Aprotic solvents are organic solvents which do not easily react with a substance dissolved in it and they do not exchange protons despite of their high ion and polar group dissolving power. Therefore, this characteristic property makes aprotic solvents very suitable intermediates in many industries producing pharmaceuticals, textile auxiliaries, plasticizers, stabilizers, adhesives and ink. Dehydration of these mixtures and recirculation of valuable materials are substantial issues in industrial applications. The conventional method for recovery of aprotic solvents has been distillation, which requires excessive amount of energy to achieve desired recovery. Hydrophilic pervaporation, which is a membrane based dehydration method with low energy consumption, may become an alternative. Because of high dissolving power of aprotic solvents only inorganic membranes can be employed for this application. In this study three types of inorganic membranes (NaA zeolite, optimized silica and HybSi) were employed. Main objective of this studys to investigate effect of membrane type and various operationg parameters (feed composition at a range of 50-5% and temperature at a range of 50-100oC) on pervaporative dehydration of aprotic solvents / dimethylacetamide, dimethylformamide and n-methylpyrrolidone. During the experiments, feed samples were analyzed with Karl Fischer Titration Method / permeate samples were analyzed with Gas Chromatography. Experiments showed that proper dehydration of aqueous aprotic solvent mixtures was succeded with all three membranes investigated. In the target feed water content range (50 to 20%wt), permeate water contents were higher than 98%wt which was quite acceptable for all membranes. Moreover, NaA zeolite membrane performed higher fluxes than optimized silica and HybSi in composition range of 50 to 15% water at 50oC. It was also observed that HybSi membrane had higher fluxes and permeate water contents than optimized silica membrane for all solvents. On the other hand, the rates of decrease in permeate fluxes changed depending on the type of solvent for optimized silica and HybSi membranes. With both membranes, permeate flux of dimethylformamide decreased much slower than that of n-methylpyyrolidone. Furthermore, the results showed that permeate fluxes of HybSi membrane increased with increasing operation temperature due to the change of solvent activity in mixture. In addition, an Arrhenious type equation was used to describe changes in fluxes with changing temperature. It was also found that activation energy of water for diffusion through HybSi membrane was calculated as 8980 cal/mol.

The goal is of this project was to identify principles to guide the development of high performance dense film membranes for natural gas sweetening using hydrogen sulfide and carbon dioxide gas mixtures as models under aggressive sour gas feed conditions. To achieve this goal, three objectives were developed to guide this research. The first objective was to study the performance of cellulose acetate (CA) and an advanced crosslinkable polyimide (PDMC) dense film membrane for H₂S separation from natural gas. The second objective was to engineer those polymers to produce membrane materials with superior performance as measured by efficiency, productivity, and plasticization resistance, and the third objective was to determine the separation performance of these engineered membrane materials under more aggressive, realistic natural gas feeds, and to perform a detailed transport analysis of the factors that impact their performance. Work on the first objective showed that in neat CA, penetrant transport is controlled by both the solubility and mobility selectivity, with the former being more dominant, leading to a high overall CO₂/CH₄ (33) and H₂S/CH₄ (35) ideal selectivities. However, in uncrosslinked PDMC, H₂S/CH₄ selectivity favored sorption only, whereas CO₂/CH₄ selectivity favored both mobility and sorption selectivity, leading to a high CO₂/CH₄ (37) but low H₂S/CH₄ (12) ideal selectivities. However, the latter polymer showed more plasticization resistance for CO₂. In the second objective, both materials were engineered. A new technique referred to as “GCV-Modification” was introduced in which cellulose acetate was grafted using vinyltrimethoxysilane (VTMS), then hydrolyzed and condensed to form a polymer network. PDMC was also covalently crosslinked to enhance its performance. GCV-Modified CA showed significant performance improvements for H₂S and CO₂ removal; the permeability of CO₂ and H₂S were found to be 139 and 165 Barrer, respectively, which represented a 30X and 34X increase compared to the pristine CA polymer. The H₂S/CH₄ and CO₂/CH₄ ideal selectivities were found to be 39 and 33, respectively. Crosslinked PDMC showed a higher CO₂/CH₄ selectivity of 38 with a better plasticization resistance for CO₂ and H₂S. In the third objective, these materials were tested under aggressive ternary mixtures of H₂S/CO₂/CH₄ with both vacuum and nonvacuum downstream. Even under aggressive feed conditions, GCV-Modified CA showed better performance vs. PDMC, and it remained were fairly stable, making it a potential candidate for aggressive sour gas separations, not only because of its significantly higher productivity, which will help decrease the surface area needed for separation, thereby reducing operating costs, but also because of the lower cost of the raw material GCV-Modified CA compared to PDMC.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2010.

