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1
Makowski, Marcin. "Solvent nanofiltration for purifying pharmaceuticals." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/29227.
Testo completoAbstract (sommario):
The projections recently published by the United Nations (UN) suggest that the global population may reach 8.9 billion people by the year 2050. Life expectancy is assumed to rise constantly with no upper limit and by the year 2100 is expected to vary from 66 to 97 years. As the population ages the demand for effective medicines is rising. At the same time the pharmaceutical industry keeps applying pressure to shorten development timelines for new chemical entities, so that new medicines can reach patients much faster. In the development and manufacturing of drugs the purification steps often consume the highest proportion of the processing time and costs. In parallel, there has been a surge in the expectations of patients regarding the purity of the desired pharmaceuticals. There are several processes available for yielding purified product: liquid chromatography, crystallization or distillation among others most of them, however have limitations. Therefore, progress is required in innovative technologies and processes characterized by higher stability, better selectivity and lower energy requirements. Applying membrane technology in the separation and purification of compounds can result in lower operating temperatures being needed, and less harsh conditions required, when compared to other processes. Thus it is of interest for Active Pharmaceutical Ingredient (API) manufacturing. Polymeric membranes are the most widely used for industrial membrane applications. However, an important challenge is to apply the existing polymeric membranes (suitable for aqueous operations) to non-aqueous solutions. Recent progress has led to the development of Organic Solvent Nanofiltration (OSN). OSN utilises solvent-resistant polymeric membranes to selectively retain solutes, and simultaneously allows smaller molecules to pass through the membrane. Nevertheless, ways in which membrane performance impacts the overall purification process have not yet been fully studied. Developing mathematical models of purification processes might help to better understand, and therefore better predict and control, the membrane process. Knowing the importance of a membrane in a filtration process, one should try to identify the areas where new membranes are desired. At the same time, one should try to understand how factors influencing membrane formation will affect membrane's final performance. As a benefit of the research conducted, by the end of this study the knowledge gained should result in the fabrication of membranes with enhanced capabilities.
2
Welfoot, J. St J. "Predictive modelling of membrane nanofiltration." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639377.
Testo completoAbstract (sommario):
The main objective of this work was to develop predictive models for nanofiltration (NF) membrane processes. A one-parameter model (pore radius) for uncharged solute rejection has been developed. The good agreement between the proposed model and experimental data confirmed that uncharged solute rejection is well described by continuum models. A two-parameter model (pore radius and membrane charge) for electrolyte rejection has also been developed. Dielectric exclusion was included as an energy barrier to ion partitioning into the pores, the reassessment of which using NaCl rejection at the membrane isoelectric point introduced a third model parameter, the average pore solvent dielectric constant. The predicted membrane charge densities with the three-parameter model were more realistic in magnitude than those from previous models and their variation with concentration for divalent salts was in better agreement with physical models of ion adsorption. Analysis of experimental rejection data with truncated pore size distributions and a variation of viscosity with pore radius resulted in model parameters that represented the average value over all pore sizes. Further, analysis of salt mixtures showed that large experimentally observed negative rejections were very well described with fitted charge densities of similar magnitude to those from single salts. Finite Difference linearisation of pore concentration gradient greatly simplified the numerical solution of the three-parameter model. The validity of the linearised model was tested both experimentally and theoretically, showing the model to be a powerful tool for characterisation of NF membranes and subsequent prediction of separation performance. Overall, the work presented in this thesis has improved the understanding of the separation mechanisms of NF membranes, especially dielectric exclusion. The developed models are more rigorous than those proposed previously and represent a significant contribution to the field of predictive NF modelling.
3
Cluff, C. Brent. "Slowsand/Nanofiltration of Surface Water." Arizona-Nevada Academy of Science, 1991. http://hdl.handle.net/10150/296460.
Testo completoAbstract (sommario):
From the Proceedings of the 1991 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 20, 1991, Northern Arizona University, Flagstaff, Arizona<br>Since the spring of 1988 the University of Arizona has conducted nanofiltration research. The major emphasis has been the treatment of both Colorado River Water and municipal effluent. The work has been sponsored by the John F. Long Foundation Inc. and the Consolidated Water Utilities, Phoenix Az. Nanofiltration is a low pressure form of reverse osmosis. It operates at about 1/3 the pressure and 3 times the flux rate of older brackish water reverse osmosis systems. This reduces both the cost as well as the operating costs to approximately 1 /10 of the older reverse osmosis systems. The City of Ft Myers is projecting costs as low as $0.50-0.60/1000 gallons for their 20 MGD plant. Nanofiltration treats water the way it needs to be treated to meet the Environmental Protection Agency's (EPA) present minimum contamination levels (MCL) as well as projected future levels. Nanofiltration removes most of the bivalent inorganic molecules such as calcium and magnesium as well as some monovalent molecules such as sodium and chloride. It also removes pathogens and dissolved organics, thus reducing the trihalomethane formation potential (THMFP). The research on recharged effluent municipal effluent below the 91st Avenue Plant in Phoenix has shown the value of nanofiltration for reclaiming municipal wastewater to potable standards. A 20,000 GPD slowsand /nanofiltration pilot plant at Apache Junction has shown the effectiveness of the treatment on Colorado River Water at a 95% recovery over the past 2 years.
4
Tanardi, Cheryl Raditya. "Organically-modified ceramic membranes for solvent nanofiltration : fabrication and transport studies." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS259/document.
Testo completoAbstract (sommario):
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<br>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
5
Da, Silva Burgal Joao Porfirio. "Development of poly (ether ether ketone) nanofiltration membranes for organic solvent nanofiltration in continuous flow systems." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/43328.
Testo completoAbstract (sommario):
Organic solvent nanofiltration (OSN) is an energy saving technology that can replace more energy demanding separation technologies, such as evaporation and distillation. Nevertheless, OSN membranes that can withstand high temperature conditions as well as acidic or basic conditions are lacking on the market. In this thesis a poly(ether ether ketone) (PEEK) membrane is investigated for its suitability for OSN applications using polar aprotic solvents, such as DMF and THF, high temperatures, and basic/acidic conditions. By studying four grades of PEEK polymer powder from two different brands (VESTAKEEP® and VICTREX®), the VESTAKEEP® 4000P was selected for the subsequent studies. The post-phase inversion drying process of membrane fabrication was also studied and the drying step was shown to be crucial in obtaining separation performance in the nanofiltration (NF) range. The degree of sulphonation (DS) was also important and had to be maintained at low levels in order to retain the chemical and thermal stability of PEEK membranes. Subsequently, the scaling-up of PEEK membranes to spiral-wound modules was successfully achieved. In order to further manipulate the performance of PEEK NF membranes, two ways of controlling the molecular weight cut-off (MWCO) of PEEK membranes prepared via phase inversion and subsequent drying were studied. The two methods explored were the change of polymer concentration in the dope solution - 8 wt. %, 10 wt. % and 12 wt. % - and the variation of solvent filling the pores prior to drying - e.g. water, methanol, acetone, tetrahydrofuran and n-heptane. For each solvent, the drying temperature was proved to have an effect on the membrane performance - the higher the drying temperature, the higher the rejection and the lower the permeance. Following the drying treatment results, the negligible aging of PEEK membranes was demonstrated; a comparison with crosslinked polybenzimidazole (PBI) and polyimide (PI) membranes was also performed. The results showed a structural change for PBI and PI membranes due to a non-equilibrium glassy state, in contrast with PEEK membranes which were in quasi-equilibrium glassy state. High temperature filtrations were also performed in DMF up to 140 °C for the three polymeric membranes. PEEK was the most robust membrane with a stable performance after 4 filtration cycles whereas PBI and PI were stable for 2 and 1 cycles respectively. Due to their stability at high temperatures, and also their compatibility with catalysts, PEEK membranes were used in two different continuous Heck coupling reactions combined with OSN separation of the catalyst in situ. Two reactor configurations were investigated: a continuous single stirred tank reactor/membrane separator (m-CSTR); and a plug flow reactor (PFR) followed by m-CSTR (PFR-m-CSTR). It was possible to decrease the catalyst leaching to the product stream and to increase the overall turnover number (TON) of the Heck reactions.
6
Karabacak, Asli. "Sulphate Removal By Nanofiltration From Water." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612748/index.pdf.
Testo completoAbstract (sommario):
ABSTRACT
SULPHATE REMOVAL BY NANOFILTRATION FROM WATER
Karabacak, Asli
M.Sc., Department of Environmental Engineering
Supervisor: Prof. Dr. Ü<br>lkü<br>Yetis
Co-advisor: Prof. Dr. Mehmet Kitis
December 2010, 152 pages
Excess sulphate in drinking water poses a problem due to adverse effects on human health and also due to aesthetic reasons. This study examines the nanofiltration (NF) of sulphate in surface water using a laboratory cross-flow device in total recycle mode. In the study, three NF membranes, namely DK-NF, DL-NF and NF-270, are used. The influence of the main operating conditions (transmembrane pressure, tangential velocity and membrane type) on the steady-state permeates fluxes and the retention of sulphate are evaluated. Kizilirmak River water is used as the raw water sample. During the experimental studies, the performance of NF is assessed in terms of the parameters of UVA254, sulphate, TOC and conductivity of the feed and permeates waters. Results indicated that NF could reduce sulphate levels in the surface water to a level below the guideline values, with a removal efficiency of around 98% with all three membranes. DK-NF and NF-270 membranes showed fouling when the surface water was fed directly to the system without any pre-treatment. MF was found to be an effective pretreatment option for the prevention of the membrane fouling, but no further removal of sulphate was achieved. Parametric study was also conducted. No change in flux values and in the removal of sulphate was observed when the crossflow velocity was lowered. The flux values were decreased as the transmembrane pressure was lowered<br>however there were not any decrease in the sulphate removal efficiency.
