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A novel polyzwitterionic hydrogel coated mixed matrix membrane (MMM) was successfully prepared, characterized and used for Cu2+, Mn2+, and Pb2+ heavy metal ions removal from water. Hydrophilic and porous covalent organic framework (COF) nanoparticles (NP) as filler were synthesized from melamine and terephthalaldehyde, and then incorporated into polyamide (PA) thin film composite (TFC) membrane. The hydrogel coating was applied by using a tailored cross‐linkable polymer system in combination with concentration polarization enabled cross‐linking. The effects of COF NP loading into PA layer and polyzwitterionic hydrogel coating on the membrane morphology and separation performance were studied using different analyses. The MMM prepared with a COF NP loading of 0.02 wt/wt% in the hexane dispersion used for NP deposition during PA layer formation (leading to 0.42 g/m2) exhibited an increased pure water permeability of around 200% compared with the neat PA TFC membrane while the Mn2+ ion rejection maintained above 98%. Scanning electron microscopy surface images and zeta potential profiles showed that the hydrogel was successfully deposited on the membrane surface. Furthermore, the hydrogel coating could decrease net surface charge of membranes but did not significantly influence the heavy metal ions rejections under nanofiltration conditions. The results of filtration experiment with protein solution indicated that the hydrogel coated membranes exhibited superior antifouling property, as shown by higher flux recovery ratio after washing with water, compared with neat PA TFC membrane and not coated MMM, respectively. [ABSTRACT FROM AUTHOR]

Nowadays most membrane separation processes utilize membranes made from organic polymers because shape and structure can be tailored to the needs of a specific application with scalable fabrication processes such as solution casting and phase separation, coating and interfacial polymerization. This short review discusses recent progress for membranes suited for molecular separation in aqueous and organic liquids by nanofiltration, dialysis, electrodiaysis or pervaporation. Important achievements for bulk polymers suited as membrane material have been made by special processing of cellulose, development of highly stable polymers, microporous polymers and microphase-segregating copolymers. Ultrathin barrier layers are critical to combine target selectivity with high flux. Hence the scope of layer-by-layer and self-assembly of polymers as well as interfacial polymerization of standard monomers and advanced building blocks has been expanded, with the aim to obtain in situ on supports microporous materials with suited functional groups or molecular cavities. Overall, there is an increasing number of approaches which enable a precise tailoring of selectivity and boosting the flux at the same time. Hence, much higher overall separation performance compared to state-of-the-art membranes is in principle feasible. [ABSTRACT FROM AUTHOR]

By integrating a water‐soluble polymer, which has the ability to complex heavy metal ions into ultrafiltration membranes, the separation process could be enhanced to enable also filtration of these species. In this work, a membrane and an adsorber polymer were functionalized with complementary reactive groups so that the adsorber polymer could be immobilized in the porous support layer of the ultrafiltration membrane via click reaction. The separation performances and membrane characteristics of the synthesized membranes are comparable to those of conventional UF membranes. [ABSTRACT FROM AUTHOR]

Abstract The variable viscosity Poiseuille model (VVPM), developed recently to treat gas-liquid displacement (GLD) porometry data for track-etched polyethylene terephthalate (PET) membranes, is applied to polyethersulfone (PES) and polypropylene (PP) microfiltration membranes prepared by phase inversion. It is found that in general aspects the pore size distribution as estimated by the model, with the intrinsic assumption of isolated capillary pores, perfectly reproduces wet and dry fluxes during porometry measurements, but the estimated porosity appeared to be much higher than unity. To eliminate the discrepancy, two additional parameters, namely non-uniformity and tortuosity coefficient, have been introduced in the flux and porosity estimating equations. The apparent viscosity of the gas in porometry analysis is found to be several fold higher than that available in literature, and also the viscosity range appeared to be membrane type dependent. The pore size distribution curve shifts along the diameter axis depending on the gas flow direction applied in porometry data acquisition. However, because the membranes had narrow pore size disribution, the estimated parameters had been averaged within acceptable confidence range. With the inclusion of non-uniformity and tortuosity of the capillaries, the revised version of the VVPM made an advancement in porometry data analysis of membranes with both isolated and interconnected pore structure; it characterizes the assumed model capillaries in terms of Young-Laplace pore diameter, but also non-uniformity and tortuosity of pores. The procedure for data treatment has been illustrated in detail and the method could easily be adapted to gas-liquid displacement porometer software system for regular data treatment. Based on a set of readily available experimental data, including the typical output from standard GLD porometry, the here established extended version of the VVPM allows the step-by-step determination of all the parameters which characterize the pore structure of the membranes. Also the absolute pore number density distributions can be obtained, including estimates of additional pore characteristics such as non-uniformity and tortuosity. Highlights • Extended variable viscosity Poiseuille model yields membrane pore size distribution, non-uniformity and tortuosity. • Model describes flow distribution, liquid permeability and membrane porosity. • Effective air viscosity estimated to describe measured permeability much higher than literature data. [ABSTRACT FROM AUTHOR]

