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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Structure and interaction of polymer thin films with supercritical carbon dioxide

Sirard, Stephen Michael, January 2003 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.
2

Liquid carbon dioxide extraction of various food flavors : evaluation and analysis /

Shinholt, Deven Lee January 2009 (has links)
Thesis (B.S.)--Butler University, 2009. / Includes bibliographical references.
3

Développement d’un procédé de traitement industriel des eaux salées, chimie et génie du procédé / Development of an industrial desalination process by solvent extraction, chemistry and chemical engineering

Dautriche, Bastien 03 March 2016 (has links)
Ce travail s’inscrit dans la convention CIFRE n°2012/0379 avec la startup Adionics pour le développement d’un procédé de dessalement par extraction liquide-liquide. La régénération de la phase organique est réalisée par désextraction du sel à chaud. Les isothermes de partage du NaCl, Na2SO4 et MgCl2 à 20 40 60 et 80°C ont été obtenues. Une stœchiométrie expliquant leur forme a été proposée et les constantes d’équilibre associées ont été déterminées. Les enthalpies d’extraction ont été déduites des variations des constantes d’équilibre avec la température.La prise en compte de l’effet de milieu en phase aqueuse a été réalisée à l’aide du modèle de Pitzer avec l’hypothèse des interactions spécifiques. Une correction pour les effets de milieu en phase organique a également été ajustée sur NaCl -Na2SO4 à 20 40 et 60°C.Les propriétés physico-chimiques du solvant (viscosité, masse volumique, chaleur spécifique, conductivité thermique, ...) ont été déterminées sur une plage de 20°C à 80°C. La tension interfaciale du solvant a également été obtenue à 20°C, avec de l'eau eau pure et salée. Une étude approchée de la solubilité du diluant en phase aqueuse a également été entreprise.Un prototype avec deux colonnes à garnissage de 4 mètres de haut a été élaboré pour tester la faisabilité du procédé en continu. L’extracteur a été modélisé par une cascade d’étages parfaitement agités avec prise en compte du mélange en retour. Les HUT (Hauteur d'une Unité de Transfert) expérimentales ont été comparées à celles calculées à l'aide de différentes corrélations des coefficients de transfert disponibles dans la littérature. Une adéquation satisfaisante a été obtenue entre modèle et expérience. Une réflexion sur le type d'extracteur doit être entreprise pour une amélioration de la performance de dessalement. / This work is a contribution to the development of an innovative desalination process by solvent extraction. The regeneration of the organic phase is achieved by desextraction of the salt at high temperature. Isotherms of distribution of NaCl, Na2SO4 and MgCl2 at 20 40 60 and 80°C were obtained. A stoichiometry able to account for their shapes was suggested and the associated equilibrium constants were determined. The extraction enthalpies were deduced from the variation of the constants with temperature.Non ideality in the aqueous phase was modeled with the Pitzer equations, simplified with the specific interaction principle. A thermodynamic correction to account for mixed salts effect in the organic phase was adjusted on binary data (NaCl, Na2SO4) at 20 40 and 60°C.Mechanical (viscosity, density) and thermal (specific heat, thermal conductivity) properties of the organic phase were characterised from 20 to 80°C. The interfacial tension was obtained at 20°C with pure water and filtrated natural seawater. The overall solubility of the solvant in water was measured. A prototype of the process with two extraction columns with a packed bed of 4 meters was tested. The HTU obtained were compared with a numerical model based on the classical stagewise backflow model expanded by a thermal balance.
4

Trace element contaminants in the Kuwait water production system

Al Anqah, Laila January 1996 (has links)
Fresh water in Kuwait is produced by non- conventional methods. About 95% of this water comes from desalinated seawater using multi-stage flash distillation technique and the remainder comes from underground brackish water. The blended water containes organic, inorganic and trace metal impurities within the recommended international standard limits. The purpose of this work is to identify the source of selected trace metals present in the drinking water in Kuwait. Chromium, copper, iron, lead, manganese, nickel, vanadium and zinc have been analysed using atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectroscopy (ICPMS). Efforts were made to improve the preconcentration of the selected metals and their separation from the high concentration of salts in seawater which affect the accuracy and cause major interference in the analysis. Solid-liquid extraction (chelex-100 resin) and liquid-liquid extraction (methyl iso-butyl ketone and freon) with and without back-extraction into nitric acid were investigated. Liquid-liquid extraction without back-extraction proved to give optimum recovery of the selected metals. Results confirmed that both AAS and ICP-MS are suitable for the analysis of trace metals in Kuwait's waters. Although AAS technique proved to be more accurate in analysing the selected metals than ICP-MS, the latter was adopted since its accuracy is acceptable (1.1-4.4%) and it is easier and faster than the former technique. The study revealed that the source of copper, iron, nickel and zinc is the construction materials of the distillation plants, while the source of lead and vanadium is the brackish water. Manganese and chromium concentrations are very low in all sources. No direct relationship between the metal concentration in the seawater and the distillate could be deduced.
5