7
Artuğ, Gamze. "Modelling and simulation of nanofiltration membranes." Göttingen Cuvillier, 2007. http://d-nb.info/986774685/04.
Testo completo
8
Wong, Hau To. "Solvent nanofiltration for organometallic catalysed reactions." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429120.
Testo completo
9
Mohammad, A. W. "Predictive models for nanofiltration membrane processes." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638212.
Testo completoAbstract (sommario):
The main objective of this work was to develop a predictive model for nanofiltration (NF) membrane processes. This was accomplished by development of a model which describes the transport of electrolytes in NF membranes in terms of three mechanisms: diffusion, convection and electromigration. The model includes the description of concentration polarisation for binary and more complex mixtures of charged electrolytes. The application and utility of the model were studied by identifying the key characteristics of NF membranes, modelling of a selected process, validation using experimental data and finally using the model for prediction including process optimisation. For one membrane (PES5), atomic force microscopy (AFM) showed that the membrane consisted of discrete pores of nanometre dimensions. Characterisation of the membrane using salts and uncharged solutes showed that it is more appropriate to model the membrane as porous rather than homogenous. The membrane was characterised in terms of the structural parameters: the effective pore radius, <I>r<SUB>p</SUB></I><SUB>, </SUB>and the effective ratio of thickness over porosity, <I>Δx/A<SUB>k</SUB></I>, and an electrical parameter: the effective charge density, <I>X<SUB>d</SUB>. </I>Such characterisation for a further membrane (CA30) was found to be very useful in predicting the process of diafiltration of dye/salt solutions. The prediction required that X<SUB>d</SUB> varied as the salt concentration decreased during processing. The model was then used to predict the processing conditions for the whole diafiltration process which includes the pre/post-concentration phases and the diafiltration phase. Finally, a simplified characterisation method was proposed whereby the membranes that are available in the market are characterised using the information given by the membrane manufacturers. Using the range of parameters obtained, analysis of the model showed that the contributions of all three transport mechanisms are very significant and should not be neglected in any predictive models.
10
Cheng, S. "Improved nanofiltration membranes by self-assembly." Thesis, Swansea University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636243.
Testo completoAbstract (sommario):
Charged ultrafiltration (UF)/nanofiltration (NF) membrane plays a very important role in membrane separation. Thus, the aim of the present study was to improve charged UF and NF membranes for increased application within the process, pharmaceutical and food industries. The main objectives of this work were to investigate the preparation, modification, characterisation and application of a group of charged UF/NF membranes. Substrate membranes were prepared with polyehterimide (PEI) and sulfonated poly(ether ether ketone) (SPEEK). The self-assembly deposition of polyelectrolytes on the membrane surface was also studied. No previous studies have so comprehensively assessed the fabrication and performance of self-assembly modified PEI/SPEEK membranes. The effects of small molecular additives were studied on membrane morphology and performance. Characterisation by scanning electron macroscopy (SEM) and atomic force macroscopy (AFM) showed that the addition of tetrahydrofuran (THF) and 1,4-dioxane induced a denser skinned top layer, which dramatically decreased the permeability. SPEEK was used to improve the hydrophilic properties of PEI membrane and permeability, as well as to provide surface charges. The membrane properties were very reproducible when the proportions of SPEEK were 3% and 6% in the total polymer content. Positively and negatively charged NF membranes were fabricated by self-assembly. Positive NF membrane was obtained by depositing polycation, polyethylenimine, on the surface of PEI/SPEEK blend membranes. The effects of Ph and ionic strength of the polyelectrolyte solution on the membrane performance were investigated and it was concluded that the high amount of adsorption of weak polyelectrolyte on the membrane surface with opposite charges was achieved close to the isoelectric point (IEP). Again, negatively charged NF membrane was fabricated by depositing poly (acrylic acid) (PAA) on the surface of positively charged membranes. Zeta potential measurements showed that the deposition of polyelectrolytes changed chemistry of the membrane surfaces. The pore sizes calculated from rejection data using and from AFM demonstrated that the adsorption of polyelectrolytes on membrane surfaces led to the decrease of pore size. The present study has shown the advantage of using phase imaging to characterise membrane morphology; the identification and sizing of pores was easier than when using standard topography. No other studies have used this technique to study pore sizes. Methylene blue (MB) and sodium cefuroxime were used to explore the industry application of obtained membranes.
11
Stawikowska, Joanna. "Characterisation of organic solvent nanofiltration membranes." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/14732.
Testo completoAbstract (sommario):
Interests in application of organic solvent nanofiltration (OSN) technology based on synthetic membranes to molecular separation processes have been growing rapidly in recent years. The main classes of OSN flat sheet polymeric membranes are integrally skinned asymmetric (ISA) and thin film composite (TFC) membranes. A general goal of OSN membrane research is to improve membrane performance for specific non-aqueous applications, or to develop new separation processes. Most of the time the research is performed via trial–and–error methods, leading to extension of development time and increase of costs. This is partially because the structure of OSN membranes, particularly the size of their permeation pathway is largely unknown. The filtration characteristics are mainly determined by the membrane structure, which is dependent on various fabrication methods as well as polymer chemistry. However, a direct correlation between these factors has not been understood in detail, because the current characterisation techniques have limitations in studying polymer structures with dimensions at the macromolecular level. The pore size in nanofiltration (NF) membranes is believed to be less than 2 nm, which is a lengthscale at the edge of most available material characterisation techniques. For this reason, advanced methods to study the membrane morphology need to be explored or developed with the aim of elucidating the NF membrane structure, transport mechanisms, and to understand the relationship between the membrane structure and the separation characteristics. These objectives guided the work to development of a nanoscale characterisation method based on imaging the porous regions via probing the NF pores with nanoparticles (NP). Given that the probes provide high electron contrast, it is possible to map the pores formed between the polymer entanglements in the transmission electron microscope (TEM). This technique measures the pore size in situ, thus, a membrane is characterised during its operational state. The pore size was found to correlate well with the solute rejection and flux measured for a range of ISA and TFC membranes. The pore size distributions were then used together with a pore–flow model to simulate rejection curves. A further insight into the membrane structure, particularly the surface structure, was provided by atomic force microscopy (AFM), particularly phase imaging. This method was applied to characterisation of polymer packing at the membrane surface, leading to analysis of the correlations between the phase shift, filtration parameters and membrane preparation methods.
12
See, Toh Yoong Hsiang. "Molecular separations with organic solvent nanofiltration." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/11320.
Testo completoAbstract (sommario):
This thesis firstly describes the application of organic solvent nanofiltration (OSN) in the recycle of asymmetric hydrogenation catalysts through the retention of the (often) larger catalyst whilst allowing the smaller products to penneate. This improves the catalyst tum over number (TON) and the further addition of the ionic liquid (IL) CyPhoslOl markedly improves the enantiomeric excess in the asymmetric hydrogenation of dimethyl itaconate using Ru-BINAP. The high molecular weight of the catalyst and IL allows them to be simultaneously recycled using an OSN membrane. Although this work identifies significant potential to further the application of OSN in homogeneous catalyst recycle, there is a lack of commercially available OSN membranes with good chemical stability across a range of organic solvents and with the ability to separate compounds in the NF range of 200-1000 g morl. The central part of this thesis addresses these issues through the development of various integrally skinned asymmetric polyimide OSN membranes. A consistent method to describe the penneation property of the molecular weight cut off (MWCO) has been developed. This allows the detennination of membrane performance and integrity across a range of different membranes and solvents. The variation of membrane separation perfonnance across the NF range has been achieved through cfanging various membrane fonnation parameters. Crosslinking of these membranes significa~tly enhances the chemical stability allowing stable perfonnances in a range of organic solvents including polar aprotic solvents. Coupling chemical crosslinking with the fonner methodology simultaneously improves the membrane chemical stability and allows membranes to be tailored for specific separations. Finally, this work also examines some initial steps leading to the scale up of OSN membranes to pilot scale through the use of spiral bound elements.
13
Cluff, C. Brent, Charles P. Gerba, and Gary L. Amy. "Slow Sand/Nanofiltration of Surface Water." Water Resources Research Center. The University of Arizona, 1990. http://hdl.handle.net/10150/306475.
