Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / This study involved the preliminary investigation into the potential liquid-liquid extraction of Os(IV/III) from hydrochloric acid solutions with ligands of type N,N-dialkyl-N′-acyl(aroyl)thioureas (HL), and ultimate selective pre-concentration and separation of Os(IV/III) from the other platinum group metals. Investigations have also been focused towards understanding the speciation of Os(IV) in hydrochloric acid medium. A series of osmium complexes with ligands of type HL have been synthesised and characterised. This has been done with a view towards understanding the interaction of Os(IV/III) with the HL ligands, and what the resultant stereochemical influences would be on the solvent extraction capabilities of the ligands. The structures of two novel osmium-containing compounds have been verified by means of X-ray crytallography. Firstly, the ion pair OsCl6[(C4H9)4N]2 was obtained as a result of liquid-liquid extraction experiments. Secondly, the only known example (in our knowledge) of an Os(III) - N,N-dialkyl-N′- aroylthiourea complex, in this case tris(N,N-diethyl-N’-benzoylthioureato)osmium(III), was successfully synthesised and characterised. Lastly, preliminary studies into the substitution reactions of ruthenium-polypyridine complexes with N,N-dialkyl-N′-acyl(aroyl)thioureas were conducted. A series of cis-bis(2,2′-bipyridine)(N,N-dialkyl-N′-acyl(aroyl)thioureato)ruthenium(II) complexes have been successfully synthesised and characterised. The electronic absorption behaviour of the formed complexes have been investigated in detail via UV-Vis spectrophotometry.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / This study describes the development of simplified analytical methods for the analysis of trace quantities of selected naturally occurring target compounds in complex biological matrices by stir bar sorptive extraction (SBSE) and gas chromatography/mass spectrometry (GC/MS). SBSE facilitates the direct extraction of organic compounds from aqueous samples by allowing the solutes to partition between the aqueous phase and a glass stir bar that is coated with a layer of polydimethylsiloxane (PDMS). The partitioning of polar compounds into the PDMS coating was enhanced by using different derivatization techniques in combination with SBSE. The derivatization of polar functional groups was performed with ethyl chloroformate, acetic acid anhydride, and O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine directly in the aqueous samples. Headspace derivatization of compounds containing a secondary alcohol group was performed directly on the stir bar coating in the presence of acetic acid anhydride vapors. The derivatized compounds were thermally desorbed (TD) and analyzed on-line by GC/MS. A number of experimental parameters, including salt addition, temperature and time were optimized to improve the recovery of the derivatized compounds by SBSE. The optimized methods were validated in terms of linearity, precision, and detection and quantitation limits prior to performing the quantification. Trace levels of tuberculostearic acid, a marker of tuberculosis, was detected in sputum samples that were decontaminated and concentrated before being analyzed by SBSE-TD-GC/MS. The method is sufficiently sensitive to detect the marker without the need to culture the organisms, namely M. Tuberculosis. The analysis of 4-hydroxynonenal has also been demonstrated by detecting trace levels of this oxidative stress marker in urine samples obtained from healthy volunteers. Furthermore, abnormally low testosterone/epitestosterone ratios were detected in a group of HIV positive patients by means of SBSE-TD-GC/MS. Further research is required to determine the clinical significance of this finding in the context of HIV infection. Finally, the excessive urinary excretion of estrone and 17β-estradiol following the administration of a high dose of the conjugated equine estrogens to a female volunteer has also been demonstrated.