Whey protein fractionation is an important industrial process that requires effective large-scale processes. Although packed bed chromatography has been used extensively, it suffers from low processing rates due to high back-pressures generated at high flow rates. Batch chromatography has been applied but generally has a low efficiency. More recently, adsorptive membranes have shown great promise for large-scale protein purification, particularly from large-volume dilute feedstocks. A new method for producing versatile adsorptive membranes by combining membrane and chromatographic resin matrices has been developed but not previously applied to whey protein fractionation. In this work, a series of mixed matrix membranes (MMMs) were developed for membrane chromatography using ethylene vinyl alcohol (EVAL) based membranes and various types of adsorbent resin. The feasibility of MMM was tested in bovine whey protein fractionation processes. Flat sheet anion exchange MMMs were cast using EVAL and crushed Lewatit® MP500 (Lanxess, Leverkusen, Germany) anion resin, expected to bind the acidic whey proteins β-lactoglobulin (β-Lac), α-lactalbumin (α-Lac) and bovine serum albumin (BSA). The MMM showed a static binding capacity of 120 mg β-Lac g⁻¹ membrane (36 mg β-Lac mL⁻¹ membrane) and 90 mg α-Lac g⁻¹ membrane (27 mg α-Lac mL⁻¹ membrane). It had a selective binding towards β-Lac in whey with a binding preference order of β-Lac > BSA > α-Lac. In batch whey fractionation, average binding capacities of 75.6 mg β-Lac g⁻¹ membrane, 3.5 mg α-Lac g⁻¹ membrane and 0.5 mg BSA g⁻¹ membrane were achieved with a β-Lac elution recovery of around 80%. Crushed SP Sepharose™ Fast Flow (GE Healthcare Technologies, Uppsala, Sweden) resin was used as an adsorbent particle in preparing cation exchange MMMs for lactoferrin (LF) recovery from whey. The static binding capacity of the cationic MMM was 384 mg LF g⁻¹membrane or 155 mg LF mL⁻¹ membrane, exceeding the capacity of several commercial adsorptive membranes. Adsorption of lysozyme onto the embedded ion exchange resin was visualized by confocal laser scanning microscopy. In LF isolation from whey, cross-flow operation was used to minimize membrane fouling and to enhance the protein binding capacity. LF recovery as high as of 91% with a high purity (as judged by the presence of a single band in gel electrophoresis) was achieved from 150 mL feed whey. The MMM preparation concept was extended, for the first time, to produce a hydrophobic interaction membrane using crushed Phenyl Sepharose™ (GE Healthcare Technologies, Uppsala, Sweden) resin and tested for the feasibility in whey protein fractionation. Phenyl Sepharose MMM showed binding capacities of 20.54 mg mL⁻¹ of β-Lac, 45.58 mg mL⁻¹ of α-Lac, 38.65 mg mL⁻¹ of BSA and 42.05 mg mL⁻¹ of LF for a pure protein solution (binding capacity values given on a membrane volume basis). In flow through whey fractionation, the adsorption performance of the Phenyl Sepharose MMM was similar to the HiTrap™ Phenyl hydrophobic interaction chromatography column. However, in terms of processing speed and low pressure drop across the column, the benefits of using MMM over a packed bed column were clear. A novel mixed mode interaction membrane was synthesized in a single membrane by incorporating a certain ratio of SP Sepharose cation resin and Lewatit MP500 anion resin into an EVAL base polymer solution. The mixed mode cation and anion membrane chromatography developed was able to bind basic and acidic proteins simultaneously from a solution. Furthermore, the ratio of the different types of adsorptive resin incorporated into the membrane matrix could be customised for protein recovery from a specific feedstream. The customized mixed mode MMM consisting of 42.5 wt% of MP500 anionic resin and 7.5 wt% SP Sepharose cationic resin showed a binding capacity of 7.16 mg α-Lac g⁻¹ membrane, 11.40 mg LF g⁻¹ membrane, 59.21 mg β-Lac g⁻¹ membrane and 6.79 mg IgG g⁻¹ membrane from batch fractionation of 1 mL LF-spiked whey. A tangential flow process using this membrane was predicted to be able to produce 125 g total whey protein per L membrane per h.