Testo completoAbstract (sommario):
Paper presented at "Membranes For Drinking Water Treatment Conference", Environmental Protection Agency, Cincinnati, OH, August 6, 1990.<br>Introduction: Through the studies published in Drinking Water and Health (1977) the nation has become more aware of the carcinogenic nature of the byproducts of disinfection such as trihalomethanes. Trihalomethanes are formed when the disinfectant chlorine reacts with the precursors, humic and fluvic acids that are naturally occuring in all surface water. The Environmental Protection Agency (EPA) has set a minimum contaminent level of 100 ppb on THM's that many in the health agencies feel need to be lowered. The problem is that when the MCL's are lowered utilities will be enclined to chlorimines and chloride dioxide which have been found to be mutagenic. Drinking Water and Health (1987) found the Suggested No-Adverse Response Levels (SNARLs) for chioramines for a child is 0.166 ppm, for an adult it is 0.581. The SNARL for chlorine dioxide is 0.06 ppm for a child and 0.210 ppm for an adult. These levels for utilities are virtually impossible to maintain and still have a residual at the end of the system.
14
Shirley, Jason Dennis. "Anomalous rejection ratios in nanofiltration experiments." Thesis, Swansea University, 2008. https://cronfa.swan.ac.uk/Record/cronfa42300.
Testo completoAbstract (sommario):
Nanofiltration by its nature is used to concentrate material. It has been found that varying the solute feed concentration had an effect on the rejection of amino acids and polar molecules. The rejection of these organic solutes has been shown to increase with concentration during nanofitration experiments for a NTR 7450 membrane. The rejection of glycine increased from 29.4% to 72.2% for a concentration of 0.004 g/1 and 4.0 g/1 respectively. Similar increases in rejection with respect to concentration were observed for glutamine and glutamic acid, as well as for glucose, sucrose and raffinose over the same concentration range. The reliability of the filtration measurements was established by error analysis and the associated error for the glycine rejection was found to be +/- 3%. Therefore, the observed rejection increase could not be attributed to experimental error. This phenomenon was further investigated by particle size analysis and osmotic pressure measurement. The results from these experiments indicated that dimerisation was not occurring, thus no association between increasing molecular weight and solute concentration. The properties of the NTR 7450 membrane were investigated by streaming potential measurements, titrations and molecular weight cut-off experiments. The molecular weight cut-off of the membrane was found to reduce for an increase in solute concentration. This result implied that the effective pore size changed as a function of concentration and was attributed to adsorption occurring on the inner pore wall. The level of adsorption was further investigated by applying the Freundlich adsorption isotherm to measured permeated flux decline for increasing solute concentration. This method was adapted to enable analysis of the effect of adsorption on rejection with concentration.
15
Low, Jian-Shen. "A study of organic solvent nanofiltration." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/35066.
Testo completoAbstract (sommario):
This thesis is concerned with the principal features of solvent resistant nanofiltration (SRNF), and in particular its potential in fuel processing. In the recent and more established literature, dense polydimethylsiloxane (PDMS) has been identified as a potential SRNF membrane with separation properties at a molecular level. This thesis investigates the transport and separation mechanisms of dense PDMS membranes in SRNF applications relating to the filtration of organic solvents (mixtures are mixed to simulate fuel). Simulated fuels were created which comprised representative organic solvents with organometallic (OM) and poly-nuclear aromatic (PNA) solutes. The solvent flux and solute rejection behaviour of the solvent-solute systems were studied using a cross-flow air-driven filtration apparatus and a range of operating regimes.
16
Lakhchaf, Nadia. "Nanofiltration d'ions et de complexes en solution. Application au traitement d'effluents nickelés par couplage complexation, nanofiltration, électrolyse." Montpellier 2, 1996. http://www.theses.fr/1996MON20122.
Testo completoAbstract (sommario):
La these decrit l'etude d'un procede couplant la nanofiltration et l'electrolyse pour l'elimination et le recyclage de cations de metaux lourds contenus dans des solutions diluees. En effet, la filtration membranaire permet d'obtenir d'une part une solution epuree et d'autre part un concentrat qui peut etre electrolyse pour recuperer le metal a l'etat solide. L'objectif fixe a ete de determiner les conditions de faisabilite d'un tel procede. La bibliographie liee a notre etude est regroupee en debut de memoire. Dans un premier chapitre sont presentes les effluents nickeles vises par le procede (traitements de surface) et quelques aspects de l'electrolyse du nickel. Ensuite, le point est fait sur les modeles physiques rendant compte du transfert d'especes a travers les membranes qui mettent en uvre un gradient de pression. Le dernier chapitre de cette partie est consacre a la nanofiltration. Viennent ensuite les resultats experimentaux et leur interpretation. Dans un premier temps, nous avons etudie la nanofiltration de solutions salines, puis la nanofiltration de complexes du nickel. Ces etudes ont permis de connaitre l'influence de la pression et de la concentration ainsi que celle du ph sur les proprietes de retention. Les regles de transfert a travers les membranes de nanofiltration ceramiques ont ete degagees. Pour la mise en uvre du procede, nous montrons que, avec de telles membranes, la complexation du cation metallique peut etre necessaire pour ameliorer la retention. Par la suite, le comportement electrochimique du nickel ainsi que les resultats d'essais d'electrodeposition du nickel sont presentes. Le principal probleme rencontre est l'acidification de la solution au cours de l'electrolyse qui favorise la reduction de l'eau au detriment de celle du nickel. En conclusion, une modelisation simple a ete effectuee pour aborder le dimensionnement d'une installation mettant en uvre ce procede
17
Jakobs, Dirk. "Stofftransport durch Nanofiltrationsmembranen unter Berücksichtigung von Biofilmen /." Aachen : Shaker, 2001. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=009461355&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Testo completo
18
Schrader, Guillo Alexander. "Direct nanofiltration of wastewater treatment plant effluent." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/55981.
Testo completo
19
Ogutverici, Abdullah. "Triclosan Removal By Nanofiltration From Surface Water." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615617/index.pdf.
Testo completoAbstract (sommario):
Nowadays, organic pollutants occurring in surface waters have raised substantial concern in public.
Triclosan (TCS) is one of the antimicrobial agents which are utilized in both domestic and industrial
application. In this study nanofiltration (NF) of TCS in surface water was investigated. Laboratory
scale cross-flow device is operated in total recycle mode and DK-NF and DL-NF membranes were
used. Kesikkö<br>prü<br>Reservoir (Ankara) water was used as raw water. Effect of natural organic matter
(NOM) content of raw water on TCS removal is searched through addition of humic acid (HA)
into the raw water as to represent for NOM. Steady state permeate fluxes are monitored
throughout the experiments to explore the flux behavior of the membranes. During the experiments,
performance of the membranes is assessed by monitoring TCS, as well as other water quality
parameters, such as UVA254 and total organic carbon (TOC) in the feed and permeates waters. Results
obtained put forward that TCS removal by NF membrane is not as same as reported in the literature.
In the literature, membrane removal efficiency is reported as above 90%. However, this study proved
that this would be true if and only if one does not considers the adsorption of TCS by the system itself,
in the absence of membrane. It is now clear that, because of adsorption of the TCS onto the
experimental set up (feed tank, pipings etc.)<br>the real TCS removal efficiency of the nanofiltration is
around 60-70%.
20
Roy, Yagnaseni. "Modeling nanofiltration for large scale desalination applications." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100096.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 91-94).<br>The Donnan Steric Pore Model with dielectric exclusion (DSPM-DE) is implemented over flatsheet and spiral-wound leaves to develop a comprehensive model for nanofiltration modules. This model allows the user to gain insight into the physics of the nanofiltration process by allowing one to adjust and investigate effects of membrane charge, pore radius, and other membrane characteristics. The study shows how operating conditions such as feed flow rate and pressure affect the recovery ratio and solute rejection across the membrane. A comparison is made between the results for the flat-sheet and spiral-wound configurations. The comparison showed that for the spiral-wound leaf, the maximum values of transmembrane pressure, flux and velocity occur at the feed entrance (near the permeate exit), and the lowest value of these quantities are at the diametrically opposite corner. This is in contrast to the flat-sheet leaf, where all the quantities vary only in the feed flow direction. However it is found that the extent of variation of these quantities along the permeate flow direction in the spiral-wound membrane is negligibly small in most cases. Also, for identical geometries and operating conditions, the flatsheet and spiral-wound configurations give similar results. Thus the computationally expensive and complex spiral-wound model can be replaced by the flat-sheet model for a variety of purposes. In addition, the model was utilized to predict the performance of a seawater nanofiltration system which has been validated with the data obtained from a large-scale seawater desalination plant, thereby establishing a reliable model for desalination using nanofiltration.<br>by Yagnaseni Roy.<br>S.M.
21
Nada, Tariq. "Characterisation of nanofiltration membranes for sulphate rejection." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5194/.
