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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

L-DOPA production in a liquid membrane enzyme reactor: process development and modeling

Simmons, Donald Karl 05 1900 (has links)
No description available.
2

Non-newtonian conversion of type II emulsion liquid membranes-solving long-standing permeability, stability, and swelling problems

Gilbert, Christopher Donald 12 1900 (has links)
No description available.
3

Determination of amines and amine N-oxides in biological samples, particularly with supported liquid membranes for sample pretreatment

Lindegård, Boel. January 1994 (has links)
Thesis (doctoral)--Lund University, 1994.
4

Determination of amines and amine N-oxides in biological samples, particularly with supported liquid membranes for sample pretreatment

Lindegård, Boel. January 1994 (has links)
Thesis (doctoral)--Lund University, 1994.
5

The recovery of copper by tubular supported liquid membranes

Aziz, Mujahid January 2006 (has links)
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, Cape Town, 2006 / During recent years, the use of liquid membranes has gained general interest in the treatment of effiuents where solute concentrations are low and large volumes of solutions should be processed, and, if possible, without generating any secondary waste. Liquid membrane processes have been proposed as a clean technology, owing to their characteristics, i.e. high specificity, low energy and utilization. Two liquid membrane processes have been used in metal recovery, which are the liquid surfactant membrane (LSM), which corresponds to double water-in-oil emulsion and solid . supported liquid membranes (SLM), which are made by dispersing or impregnating the extractant within the pores of in.ert solid support. Previously, the recovery of eu (IT) in a SLM system was conducted by other membrane models such as hollow fibre, spiral and flat sheet. Only a small measure of success on scale-up and industrialization of these models has been attained. One of the disadvantages of the hollow fibre system was the small lumen size through which the feed needed to pass. Pores became clogged by suspended particles because the pressure drop over the small diameter augments lower flow rates and therefore, pre-filtering is necessary (Rathore, et al., 2001). In this study the behaviour of a tubular SLM reactor with an inner diameter of the lumen approximately fifty times bigger than that of the hollow fibre are used in order to solve the problem of clogging. This tubular reactor was incorporated in to a bench scale plant and proved successful in copper extraction. By observing transient data, mass transport coefficients were determined and compared to published values.
6

Development of liquid membrane extraction method and ion- imprinted polymers for the analysis and removal of arsenic and selenium in water

Mafu, Lihle, D. 25 February 2014 (has links)
M.Sc. (Chemistry) / Please refer to full text to view abstract
7

The use of crosslinked polyethylene for the manufacturing of membranes / Albertus Maritz van Wyk

Van Wyk, Albertus Maritz January 1999 (has links)
Increasing environmental awareness over the past decade as well as stringent environmental laws forced all factories to invest in water treatment processes for effluent treatment before discharge or re-use. Most of these effluent treatment processes utilize membranes as the physical. barrier for separation. The membranes used in water applications are expensive and alternative materials and production techniques will increase the viability of membrane separation processes. Experiments conducted on irradiated polyethylene showed that some of its properties were enhanced while others deteriorated. However, the enhanced properties make the polyethylene, in particular ultra-high molecular weight polyethylene, an ideal membrane material. The manufactured membranes were tested in extraction experiments, and satisfactory results were obtained. Permeation studies on the membranes compared favourably with similar studies done on commercially available membranes. An extraction rate of 1.08 g/(m2h) nickel was achieved. A preliminary cost evaluation showed that these membranes can be manufactured at a low cost (R13.45/m2). and can be applied as supported liquid membranes. Future research should focus on methods to decrease the brittleness and stiffness of the membranes. / Thesis (MIng)--PU for CHE, 1999
8

The use of crosslinked polyethylene for the manufacturing of membranes / Albertus Maritz van Wyk