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Trace amounts of soluble Pt(II/IV) ions are not recovered using current refining processes. There are both economic and environmental incentives to recover these Pt(II/IV) ions from effluent. The work presented in this dissertation was aimed at producing functionalised electrospun nanofibre webs for the extraction of trace amounts of Pt(II/IV) ions in the form of [PtCl6]2- from acidic solutions. An insoluble, low molecular weight oligomeric compound, poly(N-terephthaloylthiourea)-N’,N’-piperazine, was synthesised from relatively inexpensive starting reagents using a “one-pot” two step synthesis procedure. Interest in this compound lies in its ability to extract Pt(II/IV) ions from acidic, chloride-rich solutions, as may be encountered in real process solutions in platinum group metal refineries. The product was isolated and characterised with an array of techniques, including GPC, elemental analysis, 1H and 13C NMR, as well as FTIR, and it was found to be a mixture of various molecular weight fractions with a degree of chemical variance between oligomer chains. The poly(N-terephthaloylthiourea)-N’,N’-piperazine was blended with polyacrylonitrile (PAN) and electrospun using both the classical single needle approach as well as a high throughput free-surface electrospinning process, called ball electrospinning. The nanofibres consisted of the oligomer which provided the affinity for [PtCl6]2- while PAN provided sufficient polymer chain entanglement which allowed the formation of fibrous structures. Two different solutions were found to produce nanofibres with the desired dimensions, namely: 6 wt% and 8 wt% PAN solution, both having a PAN to oligomer ratio of 7:3. The fibres produced by needle electrospinning and ball electrospinning had average fibre diameters of 172 ± 35 nm and 210 ± 49 nm, respectively. The ball electrospinning process had 86 times greater fibre production rates compared to needle electrospinning. The effects of three experimental conditions on the recovery of Pt(II/IV) ions by the poly(N-terephthaloylthiourea)-N’,N’-piperazine-containing nanofibres were determined. The conditions were: (i) the effects of specific surface area and available coordination sites over time, (ii) the effect of extraction temperature, and (iii) the effect of hydrochloric acid (HCl) concentration on [PtCl6]2- extraction. Increased availability of coordination sites caused an increase in Pt ion extraction. The Pt ion extraction also increased from 0.007 g to 0.023 g for each gram of nanofibres used as the temperature was increased from 20 °C to 60 °C when using a 114 mg/L Pt stock solution. The HCl concentration had no effect on Pt ion extraction when varied between 1.0 x 10-3 M to 1 M, while increased extraction as well as fibre damage was caused at HCl concentrations greater than 1 M. Nanofibres containing an oligomeric compound with affinity for [PtCl6]2- in acidic solutions were successfully synthesised and used to extract trace amounts of Pt(II/IV) ions from solutions under various conditions. / AFRIKAANSE OPSOMMING: In huidige verfynings prosesse word spoorelemente van oplosbare Pt(II/IV) nie herwin nie. Daar is beide ekonomiese en omgewings insentiewe om hierdie Pt(II/IV) ione te verhaal uit die afval oplossings. Hierdie tesis was gemik daarop om funksionele elektrospinde nanovesel webbe te produseer vir die herwinning van Pt(II/IV) ioon spoorelemente in die vorm van [PtCl6]2- uit aangesuurde oplossings. ‘n Onoplosbare oligomeriese verbinding met ‘n lae molukulêre gewig, poly(N-terephthaloylthiourea)-N’,N’-piperazine, was uit relatief goedkoop begin reagense gesintetiseer deur gebruik te maak van ‘n “een-pot” twee stap prosedure. Die belangrikheid van die verbinding lê in sy vermoë om Pt(II/IV) ione uit aangesuurde, chloried-ryke oplossing te onttrek, soos wat in alledaagse afval oplossings van platinum-groep metalurgiese raffinaderye ondervind kan word. Die sintese produk was geisoleer en gekarakariseer deur gebruik te maak van ‘n verskeidenheid tegnieke, waaronder GPC, elementêre analise, 1H en 13C NMR sowel as FTIR, en daar was bepaal dat die produk bestaan uit ‘n mengsel van verskeie molukulêre gewig kettings met ‘n mate van chemiese variansie tussen hulle. Die gesintetiseerde oligometriese verbinding was gemeng met poliakrielonitriel (PAN) en elektrospin deur gebruik te maak van beide die klasieke naald spin proses, sowel as ‘n hoë-produksie vrye oppervlak spin proses, genaamd die bal elektrospin proses. Die nanovesels bestaan uit die oligomeer wat die affiniteit vir die [PtCl6]2- voorsien terwyl die PAN genoegsame polimeer ketting verstrengeling veroorsaak het om die veselagtige struktuur te vorm. Nanovesels met die gewensde dimensies was gevorm deur die elektrospin proses toe te pas op twee verskillende oplossings, naamlik: ‘n 6 massa persent PAN en ‘n 8 massa persent PAN oplossing, beide met ‘n PAN tot oligomeer verhouding van 7:3. Die vesels geproduseer deur die naald en bal elektrospin prosesse het ‘n gemiddelde vesel