Testo completoAbstract (sommario):
Nanofiltration (NF) membranes are used for a range of industrial applications one of which is for the removal of the sulphate constituent in seawater. This is a mature activity for the treatment of seawater that is to be injected into oil reservoirs in the offshore oil/gas industry. Such sulphate removals have also been the subject of much interest, as a pretreatment strategy, in seawater desalination plants that is either utilising thermal technology or reverse osmosis. Nevertheless, there is a need for robust criteria, such as the comparative permeate flux and sulphate rejection, of selecting the optimum NF membrane. There is a major difficulty in the assessment of the comparative filtration performance and the role of membrane structure because the data from manufacturers and also the information from the scientific literature emanates from different testing protocols. This can result in an enigmatical situation for obtaining the optimum NF membrane for a particular application. Against the above background this PhD project has focused on undertaking a fundamental study of different commercially available NF membranes in order to facilitate improved assessment of their filtration performance for sulphate rejection applications in relevant standardised testing conditions. Moreover, on the basis that those variations in membranes’ functioning are attributed to membrane structure and characteristics, a major segment of the research was focused on correlating filtration performance and membrane features. The research comprised two main phases; the first phase involved determining the comparative filtration performance of eight commercially available NF membranes supplied from four manufacturers. The second main phase was to undertake detailed characterisation studies on the NF membranes in order to obtain a clear understanding of their sulphate separation mechanism and permeate flux. The first phase involved assessments of the permeate flux and selectivity of the eight membranes. The experimental protocol in the second, characterisation part of the work was directed to the identification and evaluation of NF active surface layer characteristics: Pore characterisation by porosity factor calculations, Hydrophilicity/Hydrophobicity nature by contact angle measurements, Surface Free Energy calculations, Surface roughness measurements by AFM, Membrane potential measurements and average charge density calculations. This approach is an acknowledged strategy for NF membrane scientific research assessment and, in the current work provided key data of membrane features that facilitated a systematic understanding of membrane functioning. These characterisation features were also linked successfully to the membrane performance parameters to yield a characterisation/performance envelope which represents a useful basis for NF membrane selection and utilisation to optimise membrane usage and consequent economic advantage. The general discussion includes a summary of the interface between the role of NF and the operational and economic features of the two main types of desalination processes. It includes an outline of a process scheme for the incorporation of NF pretreatment into an MSF plant from the conceptual design stage as opposed to the application employed hitherto where the emphasis has been on attaching NF pretreatment equipment on to an existing unit. As a result, it is expected that NF usage should increase performance ratio, reduce energy consumption, hence the running cost, and increase recovery.
22
Silva, Marta Sofia Fragoso da. "Polyimide and polyetherimide organic solvent nanofiltration membranes." Master's thesis, FCT - UNL, 2007. http://hdl.handle.net/10362/1133.
Testo completoAbstract (sommario):
Integrally asymmetric skinned Lenzing P84 and Matrimid 5218 polymide membranes and Ultem
1000 polyetherimide membranes were prepared. Crosslinking of membranes using aliphatic
diamines resulted in marked improvement in chemical stability. This however resulted in a
decline in flux with only Lenzing P84 demonstrating good flux in DMF. Further variation of
membrane dope parameters and operating conditions allowed for good control of the MWCO of
membranes made from Lenzing P84. SEM pictures of Lenzing P84 membranes revealed a
significant difference in membranes morphology. The presence of macrovoids increased when
using more DMF in the dope solution. These studies demonstrate the possibility of developing
OSN membranes using different polyimides and opens up future possibilities for controlling the
MWCO of these membranes. Preliminary modelling demonstrates that good control of the
MWCO could extend the application of OSN membranes to allow the fraction of molecules in
the NF range.
23
Aljohani, Naser Hamzah. "Characterisation and prediction of nanofiltration charge effects." Thesis, Swansea University, 2015. https://cronfa.swan.ac.uk/Record/cronfa42646.
Testo completoAbstract (sommario):
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.
24
Zhou, Mingyan, Ke Wu, James E. Kilduff, and Georges Belfort. "Modeling organic molecule transport through nanofiltration membranes." Diffusion fundamentals 16 (2011) 37, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13772.
Testo completo
25
Marchetti, Patrizia. "Organic solvent nanofiltration in the peptide industry." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11651.
Testo completoAbstract (sommario):
In recent years the application of membrane technology to molecular separation processes has stimulated interest and showed great potential in a number of industrial fields. Ultrafiltration membranes have been successfully applied to downstream separation of therapeutically active peptides, to overcome some of the limitations of the conventional techniques in terms of costs, scale-up, selectivity and solvent recovery. In this research project, Organic Solvent Nanofiltration of peptide solutions is studied, and this understanding is applied to the development of innovative membrane-based purification strategies for industrial case studies. Basic understanding of transport mechanisms was approached by investigating solvent transport through ceramic nano- and ultrafiltration membranes, and developing a predictive phenomenological model for the transport of solvents and solvent mixtures. Effects of solvent-membrane interactions strongly affected the solvent permeation through nanofiltration membranes, while they were found to be negligible in the ultrafiltration range. The effect of the organic solvent on the permeation of neutral and charged solutes (monovalent salts, a small molecule and peptides) in organic/water mixtures was studied, with particular attention to the role of preferential solvation in the solvent mixture. It was found that the solvent composition and the complex association of counter-ions and buffers highly affect membrane permeation and rejection of organic molecules. It is proposed that all these components change the relative solute-membrane affinity. Since permeation of peptides in organic/water mixtures is affected by complicated matrices of input parameters, a Design of Experiment approach was proposed to efficiently investigate the nanofiltration of model peptides in acetonitrile/water solutions. Statistical models for solvent flux, peptide and ion rejection were obtained by Analysis of Variance and interpreted from a phenomenological point of view. The statistical models were used to asisst process development for two industrial case studies: (1) concentration and salt/solvent exchange of a first therapeutic peptide were optimised, based on the integration of the statistical DoE models with the process simulation for concentration and diafiltration; (2) the nanofiltration-assisted synthesis of a second therapeutic peptide, based on the coupling between nanofiltration and reaction in one unique process, was developed and compared to the established process by techno-economical analysis. The so-called "Reactive Peptide Nanofiltration" was found to be advantageous in terms of economics, efficacy, impact on the market, and on the environment. In conclusion, nano ltration was found to be a solid and competitive technique for application to peptide processes. On the basis of the results of this research, Lonza decided to invest in a new nano ltration plant for the downstream of peptides with ceramic membranes. The advantages of nanofiltration technology, in terms of development of more efficient materials (stable in critical solvents and harsh acid/basic conditions), improvement of membrane performances (selectivity, lifetime) and integration of nanofiltration with other techniques in hybrid processes seem therefore promising in overcoming the hesitancy of industries to modify the established processes and invest in new nano ltration plants, by making the payback period for the return of investment more attractive. It is plausible to think that this technology will shortly become a primary choice for new separation and purification processes.
26
Zhou, Mingyan, Ke Wu, James E. Kilduff, and Georges Belfort. "Modeling organic molecule transport through nanofiltration membranes." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184966.
Testo completo
27
Gupta, Abhinaba. "Polydicyclopentadiene : a novel organic solvent nanofiltration membrane." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3460.
Testo completoAbstract (sommario):
Macroscopic, hollow thimbles were synthesized from dicyclopentadiene with the Grubbs second generation catalyst at a monomer:catalyst loading of 10,000:1. A series of Buchwald-Hartwig and Sonogashira coupling reactions were completed on the interior of the thimbles followed by extraction of the product to the exterior using hexane. In all examples, palladium was retained by the membranes at ≥99.9% levels. Both polar and apolar molecules with molecular weights from 101 to 583 g mol-1 permeated these thimbles with values for flux of 10-5 to 10-6 mol cm-2 h-1, but selected molecules did not permeate them and had flux values 104 to 105 times slower. The difference in flux was large between molecules that permeated and those that did not permeate, but no trend was observed that correlated flux with molecular weight or hydrophobicity. Rather, molecules that did not permeate the membranes had large cross-sectional areas that led to low rates of diffusion within the highly cross-linked polydicyclopentadiene membranes.
Membranes were fabricated from the ring opening metathesis polymerization of dicyclopentadiene with the Grubbs first generation catalyst at a monomer:catalyst loading of 5,000:1. Mixtures of fatty acid salts were separated using polydicyclopentadiene membranes. Mixtures of fatty acids could not be separated by the membranes, but when triisobutylamine was added to the fatty acids, cis-fatty acid salts had slower permeation though the membranes than saturated and trans-fatty acid salts. Oleic, petroselinic, vaccenic, linoleic, and linolenic acid salts with triisobutylamine had slower permeation relative to the permeation of stearic and elaidic acid salts.
Organic catalysts were retained from organic molecules using nanoporous polydicyclopentadiene membranes. Acid or base was added to organic catalysts that increased the critical areas of the organic catalysts to the size range (>0.5 nm2) where PDCPD membranes could retain them. The catalysts by themselves were too small to be retained by the membrane, but the salts were in the range where PDCPD retains molecules.
28
Ouali, Sara. "Étude de la dépollution des eaux par couplage des procédés : modélisation et hydrodynamique." Electronic Thesis or Diss., Rennes 1, 2022. http://www.theses.fr/2022REN1S097.
