Porous Polyethersulfone Membranes Research Articles

Comparative study of moisture transfer of polyethersulfone-based membranes and kraft paper

The efficiency of membrane-based enthalpy exchangers primarily depends on the moisture permeability of the membranes used. While traditional kraft paper membranes exhibit favorable moisture adsorption properties, they lack durability and are prone to bacterial growth. To overcome these limitations, alternative membrane materials, including polyethersulfone (PES) film, asymmetric porous PES membrane (P-MEM), and composite membrane (C-MEM) comprising PES and polyether block amide (PEBAX), have been investigated. These membranes' physical properties and water adsorption affinity were compared with that of conventional kraft paper. Experimental measurements of moisture permeation and adsorption equilibrium were conducted to evaluate the moisture transfer properties of the membranes under different operating conditions. The experimental and modeling results showed that the moisture transfer resistance of the membranes varied depending on the material and temperature, with a lower degree of dependence on the surrounding fluid humidity. C-MEM exhibited the highest moisture resistance, followed by kraft paper, while P-MEM and PES had the lowest resistance. Additionally, the moisture diffusivity and activation energies for moisture transport were determined for each membrane.

Development of Composite Thin-Film Nanofiltration Membranes Based on Polyethersulfone for Water Purification

The development of thin-film composite membranes has gained more importance as they exhibit higher permeability, higher solute rejection and improved antifouling behavior. The incorporation of hydrophilic nanomaterials within the composite thin film has reported to effectively increase the hydrophilicity and improve the membrane performance. In this study novel thin-film composite nanofiltration membranes were prepared by interfacial polymerization of trimesoyl chloride, polyvinylpyrolidone (PVP) and montmorillonite (MMT) composite on the porous polyethersulfone membrane. The effect of preparation parameters was studied as; reaction time, PVP concentration and MMT content. The properties of the prepared composite thin-film membranes were analyzed in terms of their chemical structure, surface morphological features, pure water contact angle, zeta potential, pure water permeation flux (PWP) and solutes rejection. The prepared composite thin-film membranes showed smoother surfaces, different surfaces functionality and amphoteric surfaces with points of zero charge at pH 7–7.5. The PWP was found to increase with increasing MMT content up to 0.10 wt%. The rejection of crystal violet dye (CV) was studied using the prepared membranes. The membrane with 0.5% PVP, 0.10% MMT and 6 min reaction time showed PWP of 18.1 L/m2 h bar and CV rejection of 80.01%. The rejection of Na2SO4 and MgCl2 increased with increasing MMT content and reached 96% and 35.4%, respectively. The steady state flux was decreased by 5% with increasing MMT content from 0.10 to 0.12 wt% indicating improved antifouling behavior with MMT.

Fabrication of chitosan-aminopropylsilane graphene oxide nanocomposite hydrogel embedded PES membrane for improved filtration performance and lead separation

In the present study chitosan-aminopropylsilane graphene oxide (CS-APSGO) nanocomposite hydrogel was synthesized and utilized as a hydrophilic additive in different dosages (0.5, 1, 2 and 5 wt%) in fabrication of porous polyethersulfone (PES) membranes via the phase inversion induced process by immersion precipitation method for heavy metal ion and dye removal. The modified membranes were characterized using ATR-FTIR, AFM, SEM, water contact angle, overall porosity and mean pore radius evaluations and zeta potential measurement. The addition of CS-APSGO nanocomposite hydrogel to PES doping solutions enhanced membranes hydrophilicity and consequently pure water flux permeability. Filtration performance of the CS-APSGO embedded membranes showed promising antifouling properties during BSA filtration test (FRR> 90%) and 1 wt% membranes showed the highest pure water flux of 123.8 L/m2 h with BSA rejection more than 98% and removal capability more than 82% for lead (II) ion, 90.5% and 98.5% for C.I. Reactive Blue 50 and C.I. Reactive Green 19, respectively. Therefore, the CS-APSGO nanocomposite hydrogel blending in order to modification of PES-based membranes have a noticeable potential in improving filtration performance of blended membranes.