In this work, poly(ethylene oxide)- block -poly(methyl methacrylate) (PEO- b -PMMA) diblock copolymers were established as functional additive for polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes, originally with the intention to increase their hydrophilicity and thereby decrease fouling. Additionally, however, it was found that copolymer micelles can be induced by complexing the PEO block of PEO- b -PMMA with specific metal salts. The formation of micelles as function of specific solution compositions was observed in dynamic light scattering and rheology experiments; the formation of PEO-metal ion complexes was shown via proton nuclear magnetic resonance ( 1 H NMR) spectroscopy. Integration of micelle-forming compositions into typical PVDF-based casting solutions for UF membranes could lead to a higher surface porosity and a more regular barrier pore structure through microphase separation during the nonsolvent induced phase separation process used for membrane preparation. It was found that membranes containing small amounts of PEO- b -PMMA show a significantly higher permeance than membranes made from an otherwise equal casting solution without the copolymer, while maintaining the solute rejection properties. By using different types and amounts of metal salts to complex the PEO block it was possible to tailor the molecular weight cut-off of the membranes between 30 kDa and 110 kDa. Fouling studies in lab-scale cross-flow filtration cells showed an increased relative flux recovery compared to membranes without the functional copolymer additive. The results of this study are relevant because small fractions of a tailored diblock copolymer and metal salt as additives allow tailoring the barrier and separation properties at significantly higher overall performance within an otherwise unchanged membrane manufacturing process. [ABSTRACT FROM AUTHOR]

Research and development towards sustainable chemistry includes also the development of new materials and the exploration of new ways to fabricate them. In this work, composite membranes were fabricated from fully biodegradable materials (cellulose) through a simple and scalable process, i.e., a combination of film casting, nonsolvent-induced phase separation and lamination, in which only environmentally friendly solvents are used. Filter paper was utilized as support material. Cellulose was dissolved in a mixture of an ionic liquid (1-ethyl or 1-butyl-3-methylimidazolium acetate) with a co-solvent (dimethylsulfoxide, DMSO) and used for casting the barrier layer. The influence of pre-wetting the filter paper with different liquids (water, glycerine, DMSO) was investigated. It was found that using DMSO as impregnation liquid improved both, the membrane separation performance and the strength of the lamination between the cellulose barrier layer and the filter paper as demonstrated by adhesion tests. Barrier layer thickness could be reduced to a few μm by appropriate cast film thickness. Membrane separation performance in terms of permeance and solute rejection could also be adjusted by the choice of cellulose concentration and co-solvent fraction in the casting solution. The applicability of the cellulose-cellulose composite membranes in ultrafiltration (UF) of aqueous or organic solvent-based mixtures was evaluated with dextran or polyethylene glycol and polyethylene oxide, respectively, as test solutes. Molecular weight cut-off data for one specific UF membrane type were ∼100 kDa, ∼170 kDa, or ∼390 kDa in water, dimethylformamide or DMSO. All results obtained in this study indicate that the novel membranes have potential as a more sustainable alternative material for various relevant separations. [Display omitted] • Stable composite membranes fabricated by casting cellulose solution on filter paper. • Ultrafiltration properties tunable by cellulose solution in ionic liquid/DMSO mixture and coagulation in water. • Impregnation of filter paper support prevents pore blocking to yield high permeance. • Effective lamination between filter paper support and cellulose barrier layer. • Fully bio-based membranes with potential for aqueous and organic solvent ultrafiltration. [ABSTRACT FROM AUTHOR]