Testo completoAbstract (sommario):
Cette thèse a pour but de développer une approche innovante et un système avancé intégrant "membrane et oxydation" pour le traitement des eaux. La principale innovation de cette étude réside dans l’utilisation d’une configuration monophasique où l’ozone est solubilisé à forte concentration en amont de la membrane dans une eau pure ou à faible demande en ozone. Le choix des membranes s’est porté sur des membranes organiques qui sont moins coûteuses que les membranes céramiques (mais cependant moins résistantes chimiquement). La première partie de ce travail s’est donc focalisée sur la compatibilité de membranes organiques de NF commerciales avec l’ozone pour choisir le matériau le plus robuste et le plus résistant à l’ozone pour le couplage des procédés. Dans la deuxième partie, un pilote à l'échelle du laboratoire, combinant le procédé peroxone et la nanofiltration, a été développé afin de démontrer la faisabilité d'une telle approche les résultats obtenus ont prouvé que la configuration choisie pour le procédé hybride présente différents avantages. Tout d'abord, le mélange de la solution préozonée et de l’eau à traiter dopée en peroxyde d’hydrogène permet une production intensifiée des radicaux hydroxyles dans le cœur du liquide, D’autre part, le procédé développé protège les membranes du colmatage organique, et les préserve de l’attaque de l’ozone<br>This thesis aims to develop an innovative approach and an advanced system integrating "membrane and oxidation" for water treatment. The main innovation of this study lies in the use of a single-phase configuration where ozone is solubilized at high concentration upstream of the membrane in pure or low ozone demand water. The choice of membranes was made on organic membranes which are less expensive than ceramic membranes (but less chemically resistant). The first part of this work therefore focused on the compatibility of commercial NF organic membranes with ozone to select the most robust and ozone resistant material for process coupling. In the second part, a laboratory-scale pilot, combining the peroxone process and nanofiltration, was developed to demonstrate the feasibility of such an approach. The results obtained proved that the configuration chosen for the hybrid process has different advantages. First of all, the mixture of the preozonated solution and the water to be treated doped with hydrogen peroxide allows an intensified production of hydroxyl radicals in the core of the liquid. Secondly, the process developed protects the membranes from clogging. organic, and protects them from the attack of ozone
29
Bhanushali, Dharmesh S. "SOLVENT-RESISTANT NANOFILTRATION MEMBRANES: SEPARATION STUDIES AND MODELING." Lexington, Ky. : [University of Kentucky Libraries], 2002. http://lib.uky.edu/ETD/ukychen2002d00059/DISSERTATION.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Kentucky, 2002.<br>Title from document title page. Document formatted into pages; contains xvii, 268 p. : ill. Includes abstract. Includes bibliographical references (p. 261-267).
30
Agbekodo, Koffi Marcus. "Elimination par nanofiltration des composés organiques d'une eau de surface prétraitée : caractérisation du carbone organique dissous avant et après nanofiltration." Poitiers, 1994. http://www.theses.fr/1994POIT2252.
Testo completoAbstract (sommario):
Les principaux objectifs de cette etude etaient de mesurer l'efficacite de la nanofiltration en terme d'elimination de la matiere organique naturelle, d'identifier les constituants majoritaires du fond refractaire organique du permeat et de tenter de comprendre les principaux mecanismes de retention de quelques composes organiques simples par nanofiltration. Les resultats de nos travaux, qui ont eu lieu en partie sur site industriel et en partie en laboratoire, ont montre que la nanofiltration est un excellent procede qui permet a partir de l'eau filtree sur sable de l'usine de mery/oise pretraitee, de produire un permeat de tres faible charge organique, peu consommateur de chlore et faiblement precurseur de composes organohalogenes totaux (tox). Les rendements d'elimination sur ces parametres sont generalement superieurs a 90%. Les constituants majoritaires du cod du permeat ont ete identifies comme etant les acides amines (en moyenne 30%), les aldehydes (8%) et des composes divers (10 a 20%) appartenant a la famille des acides gras aliphatiques, des acides aromatiques, des alcools, des benzenes substitues et des hydrocarbures satures et insatures de faible masse. Malgre leur nombre important, la concentration de chacune de ces structures a ete estimee a 0. 3 g l##1 c. On peut admettre d'apres la bibliographie que les hydrates de carbone representeraient une part importante du cod restant. En outre les acides amines ont une contribution importante au codb du permeat. Seuls 34% des composes inclus dans les tox ont pu etre identifies. Il s'agit des trihalomethanes et des acides haloacetiques. Cependant, puisque les acides amines totaux permettent d'expliquer a eux seuls la demande en chlore du permeat, les autres sous-produits de chloration non identifies sont probablement des nitriles chlores, des chloro-imines et des chloroaldehydes qui sont parmi les principaux intermediaires reactionnels de la chloration des acides amines. L'effet du ph sur l'elimination de quelques composes simples par nanofiltration a ete etudie de meme que l'effet du cod sur la rejection de deux s-triazines. Les resultats montrent que la diffusion, la repulsion electrostatique et l'adsorption a la surface des membranes joue un role important dans les mecanismes de rejection de ces composes
31
Toutianoush, Ali. "Polyelektrolyt-Multischichtmembranen für Pervaporation, Dialyse, Nanofiltration und Reversosmose." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971864039.
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32
Chaturvedula, Durgaprasad. "Treatment of Mililani I Well Water By "Nanofiltration"." Thesis, Water Resources Research Center, University of Hawaii at Manoa, 1995. http://hdl.handle.net/10125/21918.
Testo completoAbstract (sommario):
Two nanofiltration membranes, a thin film composite (TFC) membrane, a cellulose triacetate (CTA) membrane, were tested as pretreatment alternatives to extend the effective life of GAC at Mililani Wells I, Oahu, Hawaii. TFC membranes achieved excellent 1,2,3-trichloropropane (TCP), and 1,2-dibromo-3-chloropropane (DBCP) removal percentages whereas CTA membranes performed very poorly. TFC membranes showed promising signs of reducing total organic carbong (TOC) from the nanofiltration unit influent. In Mililani waters, only TCP is present in large amounts. It is suggested that further studies should be conducted where there is a chance of observing membrane's performance against high quantities of 1,2-dibromoethane (EDB), and DBCP. Due to the lack of trained personnel, not many TOC analyses were conducted. It is proven that nanofiltration is a viable treatment alternative and a pilot scale study should be conducted in the future taking economics also into consideration.<br>Thesis (M. S.)--University of Hawaii at Manoa, 1995.<br>Includes bibliographical references (leaves 46-48).<br>UHM: Has both book and microform.<br>Water Resources Research Center
33
Wijaya, Julie E. "Formation and characterization of solvent resistant nanofiltration membranes." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27081.
Testo completoAbstract (sommario):
In this work, a novel approach for preparing nanofiltration membranes using poly(amide imide) (TorlonRTM)/Chitosan composites by coating the Chitosan solution on top of the Torlon base membrane and subsequently curing and neutralization with sodium bicarbonate (NaHCO3) has been developed.
In general, TorlonRTM/Chitosan composite nanofiltration membranes were found to be stable in aqueous medium and when contacted with the solvents. A uniform Chitosan dense layer was successfully coated on the base membrane, which reduced the effect of chemical degradation of the membrane. Low permeability of solvents was attributed to the swelling of the Torlon RTM layer. It is proposed that by increasing the porosity in the TorlonRTM based membrane or utilizing other polymers which contain amide chains as the support membrane, permeability performance could be enhanced. (Abstract shortened by UMI.)
34
Harrison, Catherine J. "Bench-scale testing of seawater desalination using nanofiltration /." abstract and full text PDF (free order & download UNR users only), 2005. http://0-wwwlib.umi.com.innopac.library.unr.edu/dissertations/fullcit/1433104.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Nevada, Reno, 2005.<br>"August, 2005." Includes bibliographical references (leaves 80-84). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
35
Wooten, Mary K. "NANOFILTRATION MEMBRANES FROM ORIENTED MESOPOROUS SILICA THIN FILMS." UKnowledge, 2014. http://uknowledge.uky.edu/cme_etds/28.
Testo completoAbstract (sommario):
The synthesis of mesoporous silica thin films using surfactant templating typically leads to an inaccessible pore orientation, making these films not suitable for membrane applications. Recent advances in thin film synthesis provide for the alignment of hexagonal pores in a direction orthogonal to the surface when templated on chemically neutral surfaces. In this work, orthogonal thin film silica membranes are synthesized on alumina supports using block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) as the template. The orthogonal pore structure is achieved by sandwiching membranes between two chemically neutral surfaces, resulting in 90 nm thick films. Solvent flux of ethanol through the membrane demonstrates pore accessibility and suggests a silica pore size of approximately 10 nm. The permeability of ions and fluorescently tagged solutes (ranging from 4,000 to 70,000 Da) is used to demonstrate the membrane’s size selectivity characteristics. A size cut off occurs at 69,000 Da for the model protein BSA. By functionalizing the silica surface with a long chained alkyl group using n-decyltriethoxysilane (D-TEOS), the transport properties of the membranes can be altered. Contact angle measurements and FTIR results show the surface to be very hydrophobic after functionalization. Solvent flux of ethanol through the silica thin film membrane is similar before and after functionalization, but water flux decreases. Thin film silica membranes show much promise for applications in catalysis, bio-sensing, and affinity separations.
36
Moitsheki, Lesego Johannes. "Nanofiltration : fouling and chemical cleaning / Lesego Johannes Moitsheki." Thesis, North-West University, 2003. http://hdl.handle.net/10394/391.
Testo completoAbstract (sommario):
The challenge of providing developing rural areas in South Africa with
sufficient potable water is substantial. North West Province, among others, is
water-stressed, semi-arid, and largely rural with a high dependence on
groundwater as a strategic resource. Some parts of the province are having
poor water quality which ends up affecting households, farming and livestock.