The micro-volume liquid focusing effect in Janus membrane and its biosensing application

The micro-volume analysis and specific detection are both essential requirements in the field of chemical sensing and biological testing. Membrane prefiltration can be used to improve the selectivity and accuracy of detection. But for traditional porous membrane filtration, it is difficult to achieve the transmembrane transport of micro-volume liquid due to the influence of lateral diffusion on membrane surface. Herein, we studied the focused transmembrane transport of micro-volume liquid in the porous polyethersulfone membrane with asymmetric (Janus) surface wettability. The hydrophilic layer (polydopamine) and hydrophobic layer (fluoropolymer) were deposited with controllable thickness by dip-coating and roller-assisted liquid printing. The micro-volume liquid focusing effect was verified by experiments such as visual wetting circle and fluorescent tracer. The liquid focusing effect of as-prepared Janus membrane was integrated with glucose test strip in the application of micro-volume liquid biosensing. Compared with conventional porous membrane, detected signal amplitude and response time were improved 7.5× and 2.7×, respectively. In summary, this research studied the dynamics of liquid transport through Janus membrane and provides a new strategy for microfluidic detection applications through balancing detection volume, time and selectivity by the advantage of micro-volume liquid focusing effect.

Inclusion of zeolitic imidazolate framework-8 (ZIF-8) crystals within porous polyether sulfone (PES) via filtration methods as potential electrolytes for DMFC applications

The imidazolate framework-8 (ZIF-8) crystals were synthesized by in -situ growth techniques inside the pore of porous poly ether sulfone (PES) in order to fabricate a composite PES/ZIF-8 electrolyte membrane for direct methanol fuel cell (DMFC) applications. In situ techniques by adapting the filtration method was adhered in this study. It was found that the proton conductivity (17.9 × 10−3 Scm−1) was drastically increased for PES/ZIF-8 as compared to pristine PES membrane (0.21 × 10−3 Scm−1). However, the methanol barrier property was slightly decreased from 2.07 × 10−7 cm2s−1 to 3.88 × 10−7 cm2s−1 for PES and PES/ZIF-8 membranes, respectively. The introduction of ZIF-8 in PES membranes not only improve proton conductivity, but also positively affected the mechanical stability of PES/ZIF-8 with 1.73-fold lower of swelling ratio even though the water uptake increased by 2.08 folds. In spite of the increment in methanol permeability, selectivity of PES/ZIF-8 membrane was 6 folds and 2 folds higher than pristine PES and Nafion®, respectively which indicated that the potential for PES/ZIF-8 to be a good candidate for electrolyte in DMFC applications. Nonetheless, via scanning electron microscopy (SEM) showed a good distribution of ZIF-8 crystals inside the pore of PES membranes which proven that the effectiveness of filtration techniques for ZIF-8 crystals in-situ growth synthesized within the pores.

Porous polyether sulfone for direct methanol fuel cell applications: Structural analysis

Porous poly ether sulfone (PES) membranes were prepared using two different solvents which were N-methyl-2-pyrrolidone and dimethylacetamide (DMAc) via dry/wet non-solvent phase inversion (NIPS) techniques. PES with the compositions of 18 wt% is prepared for each dope solution. During the membrane casting process, 0 to 5 minutes delay prior to immersion in coagulant bath is set in order to allow solvent evaporation to take place. Water is used as the non-solvent for solvent exchange process. The prepared membranes are characterised based on their morphological aspect using scanning electron microscopy towards the effect of solvent evaporation time and solution viscosity. The changes in proton conductivity, methanol permeability, water uptake and hydrophilicity/hydrophobicity behaviours are also studied. Conclusively, the 18 wt% PES membranes prepared with DMAc as solvent at 3 minutes solvent evaporation time exhibited desirable pore size for proton conduction (0.04 × 10−3 Scm−1) and methanol resistant effect that consequently contribute to considerably low methanol permeability rate at 0.06 × 10−7 cm2 s−1 which could elevate the direct methanol fuel cell performance.