On peut imaginer dans un futur proche que des micro-robots implantés pourront suppléer la défaillance de certaines fonctions essentielles. C’est déjà le cas avec les stimulateurs cardiaques dont les piles au lithium sont bien adaptées à leur fonctionnement pendant des années de vie du patient. Cependant, pour des systèmes plus gourmands en énergie, il convient d’améliorer la longévité et la puissance volumique de ces piles. La stratégie que nous avons choisie est basée sur une approche biomimétique et deux voies ont été suivies pour créer une biopile bioinspirée : les biopiles enzymatiques génèrent un courant électrique à partir de l’oxydation de molécules organiques et la réduction d’oxygène en eau. Les biopiles à base de membranes biomimétiques génèrent un potentiel électrique à partir du transfert d’ions au travers une membrane biomimétique.Les biopiles enzymatiques, qui utilisent par exemple le glucose et l’oxygène, sont théoriquement capables de fonctionner indéfiniment car ces substrats sont toujours présents dans l’organisme. Cependant, la biocompatibilité et la performance à long terme de ces biopiles restent des verrous pour leur mise en œuvre chez l’homme. Cette thèse décrit la conception et l’implantation de nouvelles biopiles enzymatiques chez différents modèles animaux. Leur implantation constitue un véritable défi technologique et nous amenons des solutions guidées par la physiologie en abordant les problèmes de biocompatibilité mais aussi de techniques de mesure électrique.Nous sommes maintenant capables d’implanter ces biopiles chez de gros animaux en analysant en temps réel les performances de la biopile implantée.Cette thèse développe également le concept de biopile à base de membranes biomimétiques. Il s’agit d’une biopile mettant en œuvre des protéines de transport (par exemple des canaux ioniques) insérées dans des membranes biomimétiques. Nous avons démontré la faisabilité de la transformation d’un gradient de NaCl en gradient de protons. Nous avons aussi réussi à générer une différence de potentiel de 20 millivolts avec une membrane plane de 38 mm². Cette membrane biomimétique, contenant l’échangeur sodium/proton NhaA, est stable pendant plus de 15 jours. / We believe that in the near future micro-robots or artificial implanted organs can replace failing essential organs. Lithium batteries of cardiac pacemakers are well adapted to operate for years into sick patients. However, for next generation energy intensive implanted devices, longevity and volumic power of these batteries have to be improved.We chose two biomimetic approaches to create bioinspired biofuel cells: the enzymatic biofuel cells generate electrical current from the oxidation and the reduction of organic or inorganic compounds. The biomimetic biofuel cell generate an electrical potential from ion transfer across a biomimetic membrane.The enzymatic biofuel.cells, utilizing glucose and oxygen, are theorically able to work almost indefinitely as their substrates are always present in the body fluids. However, the biocompatibility and the long-term performance of these biofuel cells for a human implantation remain a real bottleneck. This thesis describes the design and the implantation of of new enzymatic biofuel cells in different animal models. The implantation of such devices is challenging and we brought creative solutions with a physiological point of view by addressing biocompatibility problems and electrical measurement techniques. We are now capable to implant these biofuel cells in big animals by analyzing the performances of the biofuel cell in real time.This thesis initiates the biomimetic biofuel cell concept. It consists in membrane transport protein (i.e ion channels) incorporated in a biomimetic membrane. The building of a biomimetic device demonstrates the transformation of a NaCl gradient into a proton gradient. We also generate a 20 mV voltage with a 38 mm² flat membrane. This biomimetic membrane containing the NhaA sodium/ proton exchanger is stable for more than two weeks.