The state-of-the-art reverse osmosis membranes for seawater desalination have limited competence to efficiently remove boron. One promising approach for boron removal is to integrate membrane-based separation with selective adsorption of boron in pre- or posttreatment of seawater desalination; the porous support layer of established filtration membranes, constituting the largest part of total membrane volume shall be utilized for this function. Therefore, this study focuses on performing in situ modification of commercial polyethersulfone (PES) microfiltration membranes toward reactive coating the pore surface with a boron affinity polymer-based hydrogel. Modification is carried out in two steps: 1) adsorption of an amphiphilic copolymer which contains tertiary amine groups as co-initiator for surface-selective free radical generation; 2) grafting of a hydrogel layer by using a monomer solution comprising polyol-containing monomer as boron ligand, a cross-linker monomer, and the redox initiator ammonium persulfate (APS). The entire modification process is performed under flow-through conditions. Membranes with different pore sizes were modified; modification parameters, such as molar mass of macromolecular co-initiator as well as composition of reactive monomer solution, were systematically varied. It was found that using an "integrated" initiation system with low molecular weight co-initiator N,N,N′,N′-tetraethyl ethylenediamine (TEMED) added to the reactive solution, yielded significantly higher degree of grafting and therefore superior adsorber properties. Boron binding capacity of modified membranes was evaluated in terms of boron adsorption isotherms, adsorption kinetics, break-through behavior under filtration conditions and regeneration of the adsorber. The trade-off between permeance and boron binding capacity of modified membrane was studied in order to identify promising materials with competitive overall separation performance, i.e. high permeance at a specific filter cut-off in combination with high boron binding capacity. [Display omitted] • In situ reactive coating of porous filtration membranes with boron affinity glycopolymer established. • Optimized balance between high boron adsorption capacity and permeance accomplished. • Functionalization and utilization facilitated by flow-through filtration conditions. [ABSTRACT FROM AUTHOR]

Abstract: Applying a hydrophilic layer to the membrane surface is one common strategy to control membrane fouling. This work focuses on hydrophilic membrane coating materials synthesized from poly(ethylene glycol) (PEG)-based hydrogels and application of thin hydrogel layers from such polymers on the surface of composite polyamide nanofiltration membranes. The approach of using macroinitiator-mediated synthesis cum anchoring of a hydrogel layer on the membrane was explored to reduce or avoid homopolymerization in bulk solution and prevent delamination of the antifouling layer from membrane surface. Cationic macroinitiators were based on poly(2-dimethylamino-ethyl methacrylate-co-2-hydroxyethyl methacrylate) obtained by radical copolymerization and comprised photoinitiator side groups linked to the poly(2-hydroxyethyl methacrylate) segments. Adsorption of the macroinitiator to the membrane surface and preparation of hydrogel coatings on polyamide composite membranes via photo-initiated in situ graft and cross-linking copolymerization were studied in detail. The modification degree and its effect on the membrane properties was characterized with respect to membrane chemistry by ATR-IR spectroscopy, surface charge by zeta potential, surface wettability by contact angle, and with respect to pure water permeability and salt rejection. The propensity to protein fouling was also investigated. The results indicate that hydrogel modified membranes have an improved fouling resistance compared to pristine membranes, and that this approach has the potential to become a generic approach for a controlled surface functionalization using a simple two-step protocol. [Copyright &y& Elsevier]

To investigate nanofiltration (NF) separation for recycling polyethylenglycol (PEG) from an ion partition process using an aqueous two-phase system, fractionation performance of five different NF membranes (NF270, SR3, SR100, SR2, and BW30) with solutions of NaNO3, KClO4, and PEG 4000 in water comprising various mixtures were studied. PEG rejections and salt passage were analyzed and explained based on size exclusion as well as electrostatic interactions. The highest permeate flux at high rejection of PEG as well as the lowest salt rejections were obtained with SR2 and NF270 membranes. Similar salt rejections were observed for mixed solute solutions and complex mixtures, all following this trend: SR3 > NF270 > SR2. The PEG rejections were well above 95%. This study also revealed that high salt passage of above 90% could be achieved with the same NF membrane only by unstirred conditions through concentration polarization mechanism; however, at the expense of low flux, especially with high PEG concentrations. [ABSTRACT FROM AUTHOR]