Method development and Validation for the determination of selected Polycyclic Aromatic Hydrocarbons (PAHs) in water by Solid Phase Extraction and High Performance Liquid Chromatography

Xoliswa, Madlanga 12 February 2014 (has links)
Polycyclic Aromatic Hydrocarbons (PAHs) are one of the pollutants in the environment. They are organic compounds that consist of more than one aromatic ring (Kanchanamayoon & Tatrahun 2008). Due to less information forthcoming regarding the levels of PAHs in Vaal area, this study is to evaluate the levels of PAHs in the rivers around Vaal Triangle. Three river sites such as Vaal, Barrage and Klip Rivers were selected to investigate the concentration of polycyclic aromatic hydrocarbons in water. Validation of an analytical method is the process by which it is established by laboratory studies, that the performance characteristics of the method meet the requirements for the intended analytical application. (Stockl et al 2009). The validation parameters tested were, linearity detection limit of quantitation, sensitivity, accuracy, specificity, selectivity, robustness and ruggedness. PAHs can be determined using High Performance Liquid Chromatography (HPLC) which is a technique for separation, identification and quantification of components in a mixture. The following ten compounds were identified and quantified with a HPLC: naphthalene, acenaphthylene, phenanthrene, anthracene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h) anthracene and indeno(1,2,3-cd)pyrene. The linear calibration ranges from 0.1-5ppm.The linearity ranges between 0.9993-0.9999.Three reversed sorbent phases (Strata-X, MFC18 and C18) were tested for PAH retention efficiency. An optimised reverse solid phase extraction (SPE) method was used after conditioning the sorbent to extract and collect compounds of polycyclic aromatic hydrocarbons (PAHs) in river water samples. LC18 sorbent showed good recoveries after extracting PAHs standard mixture of 1 mg/l. The best performing eluting solvent was acetonitrile and very good percentage recoveries that ranged from 70% to over 100 % were obtained for eight compounds. Poor recoveries were also obtained for phenanthrene (61%) and benzo(b)fluoranthene (48%). The standard deviation ranged from 0.01 to 0.05 and the detection limits ranging from 0.01 – 0.17 mg/l were obtained. Average concentration ranges of PAHs identified within the study area were: phenanthrene (0.02 – 0.42 mg/l); anthracene (0.37 – 0.39 mg/l), fluoranthene (0.11 – 0.15 mg/l); benzo(b)fluoranthene (0.09 mg/l) and indeno(1,2,3-cd)pyrene (0.26 mg/l). However, naphthalene, acenaphthylene, benzo(k)fluoranthene, benzo(a)pyrene and dibenzo(a,h)anthracene were not detected.
6

Tensidbeeinflusster Metallionendurchtritt durch Flüssig-flüssig-Phasengrenzen im elektrischen Feld

Paeslack, Ralf 26 October 2009 (has links)
Die Effektivität der Reaktivextraktion als Verfahren zur Stoffabtrennung aus wässrigen Lösungen mit organischen Lösungsmitteln lässt sich durch den Zusatz weiterer Stoffe deutlich steigern. Das können Co-Ionen, Lösungsvermittler und Stoffe sein, die die Phasengrenzfläche beeinflussen. Wichtigste Vertreter der letzteren Gruppe sind Tenside, die die Grenzflächenspannung zwischen den Phasen verringern. Sie werden in der industriellen Technik bereits seit Jahrzehnten mit gleich bleibendem Erfolg angewandt. Dabei sind die Vorgänge an der Phasengrenze, die durch die Tenside beeinflusst werden, noch nicht vollständig geklärt. In diesem Umfeld ist auch die vorliegende Arbeit entstanden. Sie soll bereits am Lehrstuhl vorliegende Arbeiten ergänzen. Gegenstand der Untersuchungen ist der Einfluss von Tensiden auf die Extraktion von Schwermetallionen im elektrischen Feld, hier untersucht an dem kationischen Tensid Hexadecyltrimethylammoniumbromid (CTAB). Als Untersuchungsmethode wird die Polarographie verwendet. Der Ladungsdurchtritt durch die Grenzfläche Wasser/Quecksilber und deren Beeinflussung durch das Tensid werden für die Metallionen von Zink, Cadmium, Blei und Chrom bei unterschiedlichen pH-Werten untersucht. Es zeigt sich, dass die Modifizierung der Grenzfläche nur einen Teil der Beeinflussung ausmacht, weitere entstehen durch die chemische Modifizierung der vorhandenen Spezies. Weiterhin kann abgeleitet werden, dass trotz chemischer Verwandtschaft der eingesetzten Systeme eine klare Vorhersage der Beeinflussung nur begrenzt möglich ist. Der grundlegende Trend von Systemen mit chemisch ähnlicher Zusammensetzung ist zwar der gleiche, jedes System reagiert jedoch individuell in Abhängigkeit der genauen stofflichen Zusammensetzung und der Versuchsbedingungen, so dass stets konkrete Voruntersuchungen notwendig erscheinen.
7

