The development of sustainable replacements for fossil fuels has been spurred by concerns over global warming effects. Biofuels are typically produced through fermentation of edible crops, or forest or agricultural residues requiring cost-intensive pretreatment. An alternative is to use photosynthetic cyanobacteria to directly convert CO2 and sunlight into fuel. In this thesis, the cyanobacterium Synechocystis sp. PCC 6803 was genetically engineered to produce the biofuel n­-butanol. Several metabolic engineering strategies were explored with the aim to increase butanol titers and tolerance. In papers I-II, different driving forces for n-butanol production were evaluated. Expression of a phosphoketolase increased acetyl-CoA levels and subsequently butanol titers. Attempts to increase the NADH pool further improved titers to 100 mg/L in four days. In paper III, enzymes were co-localized onto a scaffold to aid intermediate channeling. The scaffold was tested on a farnesene and polyhydroxybutyrate (PHB) pathway in yeast and in E. coli, respectively, and could be extended to cyanobacteria. Enzyme co-localization increased farnesene titers by 120%. Additionally, fusion of scaffold-recognizing proteins to the enzymes improved farnesene and PHB production by 20% and 300%, respectively, even in the absence of scaffold. In paper IV, the gene repression technology CRISPRi was implemented in Synechocystis to enable parallel repression of multiple genes. CRISPRi allowed 50-95% repression of four genes simultaneously. The method will be valuable for repression of competing pathways to butanol synthesis. Butanol becomes toxic at high concentrations, impeding growth and thus limiting titers. In papers V-VI, butanol tolerance was increased by overexpressing a heat shock protein or a stress-related sigma factor. Taken together, this thesis demonstrates several strategies to improve butanol production from cyanobacteria. The strategies could ultimately be combined to increase titers further.

Compressed and supercritical fluids, such as pressurized CO2, ethane, orpropane, provide a versatile and environmentally acceptable alternative to conventionalliquid organic solvents in bioprocessing applications – specifically in the areas ofproduct extraction, protein purification, microbial sterilization, and enzymatic and wholecellbiocatalysis. While their advantages have been well demonstrated, the effects ofcompressed and supercritical fluids on whole cells are largely unknown.Metabolic and structural perturbations of whole cells by compressed andsupercritical fluid solvents were examined. These perturbations exist as cell metabolismand membrane structure are influenced by pressure and the presence of a solventphase. Continuous cultures of Clostridium thermocellum (a model ethanol-producingthermophilic bacterium) were conducted under elevated hydrostatic and hyperbaricpressure to elucidate pressure- and solvent-effects on metabolism and growth.Fluorescence anisotropy was employed to study liposome fluidization due to thepresence of compressed and supercritical fluids and their partitioning/accumulation inthe phospholipid bilayer.Under elevated hydrostatic pressure (7.0 and 13.9 MPa; 333 K), significantchanges in product selectivity (towards ethanol) and growth were observed in C.thermocellum in conjunction with reduced maximum theoretical growth yields andincreased maintenance requirements. Similarly, metabolism and growth were greatlyinfluenced under hyperbaric pressure (1.8 and 7.0 MPa N2, ethane, and propane; 333K); however, severe inhibition was observed in the presence of supercritical ethane andliquid propane. These changes were attributed to mass-action effects on metabolicpathways, alterations in membrane fluidity, and the dominant role of phase toxicityassociated with compressed and supercritical fluids.Fluorescence anisotropy revealed fluidization and melting point depression ofdipalmitoylphosphatidylcholine liposomes in the presence of CO2, ethane, and propane(1.8 to 20.7 MPa; 295 to 333 K). The accumulation of these fluids within the bilayerupon pressurization and the ordering effects of pressure influenced liposome fluidity, themelting temperature, and the gel-fluid phase transition region. These resultsdemonstrate the disordering effects of compressed and supercritical fluids on biologicalmembranes and the ability to manipulate liposomes.