Van Wyk, Albertus Maritz January 1999 (has links)
Increasing environmental awareness over the past decade as well as stringent environmental laws forced all factories to invest in water treatment processes for effluent treatment before discharge or re-use. Most of these effluent treatment processes utilize membranes as the physical. barrier for separation. The membranes used in water applications are expensive and alternative materials and production techniques will increase the viability of membrane separation processes. Experiments conducted on irradiated polyethylene showed that some of its properties were enhanced while others deteriorated. However, the enhanced properties make the polyethylene, in particular ultra-high molecular weight polyethylene, an ideal membrane material. The manufactured membranes were tested in extraction experiments, and satisfactory results were obtained. Permeation studies on the membranes compared favourably with similar studies done on commercially available membranes. An extraction rate of 1.08 g/(m2h) nickel was achieved. A preliminary cost evaluation showed that these membranes can be manufactured at a low cost (R13.45/m2). and can be applied as supported liquid membranes. Future research should focus on methods to decrease the brittleness and stiffness of the membranes. / Thesis (MIng)--PU for CHE, 1999
9

Determination of quinolones in bovine kidney using hollow-fiber supported liquid membrane extraction prior to liquid chromatography tandem mass spectrometry

Gaolape, Kefilwe Precious 10 1900 (has links)
Focus of this study was on the development of one of the faster, simpler, cost effective and environmentally friendly sample pre-treatment techniques which employs a supported liquid membrane, in this case a Hollow-fiber supported liquid membrane (HF-SLM) for determination of seven (7) quinolone antibiotics (enrofloxacin, ciprofloxacin, danofloxacin, difloxacin, norfloxacin, nalidixic acid and sarafloxacin) in bovine kidney samples followed by LC-MS/MS analysis. The key parameters of the method were optimized and the method was validated following the 2002/657 EC guidelines. The optimum HF-SLM conditions were therefore; NaH2PO4 as a donor phase at pH 7, 0.1% formic acid at pH 3 as acceptor phase. Triethylamine was the optimized liquid membrane and the stirring time was optimized at 1 hour. Separation of the 7 quinolones including 3 internal standards (enrofloxacin-d5, norfloxacin-d5 and difloxacin-d3) was carried out on a Phenomenex Kinetex 2.6 μm XB-C18, 100 mm x 4.6 mm, 100Å column. Validation parameters such as Correlation coefficients (r2) ranging from 0.9714-0.9975 were obtained, while limit of detection (LOD) ranged between 3-39 ug kg-1 and limit of quantification (LOQ) ranged between 10-130 ug kg-1. The obtained limits at which it can be concluded with an error probability of α = 95% that a sample is non-compliant (CCα) ranged from 28 – 422 ug kg-1 while CCβ; the smallest content of the substance that may be detected, identified or quantified in a sample with an error probability of β = 95%, ranged from 29 – 454 ug kg-1. The method was found to be reproducible with CVs ≤ 23 %. The tested samples from Botswana local abattoirs showed no presence of quinolone antibiotics when the method was applied to real bovine kidney samples. Hollow-fiber supported liquid membrane can therefore be used for extraction of biological samples since it is a “greener technique” which uses less solvent which are less harmful to the environment when disposed as compared to dispersive Solid Phase Extraction (dSPE). / Chemistry / M. Sc. (Chemistry)
10

Fases de membranas fluidas -L3 a partir de lipídio sintético e pentanol na região diluída - e o respectivo dialisado / Phases membrane fluid - L3 from synthetic lipid and pentanol and diluted in the region corresponding dialyzed

