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Focuses on the development of concepts and materials for polymer catalytic membrane reactors. Advantages and disadvantages; Basic principles of polymeric membranes; Preparation of polymeric membranes endowed with catalytic entities; Incorporation of heterogeneous catalysts.

Municipal treated wastewater could be considered as a water source for food crop irrigation purposes. Enhancing the quality of treated wastewater to meet irrigation standards has become a necessary practice. Nanofiltration (NF) was used in the first stage to produce permeate at relatively low energy consumption. In the second stage, two membrane combinations were tested for additional water extraction from the brine generated by the NF process. The simulation results showed that using a hybrid forward osmosis (FO)–reverse osmosis (RO) system is more efficient than using the RO process alone for the further extraction of water from the brine generated by the NF process. The total specific energy consumption can be reduced by 27% after using FO as an intermediate process between NF and RO. In addition, the final permeate water quality produced using the hybrid FO-RO system was within the allowable standards for food crops irrigation. [ABSTRACT FROM AUTHOR]

Cellulose acetate (CA) as polymer, glycerol derivatives (namely triacetin, diacetin, monoacetin or glycerol-formal) as solvents and 2-methyltetrahydrofuran (2-MeTHF) as co-solvent were selected as bio-based ingredients for the preparation of full-bio-based nanofiltration membranes via non-solvent induced phase separation (NIPS). Membrane performance was investigated using an aqueous rose bengal (1017Da) solution (RB/H 2 O) as feed. Membrane morphologies were characterized using SEM (scanning electron microscopy). Both kinetic and thermodynamic aspects of the phase inversion process were studied in detail to gain more insight in the membrane formation process. When implementing a 90s evaporation step prior to coagulation, rejection increased with increasing 2-MeTHF concentration in the casting solution in the case of diacetin and triacetin solvents. In the case of monoacetin and glycerol-formal based casting solutions, evaporation had a less significant impact on RB rejection even though the same volatile co-solvent was used. The best membranes were finally obtained using diacetin as a solvent and 2-MeTHF as co-solvent with permeances ranging from 5.5 to 12.8 L/m2 h bar for membranes with >90% RB rejections. Image 1 • Full-bio-based cellulose acetate nanofiltration membranes are prepared. • Glycerol derivatives and 2-MeTHF are respectively used as solvent and co-solvent during phase inversion. • Use of bio-based-materials is in agreement with the principles of green chemistry. [ABSTRACT FROM AUTHOR]

Highly stable, well suspended TiO 2 nanoparticles (NPs) were synthesized by a sol-gel method and directly mixed with an aqueous amine solution to react at the interface with trimesoyl chloride, forming polyamide (PA) thin film nanocomposite (TFN) membranes with a uniform distribution of the nanoparticles in the PA film. Besides the presence of TiO 2 NPs, the influence of remaining chemicals such as ethanol and acid from the synthesis of the TiO 2 colloids on the film formation was also investigated. The residual ethanol and acid were found to play a role in thin film formation and properties of the final membranes. The presence of TiO 2 NPs, ethanol, and acid had a positive impact on membrane wettability, water flux, and salt rejection. Compared to the unmodified membrane, the TiO 2 -TFN membranes achieved a good separation performance with around 12% and 19% improvement in water permeability and NaCl rejection, respectively. In addition, the developed TFN membranes possessed an improved anti-fouling property with low flux decay and high flux recovery up to 94%. This simple one-pot synthesis procedure of TiO 2 NPs combined with the in-situ integration during the interfacial polymerization showed great potential for economic scaling up in industrial production of high-performance TFN membranes. [ABSTRACT FROM AUTHOR]

Polyamide (PA) thin-film composite (TFC) membranes, synthesized by interfacial polymerization (IP), are commonly applied in NF and RO. However, they have a high tendency to foul due to the rough ridge and valley surface. IP requires utilization of toxic solvents and hydrolysis of acyl chlorides can occur as undesired side reaction due to the presence of water. Therefore, a new approach to synthesize TFC membranes is now introduced: spray-based interfacial polymerization prior to solidification (s-IPS). IP is performed on a still liquid polymer film containing a first (amine) monomer while the second monomer (acyl chloride) is sprayed on top. The susceptibility of the liquid cast film to defects due to the impact of spraying, is minimized by the increased viscosity resulting from charge-transfer complex formation between the amine monomer (MPD) and the polymer (PI). This new s-IPS process is more time-efficient, uses less chemicals and produces less waste than the conventional IP. Additionally, problems in conventional IP associated with non-wetted support pores and bad adhesion of the IP layer to the support are eliminated and water-free IP is enabled, limiting hydrolysis of TMC. Properties such as high viscosity and interfacial stability lead to controllable IP and smooth PA top-layer surfaces. [Display omitted] • Spray-based IP prior to solidification is introduced as a new approach to synthesize TFC membranes. • IP is successfully performed on a liquid polymer film containing the amine monomer using spray-coating. • Defects are minimized by increasing the viscosity by formation of CTCs between MPD and PI. • Properties like high viscosity and interfacial stability lead to a controllable IP and smooth top-layer. • PA TFC membranes were synthesized with 98% RB retention and water permeances up to 3 L m-2 h-1 bar-1. [ABSTRACT FROM AUTHOR]

Engineering membranes for molecular separations in organic media is still a big challenge, especially when two closely resembling solutes have to be separated by allowing one to pass with the solvent and the other to be rejected. The so-called "resolution" of the membrane then becomes critical. Resolution reflects the difference in rejection values of the two (or more) solutes for that solvent-membrane system. Recently developed crosslinked poly(vinylidene difluoride) (XL-PVDF) and well-known crosslinked polyimide (XL-PI) membranes were prepared and tested for solvent resistant nanofiltration (SRNF). Rejections of 7 dyes (i.e. Rose Bengal (RB), Acid fuchsin (AF), Rhodamin B (RhB), Sudan Black (SB), Zinc tetraphenylporphyrin (ZTPP), and 55,10,15,20-Tetrakis(3,5-di-tert-butyl phenyl)porphyrin (TBPP) in a broad range of solvents, i.e. a set of polar solvents (water, ethanol, isopropanol), and a set of non-polar ones (butyl acetate, chloroform, xylene and toluene) were studied. As anticipated, the molecular weight cut-offs (MWCOs) of both membrane-types varied with the applied solvent type. Butyl acetate and chloroform filtrations respectively yielded the sharpest MWCO for XL-PVDF and XL-PI. The varying MWCO-curve per solvent is explained by the changing affinity of solvents and solutes for the membrane, as indicated by swelling and sorption experiments respectively. [Display omitted] • Good MW resolution in the 450–1000 Da range for crosslinked PVDF and PI membranes. • MWCO curves vary per solvent for a given membrane. • Stable performance in a range of polar and non-polar solvents. • Comparable results for XL-PVDF with XL-PI. • Important role of solvent-solute-membrane interactions on MWCO curves. [ABSTRACT FROM AUTHOR]

