Thesis (Ph. D.)--University of Kentucky, 2002. / Title from document title page. Document formatted into pages; contains xvii, 268 p. : ill. Includes abstract. Includes bibliographical references (p. 261-267).

Zugl.: Paderborn, Universiẗat, Diss., 2001.

Membrane processes have many industrial applications such as desalination, water treatment, biotechnology, food industry, pharmaceutical and power generation. The advantages of membrane processes include high selectivity, low operating costs and energy consumption. Membrane charge plays an important role in the membrane separation of ionic species. Therefore, understanding the interaction between ions and membrane charge is essential to improve the performance of the separation. This interaction is a function of pH concentration and depends on membrane type. The objective of this thesis was to investigate the role of membrane charge in separation of ionic species. Therefore the first step is to characterise membrane charge and then using the knowledge obtained along with separation data to gain insight on the mechanism governing the separation process of charged species by NF membranes. Finally correlations between membrane charge characterisation and separation process were achieved. The aim of creating such correlations is to reduce the amount of experimental work (only characterisation needed) required to evaluate the separation efficiency of a NF membrane either in a single salt system or mixtures which in turn saves time, labour work and money. The result obtained confirms the role of membrane charge in the separation of ionic species and provides insight into the mechanism of separation in NF membranes. In fact full explanations and quantitative analysis of the role of membrane charge was achieved in this thesis. To sum up, the knowledge obtained in this thesis is important for researchers and process engineers in industries such as desalination and water treatment plant as this helps to increase the efficiency of these plants and promote the use of membrane technology in the process industries. This can be done by right choice of membranes which fit the purpose and control of the feed parameters such as pH and concentration to maximize the efficiency.

The intriguing size- and shape dependent properties of nanoparticles have garnered recent attention in many science and engineering areas. When the particle size is in the nanometer size range, the material exhibits very different properties such as surface plasmon resonance (of gold nanoparticles) and superparamagnetism (of iron oxide nanoparticles). The size-dependent properties of quantum dots have made them useful as UV-Vis-NIR sensors and in telecommunications applications. However, the separation and purification of nanoparticles are still challenging due to their size, insolubility in many solvents, and irreversible adsorption to other materials. Membrane filtration is widely used to separate nano-sized biological materials such as proteins, viruses, DNA and RNA. This dissertation presents novel approaches to the use of ultrafiltration and nanofiltration membranes for nanoparticle separation and purification using dead-end and cross-flow filtration techniques. Purification of phosphine-stabilized Au₁₁ (Au₁₁(PPh₃)₈Cl₃, M.W. 4371, d[subscript core]=0.8 nm), produced in a microreactor without recrystallization, was achieved using nanofiltration membranes. The ceramic and polymer nanofiltration membranes were able to purify the Au₁₁ with rejection values higher than 90%. A novel continuous nanofiltration system design was applied and characterized. The continuous synthesis process, coupled with continuous nanofiltration, resulted in a significant reduction in synthesis time while producing higher yield than could be achieved in batch experiments. The diafiltration system was applied towards isolation of Au₁₁, and results were presented that indicate increased yield and enhanced product purity. Organic-solvent resistant nanofiltration and ultrafiltration membranes were applied for purification and size-based separation of lead sulfide nanoparticles and gold nanoparticles that were initially synthesized with a 2-8nm size distribution. The nanofiltration membranes achieved rejection values greater than 95% for each of the nanoparticle samples and retained most of the nanoparticles on the membranes. The nanofiltration membranes also exhibited high permeability, which translates to a reduced purification time. Ultrafiltration membranes were screened and successfully applied to the size fractionation of lead sulfide nanoparticles and gold nanoparticles. A templated silsesquioxane (ssq) membrane was synthesized within the pore space of an alumina support membrane and used for the separation and purification of nano-sized materials such as nanoparticles and macromolecules. The ssq membrane was fabricated by polycondensation of a silsesquioxane monomer solution in the presence of a surfactant within the macroporous space of an Anodisc alumina membrane (Whatman, CO. Ltd, Maidstone, UK). The novel ssq membranes were successfully applied for size exclusion separations of organic soluble 5-8 nm gold nanoparticles (protected with dodecanethiol). A ssq membrane also proved useful for the separation of biological macromolecules such as bovine serum albumin and myoglobin. / Graduation date: 2012

