H2SO4) and perchloric acid (HClO4), were used at different concentrations to determine the best combination for extraction. First, fluoride salts of Ta and Nb (Ta(Nb)F5) were tested and the optimum results showed that the highest extraction was obtained with PA and D2EHPA, irrespective of the type of acid used. Similarly, irrespective of the acid used, extraction with PA and D2EHPA increased with increasing acid concentration, followed by Alamine 336, Aliquat 336 and then TTA and the octanols. Extraction values of 97% Ta at 15 mol/dm3 and 85% Nb between 12 and 15 mol/dm3 were obtained. Although extraction of both Ta and Nb was achieved with all the acids tested, only H2SO4 showed sufficient separation (log D = 3) of the two metals in the 0 to 2 mol/dm3 acid range and 15 mol/dm3 for PA and D2EHPA, respectively. Precipitation, probably due to hydrolysis of the metals, occurred in the absence of acid when using Alamine 336, Aliquat 336 and TTA. The octanols showed the least amount of extraction of Ta and Nb, irrespective of the acid investigated. The optimum extraction was achieved with an E/M ratio of 3:1 of PA and D2EHPA as the extractant and 10 mol/dm3 H2SO4 in the aqueous phase. The NH4Ta(Nb)F6 salt solution was investigated using the optimum conditions for maximum extraction obtained from the Ta(Nb)F5 experiments, i.e. 4 mol/dm3 H2SO4 with an E/M ratio above 3:1 for the extractant PA and 4 mol/dm3 H2SO4 with an E/M ratio of 20:1 for the extractant D2EHPA. Kinetic equilibrium for PA was reached after 10 minutes and for D2EHPA after 20 minutes. The highest extraction of Ta (100%) above 3 mol/dm3 H2SO4 and Nb (54%) at 8 mol/dm3 with the highest separation factor of 4.7 with PA was achieved, followed by the 100% extraction of Ta above 5 mol/dm3 and 40% Nb at 10 mol/dm3 with the highest separation factor of 4.9 in D2EHPA. Although the aim of this study was the extraction and separation of Ta and Nb, the recovery or back extraction of the metals from the organic phase, as well as the membrane-based solvent extraction (MBSX) was briefly investigated. From the preliminary results obtained it became apparent that further research into the different aspects, including the type of stripping agent used, stripping agent concentration, effect of Ta to Nb ratio and different sources of Ta and Nb is needed to obtain the optimum conditions for the MBSX process and the subsequent recovery of Ta and Nb. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2013.

Thematic interrelation is an underdeveloped field of inquiry in Lukan studies. The design and elegance of Lukan theology begs for guided investigation into a possible system of organisation that governs history and theology, that is, narrative and theme. Based on the Greimasian Actantial Model, morpho–syntactical structural–critical analysis of Luke and Acts reveals that the covenant concept in its operative aspect of service functions as an organising principle, structuring the narratives and facilitating thematic interrelation. A survey of representative Lukan research consisting of five methodologically determined approaches shows a commonality regarding Lukan purpose. These all share the “plan of God” as a fundamental concept, thus intimating its plausibility as a common organisational principle in the text. This observation encourages further analysis of Lukan narrative and meta–narrative as relevant subject matter. Investigation into the purpose and goals of Ancient Jewish and Ancient Greek literature suggests that the concepts of piety/holiness and justness combined with a notion of divine order and expectation demonstrates organisational capacity. Under the terms and conditions of the Old Covenant three non–exclusive themes/concepts hold organisational functionality and ability to facilitate thematic interrelation: Exodus typology, the covenant concept and the eschaton idea. Exodus typology connects narrative with theme, developing Israel’s story. The covenant idea frames stories using parallelism and gives the meta–story progression. The eschaton idea presents the Day of YHWH as an organisational principle guiding the story of judgment to restoration. It is observed that the covenant concept is the most prevalent of these themes/ideas. Assuming the conceptual unity of Luke and Acts and adopting a morpho–syntactical structuralist approach, it was observed that the covenant concept in its operative aspect of service occurred as Helper at ten places, determining the development and structure of the meta–narrative. According to the Greimasian Actantial Model, Israel failed to fulfil its covenant–based mandate to serve God and shine God’s light of mercy to the nations. Jesus, Israel’s new Helper, becomes the Subject and by his covenant–based ministry, characterised as the greatest service, resolves the problem that prevents Israel from carrying out its divine mandate and sets the stage for its fulfilment. In Jesus Israel is given new leaders, an ethical platform of discipleship and the Holy Spirit. The apostle Paul as the epitomised and exemplary witness and servant of Jesus fulfils what Israel could not. He is vindicated in righteousness and shares in the Isaianic ministry of Jesus, to bear witness to leaders and to shine God’s light to the nations. Paul is unhindered in this ministry. Additionally, in thematic–critical terms, the key placement of the covenant concept in its operative aspect of service at plot–defining junctures features its catalytic dynamic as a “template” concept advancing the re–conceptualising of themes and providing a platform for meaningful relation. The evidence thus suggests that the covenant concept in its operative aspect structures the conjoined narratives of Luke and Acts. It also provides a basis for relation between the divine and humans in the context of the history of God’s salvation, linking history and theology, and makes possible a discernible means to thematic interrelation. The SO2 electrolysis was performed by supplying the anode of the cell with SO2 gas, while the water was fed to the cathode using graphite plates as flow fields. Initial experimental work was done at ambient pressures on the anode (SO2 gas–fed) and cathode (water–fed) after which the water pressure was increased from ambient to 1 bar. Various parameters were evaluated for SO2 electrolysis at ambient conditions, including operating temperature, membrane thickness and catalyst loading. The operating temperature was increased from 50oC to 80oC which resulted in a significant voltage improvement from 0.78V to 0.64V at 300mA/cm2. Operating the cell with thinner membranes (86 vs 170um) also resulted in an improved overall cell performance, while the catalyst loading (1 vs 0.5mgPt/cm2) had a negligible effect on the operating voltage. SEM images and EDX analysis were performed on the best performing MEA (N1135) which showed that no degradation of the MEA had occurred. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011.