With the dramatic increase in the worldwide demand for the crude oil and with the fact that the oil and gas resources are depleting, the enhanced oil recovery process plays an important role to increase the production from the existing hydrocarbon reservoirs. Chemical enhanced oil recovery is one of the most important techniques to unlock significant amount of trapped oil from oil reservoirs. Surface agent materials (Surfactants) are used to lower the interfacial tension (IFT) between water and oil phases to ultralow values and mobilize the trapped oil. When surfactant, water, and oil are mixed together they form a thermodynamically stable phase called microemulsion which can be characterized by ultralow interfacial tension and the ability to solubilize both aqueous and oil compounds. Another characteristic of microemulsion solution is its viscosity which plays an important role in the creation and movement of the oil bank. The microemulsion micro-structure is complex and its viscosity is difficult to predict. Various viscosity models and correlations are presented in the literature to describe microemulsion viscosity behavior, but they fail to represent the rheological behavior of many microemulsion mixtures. Most of these models are valid in the lower and higher ranges of solute where one of the domains is discontinuous. The majority of the models fail to calculate the rheology of microemulsion phase in bicontinuous domains. In this work, we present a systematic study of the rheological behavior of microemulsion systems and the effect of additives such as polymer and co-solvent on rheological properties of microemulsions. Several laboratory experiments were conducted to determine the rheological behavior of surfactant solutions. A new empirical model for the viscosity of microemulsion phase as a function of salinity is introduced. The model consists of three different correlations one for each phase type of Windsor phase behaviors. The proposed model is validated using a number of experimental results presented in this document. The proposed viscosity model is implemented in the UTCHEM simulator and the simulator results are compared with the coreflood experiments. Excellent matches were obtained for the pressure. We further improved the proposed viscosity model to incorporate the effect of polymer and co-solvent on the microemulsion viscosity. / text

Heavy oil resources are huge and are currently produced largely with steam-driven technology. The purpose of this research was to evaluate an alternative to steam flooding in heavy oils: chemical EOR. Acidic components abundant in heavy crude oils can be converted to soaps at high pH with alkali, reducing the interfacial tension (IFT) between oil and water to ultra-low levels. In an attempt to harness this property, engineers developed alkaline and alkaline-polymer (AP) flooding EOR processes, which met limited success. The primary problem with AP flooding was the soap is usually too hydrophobic, its optimum salinity is low and the ultra-low IFT salinity range narrow (Nelson 1983). Adding a hydrophilic co-surfactant to the process solved the problem, and is known as ASP flooding. AP floods also form persistent, unpredictable and often highly viscous emulsions, which result in high pressure drops and low injection rates. Addition of co-solvents such as a light alcohol (typically 1 wt %) improves the performance of AP floods; researchers at the University of Texas at Austin have coined the term ACP (Alkaline Co-solvent Polymer) for this new process. ACP has significant advantages relative to other chemical flooding modes to recover heavy oils. It is less costly than using surfactant, and has none of the design challenges associated with surfactant. It shows the benefit of nearly 100% displacement sweep efficiency in core floods when properly implemented, as heavy oils tend to produce significant IFT reducing soaps. The use of polymer for mobility control ensures good sweep efficiency is also achieved. Since heavy oils can be extremely viscous at reservoir temperature, moderate reservoir heating to reduce oil viscosity is beneficial. In a series of core flood experiments, moderately elevated temperatures (25-75°C) were used in evaluating ACP flooding in heavy oils. The experiments used only small amounts of inexpensive co-solvents while recovering >90% of remaining heavy oil in a core, without need for any surfactant. The most successful experiments showed that a small increase in temperature (25°) can have very positive impacts on core flood performance. These results are very encouraging for heavy oil recovery with chemical EOR. / text

<p>Mass transfer in a porous solid, partially saturated with asingle solvent and multicomponent liquid mixtures, has beenexperimentally and theoretically studied. A porous materialcontaining single liquids and mixtures of organic solvents wasisothermally dried. Experiments were performed using a jacketedwind tunnel, through which a humidity andtemperature-controlled air stream flowed. The wetted porousmaterial was placed in a cylindrical vessel, whose top isexposed to the air stream until the material became dried to acertain extent. Drying experiments with the single solventswater, methanol, ethanol and 2-propanol, were performed atdifferent temperatures and transient liquid content profileswere determined. In isothermal drying experiments with liquidmixtures,the transient concentration profiles of thecomponents along the cylindrical sample as well as the totalliquid content were determined. The liquid mixtures examinedwere water-methanolethanol and isopropanol-methanol-ethanol.Two different temperatures and initial compositions were usedin the experiments. Mathematical models that describe nonsteadystate isothermal drying of a solid containing single liquidsand multicomponent liquid mixtures were developed. In the solidwetted with a single liquid, capillary movement of the liquidwas the main mechanism responsible for mass transfer. In thesolid containing liquid mixtures, interactive diffusion inliquid phase was superimposed to the capillary movement of theliquid mixture. In addition, interactive diffusion of thevapours in empty pores was considered. The parameters todescribe the retention properties of the solid and thecapillary movement of the liquid were determined by comparingtheoretical and experimental liquid content profiles obtainedduring drying of the solid wetted with single liquids. Tosimulate the transport of the liquid mixtures these parameterswhere weighed according to liquid composition. A fairly goodagreement between theoretical and experimental liquidcomposition profiles was obtained if axial dispersion isincluded in the model when the moisture consists of amixture.</p><p><b>Keywords:</b>Internal mass transfer, capillary flow,multicomponent, diffusion, solvent mixtures</p>