Highlights • Flat-sheet membranes were developed for a magnetically induced membrane vibration system. • Membrane surface porosity was increased by PVP blending. • Leaching PVP via post-treatment was not effective to improve membrane porosity. • PVP slowly leached-out during NaOCl cleanings which improved membrane filterability. Abstract Improving the hydrodynamics on the membrane surface in a magnetically induced membrane vibration system (MMV) has been proven efficient for membrane fouling control in membrane bioreactors. This advantage can be further extended by using an optimized membrane. This was realized in this study by preparing porous polyvinylidene fluoride membranes via polyvinylpyrrolidone (PVP) blending and later by leaching out the PVP from the membrane matrix via post-treatment using NaOCl. Results show that increasing the PVP content in the casting solution increases membrane fouling resistance. Slowly leaching of PVP after several periodic NaOCl cleanings increased membrane permeance. No advantage of NaOCl post-treatment was observed. The long-term filtration confirmed the superiority of the highly porous membrane that complemented the advantages offered by the MMV system. This suggests that despite the small quantity of the remaining PVP, its leaching offered a substantial gain to improve membrane filterability. [ABSTRACT FROM AUTHOR]

Highlights • The MMV was tested in an AeMBR and AnMBR. • AeMBR and AnMBR fouling rates were significantly decreased when using the MMV. • The MMV can significantly lower aeration costs in AeMBRs. Abstract Membrane bioreactors (MBRs) are gaining more attention as they provide a viable alternative for conventional wastewater treatment. To operate efficiently, however, it is still key to select appropriate antifouling strategies. Fouling mitigation through vibration, as in the magnetically induced vibration (MMV) system, has been conceptually proven recently, but was never further optimized. This work presents a 2nd generation vibration system which was validated in both an aerobic MBR (AeMBR) and anaerobic MBR (AnMBR) improving the filtration time respectively by a factor of 133, at 60 L/m2 h, and a factor 13, at 20 L/m2 h. To prolong this filtration time even further, a combination with backwashing proved to be more effective compared to relaxation, allowing a 10-days long continuous operation for an AnMBR at a flux of 20 L/m2 h. [ABSTRACT FROM AUTHOR]

Abstract As the number of membrane applications in industrial processes keeps increasing, more and more attention is being paid to their physical and chemical stability. Especially during cleaning procedures and under actual operation conditions the lack of a sufficient stability still remains an issue thereby seriously limiting the membrane lifetime and increasing the operating cost. Currently, different methods are applied during the synthesis to improve the stability of polymeric membranes. One promising method to produce solvent resistant membranes (in this specific case supports) is by cross-linking polymeric membranes via photo-irradiation. In this study, three different UV curing conditions (e.g. UV – spark, UV – microwave and UV – LED) were studied in depth by evaluating the cross-linker conversion degree with infra-red spectroscopy. Ultimately the 365 nm UV-LED light was selected as the most optimal UV curing condition. This unit is further used to study the optimal compositional and non-compositional parameters to produce solvent resistant supports in a continuous membrane casting line for up-scaling. [ABSTRACT FROM AUTHOR]

• Decreased labour-, time- and waste consumption during membrane synthesis with combinatorial techniques. • Screening of non-compositional and compositional parameters for optimization of membranes. • Design of a multi-dimensional matrix for optimization of CTA membranes for selective removal of flavor compounds. In fermented beverages, volatile esters are trace compounds with a significant effect on the flavour profile. Some of the most important esters in beer are ethyl acetate (solvent-like aroma) and isoamyl acetate (banana aroma). These esters have a defined threshold which, when exceeded, will be experienced as unpleasant upon tasting. Therefore, the industry needs to selectively remove and fractionate esters by means of adsorption and tune the level of esters in the different process streams. Nanofiltration (NF) and Reverse Osmosis (RO) membranes are known to have a high potential towards removal of low molecular weight components from liquid streams. However, membrane preparation depends on several parameters with complex interactions to obtain the targeted membrane performance. Multi-parameter optimization strategies are thus very useful to reduce material consumption, minimize time and labour during the development of a 'bottom-up' preparation method. High throughput (HT) filtration techniques in combination with genetic algorithms (GAs) are known to be very powerful to direct such membrane preparation. This optimization strategy is used to obtain cellulose tri-acetate (CTA) membranes for filtration of high-alcoholic beverages towards ethyl acetate and isoamyl acetate depletion. Before the implementation of the proposed strategy, a successful optimization of the HT operating conditions was setup together with a selection of benchmark membranes by screening the performance of various commercially available nanofiltration (NF) and reverse osmosis (RO) membranes. Next, the non-compositional (solvent impregnation, membrane thickness, solvent evaporation time, annealing time and temperature) and compositional parameters (polymer concentration, solvents and additives selection) used during non-solvent induced phase separation (NIPS) preparation of CTA membranes were determined. Finally, CTA membranes were optimized using GAs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Applications of diverse membrane systems in biogas production, upgrading and conversion are presented. • Various membrane materials, configurations and processes along with their performance and notable features are analyzed. • Extensive experimental attempts at laboratory, pilot, semi-industrial and industrial scales are included in discussions. • Benefits and opportunities for integration of membranes in hybrid configurations for biogas upgrading are outlined. • Trends in biogas conversion are delineated by highlighting the contributions of membranes in methanation and hydrogenation processes. • Guidelines for the design, integration, and optimization of efficient and economic membrane units for biogas processing are provided. Biogas serves a reliable renewable resource and energy carrier with growing potentials based on the number and size of plants in operation and planned for future. The technical viability of membranes for biogas valorization has attracted attention towards further advancements from the materials and process perspectives. The present review aims to meticulously analyze the extensive works carried out at laboratory, pilot, semi-industrial and industrial scales pertinent to biogas with the aid of membrane separation processes. Discussions are devoted to the performance characteristics and specifications of various membrane materials, processes and configurations employed spanning the entire value chain of biogas production, upgrading and conversion. These include recovery of dissolved methane and liquids (water, ammonia) at the production stage, as well as exploitation of semipermeable and gas–liquid membranes such as membrane contactors, membrane reactors and membrane bioreactors for upgrading of raw biogas to achieve quality biomethane. Besides, valuable experiences in integration of membranes in hybrid configurations for biogas upgrading are evaluated. Also, the emerging trends in biogas conversion are delineated by focusing on methanation and hydrogenation with the aid of membranes. Finally, guidelines for the design, integration and optimization of high-performance membrane systems are set by taking into account the economic considerations. [ABSTRACT FROM AUTHOR]

PDMS-grafted alumina membranes have already demonstrated high organic solvent permeabilities; described and modeled in this paper are their retention capabilities. In contrast to pure PDMS polymeric membranes, higher retentions were found in nonpolar solvents than in polar solvents. This is attributed to a solvent-induced pore-constriction behavior: confined swelling of PDMS, grafted into the membrane pores, was found to increase retention. To test this hypothesis, pore sizes were obtained by integrating the Ferry, Verniory and steric hindrance pore (SHP) equations into the Spiegler Kedem Katchalsky (SKK) model in order to predict the retention of dyes. Ultimately, a diffusion pore size was introduced into the SKK model to reflect the ability of the solute to diffuse through the swollen PDMS graft. A better understanding of the transport mechanisms that impact performance was achieved by incorporating the unique pore structure of these ceramic-based hybrid membranes into the SKK model. [ABSTRACT FROM AUTHOR]