A series of mixed matrix membranes based on zeolites incorporated into fluorinated polyimides were fabricated and characterized in this study. The first system consisted of a polyimide (6FDA-6FpDA-DABA) with carboxylic acid groups incorporated into its backbone and amine-functionalized zeolite particles (ZSM-2). FTIR indicated that these functional groups interacted with each other through hydrogen bonding. Both SEM and TEM images revealed good contact between the polyimide and the zeolite. Permeability studies showed a drop in He permeability suggesting there were no voids between the two components. While simple gases such as O2 and N2 followed effective permeabilities predicted by mixing theories, polar gases such as CO₂ did not. The second system fabricated used the same polyimide with amine-functionalized zeolite L. This zeolite differs from ZSM-2 in that zeolite L's pores are not clogged with an organic template, and it possesses 1-D pores as opposed to ZSM-2's 3-D pore structure. XPS and zeta potential experiments were performed to verify the presence of amine groups on the zeolite surfaces. FTIR data showed that after a heat treatment, amide linkages were created between the amine group on the zeolite and the carboxylic acid group of the polyimide. SEM images showed a good distribution of zeolite L throughout the polymer matrix, and no indication of voids between the two components. Permeability experiments were performed to determine if the addition of zeolite L to the polyimide improved its separation performance. The permeability was unchanged between the pure polyimide membrane and the mixed matrix membrane, suggesting there were no voids present within the matrix. Permeability results of larger gases followed a Maxwell Model. A third system was prepared using a poly(imide siloxane) (6FDA-6FpDA-PDMS) and untreated zeolite L. The primary focus of this investigation was to determine if the addition of the flexible segment would promote direct contact with the zeolite surface and remove the need to amine-functionalize the zeolite. Poly(imide siloxane)s were synthesized at 0, 22, and 41 wt % PDMS as verified using 1H-NMR. FTIR was employed to qualitatively verify the successful imidization of the polymers. SAXS patterns and TEM images did not reveal distinct phases indicative of phase separation, however, AFM images did show the presence of phase separation of the surfaces of the poly(imide siloxane)s. Permeability results showed a decrease in selectivity and an increase in permeability as the wt % of PDMS was increased. Permeabilities and selectivities dropped as the zeolite loading was increased from 0 to 20 wt %. Upon increasing the zeolite loading from 20 to 30 wt %, increases in permeability were observed, but both the permeability and selectivity were still below that of the pure polymer. The final system studied employed the 41 wt % PDMS poly(imide siloxane) as the polymer matrix and either closed-ended or open-ended carbon nanotubes as the filler. SEM images showed regions of agglomeration for both types of nanotubes. Helium permeability dropped in both types MMMs, but more so in closed-ended carbon nanotubes MMM. Nitrogen permeability was unchanged for the closed-ended carbon nanotubes MMM, and dropped slightly in the open-ended carbon-nanotube MMM. / Ph. D.

Membrane based separation techniques have been widely used and developed over decades. Generally polymeric membranes are used in membrane based gas separation / however their gas separation performances are not sufficient enough for industrial feasibility. On the other hand inorganic membranes have good separation performance but they have processing difficulties. As a consequence mixed matrix membranes (MMMs) which comprise of inorganic particles dispersed in organic matrices are developed. Moreover, to enhance the interaction between polymer and zeolite particles ternary mixed matrix membranes are introduced by using low molecular weight additives as third component and promising results were obtained at 35 &deg / C. Better understanding on gas transport mechanism of these membranes could be achieved by studying the effect of preparation and operating parameters. This study investigates the effect of operation temperature and annealing time and temperature on gas separation performance of MMMs. The membranes used in this study consist of glassy polyethersulfone (PES) polymer, SAPO-34 particles and 2- v hidroxy 5-methyl aniline (HMA) as compatibilizer. The membranes fabricated in previous study were used and some membranes were used as synthesized while post annealing (at 120&deg / C, 0.2atm, N2 atm, 7-30 days) applied to some membranes before they are tested. The temperature dependent gas transport properties of the membranes were characterized by single gas permeation measurements of H2, CO2, and CH4 gases between 35 &deg / C-120 &deg / C. The membranes also characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Annealing time and temperature affected the reproducibility and stability of the mixed matrix membranes and by applying post annealing step to mixed matrix membranes at higher temperatures and longer times, more stable membranes were obtained. For pure PES membranes thermally stable performances were obtained without any need of extra treatment. The permeabilities of all studied gases increased with increasing operation temperature. Also the selectivities of H2/CO2 were increased while CO2/CH4, H2/CH4 selectivities were decreased with temperature. The best separation performance belongs to PES/SAPO-34/HMA mixed matrix membrane at each temperature. When the temperature increased from 35 &deg / C to 120 &deg / C H2/CO2 selectivity for PES/SAPO- 34/HMA membrane was increased from 3.2 to 4.6 and H2 permeability increased from 8 Barrer to 26.50 Barrer. This results show that for H2/CO2 separation working at higher temperatures will be more advantageous. The activation energies were found in the order of / CH4 &gt / H2&gt / CO2 for all types of membranes. Activation energies were in the same order of magnitude for all membranes but the PES/SAPO-34 membrane activation energies were slightly lower than PES membrane. Furthermore, PES/SAPO-34/HMA membrane has activation energies higher than PES/SAPO-34 membrane and is very close to pure membrane which shows that HMA acts as a compatibilizer between two phases.

