Showing papers on "Membrane published in 2011"
TL;DR: A comprehensive overview of recent progress on the production and modification of polyvinylidene fluoride (PVDF) membranes for liquid-liquid or liquid-solid separation can be found in this article.
1,776 citations
TL;DR: In this article, a semi-quantitative ranking system was proposed considering projected performance enhancement (over state-of-the-art analogs) and state of commercial readiness, while commercial readiness was based on known or anticipated material costs.
Abstract: Nanotechnology is being used to enhance conventional ceramic and polymeric water treatment membrane materials through various avenues. Among the numerous concepts proposed, the most promising to date include zeolitic and catalytic nanoparticle coated ceramic membranes, hybrid inorganic–organic nanocomposite membranes, and bio-inspired membranes such as hybrid protein–polymer biomimetic membranes, aligned nanotube membranes, and isoporous block copolymer membranes. A semi-quantitative ranking system was proposed considering projected performance enhancement (over state-of-the-art analogs) and state of commercial readiness. Performance enhancement was based on water permeability, solute selectivity, and operational robustness, while commercial readiness was based on known or anticipated material costs, scalability (for large scale water treatment applications), and compatibility with existing manufacturing infrastructure. Overall, bio-inspired membranes are farthest from commercial reality, but offer the most promise for performance enhancements; however, nanocomposite membranes offering significant performance enhancements are already commercially available. Zeolitic and catalytic membranes appear reasonably far from commercial reality and offer small to moderate performance enhancements. The ranking of each membrane nanotechnology is discussed along with the key commercialization hurdles for each membrane nanotechnology.
1,708 citations
TL;DR: A review of the development of reverse osmosis (RO) membrane materials can be found in this paper, where an overview of RO performance in relation to membrane materials and methods of synthesis is provided.
1,649 citations
TL;DR: A top-down biomimetic approach in particle functionalization is reported by coating biodegradable polymeric nanoparticles with natural erythrocyte membranes, including both membrane lipids and associated membrane proteins for long-circulating cargo delivery.
Abstract: Efforts to extend nanoparticle residence time in vivo have inspired many strategies in particle surface modifications to bypass macrophage uptake and systemic clearance. Here we report a top-down biomimetic approach in particle functionalization by coating biodegradable polymeric nanoparticles with natural erythrocyte membranes, including both membrane lipids and associated membrane proteins for long-circulating cargo delivery. The structure, size and surface zeta potential, and protein contents of the erythrocyte membrane-coated nanoparticles were verified using transmission electron microscopy, dynamic light scattering, and gel electrophoresis, respectively. Mice injections with fluorophore-loaded nanoparticles revealed superior circulation half-life by the erythrocyte-mimicking nanoparticles as compared to control particles coated with the state-of-the-art synthetic stealth materials. Biodistribution study revealed significant particle retention in the blood 72 h following the particle injection. The translocation of natural cellular membranes, their associated proteins, and the corresponding functionalities to the surface of synthetic particles represents a unique approach in nanoparticle functionalization.
1,614 citations
TL;DR: In this paper, the authors present a classification of anion exchange membranes for alkaline fuel cells, based on the nature and the properties of these membranes for both commercial and non-commercial applications.
1,431 citations
TL;DR: A review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers is presented in this article, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of phase inversion process.
Abstract: The methods and mechanisms of nonsolvent induced phase separation have been studied for more than fifty years. Today, phase inversion membranes are widely used in numerous chemical industries, biotechnology, and environmental separation processes. The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers. The key factors in membrane preparation discussed include the solvent type, polymer type and concentration, nonsolvent system type and composition, additives to the polymer solution, and film casting conditions. A brief introduction to membrane characterization is also given, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of the phase inversion process. ...
1,063 citations
TL;DR: In this article, a review examines the inspiration for high temperature proton exchange membrane fuel cells (PEMFCs) development, the technological constraints, and recent advances, and a detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided.
779 citations
TL;DR: In this paper, the authors describe the preparation, characterization and evaluation of performance and antifouling properties of mixed matrix nanofiltration membranes, which are prepared by acid oxidized multiwalled carbon nanotubes (MWCNTs) embedded in polyethersulfone as matrix polymer.
735 citations
TL;DR: This chapter describes a method for the measurement of the electrostatic potential at the electrical double layer surrounding a nanoparticle in solution, referred to as the zeta potential, for two types of nanoparticles commonly used in biological applications: colloidal gold and amine-terminated PAMAM dendrimer.
