- 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.
Search results
Showing 1 to 2 of 2 (0.1 seconds)| 1 |
Etude l'évolution des propriétés de surface d'un matériau minéral à porosité contrôlée lors de sa mise en oeuvre dans des tests d'ultrafiltration et de nanofiltration / Study of the surface properties evolution of a mineral material with controlled porosity during its implementation in ultra and nanofiltration testsBikai, Jacques 15 December 2015 (has links)
L'objet de ce travail concernait la compréhension de l'évolution des propriétés hydrauliques des membranes céramiques d'UF/NF durant l'étape du conditionnement, et suite à un traitement alcalin. Dans un premier temps, une étude expérimentale a été réalisée par des tests de flux à l'eau pure avec 6 membranes minérales asymétriques (Na-mordenite et TiO2). Ensuite, l'évolution de la perméabilité hydraulique de ces membranes a été modélisée précisément par une fonction mathématique, mettant en évidence deux phases distinctes au cours du conditionnement : une hydratation rapide de la surface des cristaux de Na-mordenite (mésoporosité intercristalline) suivie d'une hydratation lente des pores de la Na-mordenite (microporosité intracristalline). Cette étude a également permis de montrer que la cinétique d'hydratation des micropores est proportionnelle au volume microporeux des couches actives. Dans un deuxième temps, des caractérisations physico-chimiques (DRX, MEB, DFX, adsorption N2), des mesures de propriétés électriques ainsi que des tests de mouillabilité ont été réalisés sur la phase active des membranes de Na-mordenite avant et après un traitement alcalin (filtration d'une solution de carbonate de sodium) dans le but de pouvoir comprendre/expliquer la diminution de la perméabilité hydraulique observée à la suite du traitement alcalin. Les composantes de la tension de surface (polaires et apolaires) et l'énergie d'interaction entre la surface des membranes et les molécules d'eau ont été déterminées via l'équation de Young-Dupré (théorie de Lifshitz-van der Waals des états condensés). L'ensemble des résultats obtenus a montré que la modification des propriétés hydrauliques des membranes est due à une augmentation de l'hydrophilicité de surface de la zéolithe (par la présence des micro-défauts à la surface : extraction des atomes de silicium) provoquant la formation d'une couche ultra-polaire à la surface des cristaux de Na-mordenite. / The aim of this work was to understand hydraulic properties evolution of mineral UF/NF membranes during the conditioning step and after a mild alkaline treatment. First, experimental tests by filtration of pure water were carried out to determine the membrane permeation flux. Six tubular asymetric ceramic membranes were studied (Na-mordenite and TiO2) and a mathematical modelling of the hydraulic permeability (during the conditioning step) was performed. Two separate phases were identified: a fast decrease of the permeability that was attributed to the hydration of the crystal surface of Na-mordenite (inter-crystalline mesoporosity) and then a slow decrease until the stabilization of the permeability that was attributed to the hydration of the Na-mordenite internal pores (intra-crystalline microposity). During this study, it was also shown that the kinetic of micropore hydration is directly proportional to the microporous volume of the membrane active layer. Secondly, physicochemical characterizations, electric properties and contact angle measurements were carried out on the Na-mordenite active phase before and after a mild alkaline treatment (filtration of a sodium carbonate-water solution) to understand/explain the decrease of the hydraulic permeability after the alkaline treatment. The surface tension components (polar and apolar) and the energy of interaction between water molecules and the surface of the active layer were determined via the Young-Dupré equation according to the Lifshitz-van der Waals theory of the condensed states. The whole of these results showed that the modification of the hydraulic properties of the zeolite membranes is due to an increase of the surface hydrophilicity of the surface (surface defaults: extraction of the silicon atoms), leading to the formation of an ultra-polar layer on the surface of the zeolite crystals.
|
| 2 |
Development of High-throughput Membrane Filtration Techniques for Biological and Environmental Applications / Development of High-throughput Membrane Filtration TechniquesKazemi, Amir Sadegh 11 1900 (has links)
Membrane filtration processes are widely utilized across different industrial sectors for biological and environmental separations. Examples of the former are sterile filtration and protein fractionation via microfiltration (MF) and ultrafiltration (UF) while drinking water treatment, tertiary treatment of wastewater, water reuse and desalination via MF, UF, nanofiltration (NF) and reverse-osmosis (RO) are examples of the latter. A common misconception is that the performance of membrane separation is solely dependent on the membrane pore size, whereas a multitude of parameters including solution conditions, solute concentration, presence of specific ions, hydrodynamic conditions, membrane structure and surface properties can significantly influence the separation performance and the membrane’s fouling propensity. The conventional approach for studying filtration performance is to use a single lab- or pilot-scale module and perform numerous experiments in a sequential manner which is both time-consuming and requires large amounts of material. Alternatively, high-throughput (HT) techniques, defined as the miniaturized version of conventional unit operations which allow for multiple experiments to be run in parallel and require a small amount of sample, can be employed. There is a growing interest in the use of HT techniques to speed up the testing and optimization of membrane-based separations. In this work, different HT screening approaches are developed and utilized for the evaluation and optimization of filtration performance using flat-sheet and hollow-fiber (HF) membranes used in biological and environmental separations. The effects of various process factors were evaluated on the separation of different biomolecules by combining a HT filtration method using flat-sheet UF membranes and design-of-experiments methods. Additionally, a novel HT platform was introduced for multi-modal (constant transmembrane pressure vs. constant flux) testing of flat-sheet membranes used in bio-separations. Furthermore, the first-ever HT modules for parallel testing of HF membranes were developed for rapid fouling tests as well as extended filtration evaluation experiments. The usefulness of the modules was demonstrated by evaluating the filtration performance of different foulants under various operating conditions as well as running surface modification experiments. The techniques described herein can be employed for rapid determination of the optimal combination of conditions that result in the best filtration performance for different membrane separation applications and thus eliminate the need to perform numerous conventional lab-scale tests. Overall, more than 250 filtration tests and 350 hydraulic permeability measurements were performed and analyzed using the HT platforms developed in this thesis. / Thesis / Doctor of Philosophy (PhD) / Membrane filtration is widely used as a key separation process in different industries. For example, microfiltration (MF) and ultrafiltration (UF) are used for sterilization and purification of bio-products. Furthermore, MF, UF and reverse-osmosis (RO) are used for drinking water and wastewater treatment. A common misconception is that membrane filtration is a process solely based on the pore size of the membrane whereas numerous factors can significantly affect the performance. Conventionally, a large number of lab- or full-scale experiments are performed to find the optimum operating conditions for each filtration process. High-throughput (HT) techniques are powerful methods to accelerate the pace of process optimization—they allow for multiple experiments to be run in parallel and require smaller amounts of sample. This thesis focuses on the development of different HT techniques that require a minimal amount of sample for parallel testing and optimization of membrane filtration processes with applications in environmental and biological separations. The introduced techniques can reduce the amount of sample used in each test between 10-50 times and accelerate process development and optimization by running parallel tests.
|
Page generated in 0.1069 seconds