Propylene is one of the most important feedstocks of the petrochemical industry with an estimated 2015 worldwide demand of 100 million tons. Retrofitting conventional C3 splitters is highly desirable due to the huge amount of thermal energy required to separate propylene from propane. Membrane separation is among the alternatives that both academia and industry have actively studied during the past decades, however; many challenges remain to advance membrane separation as a scalable technology for energy-efficient propylene/propane separations. The overarching goal of this research is to provide a framework for development of scalable ZIF-based mixed-matrix membrane that is able to deliver attractive transport properties for advanced gas separations. Zeolitic imidazolate frameworks (ZIFs) were pursued instead of conventional molecular sieves (zeolites and carbon molecular sieves) to form mixed-matrix membrane due to their intrinsic compatibility with high Tg glassy polymers. A systematic study of adsorption and diffusion in zeolitic imidazolate framework-8 (ZIF-8) suggests that this material is remarkably kinetically selective for C3 and C4 hydrocarbons and therefore promising for membrane-based gas separation and adsorptive separation. As a result, ZIF-8 was used to form mixed-matrix dense film membranes with polyimide 6FDA-DAM at varied particle loadings and it was found that ZIF-8 significantly enhanced propylene/propane separation performance beyond the “permeability-selectivity” trade-off curve for polymeric materials. Eventually, this research advanced ZIF-based mixed-matrix membrane into a scalable technology by successfully forming high-loading dual-layer ZIF-8/6FDA-DAM asymmetric mixed-matrix hollow fiber membranes with attractive propylene/propane selectivity.

For the last two decades, the possibility of using synthetic membranes for industrial gas separations has attracted considerable interest since membrane separation technologies have the advantages of energy efficiency, simplicity and low cost. However, for wider commercial utilization there is still a need to develop membranes with higher permeant fluxes and higher transport selectivities. Conductive polymers, due to their high gas transport selectivities, give rise to a new class of polymeric materials for membrane based gas separation though poor mechanical properties obstruct the applications for this purpose of use. This problem led researches to a new idea of combining the conducting polymers with insulating polymers forming mixed matrix composite membranes. In the previous studies in our group, polypyrrole was chosen as the conductive polymer, and different preparation techniques were tried and optimized for membrane application. As the insulating polymer, previously poly(bisphenol-Acarbonate) was used to support the conductive polymer filler in order to constitute a conductive composite membrane. For this study, as the polymer matrix, hexafluorobisphenol A based poly(arylene ether ketone) was targeted due to its physical properties and temperature resistance which can be important for industrial applications. First of all, permeabilities of N2, CH4, Ar, H2, CO2, and H2 were measured at varying temperatures ranging from 25&deg / C to 85&deg / C through a homogenous dense membrane of chosen polymeric material to characterize its intrinsic properties. Measurements were done using laboratory scale gas separation apparatus which makes use of a constant volume variable pressure technique. The permeability results were used for the calculations of permeation activation energies for each gas. These permeation activation energies were found to be differing slightly for each gas independently from the kinetic diameters of gases. In this study, mixed matrix membranes of conducting polymer, polypyrrole (PPy) and insulating polymer, hexafluorobisphenol A based poly(arylene ether ketone) (PAEK) were also prepared. It was observed that PAEK and PPy form a composite mixed matrix structure, which can function as permselective membrane. The effect of conducting polymer filler content was investigated with two different filler ratios. When comparing with the pure PAEK membranes, meaningful increases for both permeability and selectivity were obtained for some of the gases.