Preparation and characterization of porous polyethersulfone (PES) membranes with improved biocompatibility by blending sulfonated polyethersulfone (SPES) and cellulose acetate (CA) – A comparative study

The current study focuses on the effective sulfonation of polyethersulfone (PES) polymer to synthesize sulfonated-polyethersulfone (SPES) and blending with PES to prepare SPES/PES blend membranes as well as preparation of cellulose acetate CA/PES blend membranes. FTIR-ATR technique was used to confirm the blending of SPES and CA into PES matrix. Water contact angle studies showed a significant reduction of hydrophobicity in SPES blend membranes (49.55 ± 1.52°) as compared with CA blend membranes (59.42 ± 2.20°) and PES base membranes (67.80 ± 1.48°). The presence of pores were analysed using scanning electron microscopy (SEM) where significant changes in the membrane morphology in the blend membranes were observed. Platelet adhesion, protein adsorption and activated partial thromboplastin time (APTT) studies were used to assess hemocompatibility of the membranes in which SPES/PES membranes exhibited improved characteristics as compared with its counterparts. The cytocompatibility of membranes were evaluated using water soluble tetrazolium (WST) assay which confirmed that both SPES/PES and CA/PES blend membranes exhibit better cytocompatibility than base PES membrane

Colour-Value Based Method for Polydopamine Coating-Stability Characterization on Polyethersulfone Membranes.

Porous polyethersulfone membranes as used in oenology were investigated in order to evaluate temperature-dependent permeances in a temperature range from 10 to 35 °C. A temperature correction factor was determined for this type of membrane to get accurate and comparable results for further developments. Moreover, the membranes were modified with a bio-inspired polydopamine coating in order to reduce fouling. The performance of the membranes could be increased with respect to permeance and flux recovery under cross-flow conditions. In order to test the applicability and stability of the coating layer, they were treated with basic and acidic cleaning agents as used in industry for fouled membranes. The chemical stability of the coating layer was studied under basic and acidic conditions, by systematic observation of the colour change of the coated membranes over treatment time.

Effects of Piper cubeba L. essential oil on methicillin-resistant Staphylococcus aureus: an AFM and TEM study.

The increasing prevalence of antibiotic-resistant bacteria is creating a real challenge for health care systems worldwide, making the development of novel antibiotics a necessity. In addition to the development of new antibiotics, there is an urgent need for in-depth characterization of the mechanisms of bacterial resistance toward new drugs. Here, we used essential oils extracted in our laboratory from Piper cubeba against methicillin-resistant Staphylococcus aureus ATCC 43300, one of the most prominent antibiotic-resistant bacteria. Effects of the essential oils extracted from Pcubeba on bacteria were mainly evaluated using 2 powerful microscopy techniques: atomic force microscopy and transmission electron microscopy. High-resolution atomic force microscopy images of the cells were obtained close to their native environment by immobilizing the cells on porous Polyether sulfone membranes, which were prepared in our laboratory with a wide range and distribution of pore sizes and depth. Inhibition zones (mm) and minimum inhibitory concentrations were determined. Two different concentrations of the oil were used to treat the cells: 50μg/mL minimum inhibitory concentration and 25μg/mL. The 50μg/mL oil solution caused severe damage to the bacterial cells at microscopic levels while the 25μg/mL solution showed no effects compared to the control. However, at nanoscopic levels, the 25μg/mL oil solution caused significant changes in the cell wall, which could potentially impair bacterial activities. These results were also confirmed by transmission electron microscopy micrographs. Our results indicate that the extract has a good biological activity against methicillin- and oxacillin-resistant Saureus and that it acts on the cell wall and plasma (cytoplasmic) membrane.

Antithrombogenicity of Fluorinated Diamond-Like Carbon Films Coated Nano Porous Polyethersulfone (PES) Membrane

A nano porous polyethersulfone (PES) membrane is widely used for aspects of nanofiltration, such as purification, fractionation and dialysis. However, the low-blood-compatibility characteristic of PES membrane causes platelets and blood cells to stick to the surface of the membrane and degrades ions diffusion through membrane, which further limits its application for dialysis systems. In this study, we deposited the fluorinated-diamond-like-carbon (F-DLC) onto the finger like structure layer of the PES membrane. By doing this, we have the F-DLC films coating the membrane surface without sacrificing the membrane permeability. In addition, we examined antithrombogenicity of the F-DLC/PES membranes using a microfluidic device, and experimentally found that F-DLC drastically reduced the amount of blood cells attached to the surface. We have also conducted long-term experiments for 24 days and the diffusion characteristics were found to be deteriorated due to fouling without any surface modification. On the other hand, the membranes coated by F-DLC film gave a consistent diffusion coefficient of ions transfer through a membrane porous. Therefore, F-DLC films can be a great candidate to improve the antithrombogenic characteristics of the membrane surfaces in hemodialysis systems.