Abstract: For surface hydrophilic and antifouling modification of polypropylene (PP) microfiltration membrane, the novel method for entrapment of the amphiphilic modifier octaethyleneglycol monooctadecylether (C18E8) was investigated in detail. The effects of the modification conditions on PP membrane and polymer structure were characterized by gas flow/pore dewetting, nitrogen adsorption/BET analysis, scanning electron microscopy and X-ray diffraction; surface properties were evaluated by ATR-FTIR spectroscopy and static water contact angle; filtration performance as well as antifouling property were investigated by water flux measurement, trans-membrane zeta potential, static and dynamic protein adsorption experiments. Furthermore, a stability study of the modified membrane was performed to offer a comprehensive understanding of this physical entrapment strategy. It can be concluded that both outer surface and inner pore walls of PP membrane were covered with oligoethylene glycol after entrapment modification by C18E8, with only very slight changes of membrane pore and polymer structures. Correspondingly, PP membrane surface hydrophilicity and antifouling performance were evidently improved. It was also found that the entrapped modifier has a tendency to leach out of the PP membrane in water at room temperature. However, after 8 weeks changes became very small, and the modified PP membrane surface still exhibited significant hydrophilicity and antifouling properties. [Copyright &y& Elsevier]

Abstract: Polyethersulfone (PES) ultrafiltration (UF) membranes were prepared by non-solvent-induced phase separation (NIPS) method using different macromolecular additives, polyvinylpyrrolidone (PVP), poly(ethylene glycol) (PEG) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronic®, Plu). Their effects on membrane structure and their stability in the polymer membrane matrix as well as the resulting membrane performance were systematically compared in order to determine the additive that should be preferred. The investigated membrane characteristics include surface hydrophilicity (by contact angle), surface charge (by zeta potential), surface chemistry (by FTIR spectroscopy), water flux and rejection of macromolecular test substances. Visualization of membrane surface and cross-section morphology was also done by scanning electron microscopy. The membrane performance was examined by investigation of adsorptive fouling and ultrafiltration using solution of bovine serum albumin as the model system. The stability of additive was examined by incubating the membrane in water (40°C) and sodium hypochlorite solution. Modification effects on membrane characteristic as well as performance via blending membrane polymer and macromolecular additive were clearly observed. Overall, the results suggest that Pluronic showed the best behavior in all respects, and, consequently, it should be considered in practical applications. [Copyright &y& Elsevier]

Abstract: A new method to prepare membrane adsorbers with structure variations of functional polymer brush, the initiator entrapping method via photo-initiated surface-selective graft-copolymerization was used in this work. Functional polymer brush structures on polypropylene (PP) microfiltration membrane pore surfaces were obtained by using acrylic acid (AA) as functional monomer. Copolymerization of AA with ‘‘diluent’’ monomer acryl amide (AAm) and ‘‘crosslinker’’ methylene bisacrylamide (MBAA) was done for variations of the grafted layer. Characterization had been done by measurements of reversible protein binding (lysozyme, Lys), stepwise change of a high concentration buffer solution to a low one having the same pH value (inadvertent pH transient) and breakthrough curves for Lys. Membrane adsorber grafted with functional monomer AA was used as reference, membrane adsorber grafted with the mixture of functional and diluent monomers (AA/AAm) show low amount of protein binding and low inadvertent pH transient value as well as early and broad breakthrough curve, while membrane adsorber grafted with a mixture of functional and crosslinker monomer (AA/MBAA) show high amount of protein binding and high inadvertent pH transient value as well as late and sharp breakthrough curve. Structure variations of the grafted functional polymer brush membrane adsorber with crosslinker monomer (AA/MBAA) show the lowest axial dispersion and thus also increase the efficiency of adsorbent utilization. [Copyright &y& Elsevier]