Membranes are a promising, effective and energy efficient separation strategy for effluent gases in the Reverse Water Gas Shift (RWGS) reaction to increase the overall conversion of CO2 to CO. This process involves a separation and recycling process to reuse the unreacted CO2 from the RWGS reactor. The carbon monoxide produced from this reaction, alongside hydrogen (composing syngas), can be used in the Fischer-Tropsch process to create synthetic fuel, turning stationary CO2 emissions into a useable resource. A literature review was performed to select suitable polymers with high CO2 permeability and selectivities of CO2 over CO and H2. PDMS (polydimethylsiloxane) was selected and commercial and in-house PDMS membranes were tested. The highest CO2 permeability observed was 5,883 Barrers, including a CO2/H2 selectivity of 21 and a CO2/CO selectivity of 9, with ternary gas feeds. HY zeolite, silica gel and activated carbon were selected from previous research for their CO2 separation capabilities, to be investigated in PDMS mixed matrix membranes in 4 wt % loadings. Activated carbon in PDMS proved to be the best performing mixed matrix membrane with a CO2 permeability of 2,447 Barrers and comparable selectivities for CO2/H2 and CO2/CO of 14 and 9, respectively. It was believed that swelling, compaction and the homogeneity of the selective layer were responsible for trends in permeability with respect to driving force. The HY and silica gel mixed matrix PDMS membranes were believed to experience constraints in performance due to particle and polymer interfaces within the membrane matrix.

abstract: Water recovery from impaired sources, such as reclaimed wastewater, brackish groundwater, and ocean water, is imperative as freshwater resources are under great pressure. Complete reuse of urine wastewater is also necessary to sustain life on space exploration missions of greater than one year’s duration. Currently, the Water Recovery System (WRS) used on the National Aeronautics and Space Administration (NASA) shuttles recovers only 70% of generated wastewater.1 Current osmotic processes show high capability to increase water recovery from wastewater. However, commercial reverse osmosis (RO) membranes rapidly degrade when exposed to pretreated urine-containing wastewater. Also, non-ionic small molecules substances (i.e., urea) are very poorly rejected by commercial RO membranes. In this study, an innovative composite membrane that integrates water-selective molecular sieve particles into a liquid-barrier chemically resistant polymer film is synthetized. This plan manipulates distinctive aspects of the two materials used to create the membranes: (1) the innate permeation and selectivity of the molecular sieves, and (2) the decay-resistant, versatile, and mechanical strength of the liquid-barrier polymer support matrix. To synthesize the membrane, Linde Type A (LTA) zeolite particles are anchored to the porous substrate, producing a single layer of zeolite particles capable of transporting water through the membrane. Thereafter, coating the chemically resistant latex polymer filled the space between zeolites. Finally, excess polymer was etched from the surface to expose the zeolites to the feed solution. The completed membranes were tested in reverse osmosis mode with deionized water, sodium chloride, and rhodamine solutions to determine the suitability for water recovery. The main distinguishing characteristics of the new membrane design compared with current composite membrane include: (1) the use of an impermeable polymer broadens the range of chemical resistant polymers that can be used as the polymer matrix; (2) the use of zeolite particles with specific pore size insures the high rejection of the neutral molecules since water is transported through the zeolite rather than the polymer; (3) the use of latex dispersions, environmentally friendly water based-solutions, as the polymer matrix shares the qualities of low volatile organic compound, low cost, and non- toxicity. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2016

The increased demand of fossil fuel along with the depletion of economical crude oil resources, environmental challenges such as the accumulation of CO2 and other greenhouse gases in the atmosphere and the reduction of the dependence on imported oil are some of the motivations for the huge interest in biofuels. Biobutanol produced from ABE fermentation has been considered to be a good partial replacement for fossil fuels. However, challenges such as the need for inexpensive feed-stocks, improved fermentation performance to achieve higher final butanol concentration and higher yield, an efficient method for solvent recovery, and water recycle are the main obstacles to make the production of this alcohol economically viable. Pervaporation, a membrane-based process, is considered to be an attractive separation method to remove butanol from ABE fermentation broth. Among the membranes used for butanol separation, PDMS membranes showed reasonable performance such as good permeability, and appropriate selectivity for butanol separation by pervaporation. However, PDMS membranes need to be improved in terms of performance to be applicable in large scale butanol production plants. In this study, activated carbon nanoparticles have been embedded