Heparin-doped affinity electromembranes for thrombin purification

Heparin-doped affinity electromembrane was fabricated by synthesizing conducting polymers polypyrrole onto porous polyethersulfone membrane using heparin as both ligand and dopant. The obtained affinity electromembrane exhibited a uniform conductivity value of 1.73 × 10 −4 S/cm. The content of heparin of affinity electromembrane was ∼0.894 mg/g membrane. Such heparin-doped affinity electromembranes were used to purify thrombin. The adsorption mechanism of thrombin and the effects of temperature, initial concentration of thrombin and potential on adsorption were investigated by batch experiments. The results showed that the adsorption capacity increased with increasing the temperature, initial concentration of thrombin and potential, and the adsorption isotherm fitted the Freundlich model well. Elution of protein showed desorption ratio was up to 93.1% using 2.0 M NaSCN solution as the desorption agent. The adsorption capacities of all the tested affinity electromembranes did not significantly change during the repeated adsorption–desorption operations.

Hydrogen Generation from Alkaline Solutions of Methanol and Ethanol by Electrolysis

In this study, electrolysis of alkaline methanol and ethanol solutions was carried out on platinized electrodes in actual cells with different cell preparation and catalyst coating methods. The electrolysis reaction products were analyzed by X-Ray and titrimetric methods. The gas phase products were analyzed by Gas Chromatography technique. Thermodynamic calculations and analysis results suggest that the carbonate formation is highly favorable in alkaline KOH solutions. However, methane formation reaction along with carbonate and oxygen formations may be possible during ethanol electrolysis. Alkaline methanol solutions were electrolyzed easily using platinum coated carbon paper electrodes. It was found that Nafion based MEA's are not essential for electrolysis of alkaline solutions of methanol and ethanol. One of the best performances was obtained using micro porous polyethersulfone membranes in a special cell configuration.

Corona-induced graft polymerization for surface modification of porous polyethersulfone membranes

Graft polymerization of acrylic acid (AA) onto porous polyethersulfone (PES) membrane surfaces was developed using corona discharge in atmospheric ambience as an activation process followed by polymerization of AA in aqueous solution. The effects of the corona parameters and graft polymerization conditions on grafting yield (GY) of AA were investigated. The grafting of AA on the PES membranes was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis. Porosimetry measurements indicate the average pore diameters and porosities of the modified membranes decrease with the increase of the GY. The hydrophilicity and surface wetting properties of the original and modified membranes were evaluated by observing the dynamic changes of water contact angles. It is found that the grafting of AA occurs not only on the membrane surfaces, but also on the pore walls of the cells inside the membrane. The permeability experiments of protein solution reveal that the grafting of PAA endows the modified membranes with enhanced fluxes and anti-fouling properties. The optimized GY of AA is in the range of 150–200 μg/cm 2. In addition, the tensile experiments show the corona discharge treatment with the power lower than 150 W yields little damage to the mechanical strength of the membranes.

Membrane Surface Modification by Plasma-Induced Polymerization of Acrylamide for Improved Surface Properties and Reduced Protein Fouling

Hydrophilic modification of porous polyethersulfone (PES) membranes was achieved by Ar-plasma treatment followed by graft copolymerization with acrylamide (AAm) in the vapor phase. Both surfaces of the modified membranes were found to be highly hydrophilic, the permanency of which depends on the grafting yield. The graft reaction was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The grafting rate was dependent on plasma exposure time. The surface and pore structures of PES membranes were viewed using scanning electron microscopy (SEM), revealing no surface damage and only a slight alteration in pore structure. As a result of the incorporation of polar functionalities, the glass transition temperature (Tg) of both the Ar-plasma treated and AAm grafted membranes increased. A moderate change in the tensile strength of the modified membranes was also observed. Most importantly, the AAm grafting made the membrane surface less susceptible to adsorption o...