The aim of this study is to evaluate the performance of nanofiltration (NF)
membranes in detrimental ion (fluoride, nitrate and sulphate) rejection and to
monitor fouling on membranes with their subsequent chemical cleaning.
Five commercial membranes (D12, D11, CTC1, NF90 and NF70) were
characterized using scanning electron microscopy (SEM), single salt
retentions and clean water permeation studies. The three-layered structure of
the membranes was observed using SEM, viz.: smooth dense layer, loosely
networked sublayer and the support. 012, D11 and CTC1 showed higher
water flux than NF90 and NF70. Membranes showed more retention of
divalent ions than of monovalent ions. All tested membranes showed a
negative surface charge density.
During treatment of sampled rural water, all the membranes tested (D12, D11,
CTC1, NF90 and NF70) gave different ion retention results and were mostly
influenced by water composition. All tested membranes satisfactorily rejected
sulphate. NF70 effectively rejected all the ions of interest (fluoride, nitrate and
sulphate) from rural water, indicating that NF70 behaves more like a reverse
osmosis (RO) than an NF-membrane.
During fouling experiments, it was found that salts crystallize on the
membrane surface, thus decreasing the membrane performance. Cake
formation was observed on the membranes fouled with rural water. During
chemical cleaning, acid was not an effective cleaning agent. Alkali and
surfactant solutions separately proved to be moderate cleaning agents (flux
recovery ranged from 50% to 75%) while their combination (alkali and
surfactant) gave the best results (100% flux recovery)<br>Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2004.
37
Diaper, Clare. "Low pressure nanofiltration membranes for dyehouse effluent treatment." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284922.
Testo completo
38
ALVES, THAIS DE LIMA. "INORGANIC FOULING IN NANOFILTRATION MEMBRANES DURING DESULPHATATION PROCESS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9206@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO<br>Um problema inerente ao processo de separação por
membranas, mais
especificamente a nanofiltração( NF) é a perda de
eficiência das membranas com
o tempo de operação do sistema, que se deve, em grande
parte, ao depósito ou
adsorção de material na superfície e/ou poros das
membranas. O desenvolvimento
de incrustações faz com que o fluxo permeado diminua muito
e torna necessário
regimes freqüentes de limpeza que ocasionam uma acentuada
diminuição na vida
útil da membrana. Este estudo enfoca o comportamento de
soluções salinas
simples, binárias e multicomponentes submetidas a processo
de nanofiltração com
membrana comercial utilizada em processos de dessulfatação
(NF-90-400- Dow)
em módulo de placa e quadros com alimentação em fluxo
cruzado, condições de
pressão elevada e baixa vazão escolhidas de modo a
favorecer a formação dos
depósitos. A membrana selecionada para o estudo mostrou
grande eficiência na
eliminação de sulfato tanto para soluções simples como
para soluções binárias, foi
observado que variação na força iônica afeta a eficiência
de remoção de sulfatos
das correntes de alimentação e ainda que variações na
diferença de pressão
aplicada no processo utilizando água do mar sintética como
solução de operação
afetam de forma significativa as características de
incrustação.<br>Fouling is a problem without a satisfactory solution in
nanofiltration process.
The fouling development causes low performance and
reduction of the membrane
time life. The aim of this work was to evaluate the
behavior of salts significantly
present in the sea water in fouling formation on the
membrane surface. A
commercial nanofiltration membrane (NF-90-400), which was
developed for
sulphates removal process, was particularly investigated.
The permeation
experiments with sulphates solution were carried out
during seven days; permeate
flux and effluent conductivities were monitored.
Temperature, transmembrane
pressure, concentration, and flow velocity of the feeding
solution were kept in
25ºC, 30 bar, 4.000 mg/L, and 0,030 m/s, respectively. The
selected membrane
showed great efficiency in the sulphate elimination for
simple solutions and for
binary solutions, it was observed that variation in the
ionic force affects the
efficiency of sulphates removal. Variations in DP when the
solution of work was
synthetic sea water affects in a significant way the
incrustation characteristics.
39
Sdika, Didier. "La nanofiltration appliquée à la fabrication d'eau potable." Paris 5, 1995. http://www.theses.fr/1995PA05P105.
Testo completo
40
Zhu, Haochen. "Multiscale modelling of transfer mechanisms through nanofiltration membranes." Rennes 1, 2011. http://www.theses.fr/2011REN1S070.
Testo completoAbstract (sommario):
Although nanofiltration (NF) has attracted increasing attention over the recent years, its current industrial applications are still limited compared to the great potentialities of this clean process. The major reason is that the physical phenomena involved in separation at the nanoscale are still poorly understood and the relative success of current NF models can be attributed in large part to the fact that key properties of membranes (like their surface charge density) and confined fluids (like the dielectric constant of the solution in the membrane pores) are most often fitting parameters that have only limited correspondence to reality. The aim of this thesis work was to improve the understanding of ion-transfer mechanisms through NF membranes. A model coupling the hydrodynamics of the system with fluid / material interactions was developed. It was shown that the inhomogeneous distribution of the surface charges inside the skin layer of a membrane significantly affects the transport of ions and the rejection capacities of the membrane material. In order to investigate the effect of confinement on the physical properties of aqueous solutions, molecular dynamics simulations of electrolyte solutions confined in a model silica nanopore were performed. The simulations revealed a structuration of the fluid in the neighbourhood of the pore surface, a significant decrease in diffusion coefficients and a strong modification of the dielectric properties of ionic solutions that can lead to either repulsive or attractive Born effects depending on the nature of ions<br>Malgré l'intérêt croissant porté ces dernières années à la nanofiltration (NF), ses applications industrielles restent limitées par rapport aux potentialités de ce procédé propre. La principale raison est que les phénomènes physiques impliqués dans des séparations à l’échelle nanométriques restent mal compris et le succès relatif des modèles actuels de NF tient en grande partie au fait que des grandeurs essentielles des membranes (comme leur densité de charge de surface) et des fluides confinés (comme la constante diélectrique de la solution à l'intérieur des pores de la membrane) sont le plus souvent des paramètres d'ajustement ne correspondant que très approximativement à la réalité. Cette thèse a eu pour objectif d’améliorer la compréhension des mécanismes de transfert d'ions à travers des membranes de NF. Pour cela, une modélisation couplant l'hydrodynamique du système et les interactions fluide / matériau a été développée. Il a été montré que la distribution hétérogène des charges de surface dans la couche active d’une membrane affecte profondément le transport des ions et les capacités de rétention matériau membranaire. Afin d’étudier l’effet du confinement sur les propriétés physiques de solutions aqueuses, des simulations de dynamique moléculaire de solutions d’électrolytes confinés dans un nanopore modèle de silice ont également été réalisées. Celles-ci ont montré une structuration du fluide au voisinage de la surface du pore, une diminution significative des coefficients de diffusion et une modification importante des propriétés diélectriques des solutions ioniques pouvant entraîner des effets de Born répulsifs ou attractifs selon la nature des ions
41
Umpuch, Chakkrit. "Séparation et purification d'un acide organique par nanofiltration." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1142/.
Testo completoAbstract (sommario):
L'objectif de ce travail a consisté à déterminer dans quelle mesure la modification de la composition ionique pouvait améliorer la séparation glucose/lactate par nanofiltration. Plus précisément, il s'agissait d’évaluer l'impact de l'addition d'un électrolyte sur la sélectivité de la séparation. En effet, l'influence de la composition ionique sur les rétentions d'espèces neutres et chargées en nanofiltration est gouvernée par des mécanismes différents. L'influence de la composition ionique sur les rétentions du glucose et du lactate a été étudiée en solutions binaires (glucose/électrolyte et lactate/électrolyte) et en solutions ternaires (glucose /lactate/électrolyte) par addition de NaCl et Na2SO4 à différentes concentrations. Les résultats ont en effet montré que les rétentions du glucose et du lactate étaient influencées de manière différente par l'ajout de sel. La présence de NaCl diminue légèrement les rétentions de glucose et de lactate. La diminution plus marquée de la rétention du lactate à faible flux de perméation, permet d'améliorer la séparation d'un facteur 1,4 par rapport au mélange sans ajout de sel. Par contre, l'addition de Na2SO4 n'a aucune influence sur la rétention du glucose tandis que celle du lactate est fortement diminuée. La séparation est alors améliorée d'un facteur 1,9<br>The present work focuses on the study of a nanofiltration step to purify solutions containing lactate and glucose. From previous results, it was concluded that, whilst good separation was expected from results obtained with single solute solutions, the NF selectivity achieved with mixed solutions was finally very poor. On the other hand, it was demonstrated that the presence of a charged solute can change significantly the retention of either neutral or charged ones. The objective of this experimental study is to investigate to what extend the addition of an electrolyte can improve the selectivity of lactate / glucose separation by nanofiltration. Experimental results were used to get the variation of the observed retentions vs. The permeation flux and to evaluate the separation efficiency from the separation factor. In presence of NaCl, both glucose and lactate retentions slightly decrease and remains very close except at low permeation fluxes where the addition of NaCl has more effect on lactate retention than on glucose one. On the contrary, whilst the addition of Na2SO4 has no influence on glucose retention, a strong effect was pointed out on the lactate retention, especially for high electrolyte concentrations for which negative retentions were obtained at low permeation fluxes. Then, the separation improvement by adding salt is much more important in presence of Na2SO4 compared to NaCl. A maximum separation factor of 1. 9 was obtained with Na2SO4 at 0. 25 M adding to the glucose / lactate solution whereas the separation was impossible without the addition of salt
42
Chevalier, Stéphanie. "Modélisation mathématique des mécanismes de séparation en nanofiltration." Bordeaux 1, 1999. http://www.theses.fr/1999BOR10529.