deursneë gehad van 172 ± 35 nm en 210 ± 49 nm, onderskeidelik. Die bal spin proses het egter ‘n 86 keer groter produksie kapasiteit van vesels gehad in vergelyking met die naald spin proses. Die effek van drie verskillende toestande op die effektiwiteit van die nanovesels, wat poly(N-terephthaloylthiourea)-N’,N’-piperazine bevat, om Pt(II/IV) ione te onttrek uit die oplossings was ondersoek. Die toestande was: (i) die effekte van spesifieke oppervlak area asook beskikbare ontginnings setels oor tyd, (ii) die effek van die ontginnings temperatuur, en (iii) die effek van die soutsuur (HCl) konsentrasie op die Pt ioon ontginning. ‘n Toename in die beskikbaarheid van die ontginnings setels het gelei tot ‘n toename in die Pt ioon ontginning. Die Pt ioon ontginning het toegeneem van 0.007 g tot 0.023 g vir elke gram van nanovesels gebruik soos die temperatuur verhoog was van 20 °C tot 60 °C wanneer ‘n 114 ppm (m/v) Pt ioon oplossing gebruik was. Daar was geen effek op die Pt ioon ontginning toe die HCl konsentrasie tussen 1.0 x 10-3 M en 1 M HCl varieer was nie, alhoewel daar by konsentrasies hoër as 1M ‘n verhoogde ontginning sowel as vesel skade was. Nanovesels wat ‘n oligemetriese verbinding bevat met ‘n affiniteit vir [PtCl6]2- in ‘n aangesuurde oplossing, was suksesvol gesintetiseerd en gebruik om spoorelemente van Pt(II/IV) te onttrek onder verskillende omstandighede.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

The experimental work conducted in this thesis was aimed at determining the thermodynamic quantities associated with the formation of complexes formed between various metal ions and KELEX 100, a ligand which is used commercially for liquid - liquid extraction. In order to accomplish this, the beats of protonation of the ligand KELEX 100 were determined calorimetrically at 25°C in a partially aqueous medium of75% (v/v) l,4-dioxane and at an ionic strength of 0.1 mol dm·3• Extraneous heat effects that usually accompany complex formation were accounted for by measuring each heat contribution separately. The complexation of the lead (II), cadmium (II) and nickel (II) ions with KELEX 100 was studied in 75%(v/v) l,4-dioxane medium. The enthalpies of complexation were measured calorimetrically and calculated using the program LETAGROP KALLE. These results were combined with the values of the Gibbs free energies available in the literature for these systems to yield the entropies of complexation. In all calorimetric determinations a constant ionic strength of 0.1 mol dm'3 and a temperature of 25°C was maintained. The calculated enthalpies and entropies are discussed in terms of a number of factors that affect the thermodynamics of the systems. These factors include the structure of the ligand molecule, the nature of the donor atoms, the degree of substitution on the ligand and the properties of the metal atom such as charge and size, and the nature of the solvent. The cumulative enthalpies and entropies of formation of the metal-ligand complexes are favourable, Le. complexation is accompanied by a decrease in enthalpy and an increase in entropy. However, the enthalpy changes contribute more to the stability of the complexes and hence are the driving forces for complex formation. In the case of the Cd(II) ion, the enthalpy and entropy changes are similar. The cumulative enthalpies of formation increase (Le., become more exothermic) in the order: Ni > Pb > Cd while the reverse order is found for the entropies of formation. The smaller enthalpy change for the Cd(II) complex is possibly due to the weak interaction between the 'soft' Cd(II) ion and the 'hard' KELEX 100 ligand while the decrease in entropy for the Ni(II) may be due to the loss of fewer solvent molecules from the Ni(II) hydration sphere on complexation with the ligand. The stepwise entropy and enthalpy changes for the formation of the ML+ complexes are dependent on the ionic radius of the metal ion. However, no linear correlations exist between the cumulative entropy or enthalpy changes of formation of the ML complexes and the size of the metal ion. The stepwise and cumulative enthalpies of formation appear to be largely independent of steric effects of the bulky alkyl substituent on the KELEX 100 ligand. The increased steric hindrance of the substituent decreases the cumulative entropy change for the formation of the Ni(II) complexes. However, in the case of the Pb(II) complexes, steric effects do not appear to affect the cumulative entropies of complex formation. / Thesis (M.Sc.)-University of Natal, 1995.

