A study of drop size distribution was carried out in a spray column by photographing the drops either through a round column or through a short square column inserted into the round column. A close-up photography technique was used and optical distortion of the round column taken into account. The drops were assumed to be oblate spheroids and a preliminary study of drop shape was undertaken to find the limitations of the oblate spheroid hypothesis. Drop size frequency distribution curves were drawn up at start-up and steady-state conditions and for one set of flow rates. The distribution was analysed in terms of the shape of the curves, mean values with confidence limits and spread of values. Volume-surface diameters were calcu-lated, leading to the determination of interfacial area of contact between the two phases and the calculation of mass transfer coefficients without an included area factor. Throughout the work the drops were treated in terms of spheres of equal volume and the bulk of the calculations was carried out on a digital computer. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The production of uniform-sized drops without small follower drops or "trailers" in liquid-liquid systems was studied using a periodic injection technique for dispersing one liquid through a sharp edged nozzle into the other. Previous investigators using a continuous flow technique found that uniform sized drops without trailers were limited to systems of higher interfacial tension. The effects of nozzle inside diameter, nozzle material, and of velocity-time profile of the dispersed fluid through a nozzle at drop formation were examined using two systems; n-butanol and water of very low interfacial tension, and methyl isobutyl ketone and water of low interfacial tension. These two systems were chosen so that the results of this study could be integrated with other work. The velocity-time profiles were obtained by using a positive displacement bellows pump, the stroke of which was controlled by a cam follower through a variable ratio linkage using three different cam profiles. The conditions under which uniform sized drops without trailers were formed, were located for both systems. The effects of surface active contaminants and the wetting of the nozzle tip by the dispersed phase were considered. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A study has been made of sampling techniques in a liquid-liquid extraction spray column using first a bell-shaped and a hook-shaped probe for the dispersed phase and for the continuous phase respectively. Later a piston method was attempted for the dispersed phase. The main interest in this research was the point concentration inside the column. At first, the time to reach steady state was considered in the absence of sampling. Later on, the rate of purging and sampling was varied for the probes up to 14.2 cc./min. for the continuous phase and 28.2 cc./min. for the dispersed phase. These rates were not sufficient to disturb the steady state. The measured point concentration was studied as a function of rate of sampling. Coalescence at the dispersed phase (bell-shaped) probe entrance did not take place. Finally, a piston sampler was set up and used in conjunction with the continuous phase (hook-shaped) probe as a second way to obtain point concentrations of the dispersed phase to compare with the results obtained with the bell-shaped probe. From these experiments, it can be concluded that sampling rate, varied from zero to 34.0 cc./min. for the continuous phase and from zero to 28.0 cc./min. for the dispersed phase, does not influence the point concentrations measured for column flows of 54.8 ft³/hr.-ft² and 72.4 ft³/hr.-ft² for the water and ketone phases respectively. The point concentration of the dispersed phase measured with the piston do not check definitively the results obtained with the bell-shaped probe; they do indicate that such agreement is fairly probable. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A study was made on the back mixing or circulation in the continuous phase of a spray type liquid-liquid extraction tower. Concentration profiles of both continuous and dispersed phases were obtained by internal sampling. Mass transfer data are presented for the transfer of acetic acid between water and methyl isobutyl ketone in the 1.5-in. I.D. columns of three different heights. Considerable circulation in the continuous water phase was observed which resulted in the reduction of the driving force for mass transfer. A driving force correction factor, F(m), was obtained from the H.T.U. data using a simplified picture of behaviour at the interface. The height of the tower did not seem to have any effect on F(m). The overall H.T.U. values, obtained from the experimental profiles, were correlated with the flow rates. The end effect due to the agitation and coalescence of the drops at the interface was measured. This end effect was correlated with the overall capacity coefficients and the dispersed phase flow rates. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Le mercure est un élément très particulier connu par sa densité et sa pression de vapeur élevé. C’est un élément omniprésent dans l'environnement et considéré comme un polluant mondial. Dans les eaux naturelles, le mercure est présent à des concentrations très faibles. Pour cette raison, un grand nombre de techniques analytiques ne permettent pas sa mesure directe, ce qui nécessite souvent une étape de préconcentration. La première partie de cette étude est axée sur le développement des méthodes analytiques pour la mesure du mercure par extraction en phase solide. Deux méthodes analytiques ont été développées, une technique basée sur le mécanisme d'échange d'anions en utilisant l'ICP-MS (Inductively Coupled Plasma Mass Spectrometry) et Une autre basée sur l'extraction en phase solide de mercure en utilisant le 5-phenylazo-8-hydroxyquinoline et la détection par CV-AFS (Cold Vapor Atomic Fluorescence Spectroscopy). La dernière partie de ce travail est consacrée à l’étude de la distribution et le comportement biogéochimique du mercure dans les rivières de la Deûle et de la Lys (Nord de France). Les résultats obtenus montrent des concentrations élevées en mercure total (HgT) dans la Deûle, site contaminé par les activités de l'ancienne fonderie "Metaleurop". Les concentrations mesurées dans la Lys sont beaucoup plus faibles. Bien que les sédiments de la Deûle soient très chargés par HgT par rapport aux sédiments de la Lys, des pourcentages de methylmercure beaucoup plus élevés ont été trouvées dans la Lys. / Mercury is a very particular element conferred by its high density and vapor pressure. It is a ubiquitous element in the environment and considered as global pollutant. Mercury is among the most hazardous environmental pollutants, given by its organic form, methylmercury (MeHg or CH3Hg). In natural waters, mercury is present at very low concentrations. For this reason, most analytical techniques do not achieve accurate direct measurement of Hg which necessitates preconcentration to meet their limit of detection. The first part of this study focuses on the development of analytical methods for the measurement of mercury by solid phase extraction. Two analytical methods have been developed; one based on the anion exchange mechanism using ICP-MS (Inductively Coupled Plasma Mass Spectrometry) and the other one based on the solid phase extraction of mercury using 5-phenylazo-8- hydroxyquinoline and detection by CV-AFS (Cold Vapor Atomic Fluorescence Spectroscopy). Part of this work also includes the distribution and biogeochemical behavior of mercury in rivers of the Deûle and Lys (Northern France). The results have showed high concentrations of total mercury (HgT) in the Deûle contaminated by a former smelter "Metaleurop". The concentrations of HgT measured in the Lys are much lower. Although Deûle sediments are highly burdened with HgT as compared to Lys sediments, much higher percentage of methylmercury is found in Lys River. Suspended particles are the major Hg carrier phase and transporters of Hg pollution from Deûle to Lys River.

Depuis l’explosion de l’industrie chimique au début du XXème siècle et l’utilisation de produits de synthèse, des quantités croissantes de substances chimiques, n’ont cessé d’être émises dans l’environnement. Toutefois, dans les dernières décennies, il y a eu une préoccupation croissante au sujet du sort de ces produits chimiques qui menacent la ressource en eau. L’accroissement des connaissances sur la performance analytiques et les données toxicologiques sur les produits actifs a conduit les autorités dans les pays industrialisés et en développement à imposer diverses restrictions. La surveillance des contaminants dans les milieux aquatiques a été mise en place pour atteindre le bon état écologique des milieux. Parmi les polluants organiques les plus dangereux et les plus couramment détectés dans les milieux aquatiques, on trouve les hydrocarbures aromatiques polycycliques, leurs dérives et les pesticides. Ces contaminants présents à l’état de trace dans les milieux aquatiques. Leurs analyses nécessitent des méthodes analytiques appropriées à la fois spécifiques et sensibles. Les travaux de cette thèse s’orientent ainsi dans une direction visant à développer des méthodes analytiques pour l’extraction de plusieurs familles de contaminants organiques (pesticides, hydrocarbures …) présents dans l’eau et dans les sédiments. Un modèle mathématique Umetrics a été employé pour étudier l’influence de chaque paramètre intérêt. Comparé à des méthodes classiques, ce modèle permet de réduire le nombre d’expériences, et d’avoir des rendements très satisfaisants. Les méthodes optimisées ont été ensuite appliquées à étudier des milieux naturels en France et au Liban. / Since the explosion of the chemical industry in the twentieth century and the use of synthetic products, increasing amounts of chemicals, have continued to be released into the environment. However, in recent decades, there has been a growing concern about the fate of these chemicals that threaten water resources. Increased knowledge on the analytical performance and toxicological data on active products has led authorities in industrialized and developing countries to impose various restrictions. Monitoring of contaminants in aquatic environments has been put in place to achieve good ecological state of the environment. Among the most dangerous and the most commonly detected in aquatic organic pollutants, polycyclic aromatic hydrocarbons, their derivatives and pesticides. These contaminants present in trace amounts in aquatic environments. Analyzes require appropriate analytical methods to be both specific and sensitive. The objective of this thesis is to develop analytical methods for the extraction of several families of organic contaminants (pesticides, hydrocarbons ...) in water and sediment. A mathematical model Umetrics was used to study the influence of each interest parameter. Compared to conventional methods, this model reduces the number of experiments, and have very good yields. The optimized methods were then applied to study the natural environment in France and Lebanon.