Membranes consisting of a semi-interpenetrating network of polysulfone (PSU) and cross-linked polyacrylate were synthesized via non-solvent induced phase inversion followed by UV-treatment. Tetrahydrofuran (THF) or 1,4-dioxane (DIO) was added as co-solvent to the N,N -dimethylformamide (DMF)-based polymer solutions and cast films were subjected to evaporation prior to coagulation. Effects of synthesis variables on the membrane morphology and solvent resistant nanofiltration (SRNF) performance were investigated by using a Rose Bengal solution in isopropanol. By increasing the evaporation time from 0 to 100 s for the membranes prepared with THF and DIO as co-solvent respectively, rejections increased from 65.3% to 94.2% and 60.1–89.1%, while permeances decreased from 0.29 to 0.01 l/m 2 h bar and 0.41–0.08 l/m 2 h bar. A similar effect was observed when the co-solvent/solvent ratio was increased from 0/100 to 100/0: rejections increased from 63.1% to 94.9% and 59.2–90.6%, while permeances decreased from 0.43 to 0.01 l/m 2 h bar for THF-based membranes and to 0.07 l/m 2 h bar for DIO-based membranes respectively. A post-treatment was performed to increase the flux by immersing UV-cured PSU-based films in DMF for 48 h. The resultant membranes showed higher permeances and lower rejections, making them especially useful as potential candidates for stable supports to apply selective layers upon, such as e.g. in thin film composite (TFC) membranes. As observed in scanning electron microscopy, higher evaporation times and lower initial co-solvent concentrations resulted in less or even no macrovoids. [ABSTRACT FROM AUTHOR]

A surprisingly simple, yet effective blending method for ionic liquids (ILs) and polysulfone (PSf) is presented in this paper. Not only is the IL properly immobilised in the polymer matrix, which is crucial in high-pressure gas separation applications, but this method also produces tunable porous surfaced membranes that can be useful in several other applications. The size and distribution of the pores are dependent on the type and amount of IL incorporated into the PSf. A membrane formation mechanism is proposed to explain the presence of such a regular surface pore structure. Several commercially available ILs were tested to examine their compatibility with the polymer, and the CO 2 /N 2 gas separation performance of the resulting membrane was screened. ATR-FTIR spectroscopy, FTIR microscopy, and SEM imaging were also employed to shed light on the observed membrane structures. [ABSTRACT FROM AUTHOR]

Unravelling synthesis-morphology-performance relations of thin-film polyamide (PA) selective layers prepared via interfacial polymerization (IP) is essential for tailor-made membrane design. Here, an approach is outlined, which links synthesis and morphology in terms of the interfacial stability of a system undergoing IP, with the notion that a transition from a stable to an unstable state corresponds to a morphological shift of the resultant film, e.g., from smooth to crumpled. Within the proposed framework, physical parameters related to a variety of synthesis conditions are identified and classified based on their effect on two defined criteria: the polymer formation rate and/or the system susceptibility to instability. A conceptual phase diagram maps the morphological regimes with respect to the relevant parameter space. Our analysis, based on available literature data, illustrates how PA morphology, as observed in published SEM images, transitions from smooth to crumpled, exhibits a remarkable correlation with the defined parameter space, and hereby the stability of the system. Re-thinking experimental results in this manner highlights not only the underlying physics, but also identifies potential pitfalls when variations of synthesis conditions result in conflicting effects. Our motivation is to encourage experimental design based on the developed framework supplemented by theoretical quantification, which will strengthen the fundamental understanding of IP for a given chemistry, with the goal of providing a clear physical toolbox for IP-based membrane design. [Display omitted] • A theoretical framework is proposed for assessing the effect of synthesis conditions on thin film morphology. • Synthesis-morphology relationship for polyamide thin film formation is based on instability mechanisms. • Literature data are re-examined within the proposed framework. [ABSTRACT FROM AUTHOR]

Membrane processes have long been applied in different stages of microalgae cultivation and processing. These processes include microfiltration, ultrafiltration, dialysis, forward osmosis, membrane contactors and membrane spargers. They are implemented in many combinations, both as a standalone and as a coupled system (in membrane biomass retention photobioreactors (BR-MPBRs) or membrane carbonation photobioreactors (C-MPBRs). To provide sufficient background on these applications, an overview of membrane materials and membrane processes of interest in microalgae cultivation and processing is provided in this work first. Afterwards, discussion about specific aspects of membrane applications in microbial cultivation and harvesting is provided, including membrane fouling. Many of the membrane processes were shown to be promising options in microalgae cultivation. Yet, significant process optimizations are still required when they are applied to enable microalgae biomass bulk production to become competitive as a raw material for biofuel production. Recent developments of the coupled systems (BR-MPBR and C-MPBR) bring significant promises to improve the volumetric productivity of a cultivation system and the efficiency of inorganic carbon capture, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A major obstacle in the widespread application of membrane microfiltration for activated sludge wastewater treatment is the rapid decline of the permeation flux with time as a result of membrane fouling. Nowadays, fouling is mostly controlled by optimal operational conditions, and physical and chemical cleaning. In this study, the efficiency of chemical cleaning and the impact of these chemicals on the membrane structure (membrane aging) has been evaluated and linked to properties of the microbial community present in the feed. Three polymeric microfiltration membranes (polyvinyldifluoride, polyethylene and polysulfone) and 3 model biofoulants with increasing complexity were used in a cross-flow filtration set-up. The cleaning efficiency was measured in terms of bacterial cell density and exopolymeric substance concentration. Membrane cleaning by 1% NaOCl and 2% citric acid had a cleaning efficiency ranging from 57 to 100% and 41 to 100% respectively, depending on the concentration and the complexity of the used biofoulants. Membrane aging by NaOCl and citric acid was reflected in an increased membrane pore size and surface porosity, while the membrane hydrophobicty and surface chemistry of the membrane surface remained unaffected. Differences in bacterial cell densities were found on aged membrane, but the results were strongly biofoulant dependent. On the other hand, significantly higher exopolymeric substances concentrations were detected on the aged membranes, suggesting that the biofoulants behave differently on aged membranes. [Copyright &y& Elsevier]

Crosslinked polyimide is a state-of-the-art membrane material for solvent-resistant nanofiltration (SRNF) and gas separation aiming for applications that involve harsh solvents or plasticizing components in the gas stream, respectively. Preparation of these membranes usually requires a multistep procedure involving hazardous diamine monomers. In this study, two hyperbranched polyethyleneimines (PEIs) with different molecular weights (800 and 25 000 g mol−1) were explored as crosslinking agents in the simultaneous (SIM) crosslinking -procedure where crosslinking takes place during coagulation in the non-solvent bath. Because of their lower volatility compared to traditional diamine crosslinkers, the manipulation of these polymeric forms of crosslinkers is intrinsically less hazardous. It is hypothesized that the conditioning step, a required post-processing step in membrane upscaling to allow subsequent potting, handling, and storage, can be omitted when crosslinking with such polymeric crosslinkers. Results showed how presence of PEI in the non-solvent bath influenced the course of phase inversion, resulting in a range of different membrane morphologies and performances. Drying unfortunately resulted in brittle membranes which lost most of their permeance. Even when residual PEI was allowed to remain in the membrane as a conditioning agent, low dried membrane permeances were obtained. By using PEI or other state-of-the-art crosslinkers prior to drying, light was shed on the structure-performance relationships governing permeance decline when drying SRNF membranes. [Display omitted] • Two hyperbranched PEIs with different molecular weight were used as less hazardous PI crosslinkers. • PEI crosslinker concentration in the coagulation medium influenced membrane morphology and performance. • PEI was unable to exert a conditioning effect as very low permeances were obtained upon drying. • Structural membrane properties were influenced by crosslinker chemistry and affected the extent of pore collapse upon drying. [ABSTRACT FROM AUTHOR]