When solutions of various metal 8-quinolinolates or beta-diketonates in an organic solvent were contacted with an aqueous phase and vigorously stirred to generate a large interfacial area, a reversible decrease in the organic phase concentration of the complex was observed. The magnitude of this decrease varied with interfacial area, solvent, temperature, and the nature and concentration of the complex. Analysis of the phenomenon using the Langmuir isotherm showed that the concentration change may be explained by adsorption of significant quantities of the complexes at the increased liquid-liquid interface generated by stirring. Such adsorption was found to complicate extraction kinetics measurements using the high-speed stirring technique when the product chelate is interfacially active, distorting the absorbance/time profile from which rate constants are derived, altering the interfacial area in the reaction vessel, and displacing reactant molecules from the interface. Neutral surfactants were observed to have similar effects. Chelate adsorption was also demonstrated to affect metal ion extraction equilibria, shifting the pH 1/2 value associated with a given metal ion. The magnitude of this shift was found to depend on the concentration of the chelate, its interfacial adsorption constant, and interfacial area. Differences in the pH 1/2 shift were shown to serve as a means of separating metal ions. Studies of the rate of nickel extraction by 8-quinolinols showed that the distribution constant and interfacial activity of the ligand are important factors governing the balance between bulk and interfacial pathways in the extraction. The interfacial rate constant for a given ligand was independent of organic solvent and was typically 10 times larger than the corresponding bulk value, indicating that the interface, although essentially aqueous in character, is a more conducive medium for the reaction of the metal ion and ligand.

Article 21 of the Insolvency Act states that the estate of the solvent spouse transfers to the curator of the insolvent spouse's sequestrated estate. The solvent spouse then has the burden to request the release of property vested in the curator of the insolvent estate. In accordance with Article 21(2), the spouse is required to prove a lawful title on the property. Should the spouse be able to prove a lawful title on the property, the curator is obligated to release the property. Although the constitutionality of this temporarily "deprivation" of the solvent spouse of her rights has already been confirmed by the Constitutional Court; it imposes drastic limitations to his/ her rights. The Insolvency Act does not incorporate procedural measures by means of which the curator has to establish whether the solvent spouse has exempted his/ her from the proof burden. In the same breath, the Constitution and the Promotion of Administrative Justice Act warrant that "everyone has the right to administrative action that is lawful. reasonable and procedurally fair." If the curator's actions, in accordance with Article 21. conform to the administrative procedures as set out in the Promotion of Administrative Justice Act, the spouse shall be entitled to administrative actions which are procedurally fair as concluded within the Promotion of Administrative Justice Act. The conclusion is proof that the actions of the curator, in accordance with Article 21 of the Insolvency Act, is indeed administrative by nature and that the solvent spouse has the right to administrative actions which is procedurally fair as prescribed in the Promotion of Administrative Justice Act, as well as the right to reasons for not being granted the release of property. / Thesis (LL.M. (Estate Law))--North-West University, Potchefstroom Campus, 2007.