L'extraction d'huile de graines d'oléagineux en milieu aqueux a pour principal objectif la suppression des solvants utilisés dans les industries de trituration. Pour extraire l'huile des graines, les mélanges enzymatiques et de nombreux paramètres physico-chimiques ont été étudiés. Deux plans d'expériences consécutifs, réalisés sur le M.I.A. ont permis de formuler des mélanges d'enzymes efficaces, constitués de 3 ou 4 préparations enzymatiques commerciales parmi les 25 retenues initialement. Cette démarche permet de réaliser des mélanges optimaux pour la dégradation des parois des graines étudiées. Les extractions d'huile font apparaître 4 phases après séparation par centrifugation : résidu solide, émulsion, phase aqueuse et huile libre. Les effets de différents paramètres physico-chimiques ont été évalués (broyage, temps, température, agitation, séparation...). Au final, l'huile libérée des graines à l'aide des mélanges formulés (85% de l'huile totale pour le colza, 92% pour le tournesol), la quantité de sucres fermentescibles produite (entre 60 et 80 g/l en fonction des conditions) ou encore la concentration de protéines solubilisées (supérieure à 30g/l) sont les résultats marquants de cette étude. Cette étude décryptant les conditions à mettre en œuvre pour maximiser l'extraction d'huile en phase aqueuse constitue un socle de connaissances permettant d'envisager le développement futur d'un bioraffinage complet des graines de colza grâce à la valorisation de chacun des co-produits huiles, protéines (napines du colza) et sucres fermentescibles. / The extraction of oil from oilseed in an aqueous medium aims to remove the solvents used in the crushing industry. To extract oil from seeds, the enzymatic mixtures and numerous physico-chemical parameters have been studied. Two consecutive experimental designs, realized on the A.I.M. prepared from treated seeds, allowed to select effective enzyme mixtures, consisting of 3 or 4 commercial enzyme preparations out of the 25 originally selected. This original approach, based on the use of statistical tools, allows to achieve optimal mixtures for the degradation of the walls of studied seeds. The extraction of oil shows 4 phases after separation by centrifugation: solid residue, emulsion, aqueous phase and free oil. The effects of different physico-chemical parameters were evaluated (grinding time, temperature, agitation, separation...). Finally, the oil released from seeds using enzymatic mixtures made (85% of the total oil for rapeseed, 92 % for sunflower), the amount of fermentable sugars produced (60 and 80 g/l depending on conditions) or the concentration of solubilized protein (greater than 30g/l) are the landmark results of this study. This study, decrypting the conditions to implement the maximization of oil extraction in aqueous phase, is an important whole of knowledge to contribute the future development of a complete biorefining of rapeseed and sunflower with the use of each co-products : oils, proteins (napins from rape) and fermentable sugars.

