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Academic collection --- 66.08 --- Physical and physicochemical processes --- Theses --- 66.08 Physical and physicochemical processes

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Membranes (Technology) --- Membrane separation. --- Membranes (Technologie) --- Membrane separation --- 66.08 --- 66.08 Physical and physicochemical processes --- Physical and physicochemical processes

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66.08 --- 66.08 Physical and physicochemical processes --- Physical and physicochemical processes --- Filters and filtration. --- Filtres et filtration --- Pharmacotechnology. Preparations --- Fysicochemical separation methods

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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. A new membrane market is arising in the chemical industry where many in-process separation problems can be tackled elegantly by sufficiently stable membranes. Since the 1990s progress has also been made in the development of solvent resistant nanofiltration membranes, opening the possibility to tackle several separation problems in non-aqueous solvents. Organic solvent nanofiltration (OSN) offers great perspectives towards wide application in the process industry as it provides a facile, energy-efficient and scalable alternative to conventional separation processes such as distillation, liquid-liquid extraction or chromatographic purification. It has been proven that OSN has an enormous potential innbsp;solvent intensive pharmaceutical and fine-chemical processes, where it can be used for the recovery, concentration and purification of valuable target molecules, as well as for the purification and recycling of spent solvents. Here, ceramic nanofiltration membranes with their broad solvent resistance and high temperature stability,nbsp;the potential to take a significant market share.The state-of-the-art nanoporous ceramic membranes for OSN are transition metal oxide membranes, containing a large amount of surface OH-groups, making them strongly hydrophilic. By exchanging these hydroxyl groups by a more apolar group (such as alkyl, perfluoroalkyl,...), the surface becomes more hydrophobic, increasing non-polar solvent fluxes. Recently, VITO and UA have developed a new versatile grafting method (modification with Grignard reagents) capable of attaching a direct, non-hydrolysablenbsp;between the membrane surface and the functional group. This results in novel membranes with a wide range of surface functionalities.The approach used in this thesis is to investigate the properties, performance and potential of these grafted membranes in organic solvent nanofiltration. The properties of the Grignard modified membranes were examined by physico – chemical characterisation (contact angle measurements, micro-ATR/FTIR-spectroscopy) in addition to performance characterisation (flux and retention measurements). All observations for modified membranes are consistent with the assumed partial replacement of the OH-groups on the membrane surface and the consequent amphiphilic character of the modified membrane surface. Moreover, the solvent filtration performance and application potential of such Grignard functionalised membranes was further evaluated and explored. To this purpose, the retention behavior of a variety of 5 different model solvent/solute mixtures was determined for a variety of grafted and ungrafted membranes. The varying retention behaviour was evaluated by considering thenbsp;affinity of solvents and solutes for the modified and unmodified membrane surfaces. To support this interpretation, a sorption test was used to quantify the solute-membrane affinity. A long-term test was performed in order to check the stability of grafted groups on the surface of the membrane.Further experimental work was directed to understand how to tune solvent-membrane-solute interactions in a controlled way in order to enhance OSN performance.nbsp;was achieved by performing an extensive retention study on two type of Grignard functionalised membranes, choosing three PEG molecules and polystyrene as solutes, all with almost the same size but different polarities, in a wide range of solvents including water, ethanol, dimethylformamide (DMF), isopropanol, acetone, dichloromethane (DCM), tetrahydrofuran (THF), methyl ethyl ketone (MEK), toluene, ethyl acetate, methyl isobutyl ketone, cyclohexane and methyl cyclohexane. To unravel the transport mechanism properly, the pressure effect of fluxnbsp;retentions was thoroughly investigated. The retention results showed in general a very different behaviour in different ranges ofnbsp;at low solvent polarity, retentions are relativelynbsp;varying with pressure and solvent polarity; at high solvent polarity, retentions are relatively high, and independent of pressure and solvent polarity. The Spiegler-Kedem theory, taking into accountnbsp;diffusion and convection transport mechanisms, was used as a basis for a fundamental explanation of the results and explaining the competing contribution of diffusion and convection in solute transport. Finally, this study demonstrates the importance of all solvent-membrane-solute interactions in the OSN transport, but also shows how theynbsp;be manipulated to enhance the membrane performance.

academic collection --- 66.08 <043> --- Physical and physicochemical processes--dissertations --- Theses --- Academic collection