Abstract: This feature article provides a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane separation processes for liquid and gaseous mixtures (gas separation, reverse osmosis, pervaporation, nanofiltration, ultrafiltration, microfiltration) and in other important applications of membranes such as biomaterials, catalysis (including fuel cell systems) or lab-on-chip technologies. Important approaches toward this aim include novel processing technologies of polymers for membranes, the synthesis of novel polymers with well-defined structure as ‘designed’ membrane materials, advanced surface functionalizations of membranes, the use of templates for creating ‘tailored’ barrier or surface structures for membranes and the preparation of composite membranes for the synergistic combination of different functions by different (mainly polymeric) materials. Self-assembly of macromolecular structures is one important concept in all of the routes outlined above. These rather diverse approaches are systematically organized and explained by using many examples from the literature and with a particular emphasis on the research of the author''s group(s). The structures and functions of these advanced polymer membranes are evaluated with respect to improved or novel performance, and the potential implications of those developments for the future of membrane technology are discussed. [Copyright &y& Elsevier]

This review presents an overview on the promising field of molecularly imprinted membranes (MIM). The focus is onto the separation of molecules in liquid mixtures via membrane transport selectivity. First, the status of synthetic membranes and membrane separation technology is briefly summarized, emphasizing the need for novel membranes with higher selectivities. Innovative principles for the preparation of membranes with improved or novel functionality include self-assembly or supramolecular aggregation as well as the use of templates. Based on a detailed analysis of the literature, the main established preparation methods for MIM are outlined: simultaneous membrane formation and imprinting, or preparation of imprinted composite membranes. Then, the separation capability of MIM is discussed for two different types, as a function of their barrier structure. Microporous MIM can continuously separate mixtures based on facilitated diffusion of the template, or they can change their permeability in the presence of the template (“gate effect”). Macroporous MIM can be developed towards molecule-specific membrane adsorbers. Emerging further combinations of molecularly imprinted polymers (MIPs), especially MIP nanoparticles or microgels, with membranes and membrane processes are briefly outlined as well. Finally, the application potential for advanced MIM separation technologies is summarized. [Copyright &y& Elsevier]

Micropatterned hydrogel‐coated polyamide thin‐film composite membranes capable of switching between strong surface hydrophilicity and surface hydrophobicity are established via consolidating surface micropatterning and dual stimuli responsivity, without impairing membranes' selectivity. More details can be found in article number 1801408 by Ibrahim M. A. ElSherbiny, Ahmed S. G. Khalil, and Mathias Ulbricht. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, polyethersulfone (PES) ultrafiltration (UF) membranes with molecular weight cut-off (MWCO) from 5 to 300kDa were analyzed with respect to fouling during filtration of humic acid (HA) model solution. The impact of MWCO and prefiltration of the feed solution on the fouling behavior of these membranes is presented. Moreover, an UV-initiated graft copolymerization of poly(ethylene glycol) methacrylate (PEGMA) onto PES membranes was performed and the effect of the applied modification was examined in terms of MWCO and water permeability changes as well as performance during filtration of HA. Moreover, the fouling behavior and principles during the filtration were compared. Membranes with higher MWCO exhibited stronger flux decline during UF but better cleanability. Prefiltration through 0.45μm filter improved the membrane performance during filtration of HA but the efficiency of physical cleaning was deteriorated. The applied modification improved the membrane performance during ultrafiltration and facilitated the physical cleaning. This work contributes to a better understanding of the relationships between membrane MWCO, solute size and size distribution, membrane surface chemistry and membrane fouling. [Copyright &y& Elsevier]

Abstract: High performance polyethersulfone microfiltration membranes with a high flux and stable hydrophilic character were successfully prepared by vapor induced phase separation coupled with non-solvent induced phase separation method. Pluronic®, a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymer and triethylene glycol (TEG) were used as hydrophilicity modification agent and non-solvent, respectively. Casting solution composition (non-solvent and additive content) and process condition (exposure time before coagulation and relative humidity) were optimized to obtain these membranes. The resulting membrane characteristics, which include hydraulic permeability, pore size distribution, surface hydrophilicity, chemical composition and membrane morphology, were investigated. The membrane performance was examined by investigation of adsorptive fouling and microfiltration using solutions of bovine serum albumin as the model system. The results suggest that the non-solvent content (TEG) and the exposure time were the most critical parameters to obtain high-flux membranes, whereas the concentration of Pluronic was important to obtain hydrophilic property. The increase in resistance towards both adsorptive and microfiltration fouling was clearly observed. The surface chemistry and wettability of the resulting membranes did not change after incubating in water (40°C) for a period of 10 days. [Copyright &y& Elsevier]