Crosslinked poly (ethylene oxide) (XLPEO) membranes are leading candidates for membrane post-combustion carbon capture, because of their high CO 2 /N 2 selectivity and CO 2 permeability. However, their crosslinked nature makes it difficult to process them into thin films through conventional coating techniques. In this study, interfacially initiated chain growth polymerization of epoxides is used to circumvent the XLPEO processing challenge whilst allowing in-situ crosslinking. The interfacial design strategy yields intrinsically crosslinked, epoxide-based PEO (eXLPEO) thin-film composite gas separation (GS) membranes consisting fully of CO 2 -philic ether bonds. An eXLPEO selective layer made from poly (ethylene glycol) diglycidyl ether was successfully deposited on a PAN support and, after introduction of densification steps and a PDMS sealing, gas selective membranes were obtained. Synthesis-structure-performance analysis revealed that multiple reaction condition combinations result in highly selective membranes with a tunable chemical structure. The best performing membranes showed CO 2 /N 2 separation factors of 58 at 35 °C, with a stable operation at pressures from 2 to 10 bar, and retaining a separation factor of 30 at 65 °C. However, all membranes had a low CO 2 permeance (<10 GPU), probably due to pore impregnation of the support layer. This work demonstrates for the first time the viability of interfacial polymerization for the synthesis of thin film eXLPEO GS membranes. [Display omitted] • Epoxide chemistry is a novel platform for thin-film composite (TFC) gas separation membrane synthesis. • Crosslinked poly (ethylene oxide) TFC were synthesized using epoxide interfacial polymerization. • The chemical structure of epoxide-TFC is controlled by the monomer/initatior ratio. • Membranes show high CO 2 /N 2 selectivity, even at elevated temperatures. • The hydrophilicity of the monomers caused pore impregnation. [ABSTRACT FROM AUTHOR]

Patterned membranes prepared via spray-modified non-solvent induced phase separation (s-NIPS) have successfully shown enhanced fluxes and better fouling control, thanks to the increased surface area and high fluid shear at the membrane/feed interface. These novel membranes are now taken a step further by using them as support for interfacial polymerization (IP) to create thin-film composite (TFC) membranes with increased fluxes. The successful deposition of a dense polyamide top layer on a wave-patterned support (pattern height:∼100 μm) is now demonstrated. Different methods were compared for the challenging removal of excess monomer above the grooved support surface. Spin-drying assisted IP (s-IP) led to the best membrane performance. Hence, s-IP was further optimized for patterned supports via systematic investigation of the effects on the membrane performance of monomer compositions, number of IP reactions, and properties of the patterned support. The micro-patterned TFC membranes prepared via s-IP showed significantly higher permeance (+280 %) than flat TFC membranes prepared via conventional IP without reduction in MgSO 4 retentions (98.7 ± 1.8 %), thanks to the corrugations and the modified IP procedure. [Display omitted] • Spin-drying assisted interfacial polymerization (s-IP) results in 3 × higher water permeance. • s-IP on μ-patterned supports further increased permeance without compromising rejections. • 22 wt% polymer concentration in the support significantly improved the membrane performance. [ABSTRACT FROM AUTHOR]

Water/solvent mixtures released from industrial processes, especially in pharma and fine chemical synthesis or in advanced oil production, are an environmental concern, necessitating the development of efficient remediation and recycling techniques. Solvent-tolerant nanofiltration (STNF), situated between aqueous nanofiltration (NF) and solvent-resistant nanofiltration (SRNF), offers a promising solution. This study investigates the potential of using aqueous NF- and SRNF-membranes to treat water/solvent mixtures. Commercial membranes (NF270, DuraMem® 300, DuraMem® 200) and a lab-synthesized polyvinylidene fluoride (XL-PVDF NF) membrane were used to treat dimethyl sulfoxide (DMSO), acetonitrile (ACN), Isopropyl alcohol (IPA), or dimethylformamide (DMF) mixtures with water. The addition of 10% DMSO, ACN, IPA, or DMF to water significantly reduced the permeance of these NF-membranes, and an increase in temperature failed to restore the initial permeance. Changes in both viscosity and surface tension of the water/solvent solutions strongly influence the permeance of the NF-membranes. Flory-Huggins and Zimm-Lundberg theories offered an explanation for the phenomenon where solvent clusters form within the dense polymer matrix of NF-membranes upon exposure to water/solvent mixtures, resulting in decreased water permeabilities. NMR analysis identified of the presence of small amounts of solvents in the STNF-membranes, even still after prolonged exposure to pure water permeation. The results emphasize the current shortcomings of aqueous and solvent-resistant membrane chemistries in handling water/solvent mixtures. Minor solvent additions significantly modify NF membrane permeance, emphasizing the need for innovative material design, especially given the variable solvent content in industrial applications. [Display omitted] • Water/solvent mixture exposure reduces permeance in NF-membranes. • High temperature filtration does not reverse the significant decrease in permeance. • Viscosity and surface tension of water/solvent impact NF-membrane permeance. • Zimm-Lundberg theory supports clustering of water/solvent mixtures in polymers. • NMR identified residual solvent in NF-membranes after water/solvent exposure. [ABSTRACT FROM AUTHOR]

Abstract: Both dense and asymmetric metal organic frameworks (MOFs) containing membranes were respectively prepared by solvent evaporation and phase inversion with Matrimid® as base polymer and three different MOFs: [Cu3(BTC)2], ZIF-8 and MIL-53(Al) as filler. Incorporation of the fillers in the membranes resulted in an increase in thermal and mechanical stability of the membranes. However, the highest filler loadings (typically 40wt%) deteriorated the properties of the membrane. An optimized priming protocol of the fillers before membrane preparation resulted in a homogeneous distribution of the MOFs, as confirmed with SEM. The possible presence of non-selective voids in the asymmetric membranes was overcome by coating a highly permeable silicone polymer layer on top of the MMMs. Dense membranes and asymmetric membranes for all the three studied MOFs showed improvement in CO2/CH4 and CO2/N2 selectivity and permeance as compared to the unfilled reference membrane. [Copyright &y& Elsevier]

Abstract: This paper describes the performance of sulfonated aromatic poly(ether ether ketone) (S-PEEK) membranes, directly prepared from the sulfonated monomer, for CO2 separation from gas mixtures containing N2 or CH4. Dense membranes with different degrees of sulfonation were prepared via solvent evaporation. Increasing degree of sulfonation simultaneously improves the permeability and selectivity of both gas pairs. The effect of counterions was investigated by converting S-PEEK membranes from the Na+-form in which they are prepared, to the H+ and multivalent cationic forms. Gas permeability and selectivity for polymers with divalent and trivalent counterions were higher than those for polymers in the monovalent and H+-forms. In order to study the stability and potential industrial application of these membranes, they were tested at different conditions of feed pressure, temperature and CO2 feed concentration. [Copyright &y& Elsevier]