La nanofiltration (NF) est un procédé applicable à la récupération des solvants organiques. Une membrane chimiquement stable est alors requise pour résister aux solvants organiques. Cette thèse traite de la préparation de membranes NF chimiquement stables par greffage de substrats céramiques mésoporeux et de l'étude de leurs propriétés de transport des solvants et des solutés. Dans le chapitre 1, l'état de l'art sur les techniques de greffage est présenté ainsi que celui sur le comportement au transport des membranes NF résistantes aux solvants.Dans les chapitres 2 et 6, des membranes d'ultrafiltration en alumine mésoporeuse sont greffées avec des groupements organiques hydrophobes ou hydrophiles. La diminution du diamètre des pores permet ainsi d'accéder à la nanofiltration. Au chapitre 5, un agent couplant est utilisé pour améliorer l'ancrage de ces groupements dans les pores. Ceci réduit cependant la perméabilité aux solvants, en comparaison aux mêmes membranes modifiées avec du polydiméthylsilane (PDMS) mais sans agent couplant. Dans le chapitre 6, la capacité de greffage de poudres d'alumine est mesurée pour des agents de greffage différant par : la masse moléculaire des chaines polyéthylènes glycol (PEG), la nature et le nombre de groupements alcoxy terminaux et la présence ou non de fonctions urée. Ces poudres sont analysés par thermogravimétrie, spectrométrie RMN du 29Si, spectroscopie FTIR, et mesures de surface spécifique. Les densités de greffage estimées varient avec la masse des greffons, la présence de fonctions urée, et le nombre de groupements alcoxy hydrolysables.Le comportement au transport de membranes greffées est étudié dans les chapitres 3, 4 et 6. Dans le chapitre 3, pour des membranes greffées avec du PDMS, ce comportement est décrit en incorporant des termes relatifs à la sorption des solvants dans l'équation Hagen-Poiseuille. Une membrane plus fermée est obtenue lorsque le solvant est fortement adsorbé dans la couche greffée. Dans le chapitre 4, la validité des modèles de rejet de soluté basés sur l'exclusion par la taille est discutée. Une forte influence du diamètre moléculaire du soluté et du rapport de ce diamètre avec celui des pores est observée, indiquant que le mécanisme d'exclusion par la taille est ici vérifié. Trois modèles de rejet sur la base d'exclusion par la taille, à savoir Ferry, Verniory et SHP, sont testés pour prédire, en l'absence de solvant, le rejet des solutés à partir des diamètres de pore mesurés par physisorption de diazote. Pour des colorants et des solutés de type PS ou PEG dans du toluène, les données expérimentales sont bien au-dessus des valeurs prédites par ces modèles. Les résultats suggèrent que le diamètre de pore effectif en présence de solvant fortement adsorbé tel que le toluène est inférieur à celui en l'absence de solvant, une hypothèse étant qu'il n'y a pas d'interactions importantes entre solvant et soluté ou entre le soluté et la surface des pores. Cela peut expliquer un rejet plus élevé des solutés dans des solvants non polaires comme le toluène que dans des solvants polaires tels que l'isopropanol pour les membranes greffées avec du PDMS. Dans le chapitre 6, la perméabilité de membranes greffées avec des PEG est étudiée pour différents solvants (polaires ou non polaires). Une relation linéaire entre le flux et la pression transmembranaire est observée, comme pour les membranes greffées avec du PDMS. Cela indique l'absence de processus induit par des effets de cisaillement dans le fluide en écoulement et variant avec la pression transmembranaire appliquée. Pour le colorant Noir Soudan, une sélectivité supérieure est observée dans l'éthanol que dans l'hexane alors que pour la perméabilité inférieure de l'éthanol est inférieure à celle de l'hexane. Ici aussi, ces phénomènes sont expliqués par la différence de sorption des solvants dans la couche greffée. Les conclusions générales et perspectives de cette étude sont présentées dans le chapitre 7. / Solvent nanofiltration is a potential technology to recover solvents. For this application, a chemically stable membrane that can endure continuous exposure towards organic solvents is