Thematic interrelation is an underdeveloped field of inquiry in Lukan studies. The design and elegance of Lukan theology begs for guided investigation into a possible system of organisation that governs history and theology, that is, narrative and theme. Based on the Greimasian Actantial Model, morpho–syntactical structural–critical analysis of Luke and Acts reveals that the covenant concept in its operative aspect of service functions as an organising principle, structuring the narratives and facilitating thematic interrelation. A survey of representative Lukan research consisting of five methodologically determined approaches shows a commonality regarding Lukan purpose. These all share the “plan of God” as a fundamental concept, thus intimating its plausibility as a common organisational principle in the text. This observation encourages further analysis of Lukan narrative and meta–narrative as relevant subject matter. Investigation into the purpose and goals of Ancient Jewish and Ancient Greek literature suggests that the concepts of piety/holiness and justness combined with a notion of divine order and expectation demonstrates organisational capacity. Under the terms and conditions of the Old Covenant three non–exclusive themes/concepts hold organisational functionality and ability to facilitate thematic interrelation: Exodus typology, the covenant concept and the eschaton idea. Exodus typology connects narrative with theme, developing Israel’s story. The covenant idea frames stories using parallelism and gives the meta–story progression. The eschaton idea presents the Day of YHWH as an organisational principle guiding the story of judgment to restoration. It is observed that the covenant concept is the most prevalent of these themes/ideas. Assuming the conceptual unity of Luke and Acts and adopting a morpho–syntactical structuralist approach, it was observed that the covenant concept in its operative aspect of service occurred as Helper at ten places, determining the development and structure of the meta–narrative. According to the Greimasian Actantial Model, Israel failed to fulfil its covenant–based mandate to serve God and shine God’s light of mercy to the nations. Jesus, Israel’s new Helper, becomes the Subject and by his covenant–based ministry, characterised as the greatest service, resolves the problem that prevents Israel from carrying out its divine mandate and sets the stage for its fulfilment. In Jesus Israel is given new leaders, an ethical platform of discipleship and the Holy Spirit. The apostle Paul as the epitomised and exemplary witness and servant of Jesus fulfils what Israel could not. He is vindicated in righteousness and shares in the Isaianic ministry of Jesus, to bear witness to leaders and to shine God’s light to the nations. Paul is unhindered in this ministry. Additionally, in thematic–critical terms, the key placement of the covenant concept in its operative aspect of service at plot–defining junctures features its catalytic dynamic as a “template” concept advancing the re–conceptualising of themes and providing a platform for meaningful relation. The evidence thus suggests that the covenant concept in its operative aspect structures the conjoined narratives of Luke and Acts. It also provides a basis for relation between the divine and humans in the context of the history of God’s salvation, linking history and theology, and makes possible a discernible means to thematic interrelation. The SO2 electrolysis was performed by supplying the anode of the cell with SO2 gas, while the water was fed to the cathode using graphite plates as flow fields. Initial experimental work was done at ambient pressures on the anode (SO2 gas–fed) and cathode (water–fed) after which the water pressure was increased from ambient to 1 bar. Various parameters were evaluated for SO2 electrolysis at ambient conditions, including operating temperature, membrane thickness and catalyst loading. The operating temperature was increased from 50oC to 80oC which resulted in a significant voltage improvement from 0.78V to 0.64V at 300mA/cm2. Operating the cell with thinner membranes (86 vs 170um) also resulted in an improved overall cell performance, while the catalyst loading (1 vs 0.5mgPt/cm2) had a negligible effect on the operating voltage. SEM images and EDX analysis were performed on the best performing MEA (N1135) which showed that no degradation of the MEA had occurred. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011.