Abstract: Asymmetric mixed-matrix membranes (MMMs) were prepared via phase inversion from Matrimid® or Matrimid®/Polysulphone blends containing a crystalline metal organic framework (MOF: [Cu3(BTC)2]) to improve the membrane gas separation performance. Physical properties of the synthesized MOF and the membrane (film density, T g, d-spacing) were analyzed. The distribution of MOF embedded in the polymer was studied with SEM. Improvement in thermal and mechanical properties of membranes with increasing [Cu3(BTC)2] loadings, as well as increasing CO2/CH4 and CO2/N2 selectivity and permeance of the silicone sealed membranes suggests defect-free membranes with good compatibility at the filler/polymer interface. Also, relative permeance was in accordance with the Maxwell model for porous materials. [ABSTRACT FROM AUTHOR]

Abstract: Polyimide (PI) based membranes are commercially attractive for CO2/CH4 separations due to their high selectivity and permeance. However, PI membranes prepared from commercially available Matrimid® become unsuitable for industrial applications at high CO2 partial pressure due to plasticization. Blending appropriate polymers with Matrimid® is known to increase this critical plasticization pressure. However, most open literature studies are based on thick symmetric films. Moreover, stability of the membranes as a function of temperature and composition of binary gas mixtures has not systematically been studied yet. The study so far of single gas feeds with thick dense membranes strongly limits the relevance with respect to the actual industrial scale separations. In this work, asymmetric membranes were prepared from Matrimid®, Ultrason polysulphone (PSf) and blends thereof with different ratios. Physical properties (T g, FFV, density and d-spacing) of the membranes were determined in addition to SEM-based membrane cross-section morphologies to better understand the membrane performance. The improvement of the Matrimid® membranes by blending was studied under elevated temperature and at varying CO2 feed composition. A membrane prepared from a 3:1 (Matrimid®:PSf) blend ratio showed consistent increase in selectivity at high CO2 feed composition (up to 90vol%), elevated temperature (up to 95°C) and pressure (up to 14bar). On the contrary, unblended Matrimid® membrane performance deteriorated under operating conditions above 90vol% CO2 feed composition, 65°C and 12bar. Moreover, prepared asymmetric membranes showed much higher permeances than corresponding dense membranes without too much compromising selectivity. [Copyright &y& Elsevier]

• Flocculation combined membrane filtration can decrease microalgae harvesting cost. • Surface patterning can significantly enhance flux, while reducing energy input. • Very low energy consumption and harvesting cost were achieved. • Patterned membranes showed a lower filtration resistance than flat membranes. • 28w% PEG in the casting solution was optimal for patterned membrane preparation. Membranes have a lot of potential for harvesting microalgae, but mainly membrane fouling and high harvesting costs linked to low fluxes are hampering their breakthrough. Patterned membranes can reduce fouling by enchancing local turbulences close to the membrane surface on one hand, and by increasing the active area per m2 of installed membrane on the other. Flocculation can further increase membrane permeance by increasing microalgal partical size and reducing the fraction of free organic matter in the feed. In current study, the effect of polyethylene glycol (PEG) in the casting solution of patterned polysulfone membranes was investigated to better tune the performance of the patterned membranes, together with the effects of cross-flow velocity and chitosan dosage on membrane fouling. The energy consumption and total harvesting cost, extrapolated to a full-scale microalgal harvesting, were then estimated. The patterned membrane prepared with a 28w% PEG concentration showed the highest clean water permeance (900±22 L/m2 h bar) and membrane permeance in a microalgal suspension (590±17 L/m2 h bar). Patterned membranes showed a lower filtration resistance (15% permeance decline at the end of filtration) than flat membranes (72%) at a cross-flow velocity of 0.0025 m/s. Increasing cross-flow velocity could increase membrane permeance in most cases. The highest stable membrane permeance (110±17 L/m2 h bar) and the lowest filtration resistance were achieved when combining patterned membrane filtration with flocculation at optimized chitosan dosage. A very low energy consumption (0.28 kWh/kg) and harvesting cost (0.16 €/kg) were achieved under these conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

The development and design of efficient olefin/paraffin separation processes requires an understanding of the physicochemical properties of the adsorbent for target gas components. This paper presents experimental assessment of the adsorption characteristics of pristine and modified MOF-808s for ethane, ethene, propane and propene gases. The modification of MOF-808s was carried out using a post-synthesis approach, involving the use of two distinct types of ligands and subsequent addition of Cu metal. The pulse inverse gas chromatography technique at infinite dilution was employed to determine adsorption properties, including Henry's adsorption constants, adsorption enthalpies and entropies of the synthesized MOFs. The highest olefin/paraffin selectivity at 1 bar was identified in MOF-808-His-Cu, with selectivity values of 15.7 for ethene/ethane at 30 °C and 26.2 for propene/propane at 50 °C. This notable selectivity is probably attributable to the formation of π complexes between the olefin and Cu atoms present in the adsorbent. This is evidenced by the distinctive asymmetric chromatogram peak with a long tail, which aligns with their adsorption isotherm concavity. Depending on the molecule and the MOF-808 variant, different isotherm shapes and adsorption capacities were obtained. [Display omitted] • Water-based synthesized MOF-808 and its modified variants are investigated for the separation of light olefins/paraffins. • Pulse IGC analysis reveals a 19.5 times higher olefin selectivity of Cu-incorporated MOF-808s compared to the pristine MOF. • All MOFs exhibit higher C 3 adsorption capacities compared to C 2 hydrocarbons. [ABSTRACT FROM AUTHOR]

Designing membranes with synthetic water channels has become an emerging topic to overcome the ubiquitous selectivity/permeability trade-off effect. In this study novel ultra-permeable thin film composite membranes with precise molecular fractionation were successfully fabricated. Per-hydroxylated pillar [5]arene (P [5]A), a macrocycle with a highly regular, cylindrical, angstrom-scale intramolecular cavity was applied as the aqueous monomer in interfacial polymerization (IP) to construct water channels in a thin film composite membrane. The competing effects of esterification and alkali-induced hydrolysis during IP were validated by investigating the effect of fabrication conditions. With almost complete rejection of model dyes >99.0% (e.g. , Congo Red & Direct Red 23) and low retention of salts (e.g. , 4.5% for NaCl & 18.9% for Na 2 SO 4), the optimal membrane exhibited an ultra-high water permeance up to 267.1 L m−2 h−1 bar−1, which is 3–10 times higher than most literature-reported membranes for similar applications. Also, the precision of dye/salt fractionation of the membrane was not affected by the increased feed salinity, with overall stable performance in 72 h continuous operation. A high flux recovery of >94.5% proved that the membrane had low fouling propensity. Overall, the new route explored in this study provided inspiration for designing ultra-permeable membranes with precise molecular separation for environmental applications. [Display omitted] • Ultra-permeable pillar [5]arene-based membranes with intramolecular water channels. • Optimal membrane obtained via balancing esterification & hydrolysis effects in IP. • Superior water permeance of 267 LMH·bar−1 & NaCl/dye selectivity of 318 were shown. • Semi-long term tests proved membrane anti-fouling property with >94.5% flux recovery. • New class of membrane successfully overcomes the permeability-selectivity trade-off. [ABSTRACT FROM AUTHOR]