Les neurones interagissent à travers leur potentiel de membrane qui a en général une évolution temporelle complexe due aux nombreuses entrées synaptiques irrégulières reçues. Cette évolution est mieux décrite en termes probabilistes, en raison de ces entrées irrégulières ou «bruit synaptique». L'évolution temporelle du potentiel de membrane est stochastique mais aussi déterministe: stochastique, car conduite par des entrées synaptiques qui arrivent de façon aléatoire dans le temps, et déterministe, car un neurone biologique a une évolution temporelle très similaire quand soumis à une même séquence d'entrées synaptiques. Nous étudions les propriétés statistiques d'un modèle simplifié de neurone soumis à des entrées à taux variable d'où en résulte l'évolution non-stationnaire du potentiel de membrane. Nous considérons un modèle passif de membrane neuronale, sans mécanisme de décharge neuronale, soumis à des entrées à courant ou à conductance sous la forme d'un processus de «shot noise». Les fluctuations du potentiel de membrane sont aussi modélisées par un processus stochastique similaire, de «shot noise» filtré. Nous avons analysé les propriétés statistiques de ces processus dans le cadre des transformations de processus ponctuels de Poisson. Des propriétés de ces transformations sont dérivées les statistiques non-stationnaires du processus. Nous obtenons ainsi des expressions analytiques exactes pour les moments et cumulants du processus filtré dans le cas général des taux d'entrée variables. Ce travail ouvre de nombreuses perspectives pour l'analyse de neurones dans les conditions in vivo, en présence d'entrées synaptiques intenses et bruitées. / Neurons interact through their membrane potential that generally has a complex time evolution due to numerous irregular synaptic inputs received. This complex time evolution is best described in probabilistic terms due to this irregular or "noisy" activity. The time evolution of the membrane potential is therefore both stochastic and deterministic: it is stochastic since it is driven by random input arrival times, but also deterministic, since subjecting a biological neuron to the same sequence of input arrival times often results in very similar membrane potential traces. In this thesis, we investigated key statistical properties of a simplified neuron model under nonstationary input from other neurons that results in nonstationary evolution of membrane potential statistics. We considered a passive neuron model without spiking mechanism that is driven by input currents or conductances in the form of shot noise processes. Under such input, membrane potential fluctuations can be modeled as filtered shot noise currents or conductances. We analyzed the statistical properties of these filtered processes in the framework of Poisson Point Processes transformations. The key idea is to express filtered shot noise as a transformation of random input arrival times and to apply the properties of these transformations to derive its nonstationary statistics. Using this formalism we derive exact analytical expressions, and useful approximations, for the mean and joint cumulants of the filtered process in the general case of variable input rate. This work opens many perspectives for analyzing neurons under in vivo conditions, in the presence of intense and noisy synaptic inputs.