An experimental investigation was undertaken to study the factors affecting phase separation in a specially constructed, laboratory scale mixer-settler. Two phase systems were used: 1. A laboratory prepared HSLIX64N-copper phase system, similar to that used in commercial copper solvent extraction processes. 2. A phase system obtained directly from the uranium extraction circuit of the Key Lake Mining Corporation, Sask., millsite. A settler scale-up criterion relating dispersion band thickness to specific settler flow of dispersed phase, was found to have considerable merit. Besides being dependent on specific settler flow, the dispersion band thickness was found to be a function of the phase ratio (for system 2 only), dispersion introduction level (for system 2 only), and temperature. Mixing intensity had no appreciable effect with either system. Microscopic examination of the dispersion produced with system 2 revealed the existence of double dispersions; that is, drops within drops. A photomicroscopic technique was used to undertake a drop size investigation of the dispersion produced with system 2. Drop size was found to be independent of dispersion throughput, a weak function of impellor speed and a relatively strong function of the phase ratio. With the exception of organic continuous operation with system 1, it was possible, based on the holdup and drop size profile within the dispersion band, to distinguish two horizontal sublayers within the dispersion band. In the "even concentration sublayer", comprising the majority of the dispersion band, the holdup and average drop size is nearly constant throughout. In the "dense concentration sublayer", both the holdup and the average drop size increase sharply as the coalescence front is approached. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

L’entretien des cours d’eau génère des volumes conséquents de sédiments, qui, en zones urbanisées, sont souvent contaminés en métaux. Une fois curés, ces sédiments sont déposés à terre de façon pérenne ou transitoire ; se pose alors la question de leur impact environnemental. L’objectif de ce travail était d’évaluer l’évolution du potentiel mobilisable de métaux et les paramètres en jeu dans le vieillissement des dépôts. Ce dernier a été simulé en conditions contrôlées au laboratoire à l’aide de deux protocoles de vieillissement : le premier visant à simuler un dépôt en conditions drainantes, le second en conditions hydromorphes. La mise en solution des métaux et l’évolution de leur distribution dans les compartiments de la phase solide ont été suivies au cours du temps. La mise en dépôt provoque un départ rapide de Cd, Cu, As et Zn vers le compartiment matière organique, associations stables avec le vieillissement du dépôt sauf pour le Cd. Le transfert de Cd, Cu, As et Pb vers le compartiment oxyhydroxydes intervient plus tardivement et ces associations perdurent avec le temps. Seule l’association Zn-oxyhydroxydes est rapide mais elle est instable au cours du temps. Le compartiment acido-soluble devient rapidement prépondérant pour le Zn, le Cd et le Pb suite à la mise en dépôt et le reste avec le vieillissement. Les conditions de dépôt ont un impact mineur durant les premiers temps suivant la mise à terre. Par contre, avec le temps de dépôt, les conditions d’hydromorphie entraînent un départ de quantités plus élevées de Cd, Cu et Zn vers les eaux de drainage et dans le compartiment échangeable du sédiment par rapport au dépôt en conditions drainantes. / Canal dredging generates high volumes of sediments which are often heavily contaminated with metals, especially in industrialized zones. Dredged sediments are usually deposited on land for long or temporary periods, and may impact surrounding environments. The aim of this study was to assess the potential of metal mobilisation during the ageing of sediment deposits. Sediment ageing was simulated in laboratory under controlled conditions with two protocols of wetting-drying : le first one simulated a sediment disposal in drained conditions and the second one hydromorphic conditions. The solubilisation of metals and their speciation in solid phase were followed over time. The distribution of metals was determined by selective dissolution. Sediment deposit on land leads to a fast transfer of Cd, Cu, As and Zn into the organic matter pool and these associations are stable with time excepted for Cd. The transfer of Cd, Cu, As and Pb into the oxyhydroxydes pool takes place later on following the disposal of sediment, excepted for the Zn-oxyhydroxides association, which is rapid but not stable with time. The acido-soluble pool becomes rapidly predominant for Zn, Cd and Pb after the sediment disposal and persists over time. Deposit conditions have no impact during the first time of the deposit. But, with time, hydromorphic conditions lead to a transfer of higher quantities of Cd, Cu and Zn into draining water and into exchangeable positions than the deposit in drained conditions.

Magister Scientiae Dentium - MSc(Dent) / It is common practice to remove impacted mandibular third molars due to pathology associated with these impactions. Alternatively, impactions can be treated conservatively through a closely guarded follow-up regiment. However, many symptoms associated with impacted third molars may be prevented by elective removal of potentially problematic teeth. To determine the risk of developing pathology associated with impacted mandibular third molars, a ransom sample of 200 pantomographs were analyzed displaying 324 impactions from patients who presented for treatment at the Maxillo-Facial and Oral Surgery Department, Faculty of Dentistry, University of the Western Cape. / South Africa