The introduction of patterns on a membrane-solute interface has been suggested as an effective method to tackle the reduced flux and fouling issues. Herein, the effectiveness of using spray-modified non-solvent induced phase separation (s-NIPS) to create a variety of micrometer-level structured interfaces is now studied. Circular, triangular and rectangular patterns with different dimensions were successfully created on polyacrylonitrile membranes. The rectangular pattern height was varied from 500 to 1500 µm, which resulted in a proportional increase in clean water permeance from 590 ± 47 L m−2 h−1 bar−1 to 1345 ± 108 L m−2 h−1 bar−1 respectively. This coincided with some BSA rejection loss for the highest patterns, indicating the fragile nature of these tall features. No significant rejection losses were found for the smaller pattern heights (145–250 µm) as compared to flat membranes, while fluxes more than doubled still. The critical pressure was also increased substantially for patterned membranes and showed a proportionality with the pattern height. These experimental findings were correlated with the reduced foulant adhesion due to a shear-induced slip boundary layer at the membrane-solution interface. Computational fluid dynamics simulations further showed higher shear stress values due to flow constriction within the membrane's valley regions. These findings indicate the high potential of s-NIPS patterned membranes in long-term industrial applications by requiring less membrane area for a given application and reducing cleaning interventions. [ABSTRACT FROM AUTHOR]

Concerns of energy shortage and pollution, have rapidly increased the demand for efficient separation processes. In this respect, solvent resistant nanofiltration has become an emerging technology with great potential as an energy-efficient and waste-free separation method. Unfortunately, the lack of sufficient stability (especially chemical stability of the support) still restricts the utilization of this separation technique to the more mild industries, leaving several unexploited. As already detailed in part I of this research, one promising approach to increase the chemical stability of supports, used afterwards as starting point for the synthesis of thin film composite nanofiltration membranes, is cross-linking polymeric UF membranes by UV-irradiation. Whereas in the previous part, the 365 nm UV-LED light was selected as the best setup to achieve a high cross-linking efficiency at high throughputs, in this second part the impact of (non-)compositional parameters on the cross-linking efficiency was investigated. The most important parameters with the largest impact on the degree of conversion (DC) were shown to be the cross-linker content, the membrane thickness and the incorporation of a non-woven support. Finally and more importantly, after curing the membranes did not only show enhanced solvent stabilities (viz. part I), they also exhibited greater physical strength while at the same time maintaining the retention at a similar level as the non-cured membrane clearly indicating their industrial importance. [ABSTRACT FROM AUTHOR]

Polyamide (PA) thin film composite membranes are the commercial standard for nanofiltration and reverse osmosis. Establishing their synthesis-structure-performance relationships (SSPs) is imperative for rational membrane design. Complementary to detailed post-manufacturing characterization, real-time measurements during interfacial polymerization (IP) are key to understand the SSPs. A new method for in situ characterization of IP was developed by combining simple droplet-based experiments and fluorescence microscopy. Simultaneously, real-time data from droplet- and microfluidic-based experiments were demonstrated to agree. Eight commercial and tailormade dyes were tested and the associated pitfalls in the IP system were identified. Four main conclusions are drawn. First, pH measurements show a pH drop from ∼9 to a minimum of ∼5.3 within 70 ms after initiation of IP. Second, dye partitioning can be exploited to probe densification of the forming PA film. Third, within the first 70 ms of IP, a diffusion-limiting barrier for molecules >260 g mol−1 is formed. Yet, the film requires 30–40 s to acquire its full rejecting potential. Fourth, overlaying in situ and performance data supports the proposed SSP for varying TMC concentration, based on step-growth polymerization kinetics. Testing other fluorescent markers and synthesis conditions will expand the opportunities generated by in situ monitoring using fluorescence microscopy to establish SSPs. [Display omitted] • Development of a simple droplet-based experiment for real-time measurements of interfacial polymerization. • Screening fluorescent organic dyes for in situ characterization of IP. • Monitoring real-time polyamide film densification. • Combining droplet-based and microfluidic-based experiments help establish a mechanistic explanation for varying TMC concentration. [ABSTRACT FROM AUTHOR]

Polyamide thin film composite membranes are the commercial standard for aqueous nanofiltration and reverse osmosis. Establishing their synthesis-structure-performance relationships (SSPs), needed for rational membrane design, is hampered by the small scale and high reaction rate of interfacial polymerization (IP). Microfluidic devices, compatible with microscopic real-time visualization of IP and performance testing of the formed film, are interesting within this respect. In this study, a new microfluidic design and operational protocol for in situ characterization of IP is developed. Difficulties encountered with microfluidics and coping strategies are highlighted. The outcome of the optimization study proves that a parylene-coated PDMS-glass chip comprising a channel lay-out with 4 inlets, 2 outlets, a channel height of 20 μm, and a reaction channel length ≤50 μm is most compatible with IP and performance testing. Varying synthesis conditions show changing film morphology and water flux in line with trends for dip-coated membranes. Addition of NaHCO 3 and ethyl acetate induce morphological features and increase water flux. Increasing TMC concentrations decrease water flux until an excess is generated. By combining the developed protocol and microfluidic device with an online measurement technique to probe film formation dynamics, such as fluorescence microscopy, SSPs can be derived in the future. [Display omitted] • A new microfluidic design and operational protocol for in situ characterization of IP is developed. • A parylene-coated PDMS-glass microfluidic device was designed with channel widths and height of 120 and 20 μm respectively. • Integration of an orifice with 30–50 μm length ensures stable contact of both monomer phases to form the polyamide film. • Morphology and performance of the film formed within the microfluidic device are assessed as function of synthesis conditions. • Combining developed protocol and microfluidic device with on-line measurement allows study of IP-kinetics. [ABSTRACT FROM AUTHOR]

Epoxy-based nanofiltration (NF) membranes have great potential to allow untapped applications such as the treatment of water/solvent mixtures. However, achieving reproducible membrane performance with concurrent high permeances for water/solvent mixtures and high solute rejections remains challenging. Herein, such a solvent-tolerant NF (STNF) membrane with superior performance characteristics is synthesized through optimizing the non-solvent induced phase separation (NIPS) method by simultaneously curing 2 epoxide building blocks (EPON 1009F (20 wt%) and EPON SU-8 (10 wt%)) with hyperbranched polyethylene imine (PEI) in dimethyl sulfoxide (DMSO). As a multifunctional crosslinker, the hyperbranched PEI, compared to the difunctional linear hexane diamine (HDA), increases the synthesis reproducibility, the membrane flexibility and permeability, offering a remarkable water/DMF (80/20) permeance of 5.7 L m-1 h-1 bar-1 and a rejection of rose bengal (1018 g mol−1) of 93.3%. A decreased permeance and rejection was observed when increasing the solvent content in the water/DMF or water/ethanol feed from 0 to 30 wt%, while a change in water permeance occurred before and after water/solvent filtrations. The epoxy-based membrane is also intrinsically stable in many solvents, and is easy to tune and produce, making it an ideal candidate for the purification of solvent-containing wastewaters from e.g. , the pharmaceutical and chemical industries. • An optimized phase inversion process to prepare epoxy-based solvent-tolerant nanofiltration (STNF). • Membrane formation via epoxy curing with hyperbranched polyethylene imine in DMSO. • Water/DMF (80/20) permeance of 5.7 L m-2 h-1 bar-1 and a RB rejection of 93.3%. • A change in water permeance occurred before and after water/solvent filtrations/ethanol and water/DMF filtrations. • Membranes are stable in toluene, ACN, ethanol and 200 ppm NaOCl in water. [ABSTRACT FROM AUTHOR]