This thesis involves the design and development of reagents for the recovery of base metals (specifically zinc, nickel and cobalt) in hydrometallurgical solvent extraction processes. The work aims to demonstrate how ligand design can affectively tune the strength and selectivity of extractants to achieve efficient recovery of the desired base metals. Chapter 1 reviews current solvent extraction processes used in extractive metallurgy, encompassing both the well established technologies developed for sulfate streams as well as those more recently explored for treating chloride streams. Also reviewed, is the nature of the chemical binding involved in the three key modes of extraction; namely cation transport, anion transport and metal salt transport. Chapter 2 summarises the methodologies that have been established during this research for the appropriate testing of these reagents. Chapter 3 deals exclusively with the processing of zinc sulfide ores with an aim to design reagents to achieve concentration and separation of zinc in chloride hydrometallurgical circuits. The amido functionalised reagents that are reported have a common structural feature with ligands that have been previously studied by the Tasker group (Ross J. Ellis Thesis, University of Edinburgh, 2009). A six membered chelate ring is formed by a protonated amino nitrogen atom and an amido oxygen atom in a sequence of the type R2HN+-CH2-NR-CO-R. This differs from those previously studied which have a sequence of the type R2HN+-CH2-CHR-CO-NR2. The pro-ligands (L) operate via an anion exchange mechanism (Equation 1) whereby two protonated ligands (LH+) coordinate to the outersphere of anionic zinc(II) or iron(III) chloridometalates from acid chloride solutions using both N-H and C-H hydrogen-bond donors. pH dependent solvent extraction experiments have concluded that this reagent series achieves zinc(II) loading with pH0.5 values that are competitive with the previous ligand series (Ross J. Ellis Thesis, University of Edinburgh, 2009). Chloride concentration dependent solvent extraction experiments have demonstrated that the reagents show an unusually good selectivity for ZnCl4 2- over chloride or FeCl4 - in equilibrium of the type; yLorg + yH+ +MClx y- ⇌ [(LH)yMClx](org) (1) The development of bidentate and tridentate pyrazolone-based pro-ligands for the extraction of nickel and cobalt from mixed metal sulfate streams is considered in Chapters 4 and 5. These reagents (LH) operate via metal cation transport, where an inner-sphere complex of nickel(II) or cobalt(II) is formed with the ligand (L-) see Equation 2. A combination of N, O and S donors has been incorporated into 1-phenyl-3-methyl-4- acylpyrazol-5-ones and their respective 4-acylpyrazolone oximes in order to tune the bidentate ligands (L-) for optimal coordination with nickel(II) or cobalt(II). Substituent effects have also been investigated, by synthesising a series of 1-(2-X-phenyl)-3-methyl-4- acylpyrazol-5-one oximes [X = Cl, H]. Substitution in the 3-position of the phenol group in phenolic oximes has been reported to increase extractant strength for copper by two orders of magnitude (Ross S. Forgan Thesis, University of Edinburgh, 2008). Similar improvements were not observed in this study. The nature of this effect has been attributed to buttressing of hydrogen-bonds, where the substituent forms a stabilising, bifurcated hydrogen-bond between the oximic hydrogen and the pyrazolonic oxygen. yLHorg + My+ ⇌ [(L)yM]org + yH+ (2) Tridentate analogues of the oxime reagents above have been prepared as imines derived from anilines contained o-O, S or N donor atoms. It was hoped that these would give high spin octahedral nickel(II) complexes in extraction processes. They proved to be weak extractants. Chapter 6 focuses of the development of bidentate pyrazolethiones for the selective extraction of cobalt from manganese in acidic sulfate streams. These reagents have been designed to favour coordination to metals in a tetrahedral geometry as shown by L. Emeleus and A. Smith for copper and zinc (Lucy Emeleus Thesis, University of Edinburgh 1999 and Andrew Smith Thesis, University of Edinburgh 2000).

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering (Metallurgy and Materials Engineering), May 2016 / The solvent extraction of iron and titanium from solution generated by the two-step sulphuric acid leaching of coal fly ash by Primene JMT was investigated. The influence of hydrogen ion concentration, Primene JMT concentration, aqueous to organic volume phase ratio and temperature on the extraction of iron and titanium was determined by the use of Design of Experiments. Hydrogen ion concentration and the interaction between the aqueous to organic volume phase ratio with Primene JMT concentration had a significant effect on the extraction of iron while temperature did not. Hydrogen ion concentration and temperature did not have a significant effect on the extraction of titanium, while the interaction between Primene JMT concentration and aqueous to organic volume phase ratio had a significant effect. Extraction improvement tests showed that at a hydrogen ion concentration of 0.28M, 88% iron and 99% extraction of titanium from coal-fly ash leach solution could be achieved. Construction of a McCabe-Thiele diagram showed that a four-stage solvent extraction system with Primene JMT could reduce the iron and titanium concentration in the coal fly ash leach solutions to below 0.05g/L / GS2016