Abstract: The recent developments in combining photo-irradiation-based and membrane technologies are analyzed in this review. It is emphasized that the effects of photo-initiated reactions onto properties of polymeric membranes will largely depend on the nature of the membrane''s barrier (i.e., porous vs. non-porous, uncharged vs. charged, or involving affinity interactions). For de novo preparation of membranes from low molar mass or soluble precursors, photo-initiated polymerization and photo-cross-linking are the main pathways, while photo-degradation for pore formation is only rarely applied. Membrane functionalization (modification) is described with many examples, organized into photo-cross-linking of membranes and photo-grafting of membrane surfaces, either via “grafting-to” or via “grafting-from” routes. Photo-stimulation of barrier properties is an attractive concept to create stimuli-responsive membranes, and various ways to use photo-chromic moieties for that purpose are discussed. Overall, photo-irradiation-based methods can be very versatile enabling technologies to improve the performance of polymeric membranes in technical separations (e.g., in gas separation, pervaporation, ultra- and microfiltration or as membrane adsorbers) and other processes (e.g., for controlled release or in sensor systems), and they will definitely also contribute to the development of entirely novel membrane-based materials. [Copyright &y& Elsevier]

Virus filtration membranes contribute to the virus safety of biopharmaceutical drugs due to their capability to retain virus particles mainly based on size-exclusion mechanisms. Typical product molecules like monoclonal antibodies with 9–12 nm in hydrodynamic diameter have to be transmitted by >95% while small viruses, e.g. parvoviridae (B19, MVM, PPV) with a diameter of 18–26 nm, have to be retained by at least 99.99%. Therefore, membrane fouling caused by product aggregates, which are similar in size compared to the viruses that have to be retained, is a common observation. Minimal membrane fouling is a requirement for economical processes and is influenced by both the membrane surface chemistry and the membrane structure, particularly with regard to the pore size gradient (PSG). In this work, virus filtration membranes were challenged with gold nanoparticles (GNPs) in order to determine PSGs for a wide range of different commercial and non-commercial parvovirus retentive membranes differing in structure, material and surface chemistry. GNP adsorption to the membrane material was suppressed by the use of an anionic surfactant, allowing to gain insights into size-exclusion properties of the membranes. Membrane performance with regard to fouling was further investigated by determination of protein mass throughputs up-to a defined membrane flux decay using solutions containing intravenous immunoglobulin (IVIG) as model protein. Additionally, the fouling mechanism of IVIG was investigated and confirmed to be caused by trace amounts of species larger than IVIG monomers and dimers, which were already present in the feed. The fouling results are discussed in relationship to the determined PSGs, since the porous support structure of virus filtration membranes can act as a depth pre-filter protecting the separation-active layer from particulate foulants. [ABSTRACT FROM AUTHOR]

• Micro-patterned PES membranes exhibit underwater superoleophobic of 150 ± 2°. • Micro-patterned membranes have water permeance of 8036 L·h−1·m−2·bar−1. • Membranes show excellent oil-in-water emulsion separation efficiency. • Developed membranes demonstrate flux recovery ratio (FRR) of 99 % over three subsequent cycles. • Comprehensive separation mechanisms for oil removal are introduced and discussed. Developing polymeric membranes for oily wastewater treatment has attracted great interest over the last few years. However, the low permeance and poor fouling resistance are considered the most challenging issues. Introducing topographic patterns on the membrane surface to increase active area and surface roughness is one practical strategy for reducing membrane fouling. Here, isotropic polyethersulfone (PES) membranes with line patterns and continuous sponge-like porous structure were prepared using phase separation micro-molding processes. Various techniques were used to characterize the morphologies and physicochemical properties of the as-prepared membranes. The surface wettability of the membranes was evaluated by measuring contact angle of a water drop in air and of industrial crude oil under water. The as-prepared membranes separation and antifouling performance were assessed using water permeance, oil rejection, and flux recovery ratio after emulsion filtration. The results showed that the patterned PES membrane has superior hydrophilic and antifouling capabilities, with a lower static water contact angle (CA) of 32° as compared to a flat PES membrane (CA = 39°). Furthermore, the patterned membrane had pure water permeance (PWP) of 8036 ± 65 L·h−1·m−2·bar−1, which was ∼ 68 % greater than that of the flat PES membrane. This is mainly attributable to the discernible increase in the membrane pore size distribution and the enhancement in membrane surface hydrophilicity due to the increase in surface roughness as a result of micro-patterning. The patterned membranes showed superior separation efficiency (>99.0 %) and permeance (7031 ± 65 L·h−1·m−2·bar−1) for the oil-in-water emulsion of 0.1 g·L−1. At a higher concentration of crude oil-in-water emulsion (50 g·L−1), the patterned PES membranes achieved promising permeance of 90 L/h.m2.bar and 99.9 % rejection. Furthermore, the flux recovery ratio of the patterned membrane exceeded 91 % after three consecutive cycles of dead-end filtration and backwashing with water, demonstrating the benefit of using micro-patterned membranes for treating high concentration and industrial oil-in-water emulsions. [ABSTRACT FROM AUTHOR]