Les ATPases-P4 sont des transporteurs membranaires couplant l'hydrolyse de l'ATP au transport de lipides dans les membranes cellulaires eucaryotes. Avec leurs partenaires, les protéines CDC50, les ATPases-P4 transportent les phospholipides, en particulier la phosphatidylsérine (PS) et la phosphatidyléthanolamine (PE), du feuillet exoplasmique au feuillet cytosolique des membranes, assurant ainsi le maintien de l'asymétrie membranaire.Drs2p est l'une des cinq ATPases-P4 de la levure Saccharomyces cerevisiae. Elle est localisée dans les membranes du trans-Golgi (TGN), et elle a comme partenaire la protéine Cdc50p, qui est nécessaire à l'adressage correct et probablement au transport catalysé par Drs2p. Drs2p est principalement responsable du transport de la phosphatidylsérine (PS) dans les membranes du TGN et son activité est essentielle pour le maintien de la PS dans le feuillet cytosolique de ces membranes. En raison du rôle crucial de la PS dans de nombreuses voies de signalisation, aussi bien à l’extérieur (au cours de l’apoptose par exemple) qu’à l’intérieur de la cellule (par le recrutement de protéines impliquées dans des processus cellulaires essentiels), il est important de comprendre le mécanisme par lequel l’asymétrie de la PS est établie.Afin de progresser dans la compréhension du mécanisme moléculaire du transport de lipides, nous avons mis au point une procédure qui nous a permis de co-exprimer Drs2p et Cdc50p dans Saccharomyces cerevisiae. La purification de Drs2p par chromatographie d'affinité sur résine streptavidine a permis d'obtenir une fraction purifiée contenant très majoritairement Drs2p et Cdc50p, à raison de 1-2 mg/L de culture. Les deux protéines sont sous forme de complexe avec une stœchiométrie d'association de 1:1. Le complexe purifié est fonctionnel, et présente une activité d’hydrolyse de l’ATP stimulée par son substrat, la PS. Cette stimulation n’est cependant possible qu’en présence de PI4P, un phosphoinositide impliqué dans la régulation du trafic membranaire.De par leur rôle crucial dans le maintien de l'asymétrie membranaire, les ATPases-P4 ne peuvent qu'être régulées. Comme de nombreuses ATPases de type P sont soumises à une auto-régulation de leur activité, nous avons examiné la possibilité d’une telle auto-régulation dans le cas des ATPases P4. Pour ce faire, une approche par mutagenèse dirigée et protéolyse ménagée associée à l’identification par spectrométrie de masse des peptides ont été effectuées. La protéolyse ménagée du complexe purifié Drs2p/Cdc50p montre une activité ATPasique dépendante au PI4P de 30-50 fois plus importante. La protéolyse par la thrombine engendre un Drs2p dépourvu d'une partie N-terminale (R104) et d'une partie C-terminale (R1290) qui reste toujours associé à Cdc50p. Ce résultat montre qu'une coupure appropriée au niveau des extrémités terminales de Drs2p peut augmenter de façon significative, en présence du PI4P, l'activité ATPasique du complexe, nous amenant ainsi à identifier un rôle auto-inhibiteur des extrémités N- et/ou C-terminales de Drs2p.Ce travail ouvre des perspectives quant à la caractérisation structurale et fonctionnelle du mécanisme de transport de lipides par le complexe. Par ailleurs, il laisse entrevoir la possibilité d’étudier les bases moléculaires des pathologies associées aux mutations de certaines ATPases P4 humaines. / Maintenance of phospholipid asymmetry in eukaryotic cell membranes is essential for cellular integrity and function. P4-ATPases, from the P-type ATPases family, are energy-dependent transporters, together with their CDC50 accessory subunits couple ATP hydrolysis to lipid transport from the exoplasmic to cytoplasmic leaflet to maintain membrane asymmetry.Drs2p is one of these P4-ATPases in the yeast Saccharomyces cerevisiae. Drs2p is localised in trans-Golgi (TGN) membranes in association with its binding partner Cdc50p, which contributes to the correct addressing of Drs2p and probably in the catalyzed transport by Drs2p. Drs2p transport principally phosphatidylserine (PS) in TGN membranes. The PS is important for a several signalling pathways, for example, in apoptosis and recruitment of the proteins implied in various essential cellular process, so, it's very important to understand the mechanism that establishes this asymmetry.To gain in comprehension of molecular mechanism of lipid transport, robust protocols for expression and purification are required. In this work, we present a procedure for high-yield co-expression of Drs2p and Cdc50p. The purification of Drs2p and Cdc50p is achieved in a single step by affinity chromatography on streptavidin beads, yielding, 1-2 mg purified Drs2p/Cdc50p per liter of culture. This procedure allows purification of the complex Drs2p/Cdc50p with stoichiometry to 1:1. Our complex is functional, overal ATP hydrolysis by the complex is dependent of PS, favourite substrate of Drs2p. This hydrolyze is critically dependent on the presence of PI4P, a phosphoinositide involved in regulation of membrane trafficking.Like many P-type ATPases auto-regulate their activity, we examined the possibility that P4-ATPases are auto-regulated. In this work, we use directed mutagenesis and limited proteolysis associated with mass spectrometry for identify peptides. We show that limited proteolysis of a purified complex Drs2p/Cdc50p resulted in up to a 30-50 fold increase of it ATPase activity, which however remained dependent on PI4P. Using thrombin as the protease, Cdc50p remained intact and in complex with Drs2p, which was cleaved at two positions, namely after R104 and after R1290. Our results therefore reveal that trimming off appropriate regions of the terminal extensions of Drs2p can increase its ATPase activity in the presence of PI4P by an enormous factor, thereby identifying a role of N and/or C-terminal extensions in auto-inhibition of Drs2p.Our results open perspectives on the structural and the functional characterization of the lipid transport mechanism by the complex Drs2p/Cdc50p. Furthermore, our procedures open up the possibility of studying the molecular bases of the pathologies associated with the mutations of human P4-ATPases.