Nenhuma / Foi realizado neste trabalho o estudo da recuperação de európio e ítrio de monitores de computadores sucateados por meio de técnicas hidrometalúrgicas. O trabalho foi composto de três etapas: (i) lixiviação ácida do pó de revestimento da tela de monitores CRT; (ii) separação dos elementos de interesse por extração por solventes em escala de bancada testes descontínuos e (iii) otimização da etapa (ii) em escala micro piloto testes contínuos. Na etapa de lixiviação ácida investigou-se a influência do agente lixiviante, da relação ácido/amostra, tempo e temperatura de reação na porcentagem de solubilização de európio e ítrio do resíduo em estudo. Obteve-se um máximo de solubilização destes (98% p/p) com o emprego de H2SO4 na relação ácido/amostra 1250g/kg em temperatura ambiente (25 C), 10% de sólidos e com agitação mecânica por 30 minutos. O licor obtido no processo de lixiviação, contendo 11,9 g/L de ítrio e 0,72 g/L de európio, foi submetido a testes descontínuos de extração por solventes com a finalidade de separação dos dois íons metálicos. Investigou-se o desempenho dos seguintes extratantes orgânicos no rendimento de extração das espécies de interesse: DEHPA, IONQUEST 801, CYANEX 272 e PRIMENE JMT. O DEHPA na concentração de 1,0 mol/L mostrou-se mais eficiente na separação do par Y/Eu, fator de separação igual a 111,4 na relação de fase A/O = 1 e agitação mecânica por 10 minutos. A partir da isoterma de extração e construção do diagrama McCabe-Thiele, observou-se que dois estágios de extração na relação A/O = 1,1 são suficientes para extrair todo o ítrio da fase aquosa para a fase orgânica, enquanto que o európio fica na fase aquosa. Na lavagem do orgânico carregado, uma solução de H2SO4 0,75 mol/L na relação de fase O/A = 5 foi suficiente para retirar todas as espécies coextraídos na etapa de extração. No processo de reextração, obteve-se 67% de reextração de ítrio da fase orgânica para a fase aquosa com o emprego de HCl 5,0 mol/L na relação de fase O/A = 1. A partir da curva de equilíbrio de reextração, determinou-se que são necessários no mínimo 12 estágios de reextração para se reextrair todo o ítrio da fase orgânica. Após definidas as melhores condições de extração, lavagem e reextração na etapa descontínua, realizou-se cinco ensaios contínuos de extração por solventes em escala micro piloto até se atingir a condição ótima de separação dos elementos em estudo. A melhor separação foi alcançada quando o circuito operou com três estágios de extração, sete de lavagem e quinze de reextração. Ao final do processo obteve-se um rafinado com 0,55 g/L de Eu, 16,7 g/L de Zn e concentração de Y menor que 0,001 g/L. No reextrato, a concentração de Y é de 41,4 g/L e 0,06 g/L de Eu, enquanto que a concentração de Zn foi menor que 0,001 g/L. / This work deals with the study of the recovery of europium and yttrium from discarded computer monitors through hydrometallurgical techniques. It comprises three phases: (i) acid leaching of the coating powder of the monitor screens CRT; (ii) separation of the concerning elements through solvent extraction in a laboratory bench scale discontinuous tests, and (iii) optimisation of phase ii in a micro pilot scale continuous tests. In the acid leaching phase, it was investigated the influence of the leaching agents, the relation acid/sample, time and temperature of the reaction in the percentage of solubilisation of europium and yttrium from the studied residue. The maximum solubilisation achieved (98 w/t%) occurred when H2SO4 in an acid/sample relation of 1250g/kg at room temperature (25 C), 10% of solids and mechanical agitation for 30 minutes were used. The liquor obtained in the leaching process, containing 11.9 g/L of yttrium and 0.72 g/L of europium, was submitted to solvent extraction discontinuous experiments aiming at the separation of the two metallic ions. The behaviour of the following organic extractants - DEHPA, IONQUEST 801, CYANEX 272 and PRIMENE JMT was investigated in relation to the performance of the extraction of the concerned species. DEHPA in concentration of 1.0 mol/L showed to be more efficient in the separation of the pair Y/Eu, with a separation factor equal to 111,4 for phase relation A/O =1, under mechanical agitation for 10 minutes. Based on the McCabe-Thiele diagram, it could be observed that two extraction stages in the relation A/O =1.1 were enough to extract all the yttrium in the aqueous phase to the organic phase, whereas the europium remains in the aqueous phase. In the loaded organic scrubbing, a H2SO4 0.75 mol/L solution in the relation phase O/A of 5 proved to be sufficient to remove all the co-extracted species in the extraction phase. In the stripping phase, 67% of the yttrium extraction was obtained from the organic phase to the aqueous phase by employing HCl 5.0 mol/L in the relation phase O/A = 1. From the stripping isotherm, it was determined that at least 12 stages of stripping are necessary in order to extract all the yttrium in the organic phase. After defining the best extraction, scrubbing and stripping conditions in the discontinuous phase, five continuous solvent extraction experiments were carried out in a micro pilot scale, until the optimum condition for separation of the elements under study was achieved. This degree of separation was attained when the circuit operated with three separation stages, seven washing stages and fifteen stripping phases. At the end of the process, a raffinate containing 0,55 g/L of Eu and 16,7 g/L of Zn and a pregnant stripping solution with 41,4 g/L of Y and 0,06 g/L of Eu was achieved.