In this work, filtration studies were performed with particles of soft or super-soft nature, made from polyacrylamide copolymers, and hard polystyrene reference particles, all having average diameters between 180 and 200 nm, at relatively high particle concentrations and different transmembrane pressures under stirred and non-stirred dead-end filtration conditions in order to evaluate the separation and fouling behavior of a commercially available high-flux microfiltration membrane (experimentally determined barrier pore diameter 210 nm). In order to identify the underlying fouling processes the dependencies of the flux on cumulative volume or time were analyzed in the frame of established models. It was found that low transmembrane pressures of 0.1 bar lead to immediate filter cake formation, that facilitates a high retention of the particles and leads to less fouling that cannot be removed by external washing. Medium to high pressures (0.5–2.0 bar) resulted in a pronounced penetration of microgel particles into the membrane structure and pore blocking in the first phase (I) of the filtration, before entering the cake formation phase (II); the particle rejection in phase I was lower and the extent of fouling remaining after washing was larger. Super-soft microgels showed a significantly more pronounced pore blocking phase (I), compared to their soft counterparts or the hard sphere reference particles. The results of the study yield deeper insights into retention and blocking mechanisms during filtrations of deformable microgels as model colloids with a benchmark sterile filtration membrane. This is relevant for purification of such polymeric materials after their synthesis or for the development of test systems mimicking the removal of microorganisms by sterile filtration. [Display omitted] • Soft and super-soft microgel particles synthesized and used as model colloids for microfiltration studies. • Influences of feed concentration, transmembrane pressure and particle deformability on separation performance identified. • Interplay of particle retention and membrane blocking mechanisms for a standard sterile filter membrane. • Relevant implications for utilization of microfiltration for purification of polymeric microgel particles. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, polyethersulfone ultrafiltration membranes were UV-initiated grafted with poly(ethylene glycol) methacrylate by varying the UV irradiation dose. The flux and selectivity performance of the prepared low-fouling thin-layer hydrogel composite membranes were tested in cross-flow filtration experiments and compared to unmodified commercial membranes with similar properties (water permeability and molecular weight cut-off). Here, the effects of feed composition (single proteins and protein mixtures), pH and cross-flow velocity were evaluated. Furthermore, the stability of these membranes was tested during three cycles of ultrafiltration and cleaning. The results showed that the performed surface hydrophilization increased the permeate flux and stabilized the membrane selectivity (relevant for separation of protein mixtures). The proteins charge was still important for flux and rejection during ultrafiltration with functionalized membranes. Increasing cross-flow velocity was more efficient for these membranes, since fouling effects were minimized by the grafted hydrogel layer. Furthermore, the membrane stability after three cycles of ultrafiltration and chemical cleaning at pH=13 was proven and the cleanability of the hydrogel composite ultrafiltration membranes was much better compared to that of comparable unmodified polyethersulfone ultrafiltration membranes. [Copyright &y& Elsevier]

For affinity separation filtration we developed a tailored membrane based on covalently bound receptors such as proteins like recombinant Protein A (rPA). Microfiltration membrane pores were grafted with thin layers containing epoxy groups using photopolymerization. We compared two types of membranes based on polypropylene, an unmodified one (PP) and a hydrophilized one (GHPP). With photo-grafting a similar amount of functional groups was introduced to both membranes. We characterized the grafted membranes with respect to their hydrophilicity, total porosity and water permeability obtaining similar data for PP and GHPP. However, a different pore surface structure seemed to be present for the two types of membranes. The immobilization capacity of bovine serum albumine as a reference protein was about 10-fold higher for the grafted PP compared to the grafted GHPP. Therefore, only the Protein A-membrane, based on unmodified PP, was further evaluated with respect to the isolation and concentration of immunoglobulins. [Copyright &y& Elsevier]