Medugno, Cláudia Conti 21 August 2018 (has links)
Orientador: Elias Basile Tambourgi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-21T02:38:39Z (GMT). No. of bitstreams: 1 Medugno_ClaudiaConti_D.pdf: 3413427 bytes, checksum: 721bb3035fab10b9b0a1619381a0b4e0 (MD5) Previous issue date: 2012 / Resumo: A fase L3 (esponja) foi observada no final dos anos 80 e representa uma nova classe de auto moldagem para sistemas surfactantes em água. Esse trabalho descreve a descoberta e a posterior caracterização de uma fase ternária composta do lipídio sintético catiônico brometo de dioctadecildimetil amônio (DODAB), pentanol e água, em uma região diluída. Esta é a primeira descrição de uma fase L3 preparada com um lipídio com uma cabeça polar relativamente pequena e duas cadeias de hidrocarboneto com 18 carbonos cada. A região no diagrama triangular pentanol/água/DODAB na qual a fase existe foi caracterizada utilizando as técnicas de isotropia óptica e anisotropia em relação a uma sonda de espectroscopia de ressonância paramagnética do elétron. A proposta de uma fase L3 foi feita por comparação com um sistema similar relatado pelo grupo de Monpellier. A descrição aceita é que, em uma relação estreita de concentração surfactante e cosurfactante, ocorre fusão de membrana com a formação de uma rede de bicamadas altamente interligadas e distribuídas aleatoriamente no espaço. A hipótese de formação da fase L3 é que o grupo hidroxila do pentanol se pareie com as cabeças de lipídios e esse fato é capaz de alterar a curvatura das bicamadas. As várias preparações de DODAB e pentanol mantiveram-se inalteradas durante pelo menos cinco anos apenas até 3 mM, a concentração máxima que pode ser chamada de L3, que é termodinamicamente estável. Para tornar o sistema mais atraente para muitos usos potenciais, é necessário aumentar a concentração do lipídio. Concentrações até 10 mM decompõem-se após algumas horas em pequenas gotas e cristais, a chamada multifase. O passo seguinte foi remover completamente o álcool por diálise contínua. O resultado foi o aparecimento de uma fase semelhante à água, que não pode ser obtida de outro modo. Uma sequência de medidas espectroscópicas e cromatográficas demonstrou que o álcool foi eliminado totalmente por diálise e o lipídio permanece retido. Há uma notável diferença com outros sistemas binários água/DODAB. Na mesma concentração, todos têm acentuada turbidez. A hipótese é que a presença de álcool na bicamada promove uma reorganização capaz de transformar um sistema particulado em bicontínuo. Está agora bem aceito que a força motriz dessas transformações são as mudanças de curvatura na bicamada. Os esforços para caracterizar esses sistemas são justificados, uma vez que são fáceis de preparar e têm utilizações potenciais como a síntese de compostos com poros mesoestruturados, transporte de drogas e cristalização de proteínas / Abstract: The amphiphilic L3 (sponge) phase was observed in the late 80's and represents a new class of self-assembly for surfactant-water systems. This work describes the discovery and subsequent characterization of a ternary phase composed of synthetic cationic lipid dioctadecildimetil ammonium bromide (DODAB), pentanol and water in a diluted region. This is the first description of a L3 phase prepared from a lipid with a relatively small polar head and two hydrocarbon chains with 18 carbons each one. The region of the triangle diagram in which there is L3 phase was characterized using optical isotropy and anisotropy to a probe with electron paramagnetic resonance spectroscopy technique. The proposal of an L3 phase was made by comparison with a similar system reported by the group of Montpellier. The description accepted is that in a narrow close ratio of surfactant/cosolvent concentrations, membrane fusion occurs with the formation of a highly interconnected and randomly distributed network of bilayers in space. The assumption of formation of the L3 phase is that the hydroxyl group of pentanol pairs with the lipid heads and this fact is able to change the bilayer curvature. The various DODAB/pentanol preparations remained unchanged and stable for five years only up to the concentration of 3 mM of lipid, the maximum concentration that can be called L3 phase, which is thermodynamically stable. To make the system more attractive for many potential uses it was necessary to increase the weight of the lipid. Concentrations up to 10 millimolar, after a few hours, break down into tiny droplets and small crystals, so-called multiphase. The next step was to completely remove the alcohol by continuous dialysis. The result was the appearance of a phase similar to water, which cannot be obtained otherwise. A sequence of spectroscopic and chromatography measurements showed that the alcohol was entirely eliminated by dialysis as the lipid was retained. There is a notable change when compared with other DODAB/water binary preparations. In the same concentration, all of them have pronounced turbidity. The hypothesis is that the presence of alcohol in the bilayer promotes reorganization, transforming a particulate into a bicontinuum system. Efforts to characterize these systems are justified because they are easy to prepare and have potential uses in the synthesis of inorganic solid new materials with nanostructured pores, and as drug carriers and vehicles for the crystallization of proteins / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutora em Engenharia Quimica

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