into the matrix of the PDMS membrane to improve its separation performance and, in particular, the permeation flux and butanol selectivity. Result showed that the presence of nanoparticles improves the PDMS membrane performance up to a certain particle loading. Moreover, it was shown that the operating conditions have a major impact on the pervaporation membrane separation process. The best membrane for pervaporation separation of butanol from binary aqueous solutions was obtained for a 6 wt% particle concentration where the total permeation flux and butanol selectivity increased by 42.6% and 51.9%, respectively, compared to neat PDMS membranes. Moreover, the best performance for the separation of butanol from ABE model solutions was achieved for an 8 wt% nanoparticle loading. Both the selectivity for butanol and the total permeation flux more than doubled in comparison to neat PDMS membranes prepared in this study. Moreover, in order to compare the PDMS/AC mixed matrix membrane performance for pervaporation separation of butanol from binary and ABE model solutions with PDMS membranes available on the market, experiments were also performed with a commercial PDMS membrane. Result of butanol separation from ABE model solutions showed that mixed matrix membranes with 8 wt% nanoparticles loading had a higher permeation flux than that of the commercial membranes. It was clearly shown that the presence of activated carbon nanoparticles in the matrix of the PDMS would be beneficial for the pervaporation separation of butanol from ABE fermentation broths. To better comprehend how the presence of activated carbon nanoparticles in the polymeric membranes enhance the performance of the membranes, a series of numerical simulations were performed. A finite difference model was developed to simulate the mass transfer of permeating components through mixed matrix membranes by pervaporation for a wide range of relative permeability, nanoparticle loading, particle shape, particle size and different filler adsorption isotherms. Finally, an investigation has been performed to optimize the butanol pervaporation separation process from ABE fermentation broth at an industrial scale.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22895号 / 工博第4792号 / 新制||工||1749(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 SIVANIAH Easan, 教授 田中 庸裕, 教授 今堀 博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

In this study, pervaporation, a membrane-based process was studied for in-situ separation of butanol. This technique has a great potential due to its high selectivity, low energy requirement and high efficiency. The primary objective was to improve the performance of the Polydimethylsiloxane (PDMS) membrane for the pervaporation separation and the recovery of butanol by adding nanoparticles into its matrix to make mixed matrix membrane (MMM). These nanoparticles included zinc-based Metal Organic Frameworks (MOFs) and zinc oxide. Different particle sizes of zeolitic imidazolate framework (ZIF-8) were synthesized. The separation performance of MMMs incorporating different sizes of ZIF-8 nanoparticles was compared to the performance of mixed matrix membranes incorporating zinc oxide as well as pure PDMS membrane. Different characteristics of ZIF-8 and their impact on the performance of the host membrane were discussed. Result showed that the presence of nanoparticles improves the PDMS membrane performance up to a certain particle loading. Moreover, it was shown that the particle size and interfacial bond between polymer and particles have a major impact on the pervaporation membrane separation process. The best membrane for pervaporation separation of butanol from binary aqueous solutions was obtained for the 8 wt% small-size ZIF-8/PDMS MMM where the total permeation flux and butanol selectivity were increased by 350% and 6%, respectively, compared to neat PDMS membranes. In addition to the MOFs, nanotubes are considered emerging nanostructured materials for use in membrane separation applications due to their high molecular diffusivity and unique geometry. Recent progress has also been made on the modification of nanotube surface functionality, and the fabrication of nanotube mixed matrix membranes as well as the ability to align them in MMMs. Since numerous types of nanotubes are available and the process of producing well-aligned nanotube MMMs is very challenging, a theoretical model using finite difference method (FD) was used to gain a deeper understanding on the effect of nanotubes on the separation performance of mixed matrix membranes. A series of numerical simulations were performed and the effects of various structural parameters, including the tubular filler volume fraction, orientation, length-to-diameter aspect ratio, and permeability ratio, were assessed. The results showed that the relative permeability is enhanced by vertically-aligned nanotubes and further increased with an increase of the permeability ratio, filler volume fraction and the length-to-diameter aspect ratio. In addition, comparing the simulation results with existing analytical models for the prediction of the relative permeability acknowledges a need to develop a new correlation that would provide more accurate predictions of the relative permeability of MMMs with embedded nanotube fillers.