Membrane rafts (also referred as nanodomains) are membrane structures responsible for many cell processes. Their characterization is challenging because of the transparency, dynamics and small size of those structures. Moreover, high variability of cells makes their study even more complicated. In order to simplify the studies of membrane processes including the formation of those rafts often model membranes like Giant Unilamellar Vesicles (GUVs) and Supported Phospholipid Bilayers (SPBs) are used. In this Thesis new fluorescent tools for studying such membrane processed were developed, tested, or improved. Specifically, the phasor plot an approach applicable to the analysis of the fluorescence lifetime data, was theoretically and experimentally tested and afterwards applied to the characterization of the membrane nanodomains in GUVs. First, we introduced the phasor plots to the excitation state processes like solvent relaxation and Förster resonance energy transfer (FRET) in lipid vesicles. We also employed the phasor plots in protein-ligand interaction, protein folding and denaturation studies. Finally, the phasor plot analysis of FRET data in combination with Fluorescence Correlation Spectroscopy (FCS) was used in characterization of membrane nanodomains in terms of the size, mobility and...

Reverse osmosis (RO) is widely used for water reclamation and is one of the most feasible technologies for addressing water scarcity around the world. RO membrane fabrication procedures are continually being optimized and modified to enhance the treatment performance and efficacy of the RO process. A review of the existing literature published on membrane fabrication revealed that a detailed and reproducible methodology consistent among prior studies was not available. Therefore, the primary objective of this study was to utilize techniques from prior research to develop a reliable lab-scale membrane fabrication process for studying the potable reuse applications of TFC RO membranes. Phase inversion was used to create a polysulfone (PSF) support layer on a non-woven fabric sheet. Then, the process of interfacial polymerization (IP) between amine and acyl chloride monomers was utilized to form a highly selective and ultrathin polyamide (PA) layer on the PSF support surface. The resulting membrane composition and performance was dependent on a wide range of parameters during the fabrication process. The optimal support materials, reactant types and concentration, and reaction conditions were determined through trial and error. The best performing membranes utilized N-methyl-2-pyrrolidone (NMP) as the solvent, Novatexx-2471 non-woven fabric for mechanical support, and 15 wt% PSF concentration for phase inversion. The optimal immersion duration was five minutes for the aqueous amine monomer solution during the IP process. The flux for membrane triplicates was 20.2  3.6 liters per square meter per hour (LMH) while the salt rejection was 96.8  2.0%. The relatively low standard deviation for flux and salt rejection indicates that the fabrication method developed herein is consistent. A commercial Dow Filmtec BW30 flat sheet PA-TFC RO membrane was tested for comparison and exhibited a flux of 44.9 LMH and a salt rejection of 98.5%. Thus, the membranes developed in this study achieved salt rejection on par with commercial membranes but exhibited a flux that was significantly lower. Furthermore, this study investigated modifications to the traditional TFC membrane using engineered silica nanomaterials with the goal of enhancing the membrane flux while maintaining high salt rejection. Two types of nonporous silicon dioxide nanoparticles (SDNPs), non-functionalized and amine functionalized, were dispersed in the aqueous and organic IP solutions. Ultrasonication