Epoxy curing is a versatile chemistry that can be applied in membrane preparation, both via phase inversion and interfacial polymerization. Here, fully epoxy-based TFC membranes are demonstrated for the first time and tested for solvent-tolerant nanofiltration (STNF) applications. First, UF membranes with a retention for bovine serum albumin (BSA, ∼66000 g mol−1) of ∼40% and a water permeance of 171 L m−2 h−1 bar−1 were prepared via phase inversion by pre-curing epoxide resins (EPON™ resin 1009F and EPON™ resin SU-8) with 1,6-hexanediamine (HDA) prior to phase inversion in water. Subsequently, selective top layers were synthesized on these supports layers via interfacial polymerization (IP) or interfacial initiation of polymerization (IIP) of the same epoxy resins, resulting in a thin selective top layer of the same material. By using different amines, different epoxide ring-opening polymerizations (ROP) could be targeted. These TFC membranes were then tested for use in water-solvent mixtures and achieved a 92.8% methyl orange (MO, 327 g mol−1) retention and a permeance of 0.21 L m−2 h−1 bar−1 in a 20/80 DMF/water feed solution. Cured epoxy chemistry is known for its excellent chemical stability, making these membranes suitable for a wide variety of solvent-resistant NF (SRNF) and STNF applications. [Display omitted] • Proof of concept of fully epoxy-based TFC membranes. • Epoxy curing was applied both during phase inversion and interfacial polymerization. • UF membranes with R BSA = ∼40% and P = 171 L m−2 h−1 bar−1 in water. • STNF membranes with R MO = 92.8% and P = 0.21 L m−2 h−1 bar−1 in 20/80 DMF/water. • Excellent chemical stability is obtained, suited for solvent/water mixtures. [ABSTRACT FROM AUTHOR]

Highlights • Solvent-treatment to adapt membrane pores was extended to non-aqueous applications. • The mechanism behind the pore sizes changes upon solvent-treatment was elucidated. • The pore size changes were characterized via solvent permeation and PALS. Abstract Tuning the cohesive and swelling forces in porous membranes by post-synthesis solvent-treatment was already proven to be a successful way to increase the membrane selectivity in aqueous redox flow battery application without sacrificing too much permeability of the membranes. This method was now extended to non-aqueous applications and the mechanism behind the tuning of the pore sizes upon solvent-treatment was studied in more detail. Porous polyvinylidene fluoride (PVDF) and polysulfone (PSF) membranes were thus prepared via phase inversion and subsequently treated with different solvents followed by the evaporation of this solvent to adjust the structural porosities of these asymmetric membranes and better understand the underlying mechanism. For this purpose, water and acetonitrile permeances were determined before and after the solvent-treatment and these permeances were linked to the (solvent)-(membrane polymer) Hansen solubility parameters. The membrane density changes were characterized by positron annihilation lifetime spectroscopy (PALS). It was proven that the pore adjustment that was created by the solvent-treatment was reversible when the membrane was later on applied in a feed solution with high affinity for the membrane polymer. [ABSTRACT FROM AUTHOR]

Highlights • Thermal/salt annealing of PEM-based nanofiltration membranes is studied in terms of MP removal. • PEMs become less hydrated by thermal annealing, and more hydrated with salt annealing. • No improved performance is observed for thermally-annealed membranes. • Enhanced MP rejection is observed for salt-annealed membranes, while keeping low ion retention. • The fouled membrane could be easily cleaned by a sacrificial layer approach, without shear forces. Abstract The ever-increasing concentrations of micropollutants (MPs) found at the outlet of conventional wastewater treatments plants, is a serious environmental concern. Polyelectrolyte multilayer (PEM)-based nanofiltration (NF) membranes are seen as an attractive approach for MPs removal from wastewater effluents. In this work, PEMs of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were coated in a layer by layer (LbL) fashion on the surface of a polyacrylonitrile ultrafiltration support to obtain PEM-based NF membranes. The impact of PEM post-treatment, by applying salt and thermal annealing, was then investigated in terms of swelling, hydrophilicity, permeability, and ion rejection. While thermal annealing produced a more compact structure of PEM, it did not improve the ion rejection. Among the different salt concentrations examined for the salt-annealing process, the highest ion rejection was observed for (PAH/PAA) 15 membranes annealed in 100 mM NaNO 3 , interestingly without any decrease in the water permeability. This membrane was studied for the rejection of four MPs including Diclofenac, Naproxen, 4n-Nonylphenol and Ibuprofen from synthetic secondary-treated wastewater, over a filtration time of 54 h. At an early stage of filtration, the membrane became more hydrophobic and a good correlation was found between the compounds hydrophobicity and their rejection. As the filtration continued until the membrane saturation, an increase in membranes hydrophilicity was observed. Hence, in the latter stage of filtration, the role of hydrophobic interactions faded-off and the role of molecular and spatial dimensions emerged instead in MPs rejection. To test the suitability of the membranes for the ease of cleaning and repeated use, the sacrificial PEMs and foulants were completely removed, followed by re-coating of PEMs on the cleaned membrane. The higher MPs rejection observed in salt-annealed membranes compared to the non-annealed counterparts (52–82% against 43–69%), accompanied with still low ion rejection, confirm the high potential of PEM post-treatment to achieve better performing PEM-based NF membranes. [ABSTRACT FROM AUTHOR]

Highlights • MMMs based on PDMS and ZIF-67 nano-fillers. • Good dispersion of the functionalized fillers in the polymer matrix. • Significant increase in permeability and retention was obtained. Abstract Zeolitic imidazole frameworks (ZIFs), a subclass of metal organic frameworks (MOFs), are composed of metal ions linked by organic ligands which offer an exceptionally high surface area and appealing separation potential. In this study, mixed matrix membranes (MMMs) were prepared using polydimethylsiloxane (PDMS) as a hydrophobic polymer and ZIF-67 as inorganic filler particle. ZIF-67 particles and MMMs were characterized by XRD, SEM, FTIR, BET and contact angle measurements. The prepared membranes were tested for the separation of ethanol/water mixtures via pervaporation. Compared to unfilled PDMS membranes, MMMs loaded with 20 wt% ZIF-67 showed an increase in flux and a doubled separation factor. The easy synthesis of ZIF-67 and its enhanced separation performance make ZIF-67 an attractive candidate to prepare MMMs for a variety of membrane applications. [ABSTRACT FROM AUTHOR]