Abstract: This chapter describes a method for the measurement of the electrostatic potential at the electrical double layer surrounding a nanoparticle in solution. This is referred to as the zeta potential. Nanoparticles with a zeta potential between -10 and +10 mV are considered approximately neutral, while nanoparticles with zeta potentials of greater than +30 mV or less than -30 mV are considered strongly cationic and strongly anionic, respectively. Since most cellular membranes are negatively charged, zeta potential can affect a nanoparticle's tendency to permeate membranes, with cationic particles generally displaying more toxicity associated with cell wall disruption. This technique is demonstrated for two types of nanoparticles commonly used in biological applications: colloidal gold (strongly anionic) and amine-terminated PAMAM dendrimer (strongly cationic).
731 citations
TL;DR: A class of amorphous MOP, prepared by [2+3] cycloaddition modification of a polymer containing an aromatic nitrile group with an azide compound, showing super-permeable characteristics and outstandingCO(2) separation performance, even under polymer plasticization conditions such as CO(2)/light gas mixtures is shown.
Abstract: Microporous organic polymers (MOPs) are of potential significance for gas storage, gas separation and low-dielectric applications. Among many approaches for obtaining such materials, solution-processable MOPs derived from rigid and contorted macromolecular structures are promising because of their excellent mass transport and mass exchange capability. Here we show a class of amorphous MOP, prepared by [2+3] cycloaddition modification of a polymer containing an aromatic nitrile group with an azide compound, showing super-permeable characteristics and outstanding CO(2) separation performance, even under polymer plasticization conditions such as CO(2)/light gas mixtures. This unprecedented result arises from the introduction of tetrazole groups into highly microporous polymeric frameworks, leading to more favourable CO(2) sorption with superior affinity in gas mixtures, and selective CO(2) transport by presorbed CO(2) molecules that limit access by other light gas molecules. This strategy provides a direction in the design of MOP membrane materials for economic CO(2) capture processes.
667 citations
TL;DR: In this paper, a review of the preparation of copolymers and polymeric materials as starting materials for solid alkaline fuel cells membranes is presented, and the requirements for such membranes are also summarized.
TL;DR: The how membranes work is discussed, and some notable new approaches for improving their performance are discussed.
Abstract: Synthetic membranes are used in many separation processes, from industrial-scale ones—such as separating atmospheric gases for medical and industrial use, and removing salt from seawater—to smaller-scale processes in chemical synthesis and purification. Membranes are commonly solid materials, such as polymers, that have good mechanical stability and can be readily processed into high–surface area, defect-free, thin films. These features are critical for obtaining not only good chemical separation but also high throughput. Membrane-based chemical separations can have advantages over other methods—they can take less energy than distillation or liquefaction, use less space than absorbent materials, and operate in a continuous mode. In some cases, such as CO2 separations for CO2 capture, their performance must be improved. We discuss how membranes work, and some notable new approaches for improving their performance.
TL;DR: The mechanisms and factors controlling colloidal fouling of both RO and NF membranes are reviewed and major colloidal foulants (including both rigid inorganic colloids and organic macromolecules) and their properties are summarized.
TL;DR: The synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI are demonstrated, which allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes.
Abstract: Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of their lamellar precursors have been hampered because of their structure deterioration and morphological damage (fragmentation, curling, and aggregation). We demonstrated the synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI. The purity and morphological integrity of these nanosheets allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes.
TL;DR: In this article, a review describes palladium and palladium alloy membranes for hydrogen separation prepared by different fabrication methods and using different membrane supports, and several correlations of structure and function for those membranes are provided based on mechanistic considerations of permeance along with structural properties and membrane morphologies.
18 Jul 2011
TL;DR: In this article, the roles of cholesterol in the Biology of cells were discussed and the role of G-protein-protein coupled receptive receptors was discussed. But the authors focused on the structure and function of the G-Protein Coupled Receptors.