required. This thesis deals with the preparation of chemically stable NF membranes through modification of mesoporous ceramic substrate by means of grafting and studying of their solvent and solute transport properties. In Chapter 1, the background of the grafting technique as well as studies on the SRNF transport behavior found in the literature was presented.In Chapter 2 and 6 of this thesis, mesoporous y-alumina UF membranes were grafted by hydrophobic and hydrophilic organic moieties to decrease the membrane pore diameter of the existing y-alumina UF membrane down to the nanofiltration range. In Chapter 5, the use of coupling agent to couple the grafted moiety forming a polymer network inside the ceramic pores during grafting results in a smaller membrane pore, but at the cost of a lower solvent permeability, when compared with PDMS-grafted alumina membranes where no coupling was applied. In Chapter 6, the grafting performance of γ-Al2O3 powder with various PEG grafting agents having different molecular weights, alkoxy groups, and ureido functionalities were analysed by TGA, 29Si-NMR, FTIR, and BET. The grafting densities are influenced by the molecular weights, the presence of the ureido functionality, and the number of hydrolyzable groups of the grafting agents. The transport behavior of PDMS grafted ceramic membranes and PEG grafted ceramic membranes were studied in Chapter 3, 4, and 6. In Chapter 3, the solvent transport behavior of PDMS grafted ceramic membranes was described by incorporating solvent sorption terms in the Hagen-Pouiseuille equation. A more closed membrane structure is realized when the solvent is strongly sorbed in the grafted moiety. In Chapter 4, the applicability of the existing solute rejection models based on size-exclusion mechanism to describe the solute rejection of membranes towards different types of solvent and solute were assessed. A strong function of rejection behavior with the ratio of the solute diameter versus the membrane pore diameter was observed, indicating that the size-exclusion mechanism may be applicable. Three rejection models based on size-exclusion, namely the Ferry, Verniory, and SHP models were used to predict the rejection of several solutes using pore diameter information from the N2 physisorption measurement when no solvent is present. For dye, PS, and PEG solutes in toluene, the experimental data fall well above the predicted σ for Ferry, Verniory, and SHP model suggesting that the membrane actual pore diameter in the presence of strongly sorbed solvent like toluene is smaller than that when no solvent is present, assuming that there is no important solvent-solute or solute-membrane interaction present in the observed rejection behavior. This may explain the higher rejection of solutes in nonpolar solvents like toluene than that in polar solvents such as isopropanol for PDMS grafted ceramic membranes. In Chapter 6, the permeability behavior of PEG grafted y-alumina membranes with respect to different types of permeating solvent (polar and nonpolar) was studied. A linear relationship between flux and TMP was observed, as was also found for PDMS grafted y-Al2O3 membranes. This indicates the absence of shear-flow induced behaviour in the applied TMP. A higher selectivity of Sudan Black in ethanol than in hexane accompanied by a lower permeability of ethanol than hexane were observed. Here also this phenomenon is explained by the difference in solvent sorption of the grafted moiety for different types of permeating solvents. Finally, the general conclusions and future work are presented in Chapter 7.

Thesis (Ph. D.)--Ohio State University, 2006. / Full text release at OhioLINK's ETD Center delayed at author's request

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 148-158). Also available in print.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 95-99). Also available on the World Wide Web.

Thesis (Ph.D.)--McMaster University, 2002. / Adviser: James Dickson. Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph.D.)--McMaster University, 2002. / Adviser: James Dickson. Includes bibliographical references. Also available via World Wide Web.