Separation processes are fundamental to all chemical engineering industries. Solvent separation, either liquid-liquid extraction or extractive distillation, is a specialised segment of separation processes. Solvents can be used either to optimise conventional distillation processes or for azeotropic systems, which can not be separated by conventional means. This work focuses on the performance of monoethanolamine (MEA) as a solvent in extractive distillation. Furthermore, the methodology of solvent evaluation is also studied. The preliminary assessment of solvent selection requires the determination of selectivity factors. The selectivity factor is defined as follows: P• = y,." . y, where y" is the activity coefficient at infinite dilution of the solute in the solvent. Subscript 1 and 2 refer to solute 1 and 2. A large selectivity factor implies enhanced separation of component 1 from 2 due to the solvent. Activity coefficients at infinite dilution were determined experimentally (gas-liquid chromatography) and predicted theoretically (UNIFAC group contribution method) for twenty-four solutes at three temperatures. Solutes used were alkanes, alkenes, alkynes, cyclo-alkanes, aromatics, ketones and alcohols. Most of this experimental work comprises data for systems which have not been measured before. Predicted and experimental values for y' were compared. For systems such as these (with polar solvents and non-polar solutes), UNIFAC results are not accurate and experimentation is vital. The experimental selectivity factors indicated tihat MEA could be an excellent solvent for hydrocarbon separation. Three binary azeotropic systems were chosen for further experimentation with MEA n-hexane (1) - benzene (2): fJ,~ = 31. Compared to other industrial solvents this is one of the largest values and MEA could serve as an excellent solvent. cyclohexane (1) - ethanol (2): fJ,~ = 148. This high value indicates an excellent solvent for this system. Acetone (1) - methanol (2): fJ,~ = 7.7. Further work involved vapour-liquid equilibrium experimentation at sub-atmospheric pressures in a dynamic recirculating stil l. The binary components with a certain amount of MEA were added to the still. The vapour and liquid mole fractions for the binary azeotropic components were measured and plotted on a solvent-free basis. The results are summarised below: n-hexane - benzene: Amount MEA added to still feed: 2%. MEA improved separability slightly. Further addition of MEA resulted in two liquid phases forming. cyclohexane - ethanol: Amount MEA added to still feed: 5% and 10%. Two liquid phases were formed for cyclohexane rich mixtures. Addition of MEA improved separability but did not remove the azeotrope. acetone - methanol: Amount MEA added to still feed : 5%, 10% and 20%. The ternary mixture remained homogenous and separability improved with addition of MEA. The binary azeotrope was eliminated. Due to the hetrogenous nature of the cyclohexane - ethanol system liquid-liquid equilibrium experimentation was performed to complete the analysis. Viable separation processes are possible for (a) cyclohexane - ethanol mixtures and for (b) acetone - methanol mixtures using MEA as the solvent. Comparison of various solvents used for the separation of acetone from methanol was possible by constructing equivolatility curves for the ternary systems. Results showed that MEA may possibly be the best solvent for this extractive distillation process. This study provides the following results and conclusions: • New thermodynamic data, important for the understanding of MEA in the field of solvent separations, was obtained. • Results show that the UNIFAC contribution method cannot be used to accurately predict polar solvent - non-polar solute y«> values. Experimentation is essential. • Selectivity factors indicate that MEA could be an excellent solvent for hydrocarbon separation. • The separation of the azeotropic cyclohexane - ethanol mixture is possible with a combination of extractive distillation and liquid-liquid extraction or simply liquid-liquid extraction using MEA as the solvent. • The separation of the azeotropic acetone methanol mixture is possible with extractive distillation using MEA as the solvent. The solvent MEA is possibly the best solvent for this separation. / Thesis (M.Sc.Eng.)-Univeristy of Natal, Durban, 2000.