Abstract: MEMBRANE LIPID STRUCTURE AND FUNCTION Lipid Structure, Helmut Hauser and Guy Poupart The Mesomorphic Phase Behavior of Lipid Bilayers, Ruthven N.A.H. Lewis, Ronald N. McElhaney Lipid Bilayer Interdigitation, James L. Slater and Ching-hsien Huang The Dynamics of Membrane Lipids, Klaus Gawrisch Non-Lamellar Lipid Phases, Sol M. Gruner The Forces Between Interacting Bilayer Membranes and the Hydration of Phospholipid Assemblies, Richard P. Rand and V.A. Parsegian The Roles of Cholesterol in the Biology of Cells, Philip L. Yeagle Lipid Membrane Fusion, David P. Siegel Membrane Rafts, Kathleen Boesze-Battaglia MEMBRANE PROTEIN STRUCTURE AND FUNCTION Passive and Facilitated Transport, Shinpei Ohki, Robert A. Spangler Membrane Protein Dynamics: Rotational Dynamics, Richard J. Cherry Translational Diffusion of Membrane Proteins, Michael Edidin Inorganic Anion Transporter AE1, Michael L. Jennings The Structures of G-Protein Coupled Receptors, Philip L. Yeagle Role of Membrane Lipids in Modulating the Activity of Membrane-Bound Enzymes, Richard M. Epand Viral Fusion Mechanisms, Aditya Mittal and Joe Bentz
TL;DR: In this article, a combination of chemical and mechanical modifications was found to have significant effects on surface free energy, roughness, surface pore size and protein absorption resistance as well as hydrophilicity.
TL;DR: In this article, a thin film composite (TFC) polyamide forward osmosis (FO) membranes with tailored support structure were prepared via phase inversion, and the polyamide rejection layers were synthesized by interfacial polymerization.
TL;DR: It is demonstrated that the nanoparticles disrupt microbial walls/membranes selectively and efficiently, thus inhibiting the growth of Gram-positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA) and fungi, without inducing significant haemolysis over a wide range of concentrations.
Abstract: Macromolecular antimicrobial agents such as cationic polymers and peptides have recently been under an increased level of scrutiny because they can combat multi-drug-resistant microbes. Most of these polymers are non-biodegradable and are designed to mimic the facially amphiphilic structure of peptides so that they may form a secondary structure on interaction with negatively charged microbial membranes. The resulting secondary structure can insert into and disintegrate the cell membrane after recruiting additional polymer molecules. Here, we report the first biodegradable and in vivo applicable antimicrobial polymer nanoparticles synthesized by metal-free organocatalytic ring-opening polymerization of functional cyclic carbonate. We demonstrate that the nanoparticles disrupt microbial walls/membranes selectively and efficiently, thus inhibiting the growth of Gram-positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA) and fungi, without inducing significant haemolysis over a wide range of concentrations. These biodegradable nanoparticles, which can be synthesized in large quantities and at low cost, are promising as antimicrobial drugs, and can be used to treat various infectious diseases such as MRSA-associated infections, which are often linked with high mortality.
TL;DR: A theoretical model to predict the water flux in pressure retarded osmosis, from which the power density that can be achieved by a membrane is predicted, is presented, the first to incorporate external concentration polarization, a performance limiting phenomenon that becomes significant for high-performance membranes.
Abstract: Pressure retarded osmosis has the potential to produce renewable energy from natural salinity gradients. This work presents the fabrication of thin-film composite membranes customized for high performance in pressure retarded osmosis. We also present the development of a theoretical model to predict the water flux in pressure retarded osmosis, from which we can predict the power density that can be achieved by a membrane. The model is the first to incorporate external concentration polarization, a performance limiting phenomenon that becomes significant for high-performance membranes. The fabricated membranes consist of a selective polyamide layer formed by interfacial polymerization on top of a polysulfone support layer made by phase separation. The highly porous support layer (structural parameter S = 349 μm), which minimizes internal concentration polarization, allows the transport properties of the active layer to be customized to enhance PRO performance. It is shown that a hand-cast membrane that bal...
TL;DR: IAST calculations using single-component-isotherm data and a 15/85 CO(2)/N(2) ratio at 295 K and 1 bar revealed that the sulfonate-grafted PPN-6 networks show exceptionally high adsorption selectivity for CO( 2) over N(2).
Abstract: A porous polymer network (PPN) grafted with sulfonic acid (PPN-6-SO3H) and its lithium salt (PPN-6-SO3Li) exhibit significant increases in isosteric heats of CO2 adsorption and CO2-uptake capacities. IAST calculations using single-component-isotherm data and a 15/85 CO2/N2 ratio at 295 K and 1 bar revealed that the sulfonate-grafted PPN-6 networks show exceptionally high adsorption selectivity for CO2 over N2 (155 and 414 for PPN-6-SO3H and PPN-6-SO3Li, respectively). Since these PPNs also possess ultrahigh physicochemical stability, practical applications in postcombustion capture of CO2 lie well within the realm of possibility.