of the non-functionalized SDNPs in the aqueous solution was observed to produce the most stable dispersion. Compared to the unmodified TFC membranes, the average flux of the SDNP-modified (TFC-NP) RO membrane triplicates was higher at 25.4  2.0 LMH with 0.1% (w/v) SDNPs incorporated in the PA layer. The salt rejection was lowered to 92.3  0.1% for the TFC-NP membranes. In addition, the membranes fabricated in this study were characterized using scanning electron microscopy (SEM), Fourier Transport Infrared Spectroscopy (FTIR), atomic force microscopy (AFM), and goniometry measurements. SEM images showed that the TFC-NP membranes contained larger spaces between ridges and valleys of the PA pore structure. FTIR confirmed the PA layer formation on the membranes fabricated herein but a spectral peak from the SDNPs was not observed for the TFC-NP membranes. AFM measurements indicated an increase in surface roughness of the modified membranes, likely because of the incorporation of SDNPs. The surface of TFC-NP membranes was found to be more hydrophilic than the unmodified TFC membranes based on contact angle measurements. Further optimization of the fabrication method developed herein is warranted before pursuing additional RO research topics, such as the disinfection byproduct precursor removal of TFC membranes.

This thesis describes a new technique for the preparation of ultrathin Pd based membranes supported on a hollow-fiber α-alumina substrate for H₂ separation. The effectiveness of the membranes is demonstrated in the ethanol steam reforming (EtOH SR) reaction in a membrane reactor (MR) for H₂ production. The membrane preparation technique uses an electric-field to uniformly deposit Pd nanoparticle seeds on a substrate followed by deposition of Pd or Pd-Cu layers on the activated surface by electroless plating (ELP). The well distributed Pd nanoparticles allow for enhanced bonding between the selective layer and the substrate and the formation of gas tight and thermally stable Pd or Pd-Cu layers as thin as 1 µm, which is a record in the field. The best Pd membrane showed H₂ permeance as high as 5.0 × 10⁶ mol m²s⁻¹Pa⁻¹ and stable H²/N₂ selectivity of 9000 - 7000 at 733 K for 5 days. The Pd-Cu alloy membrane showed H₂ permeance of 2.5 × 10⁶ mol m⁻²s⁻¹Pa⁻¹ and H₂/N₂ selectivity of 970 at the same conditions. The reaction studies were carried out with a Co-Na/ZnO catalyst both in a packed bed reactor (PBR) and in a MR equipped with the Pd or Pd-Cu membrane to evaluate the benefits of employing membranes. For all studies, ethanol conversion and hydrogen product yields were significantly higher in the MRs compared to the PBR. Average ethanol conversion enhancement and hydrogen molar flow enhancement were measured to be 12 % and 11 % in the Pd MR and 22 % and 19 % in the Pd-Cu MR, respectively. These enhancements of the conversion and product yield can be attributed to the shift in reaction equilibria by continuous hydrogen removal by the Pd based membranes. The comparative low enhancement in the Pd MR was found to be the result of significant contamination of Pd layer by CO or carbon compounds deposition during the reaction. A one-dimensional modeling of the MR and the PBR was conducted using identical conditions and their performances were compared with the values obtained from the experimental study. The model was developed using a simplified power law and the predicted values matched experimental data with only minor deviations indicating that the model was capturing the essential physicochemical behavior of the system. Enhancements of ethanol conversion and hydrogen yield were observed to increase with rise in space velocity (SV), which could be explained by the increase in H₂ flux through the membranes with SV in the MRs. / Ph. D.