Abstract Crosslinked poly(vinylidene difluoride) (PVDF) nanofiltration membranes were prepared and tested for solvent resistant nanofiltration (SRNF) and solvent tolerant nanofiltration (STNF, i.e. in solvent/water media) applications. The performance of the membranes was assessed by filtering ethanol (EtOH), iso -propanol (i PrOH), acetonitrile (ACN), dimethylformamide (DMF) or toluene (Tol) solutions containing Rose Bengal (RB), a 1017 Da solute. During these consecutive filtrations, the membranes displayed a solvent activation effect which was characterised by TEM, ATR-FTIR and via intermediate EtOH filtrations. This solvent activation resulted in a more permeable membrane (by a factor of 11), without loss in retention. Drying the membranes from MeOH resulted in a further increase of the RB retention in ACN and Tol to 98%. The stability of the membranes was characterised using SEM, weight loss analysis and ATR-FTIR. In STNF, a 99% RB retention was achieved from a 1:4 DMF/water mixture. Highlights • One-pot diamine crosslinked PVDF-membranes were tested in SRNF and STNF. • Membranes could be applied in EtOH, i PrOH, ACN, Tol and DMF. • Solvent activation improved the membrane permeance by a factor of 11. • Membrane drying further improved the retention in ACN, DMF and Tol. [ABSTRACT FROM AUTHOR]

This study focuses on using a (3-aminopropyl)trimethoxysilane and acetate ion based ionic liquid to modify zeolite 4A as a filler in a polysulfone (PSf) membrane for CO 2 /CH 4 and CO 2 /N 2 separation, aiming at improving the polymer-filler interaction and separation performance of the mixed matrix membrane (MMM). The ionic liquid was covalently attached onto the zeolite surface. Zeolite modification was confirmed through FTIR analysis of pristine and modified filler. N 2 sorption isotherms were used to characterize the porous structure, which showed decrease in surface area and pore volume after surface modification of zeolite. The crystal structure of zeolite 4A remained unaffected after modification with ionic liquid, as shown by XRD and SEM. Moreover, the synthesized PSf-based MMMs were tested in the separation of CO 2 from CH 4 . Experiments were conducted at different temperatures and feed conditions, and pure and mixed gas permeability/selectivity data was reported. This modification of zeolites with methoxy groups containing cation and acetate anion based ionic liquid, resulted in an improved separation performance, as the modified filler enhanced the MMMs selectivity of CO 2 /CH 4 by 37% and for CO 2 /N 2 by 43% at 30 wt% filler loading as compared to pristine filler MMMs. The 3-(trimethoxysilyl)propan-1-aminium acetate coating acts as a selecting film which notably improves the selectivity at marginal expense of CO 2 permeance. [ABSTRACT FROM AUTHOR]

The majority of commercial membrane units for large-scale natural gas sweetening are based on cellulose acetate (CA). However, the low selectivity and risk for and plasticisation affect adversely the performance of CA-based systems. Herein, we present a new class of CA-derived poly(ionic liquid) (PIL) as a thin film composite (TFC) membrane for CO 2 separations. CA is modified with pyrrolidinium cations through alkylation of butyl chloride, substituting the hydroxyl group in the polymer backbone, and further anion exchange to bis(trifluoromethylsulfonyl)imide, P[CA][Tf 2 N]. The synthesised PIL material properties are extensively studied. The CO 2 separation performance of the newly synthesised materials is evaluated by gravimetric gas sorption experiments, single gas time-lag experiments on thick membranes, and mixed-gas separation experiments on TFC membranes. The results are compared to the parent material (CA) as well as a reference PIL (poly(diallyldimethyl ammonium) bis(trifluoromethylsulfonyl)imide (P[DADMA][Tf 2 N])). The ideal CO 2 /N 2 sorption selectivity of P[CA][Tf 2 N] is constant up to 10 bar. The single gas transport measurements in P[CA][Tf 2 N] reveal improved ideal CO 2 selectivity for the CO 2 /N 2 gas pair and increased CO 2 permeability for the CO 2 /CH 4 gas pair compared to the reference PIL. Mixed-gas permeation tests demonstrated that P[CA][Tf 2 N]-based membranes with a 5 µm thick selective layer has a two-fold higher CO 2 flux compared to conventional CA. These results present CA modification into PILs as a successful approach promoting the higher permeate flows and improved process stability in a wide range of concentrations and pressures of CO 2 /N 2 and CO 2 /CH 4 gas mixtures. [ABSTRACT FROM AUTHOR]

Incorporation of MOFs in interfacially polymerized Thin-Film Nanocomposite (TFN) membranes has widely been shown to result in increased membrane performance. However, the exact functioning of these membranes is poorly understood as large variability in permeance increase, filler incorporation and rejection changes can be observed in literature. The synthesis and functioning of TFN membranes (herein exemplified by ZIF-8 filled polyamide (PA) membranes prepared via the EFP method) was investigated via targeted membrane synthesis and thorough characterization via STEM-EDX, XRD and PALS. It is hypothesized that the acid generated during the interfacial polymerization (IP) at least partially degrades the crystalline, acid-sensitive ZIF-8 and that this influences the membrane formation (through so-called secondary effects, i.e. not strictly linked to the pore morphology of the MOF). Nanoscale HAADF-STEM imaging and STEM-EDX Zn-mapping revealed no ZIF-8 particles but rather the presence of randomly shaped regions with elevated Zn-content. Also XRD failed to show the presence of crystalline areas in the composite PA films. As the addition of the acid-quenching TEA led to an increase in the diffraction signal observed in XRD, the role of the acid was confirmed. The separate addition of dissolved Zn 2+ to the synthesis of regular TFC membranes showed an increase in permeance while losing some salt retention, similar to observations regularly made for TFN membranes. While the addition of a porous material to a TFC membrane is a straightforward concept, all obtained results indicate that the synthesis and performance of such composite membranes is often more complex than commonly accepted. [ABSTRACT FROM AUTHOR]

Solvent resistant nanofiltration (SRNF) and solvent tolerant nanofiltration (STNF) are energy-efficient membrane-based technologies to purify solvents or water-solvent mixtures, respectively, and/or to recover solutes from these streams. SRNF and STNF are rapidly gaining importance as they contribute to process intensification and to a circular economy. Whilst solute-solvent-membrane interactions determine the membrane performance, they are often not sufficiently taken into account, which possibly leads to misinterpretation of the obtained data. This review focusses specifically on the environment-dependent behavior and properties of commonly used solutes (dyes, oligomers, n -alkanes, esters, triglycerides, sugars and inorganic salts) through a theoretical physicochemical lens that focusses on molecular interactions. It reveals that the assumed fixed solute properties do not necessarily coincide with those in the chosen solvent medium. Indeed, solutes can adopt different configurations, charges or sizes in different (hydro-)organic media and this can significantly impact the membrane performance. By highlighting these complex solute-solvent interactions from a theoretical point of view, this review aims at more correctly interpreting, describing and representing membrane performance data, and to facilitate the selection of suitable solutes for a specific separation. Furthermore, the most adequate characterization techniques per solute class are discussed and some solutes that are less environment-dependent are proposed as more appropriate alternatives. In addition to achieving a better understanding of the fundamental solute-solute and solute-solvent interactions, the outlined insights aim at assisting membrane selection by end-users and at promoting improved data reliability. [Display omitted] • Solute-solvent-membrane interactions determine membrane performance. • Solutes can adopt different shapes, charges or sizes in different (hydro-)organic media. • The environment-dependent properties of commonly used solutes are discussed. • The most adequate characterization techniques per solute class are discussed. • High-potential solutes that are less environment-dependent are proposed. [ABSTRACT FROM AUTHOR]