TL;DR: The most common methods to evaluate mucoadhesive properties of various dosage forms are described, and the main classes of mucoADhesives are discussed, which are typical for hydrophilic polymers possessing charged groups and/or non-ionic functional groups capable of forming hydrogen bonds with mucosal surfaces.
Abstract: Mucoadhesion is the ability of materials to adhere to mucosal membranes in the human body and provide a temporary retention. This property has been widely used to develop polymeric dosage forms for buccal, oral, nasal, ocular and vaginal drug delivery. Excellent mucoadhesive properties are typical for hydrophilic polymers possessing charged groups and/or non-ionic functional groups capable of forming hydrogen bonds with mucosal surfaces. This feature article considers recent advances in the study of mucoadhesion and mucoadhesive polymers. It provides an overview on the structure of mucosal membranes, properties of mucus gels and the nature of mucoadhesion. It describes the most common methods to evaluate mucoadhesive properties of various dosage forms and discusses the main classes of mucoadhesives.
TL;DR: A well-controlled multiblock structure was responsible for the developed hydrophobic/hydrophilic phase separation and interconnected ion transporting pathway, and the ionomer membranes showed considerably higher hydroxide ion conductivities, than those of existing anion conductive ionomers.
Abstract: Anion conductive aromatic multiblock copolymers, poly(arylene ether)s containing quaternized ammonio-substituted fluorene groups, were synthesized via block copolycondensation of fluorene-containing (later hydrophilic) oligomers and linear hydrophobic oligomers, chloromethylation, quaternization, and ion-exchange reactions. The ammonio groups were selectively introduced onto the fluorene-containing units. The quaternized multiblock copolymers (QPEs) produced ductile, transparent membranes. A well-controlled multiblock structure was responsible for the developed hydrophobic/hydrophilic phase separation and interconnected ion transporting pathway, as confirmed by scanning transmission electron microscopic (STEM) observation. The ionomer membranes showed considerably higher hydroxide ion conductivities, up to 144 mS/cm at 80 °C, than those of existing anion conductive ionomer membranes. The durabilities of the QPE membranes were evaluated under severe, accelerated-aging conditions, and minor degradation was ...
TL;DR: An overview of the morphology and transport properties of ion-containing block copolymers that have been studied to gain insight into the fundamental behavior of these materials and, in some cases, are targeted toward applications in fuel cells and other electrochemical devices is presented in this article.
Abstract: Ion-containing block copolymers hold promise as next-generation proton exchange membranes in hydrogen and methanol fuel cells. These materials’ self-assembled ordered nanostructures facilitate proton transport over a wide range of conditions, a requirement for robust fuel cell performance. In this perspective, we will present an overview of the morphology and transport properties of ion-containing block copolymers that have been studied to gain insight into the fundamental behavior of these materials and, in some cases, are targeted toward applications in fuel cells and other electrochemical devices. We will discuss the challenges associated with predicting and obtaining well-ordered morphologies in block copolymers with high ion content, particularly those with chemistries that can withstand the chemical and mechanical stresses of the fuel cell, such as aromatic backbone block copolymers. New opportunities for ion-containing block copolymers in alkaline membrane fuel cells will also be reviewed.
TL;DR: The propulsion characteristics and optimization of these microtubular engines are described, along with their efficient operation in different biological environments which holds great promise for biomedical applications.
Abstract: Highly efficient catalytic microtubular engines are synthesized rapidly and inexpensively using an electrochemical growth of bilayer polyaniline/platinum microtubes within the conically shaped pores of a polycarbonate template membrane. These mass-produced microtubular engines are only 8 μm long, are self-propelled at an ultrafast speed (of over 350 body lengths s–1), and can operate in very low levels of the hydrogen peroxide fuel (down to 0.2%). The propulsion characteristics and optimization of these microtubular engines are described, along with their efficient operation in different biological environments which holds great promise for biomedical applications.
TL;DR: This critical review presents a discussion on the major advances in the field of organic-inorganic hybrid membranes for fuel cells application with a promising family for controlling conductivity, mechanical and chemical properties.