Fresh water scarcity is an alarming issue for communities across the globe. The development of water recycling and reuse technologies has become crucial in expanding the limited water resources. Reverse osmosis (RO) is among the key processes that can treat wastewater to meet potable water reuse standards. Despite the advancements in RO membrane technologies, many challenges persist regarding the operation and maintenance of RO membranes, such as membrane fouling. Extensive research investigations have focused on developing RO membrane modifications to combat the decreased performance due to fouling. Polyethylenimine (PEI) is a promising polymer used for enhancing the anti-fouling properties of thin film composite (TFC) RO membranes. PEI, a positively charged polymer with high charge density, is commonly grafted on TFC RO membrane surfaces to produce smoother, more hydrophilic membranes to minimize fouling. However, little research is available on the optimal PEI placement within the composite RO membrane layers for enhancing antifouling properties. The current study aimed to investigate whether alternative positions within the membrane layers could yield better anti-fouling performance compared to incorporation PEI on the membrane surface. Unmodified (i.e., control) and PEI-modified TFC RO membranes were fabricated in the laboratory. The PEI-modified membranes were produced in two variations with regards to the position of PEI in the composite membrane layer. The first variation, named PEI-1, involved immersing the polysulfone (Psf) support layer of the membrane in an aqueous PEI solution, before the active polyamide (PA) layer was formed. The second variation, named PEI-2, consisted of immersing the fully formed TFC RO membrane in an aqueous PEI solution to incorporate PEI on the surface of the active PA layer. The PEI used in the study for membrane modification had branched configuration with molecular weight of 1200 g/mole. The laboratory-scale TFC RO membranes produced herein were characterized and tested for water flux, salt rejection, and fouling behavior. The water flux and salt rejection, commonly referred to as permselectivity, of all the membranes produced were evaluated in a crossflow filtration unit. On the other hand, the fouling tests were conducted in a dead-end membrane filtration unit because of operational limitations of the crossflow unit. The PEI-1 membrane produced a water flux of 18.7 LMH (L/m2hr) and a stable salt rejection of 82.1%. The PEI-2 membrane resulted in a water flux of 22.4 LMH and a salt rejection of 85.2%. These results indicate that incorporating PEI on the membrane PA active surface layer achieved better permselectivity compared to PEI-1, which is the membrane with PEI incorporated inside the structure (i.e., incorporated on the Psf support layer). However, both PEI-modified membranes exhibited lower permselectivity performance compared to the unmodified control membrane, which produced a water flux of 23.9 LMH and salt rejection of 88.2%. To test fouling of the unmodified and PEI modified RO membranes, bovine serum albumin (BSA) was chosen as a model foulant based on preliminary investigations conducted herein to compare BSA to sodium alginate. After the foulant was introduced in the feed, the unmodified membrane exhibited a 31.8% total fouling ratio, the decrease in flux from the foulant solution compared to running clean DI water. However, a 90.7% flux recovery ratio was achieved when a final DI water rinse was performed. The PEI-1 membrane had a 39.7% total fouling ratio and a 81.6% flux recovery ratio after rinsing with DI water. The PEI-2 membrane showed a 43.1% total fouling ratio as a result of BSA fouling and a 94% flux recovery ratio when rinsed with DI water at the end of the fouling test. Water contact angle (WCA) analysis confirmed that the PEI-2 membrane had the most hydrophilic surface (WCA 25.1°) compared to the control membrane (WCA 52.9°). The higher hydrophilicity of PEI-2 aligns with its higher flux recovery results, which indicated reduced membrane fouling. Furthermore, the PEI-2 membrane had a drastically lower WCA than those reported in the literature for PEI-modified membranes, which ranged from (63° – 80°). In conclusion, the increased flux recovery and surface hydrophilicity of the PEI-2 membrane indicated that the best anti-fouling performance would likely be obtained when PEI is grafted onto the surface of the active PA membrane surface. Future research is warranted to optimize the PEI-2 membrane by exploring the effect of PEI concentration, molecular weight, and structural configuration (i.e., branched versus linear), on anti-fouling performance of the membranes.