Submitted in fulfillment of the academic requirements for the degree of Master of Applied Sciences (Chemistry), Durban University of Technology, Durban, South Africa, 2016. / Globally there is a drive for the use of renewable materials for the production of biofuels or high-end value chemicals. The current production of chemicals from crude oil refining is unsustainable and leads to global warming effects. Biomass is the most attractive renewable energy source for biofuel or fine chemical production. Sugarcane bagasse is a by-product of the sugar milling industry and is abundantly available. In this study lignin was sequentially extracted using ionic liquids. The ionic liquids (ILs) 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) and triethylammonium hydrogen sulfate ([HNEt3][HSO4]) were used to fractionate the sugarcane bagasse. The pre-treatment of sugarcane bagasse was carried out at different temperatures ranging from 90 - 150 0C and reaction times ranging from 1 - 24 h in a convection oven at a 10 % biomass loading. Both ILs were able to dissolve the raw bagasse samples at 120 0C with [Emim][OAc] giving a lignin maxima of 28.8 % and a low pulp yield of 57 % after 12 h; [HNEt3][HSO4] gave a lignin recovery of 17.2 % and low pulp yield of 58.5 % after 6 h. Regenerated lignin was obtained by adding ethanol/ water to the mixture followed by vacuum filtration. The regenerated pulp materials were characterized by Scanning Electron Microscope (SEM) to study the morphology; Fourier Transform Infrared Spectroscopy (FTIR) to study the characteristic bands and thermal analysis to study the thermal stability. / M

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

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2014. / Heavy metal pollution is an increasing phenomenon and contamination of these heavy metals has detrimental effects on the environment and humans. The concentrations of metals in the soil, leaves, stem bark and flowers of Moringa ovalifolia sampled from Okahandja, Okaukuejo, Halali and Tsumeb in Namibia were investigated. Acid digestion of all samples was performed utilising the microwave technique. Determination of elements from the extracts were analysed by inductively coupled plasma - optical emission spectroscopy (ICP-OES). No lethal amounts of heavy metals were found in the soil, leaves, stem bark and flowers of Moringa ovalifolia. The results from Moringa ovalifolia was compared to spinach from another similar study. On average, Moringa leaves contained more or less similar amounts of Zn (29.4 mg kg-1) and Cr (13.2 mg kg-1) but higher higher amounts of Fe (263.8 mg kg-1) concentrations than spinach, with values of Zn (30.0 mg kg-1), Cr (20.0 mg kg-1) and Fe (190 mg kg-1) from a previous study. In this study, selected statistical methods such as correlation analysis and principal component analysis were used to identify the origin of these metals in the soil, leaves and stem bark collected from the Moringa farm, national parks and the road side in Namibia. From the correlation analysis, it was found that Co, Mg, Cr and Mg pairs were highly significant to each other. The principal component analysis revealed that heavy metals gave 53.41% of the total variance in factor 1. Sources of Mg and Ni could be from vehicle emissions. Factor 2 revealed As, Co, Al, and Si contributing to a total variance of 25.15% Co suggesting that the metals present could be as a result of geologic sources. This iii study proves that statistical analysis may provide a scientific foundation for the observation of heavy metal accumulation in samples. Pressurised hot water extraction (PHWE) was used for the extraction of bioactive compounds from the leaves and stem bark of Moringa ovalifolia and Moringa oleifera samples. The aim of the study was to assess the effect of temperature and extraction process of the Moringa extracts on Staphylococcus aureus (S. areus), Enterococcus faecalis (E. faecelis) and Pseudomonas aeruginosa (P. aeruginosa). The antibacterial activities of the extracts at varying temperatures were evaluated using the disk diffusion method where the zones of inhibition were recorded. ANOVA, which was calculated at a significance level of 0.05, was used to analyse the data. Antimicrobial activity of the stem bark extracts and leaf extracts from different sites extracted at 25˚C and 80˚C showed significant difference. As temperature increased, a decrease in inhibition was observed for stem bark extracts from different sites tested again S. areus, E. faecelis and P. aeruginosa. When the PHWE stem bark extracts collected in Tsumeb, were compared with ethanol and cold water extractions, the PHWE had more activity than other two methods. This proves that PHWE may be used as a novel extraction to get essential compounds from indigenous plant materials.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN SCIENCE AND ARCHIVES. Science copy in 2 v. / Vita. / Bibliography: leaves 320-331. / by Ronald Ted Kurnik. / Sc.D.