Abstract: This critical review presents a discussion on the major advances in the field of organic–inorganic hybrid membranes for fuel cells application. The hybrid organic–inorganic approach, when the organic part is not conductive, reproduces to some extent the behavior of Nafion where discrete hydrophilic and hydrophilic domains are homogeneously distributed. A large variety of proton conducting or non conducting polymers can be combined with various functionalized, inorganic mesostructured particles or an inorganic network in order to achieve high proton conductivity, and good mechanical and chemical properties. The tuning of the interface between these two components and the control over chemical and processing conditions are the key parameters in fabricating these hybrid organic–inorganic membranes with a high degree of reproducibility. This dynamic coupling between chemistry and processing requires the extensive use and development of complementary ex situ measurements with in situ characterization techniques, following in real time the molecular precursor solutions to the formation of the final hybrid organic–inorganic membranes. These membranes combine the intrinsic physical and chemical properties of both the inorganic and organic components. The development of the sol–gel chemistry allows a fine tuning of the inorganic network, which exhibits acid-based functionalized pores (–SO3H, –PO3H2, –COOH), tunable pore size and connectivity, high surface area and accessibility. As such, these hybrid membranes containing inorganic materials are a promising family for controlling conductivity, mechanical and chemical properties (349 references).
TL;DR: The carbon nanotube content of the C/P membranes was shown to alleviate the membrane fouling caused by natural water.
TL;DR: A better understanding of the mechanisms of RBC-MSN interaction and the hemolytic activity of MSNs is provided and will assist in the rational design of hemocompatible MSNs for intravenous drug delivery and in vivo imaging.
Abstract: The interactions of mesoporous silica nanoparticles (MSNs) of different particle sizes and surface properties with human red blood cell (RBC) membranes were investigated by membrane filtration, flow cytometry, and various microscopic techniques Small MCM-41-type MSNs (∼100 nm) were found to adsorb to the surface of RBCs without disturbing the membrane or morphology In contrast, adsorption of large SBA-15-type MSNs (∼600 nm) to RBCs induced a strong local membrane deformation leading to spiculation of RBCs, internalization of the particles, and eventual hemolysis In addition, the relationship between the degree of MSN surface functionalization and the degree of its interaction with RBC, as well as the effect of RBC−MSN interaction on cellular deformability, were investigated The results presented here provide a better understanding of the mechanisms of RBC−MSN interaction and the hemolytic activity of MSNs and will assist in the rational design of hemocompatible MSNs for intravenous drug delivery and i
TL;DR: In this article, a highly oriented zeolitic imidazolate framework 8 (ZIF-8) composite membrane was prepared by seeding and secondary growth by dip-coating.
Abstract: A highly oriented zeolitic imidazolate framework 8 (ZIF-8) composite membrane was prepared by seeding and secondary growth. By dip-coating, preformed ZIF-8 nanocrystals were attached to the surface of a porous α-alumina support using polyethyleneimine as the coupling agent. After solvothermal treatment, a continuous and well-intergrown ZIF-8 layer was obtained. X-ray diffraction analysis of the membrane showed preferred orientation of the {100} plane parallel to the support. Further time-dependent investigations by scanning and transmission electron microscopy as well as X-ray diffraction indicated that the preferred orientation develops during an evolutionary growth process. In gas mixture permeation experiments, the membrane showed good performance in H2/hydrocarbon separation. A sharp molecular sieve separation is observed for an equimolar H2/C3H8 mixture with a separation factor above 300.
TL;DR: It was found that fouling can be controlled if membranes are placed directly in contact with the granular activated carbon (GAC) in an anaerobic fluidized bed bioreactor (AFMBR) used here for post-treatment of effluent from another an aerobic reactor treating dilute wastewater.
Abstract: Anaerobic membrane bioreactors have potential for energy-efficient treatment of domestic and other wastewaters, membrane fouling being a major hurdle to application. It was found that fouling can be controlled if membranes are placed directly in contact with the granular activated carbon (GAC) in an anaerobic fluidized bed bioreactor (AFMBR) used here for post-treatment of effluent from another anaerobic reactor treating dilute wastewater. A 120-d continuous-feed evaluation was conducted using this two-stage anaerobic treatment system operated at 35 °C and fed a synthetic wastewater with chemical oxygen demand (COD) averaging 513 mg/L. The first-stage was a similar fluidized-bed bioreactor without membranes (AFBR), operated at 2.0−2.8 h hydraulic retention time (HRT), and was followed by the above AFMBR, operating at 2.2 h HRT. Successful membrane cleaning was practiced twice. After the second cleaning and membrane flux set at 10 L/m2/h, transmembrane pressure increased linearly from 0.075 to only 0.1 bar...