Testo completoAbstract (sommario):
La nanofiltration est un procede membranaire utilise dans des secteurs aussi divers que l'industrie alimentaire, automobile ou pharmaceutique. La modelisation des processus de transfert et de separation de la matiere a travers les nanofiltres est delicate car ceux-ci resultent de la combinaison de nombreux phenomenes physico-chimiques complexes. Les principales etapes de ce travail sont les suivantes : - description des principaux mecanismes de transport et de retention des especes en solution aqueuse par une membrane solide a travers laquelle on impose une difference de pression hydrostatique, - revue bibliographique des modeles mathematiques de filtration deja existants, - caracterisation experimentale des proprietes physico-chimiques intrinseques (distribution de taille des pores, surface specifique, porosite, epaisseur, composition chimique, charge electrique de surface) d'une gamme de membranes organiques de nanofiltration, - mise en place du modele mathematique de nanofiltration correspondant (modele dit de retention sterique, chimique et electrique), - etalonnage, - validation a partir d'essais experimentaux, - application du modele a la nanofiltration de melanges aqueux complexes (calcul des taux de retention et des profils des proprietes des solutes a travers les membranes). A l'issue de cette etude, nous disposons d'un outil numerique qui permet de simuler la nanofiltration de melanges quelconques d'ions et/ou de molecules organiques neutres dans une large gamme de conditions operatoires (pression et en concentration). Ce code devrait permettre aux industriels d'adapter la nature du nanofiltre et les conditions operatoires au melange a filtrer, de facon a obtenir le meilleur rendement.
43
Soroko, Iwona. "Polyimide organic solvent nanofiltration membranes-formation and function." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6882.
Testo completoAbstract (sommario):
This thesis offers a comprehensive study that analyses the relationship between polyimide (PI) organic solvent nanofiltration (OSN) membrane formation parameters, membrane structure, and membrane functional performance. The dissertation starts by addressing the structure-related problem of macrovoid formation, which arises when more open membranes are prepared. Incorporation of TiO2 nanofillers into the membrane matrix results in macrovoid-free, organic/inorganic PI/TiO2 mixed matrix membranes without compromising rejection. Subsequently, a detailed analysis of the membrane formation process, considering the dope solution composition, evaporation step, and structural properties of polyimides, was conducted. The effect of the choice of polymer/solvent/co-solvent/non-solvent was found to be very profound and qualitatively predictable through introduction of a complex solubility parameter. Increasing value of complex solubility parameter can predict higher rejections. The study of the evaporation in PI OSN membrane formation has shown that this optional step is undesirable, as its presence results in unaltered rejection and significantly lower flux. Nevertheless, the presence of a co-solvent, regardless of whether it is volatile or not, was found to be required as it promotes formation of a dense membrane top layer. We have also studied sensitivity of PI OSN membranes to small perturbations in polymer characteristics, such as: molecular weight, alternating diisocyanates to form the PI chain, and copolymerisation method (block vs random). Finally, we proposed a less hazardous route for the PI OSN membrane formation process, which would reduce environmental impact without compromising the separation performance of the existing membranes.
44
Loh, Xun Xing. "Polyaniline membranes for use in organic solvent nanofiltration." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/11347.
Testo completo
45
Lim, King Zheng. "Separation of solvent from microalgal hydrocarbon using nanofiltration." Thesis, Lim, King Zheng (2016) Separation of solvent from microalgal hydrocarbon using nanofiltration. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/33944/.
Testo completoAbstract (sommario):
The need for searching an alternative technology to separate solvent efficiently from the post-extraction process in the algae fuel production process has been long researched for, and little to no convincing findings were found to rectify the current energy crisis. This report aims to evaluate the viability of implementing nanofiltration technology that could replace the use of a distillation column in the post-extraction process. Aspen Plus was used to assess the thermodynamic feasibility of utilising chemical process unit operations. This includes the following: investigation of the effect of thermodynamic property methods to generate a more realistic separation process based on the nonideality of the feed mixture, optimization of the simulation via sensitivity analysis, and an overall energy balance to determine its sustainability based on the calorific value of the hydrocarbon extracted from an algae culture. Nanofiltration experiments were carried out to establish the applicability of the membrane purchased from Sterlitech and possibly fill a current void in research for utilising the Duracid membrane in a heptane solution. The experiments covered: the effect of different contact times with heptane, the effect of pressure and feed concentration variance. A stirred cell was used to facilitate the experiment, and several parameters were done to determine the characteristics of the membrane, which included permeating de-ionised water, heptane, and squalene-heptane. Results showed that prolonged contact times with heptane worsen the permeating performance of the membrane over time, and a maximum of 6% rejection value was attained when using Duracid membrane. Higher operating pressure and lower feed concentration also enhanced the permeate flux. Possible explanation for such occurrence includes the nanofiltration driving force, membrane polarity difference to the solvent, and membrane swelling. Although GCMS showed a little rejection value for retaining squalene in heptane solution, the finding is significant that could prove solvent separation via nanofiltration is possible and future work is needed to improve the outcome. Alternative separation technology and solvent resistant nanofiltration membrane had been proposed, and that could serve as another starting point for an efficient separation process.
46
Altun, Veysi. "Solvent stable UV and EB cross-linked polysulfone-based membranes." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30393/document.
Testo completoAbstract (sommario):
La part des technologies membranaires en tant que technique de séparation a rapidement augmenté au cours de ces dernières années grâce à leur large gamme d'applications. Le marché en pleine expansion nécessite des matériaux polymères avancés qui montrent une résistance accrue vis-à-vis du gonflement et de la plastification en séparation de gaz (GS) ou vis-à-vis de solvants forts et des conditions de pH extrême en nanofiltration en milieu organique (SRNF). Aujourd'hui, la réticulation apparait comme une technologie prometteuse pour répondre à ces nouveaux besoins. La réticulation chimique est l'une des techniques les plus couramment utilisées et est basée sur une réaction chimique entre un polymère (par exemple un polyimide) et un réticulant (par exemple une diamine ou un diol). Cependant pour des polymères, tels que les polysulfones (PSU), qui ne contiennent pas de groupes fonctionnels chimiquement réactifs dans leur squelette, cette technique n'est pas viable. Enfin la réticulation chimique implique plusieurs étapes de traitement et induit des flux de déchets nocifs. La recherche d'une technique de traitement rapide et verte généralement applicable est donc d'une première importance. Deux nouvelles techniques de réticulation, que sont les traitements par rayons ultraviolets (UV) pour par faisceaux d'électrons (EB), ont donc été explorées dans cette thèse afin d'obtenir des membranes stables chimiquement et thermiquement, ce qui est intéressant pour les applications SRNF. Des membranes asymétriques, composées d'un réseau polymère semi-interpénétrant (SIPN), ont été préparées par séparation de phase induite par un solvant (NIPS). Le PSU a été choisi comme polymère grâce à ses caractéristiques intrinsèques suivantes : propriétés thermiques et mécaniques importante, photosensibilité et absence de groupes réactifs. Les membranes réticulées à structure SIPN ont été obtenues par traitement UV et EB. Ces techniques possèdent plusieurs avantages par rapport à la réticulation chimique : une réduction de la production de déchets, des besoins énergétiques plus faibles et des temps de traitement rapides. Dans une première partie, nous avons étudié l'influence de la fonctionnalité du réticulant, de l'énergie du rayonnement et du rapport polymère / réticulant sur l'efficacité de la réticulation par EB. Des agents de réticulation à base d'acrylate ont été utilisés. Les membranes obtenues ont été caractérisées par des expériences en ATR-FTIR, SEM et de filtration, ainsi que des essais de stabilité contre des solvants forts. Le meilleur type de réticulant et sa concentration optimale sous une dose d'EB optimale ont ensuite été sélectionnés pour les études suivantes. Dans la seconde partie, nous avons exploré les effets du rapport solvant / co-solvant et du temps d'évaporation avant la précipitation des membranes en PSU réticulées par la suite soit par UV et soit par EB; le tétrahydrofurane (THF) ou le 1,4-dioxane (DIO) étant utilisés comme solvant. Dans les deux cas, les morphologies membranaires différent en fonction des paramètres étudiés de l'inversion de phase. L'augmentation du temps d'évaporation réduit la formation de macrovides et permet l'apparition de structures spongieuses. Les flux de solvant sont généralement restés trop faible pour que les membranes soient vraiment utiles en SRNF. Un post-traitement a été effectué pour augmenter le flux en immergeant les membranes réticulées dans du dimethylformamide (DMF) pendant 48 h. Les membranes résultantes ont des perméances plus élevées et des taux de rejets plus faibles<br>The importance of membrane technology as a separation technique has increased rapidly over the past decades thanks to its broad range of applications. The expanding market brings along the requirement of advanced polymeric materials, which show resistance