Monitoring anti-infectives and antibiotic resistance genes : with focus on analytical method development, effects of antibiotics and national perspectives

Khan, Ghazanfar Ali January 2012 (has links)
Antibiotics are biologically active and are globally used in humans and animal medicine for treatment and in sub-therapeutic amounts as growth promoters in animal husbandry, aquaculture and agriculture. After excretion, inappropriate disposal and discharge from drug production facilities they enter into water bodies either as intact drugs, metabolites or transformed products. In water environments they promote development of antibiotic resistance genes (ARGs) which could serve as a reservoir and be horizontally transferred to human-associated bacteria and thus contribute to AR proliferation. Measurement of antibiotics has been revolutionized with the usage of solid phase extraction (SPE) for enrichment followed by Liquid chromatography mass spectrometry (LC-MS). On-line SPE coupled to LC-MS/MS has the advantages of high sample throughput, low sample preparation time and minimal solvent utilization.  Constructed wetlands (CWs) are potential alternatives to conventional treatment plants to remove organic pollutants. A study at Plönninge, Halmstad was performed to assess the impact of bacterial community pattern and development of resistance in spiked (n=4) and control (n=4). CWs were spiked with antibiotics at environmentally relevant concentrations continuously for 25 days. Shannon Index (H’) were used to determine the bacterial diversity and real-time PCR detected and quantified antibiotic resistance genes (ARGs) sulI, tetA, tetB, erm, dfrA1, qnrS and vanB and class 1 integrons intI1. No significant differences in bacterial compositions or in ARGs or integron concentrations could be discerned between exposed and control wetlands. A study conducted in Northern Pakistan showed that the antibiotic levels in most studied rivers were comparable to surface water measurements in unpolluted sites in Europe and the US. However, high levels of antibiotics were detected in the river in close vicinity of the 10 million city Lahore, e.g. 4600 ng L−1 sulfamethoxazole. Highest detected levels were at one of the drug formulation facilities, with measured levels up to 49000 ng L−1 of sulfamethoxazole for example. The highest levels of ARGs detected, sul1 and dfrA1, were directly associated with the antibiotics detected at the highest concentrations, sulfamethoxazole and trimethoprim. In the study in UK, sewage epidemiology surveillance is used to measure the oseltamivir carboxylate (OC), metabolite of oseltamivir (parent drug) in twenty four time proportional hourly influent samples from two WWTPs and then back-calculations were made to assess the compliance of drug.  Predicted users of oseltamivir, based on measured OC in waste water, ranged from 3-4 and 120-154 people for the two WWTP catchments, respectively, which are consistent with the projected use from national antiviral allocation statistics, 3-8 and 108-270, respectively. Scenario analysis suggests compliance was likely between 45-60% in the study regions.
8

Studium průniku PBDE a perfluorovaných sloučenin do vodních ekosystémů / Study of Exposure PBDE and Perfluorinated Compounds into Aquatic Ecosystem

Vondráčková, Ilona January 2015 (has links)
In the presented PhD. thesis, problems covering occurrence of polybrominated diphenyl ethers (PBDE) and perfluorinated compounds in the environment were solved. The study was focused on identification and further verification of optimal methods in order to determine PBDEs and perfluorinated compounds sampled from the aquatic ecosystem. Polybrominated diphenyl ethers belong to persistent compounds classified as main pollutants; within the environmental constituents, they have been observed particularly in the last decade. For these studies, there were selected surface water matrices and sediments taken in various localities within the river Svratka basin. The analyses were to demonstrate whether they accumulate and remain in these specific matrices for longer time. There we assessed the congeners of polybrominated diphenyl ethers as follows: BDE-28, 47, 66, 85, 99, 100, 153, 154 and 183. In order to isolate them from matrices, various extraction techniques were used, i.e., ultrasonic extraction, microwave extraction, and pressure solvent extraction. Gas chromatography method with electron capture detection (GC/ECD) was selected for determination. The accomplished studies also assessed basic chemical, physical and environmental characteristics of diphenyl ethers in the environmental constituents. The attention was also paid to perfluorooctanoic compounds (PFOA), (PFOS) and (FOSA); physico-chemical properties of these organic pollutants were characterised and their toxicological and environmental aspects were evaluated. Usability of extraction techniques (ultrasonic extraction, pressure solvent extraction, solid phase extraction) applied to PFCs isolation from sediments samples was assessed. Identification and quantification of these analytes were performed using a high performance liquid chromatography/mass spectrometry method (HPLC/MS). After that, the optimized methods applied to real samples. Surface water and sediments were sampled within the river Svratka basin, in particular, from 19 sampling localities. PBDE occurrence was confirmed in sediments samples from the Svratka river (g.kg-1), PBDE were not detected in the surface water samples, their concentrations were below the detection limit, resp.; perfluorinated compounds were not detected in sediments and water samples at all.

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