• Isotropic polyethersulfone (PES) membrane was successfully developed via the vapor-induced phase separation (VIPS) method. • The isotropic PES membrane demonstrated outstanding underwater superoleophobicity (OCA of crude oil, 145 ± 2.0) and oil-repellency properties. • The isotropic PES membrane has superior water permeability of 4721 L/h⋅m2⋅bar that is about 13.6 times higher than that recorded by anisotropic PES. • The isotropic PES membrane showed excellent oil-in-water emulsion separation efficiency (>98%) for different heavy oil concentrations. • The isotropic PES membrane showed durable oil-fouling repellency, which could be easily recycled with a flux a recovery ratio of 59.5% over three subsequent cycles. Isotropic polyethersulfone (PES) membrane for separation of oil-in-water nanoemulsion was successfully developed using non-solvent vapor-induced phase separation (VIPS). The surface and structural properties of the fabricated PES membranes were thoroughly characterized using various techniques. The membrane separation performance was evaluated in terms of permeate flux, oil rejection, antifouling capability, and water flux recovery. Remarkably improved surface hydrophilicity for isotropic PES membrane (contact angle, CA = 39°) compared to anisotropic PES membrane (CA = 70°), resulting in superior pure water permeance, attaining 4721 L/h⋅m2⋅bar at operating pressure of 0.5 bar. The isotropic PES membrane achieved superior crude oil-in-water nanoemulsion separation (permeance of 713 L/h⋅m2⋅bar and 100% rejection) at oil concentration of 1 g/L. At extremely high oil concentration of 50 g/L, the PES membrane was not completely fouled and showed permeance of 65 L/h⋅m2⋅bar and 98.2% rejection. Moreover, the flux recovery of the fouled isotropic PES membrane exceeded 59.5% over three subsequent cycles of filtration and back-washing with water. Overall, this study might provide substantial guidance for large-scale manufacturing and application of isotropic PES membrane in treating practically challenging emulsified oil-in-water nanoemulsion under harsh conditions. [ABSTRACT FROM AUTHOR]

• Influence of hydrophobic functionalization on dissolution rate of MSN in water at pH 5 and pH 9 elucidated. • TFN membrane performance containing different kinds of MSN nanofillers investigated. • Long-term desalination performance of TFC and TFN membranes compared. • Controlled functionalization of nanofillers improved the stability of the respective TFN membranes. With the aim to improve the intrinsic separation performance, integration of nanofillers toward polyamide thin-film nanocomposite (TFN) membranes is a very active research area. Mesoporous silica nanoparticles (MSN), among other types of nanomaterials, are often used for that purpose. However, one of the distinguishing features of MSN is their dissolution in basic aqueous solutions. To date, no investigation in the literature has considered to study the influence of MSN nanofillers dissolution on the separation performance of the respective TFN polyamide membranes. This paper investigates how hydrophobic functionalization of MSN can improve the stability of MSN in aqueous solutions and enhance the stability of the respective TFN membranes over a prolonged filtration time at different pH values. The results showed that TFN membranes containing the octadecyltrichlorosilane-functionalized MSN had only ≈ 6% decline in salt rejection compared to ≈ 35% decline for the membrane containing unfunctionalized nanofillers accompanied by increasing water permeability after 240 h filtration time (120 h at pH 5, then 120 h at pH 9). Furthermore, the durability of the barrier layer after a prolonged use for desalination was also investigated via filtration of solutions of dextran with different molecular weight and assessing the dextran rejection for the native and used membranes. From the results of all parallel analyses of nanofiller and TFN membrane structure it is concluded that OTS functionalization of MSN cannot only enhance the TFN membrane separation performance, but also reduce the dissolution tendency of MSN. This was attributed to the formation of a protective organic layer leading to significantly enhanced long-time stability of the respective TFN membranes. [ABSTRACT FROM AUTHOR]