towards swelling and plasticization in gas separation (GS) and towards harsh solvents and extreme pH conditions in solvent resistant nanofiltration (SRNF). At this stage, cross-linking has emerged as a promising technology to overcome these issues. Chemical cross- linking is one of the most commonly used techniques and is based on a chemical reaction between a polymer (e.g. polyimide) and a cross-linker (e.g. diamine or diol). However, for polymers which do not contain chemically reactive groups in their backbone, such as polysulfones (PSU), this technique is not feasible. Additionally, chemical cross-linking involves several processing steps and causes harmful waste streams, triggering the quest for a generally applicable, fast and green curing technique. Two new curing techniques, namely ultraviolet (UV) and electron beam (EB) curing, were explored in this thesis, in order to obtain chemically and thermally stable membranes, hence being attractive for SRNF applications. Asymmetric membranes, composed of a semi-interpenetrating polymer network (SIPN), were prepared via non-solvent induced phase separation (NIPS). PSU was chosen as polymer because of its robust thermal and mechanical properties, photosensitivity and lack of reactive groups. Cross-linked membranes with SIPN structure were obtained via UV and EB-curing. In the first part, the influence of cross-linker functionality, radiation energy dose and polymer/crosslinker ratio on the EB-curing efficiency was investigated. Acrylate-based cross-linkers were employed. The obtained membranes were characterized with ATR-FTIR, SEM and filtration experiments, together with stability testing against harsh solvents. The best type of cross-linker and its optimum concentration under optimum EB-dose were then selected for further studies. In the second part, the effects of solvent/co-solvent ratio and the evaporation time before precipitation of UV and EB-cured PSU SRNF-membranes were explored, using tetrahydrofuran (THF) or 1,4-dioxane (DIO) as co-solvent. Both UV and EB-cured PSU membrane morphologies differed as function of the studied phase inversion parameters. Increasing evaporation time reduced macrovoid formation with appearance of spongy structures. The flux generally remained too low for membranes to become really useful in SRNF. A post treatment was performed to increase the flux by immersing UV-cured PSU-based membranes in dimethylformamide (DMF) for 48 h. The resultant membranes showed higher permeances and lower rejections, making them especially useful as potential candidates as stable supports in the preparation of thin film composite membranes. In a third part, the mechanical characteristics, the effect of casting thickness and the surface properties of the membranes cross-linked by both irradiation methods were further studied. Additionally, the swelling behavior of UV-cured thin PSU films as function of different curing parameters (i.e. radiation dose and cross-linker functionality) was analyzed with ellipsometry. In conclusion, solvent stable asymmetric PSU membranes were developed by two simple, environmentally friendly and highly effective methods. The performance and enhanced chemical resistance of the cured membranes show high potential for implementing both cross-linking procedures in adequate industrial applications after further optimization
47
Ellouze, Fatma. "Purification et fractionnement de mélange de cyclodextrines par procédés membranaires." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20177.
Testo completoAbstract (sommario):
Cette étude a été consacrée à la purification et au fractionnement de mélanges de cyclodextrines par procédés membranaires (NF, UF). Les cyclodextrines (CD) sont des oligosaccharides cycliques constituées de 6 à plus de 60 unités de glucose (CD6-CD60). Elles sont synthèsées en mélange à partir de la bioconversion de l'amidon. Dans un premier temps, la complexation ultrafiltration a été appliquée pour séparer la CD6 et la CD7. Au cours de cette étude, différents paramètres comme la pression, le rapport stœchiométrique entre CD et agent complexant et le rapport massique entre CD ont été étudiés. Il s'est avéré que ces facteurs pouvaient agir sur la sélectivité de séparation. La diafiltration avec un facteur de réduction volumique de 3 a été utilisée, en présence d'Igepal (agent complexant), pour séparer la CD6 et la CD7. Les résultats obtenus sont assez intéressants vu qu'après 4 diafiltrations la CD6 a été récupérée dans le perméat avec une pureté et un rendement respectivement égal à 86 et 71%.Dans une deuxième partie, nous nous sommes intéressés au fractionnement d'un mélange brut de cyclodextrines à large cycle par procédé multi étagé avec le but de : (1) purification du mélange en réduisant la fraction des co produits (glucose, CD6-CD8) et (2) fractionnement du mélange pour obtenir des fractions majoritairement enrichies en CD9-CD21 et CD22-CD60. Une simulation mathématique a été appliquée pour sélectionner les stratégies de fractionnement à deux concentrations différentes (1 et 3 g/L). Les résultats obtenus pour une concentration initiale de 1 g/L sont assez intéressant vu que la pureté des cyclodextrines à large cycle dans le rétentat final est de 97%<br>This study was devoted to the purification and fractionation of cyclodextrins mixtures by membrane processes (NF, UF). Cyclodextrins CDs are produced in mixture by enzymatic degradation of starch. They are cyclic oligosaccharides containing from 6 to more than 60 glucose units (CD6 to CD60).In a first part, complexation ultrafiltration was applied to separate CD6 and CD7. In this study, different parameters such as the pressure, the stoichiometric ratio between CD and complexing agent and the mass ratio between CD were studied. It seems that these factors could influence the selectivity of separation. Diafiltration with a volume reduction factor of 3 was used, with Igepal as complexing agent, to separate the CD6 and CD7. The obtained results are interesting since after four diafiltrations the CD6 was recovered in the permeate with a purity and yield respectively equal to 86 and 71%.In the second part, we were interested in the fractionation of a crude mixture containing large ring cyclodextrins by a multi stage process in order to: (1) purify the mixture from co products (glucose and CD6-CD8) and (2) fractionate the mixture to obtain fractions predominantly enriched in CD9-CD21 and CD22-CD60. A mathematical simulation predicting the composition of the CD mixture after diafiltration was applied to select the strategy of fractionation at two different concentrations (1 and 3g/L). The results obtained for an initial concentration of 1g /L are quite interesting since the purity of large ring cyclodextrins in the final retentate is 97%
48
Idil, Mouhoumed Elmi. "Étude des propriétés de charge et de transport de membranes de nanofiltration." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S007/document.
Testo completoAbstract (sommario):
Aujourd'hui, la nanofiltration (NF) est perçue comme un procédé de séparation efficace et propre permettant d’extraire ou de concentrer des solutés ioniques ou neutres. Son développement à l’échelle industrielle n’est cependant pas encore optimal car les différents mécanismes de séparation sont encore mal compris. Cette thèse a porté d’une part sur l’étude des propriétés charge de surface des membranes de NF/OI et d’autre part sur les mécanismes de transport à travers des membranes de NF. Il a tout d’abord été montré, grâce à des mesures électrocinétiques réalisées sous atmosphère contrôlée, que certaines membranes commerciales subissent un post-traitement afin d’améliorer leurs performances de filtration. La détermination du potentiel zêta, grandeur caractéristique de la charge de surface, s’est révélée être une méthode adaptée pour mettre en évidence la présence d’une couche de post-traitement à la surface d’une membrane. La suite de l’étude a été consacrée à la compréhension des mécanismes de transport lors de la NF de mélanges ternaires contenant deux cations différents (Na+ et Ca2+) et un anion commun (Cl-). L’utilisation du modèle de transport SEDE a permis de montrer que les performances des membranes de NF résultent de la combinaison d’effets stériques, électriques et diélectriques. La dernière partie de ce travail a été consacrée à la NF d’un coproduit de l’industrie agro-alimentaire, le produit fermenté de soja (PFS). Il a été montré que la NF est potentiellement adaptée au dessalement du PFS (réduction de la teneur en cations monovalents) sans perte des sucres d’intérêt<br>Today, nanofiltration (NF) is acknowledged as an efficient and environmentally-friendly separation process suited to extract or to concentrate neutral or ionic solutes. However, its development at industrial scale is not yet optimal because separation mechanisms are still poorly understood. This thesis focused on studying surface charge properties of NF/RO membranes and transport mechanisms through NF membranes as well. Firstly it was shown through electrokinetic measurements performed under controlled atmosphere that some commercial membranes undergo a post-treatment to improve their filtration performance. Determining the zeta potential, a physical quantity representative of the membrane surface charge, was shown to be a reliable method to highlight the presence of a post-treatment layer on the membrane surface. The second part of the study dealt with the understanding of transport mechanisms involved in NF of ternary mixtures containing two different cations (Na+ and Ca2+) and a common anion (Cl-). Using the SEDE transport model it was shown that the performance of NF membranes results from the combination of steric, electric and dielectric effects. The last part of this work was concerned with nanofiltration of a food industry co-product, the fermented soy product (PFS). It was shown that NF is potentially suitable for PFS desalination (reduction in the monovalent cation concentration) without loss of the sugars of interest
49
Hajarat, Rasha. "The use of nanofiltration membrane in desalinating brackish water." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/the-use-of-nanofiltration-membrane-in-desalinating-brackish-water(870d69f0-073d-4474-b591-e9fe85a92af7).html.
Testo completo
50
Stolp, Wynand. "Nickel recovery from spent electrolyte by nanofiltration / Wynand Stolp." Thesis, North-West University, 2007. http://hdl.handle.net/10394/1618.
Testo completo