Plain Membrane Research Articles

Ultrafiltration study of the polysulfone membrane modified with branched polyethyleneimine

Abstract This work discussed the fabrication of polysulfone (PSF) ultrafiltration membranes with hydrophilic behaviour by adding branched polyethyleneimine (PEI) as an additive. By directly blending the base polymer and the additive in the organic solvent, the casting solution is prepared. An asymmetric ultrafiltration membrane was fabricated by the phase inversion method. The presence of PEI was confirmed by comparing the IR spectra of the plain PSF membrane and the modified PSF membrane. A scanning electron microscope was used for the comparison of morphological changes in plain and modified membranes. The membrane was characterised with respect to bovine serum albumin (BSA) adsorption, pure water flux, permeability, compaction factor, humic acid (HA) rejection, and water uptake. The fouling resistance behaviour is prompted due to the presence of hydrophilic PEI chains in the membrane. As a result, pure water flux and flux recovery ratio increased from 28.84 to 326.54 L/m2h and from 0.526 to 0.954 L/m2hkPa for the modified membrane with respect to the plain membrane, respectively.

MetaMembranes for the Sensitivity Enhancement of Wearable Piezoelectric MetaSensors.

The low stretchability of plain membranes restricts the sensitivity of conventional diaphragm-based pressure and inflatable piezoelectric sensors. Using theoretical and computational tools, we characterized current limitations and explored metamaterial-inspired membranes (MetaMems) to resolve these issues. This paper develops two MetaMem pressure sensors (MPSs) to enrich the sensitivity and stretchability of the conventional sensors. Two auxetic hexagonal and kirigami honeycombs are proposed to create a negative Poisson’s ratio (NPR) in the MetaMems which enables them to expand the piezo-element of sensors in both longitudinal and transverse directions much better, and consequently provides the MPSs’ diaphragm a higher capability for flexural deformation. Polyvinylidene fluoride (PVDF) and polycarbonate (PC) are considered as the preferable materials for the piezo-element and MetaMem, respectively. A finite element analysis was conducted to investigate the stretchability behavior of the MetaMems and study its effect on the PVDF’s polarization and sensor sensitivity. The results obtained from theoretical analysis and numerical simulations demonstrate that the proposed MetaMems enhance the sensitivity of pressure sensors up to 3.8 times more than an equivalent conventional sensor with a plain membrane. This paper introduces a new class of flexible MetaMems to advance wearable piezoelectric metasensor technologies.

P(HEMA)-RR241 hydrogel membranes with micron network for IgG depletion in proteomic studies

Serum proteins can generally be considered a good source for the illness’ indication and are precious resources to detect diseases such as inflammation, cancer, diabetes, malnutrition, cardiovascular diseases, Alzheimer’s, other autoimmune diseases, and infections. However, one of the biggest difficulties for proteomic studies is that the majority of serum protein mass consists of only a few proteins. Albumin and Immunoglobulin (IgG) constitute 80% of total serum protein. In this study, dye ligand affinity-based hydrogel membranes were proposed as new materials with micron mesh structures. Micron mesh p(HEMA) hydrogel membranes were synthesized by using the UV-photopolymerization method, then modified with Reactive Red 241 (RR241) dye ligand to increase the affinity towards IgG. Characterizations of synthesized micron mesh p(HEMA)-RR241 hydrogel membranes were also performed. It was demonstrated by the characterization studies that; the dye was successfully incorporated into the membrane structure with the amount of 119.38 mg/g. The hydrophilic property of the hydrogel membrane was demonstrated by swelling tests and the swelling value of dye modified membrane was found to be 8 times higher than that of the plain membrane. Micron network structure, as well as the porosity, were demonstrated with SEM/ESEM studies. Optimization of IgG adsorption conditions was also studied at different parameters (pH, temperature, ion strength, initial IgG concentration). Optimum pH, temperature, and ionic strength were found to be 6.5, 25 °C, 0.05 M, respectively, and the maximum IgG absorption value was 10.27 mg/g. Finally, it was shown that the proposed materials can be used repeatedly by 5 adsorption-desorption cycles.

High Retention and Purification of Bromelain Enzyme (Ananas comosus L. Merrill) from Pineapple Juice Using Plain and Hollow Polymeric Membranes Techniques.

The demand for bromelian and pineapple fruit has been increasing substantially in the world because of their benefits for the human health and use in diverse areas. In this context, this work aimed to study the capacity of higher retention (concentration); bromelain activity underwent ultrafiltration from pineapple juice (Ananas comusus L. Merrill). All assays were carried out at pH 7.0 and 7.5, and at 0.05 and 0.40 bar of transmembrane pressures. Results have shown that at the best operating conditions, between 85 and 87% of bromelain activity was recovered using the plain membrane separation process at 0.05 bar. The ultrafiltration has shown the capacity to retain 100% of proteolytic activity of the bromelain extracted. The samples have kept the same physics properties after ultrafiltration, and the result was verified via electrophoresis. The bromelain enzyme obtained was characterized, and pH 7 and between 30 and 40 °C were the best conditions. Therefore, this work shows that the use of both polymeric membranes has shown high efficiency, and can be used in the purification of bromelain enzymes.

Hydrophilic modification of poly(ether)sulfone membrane by atmospheric pressure argon jet plasma: pH dependence of ultrafiltration performance and cleaning efficiency

AbstractThe studies focused on plasma surface modification of poly(ether)sulfone (PES) ultrafiltration (UF) membrane show its potent effect on antifouling propensity but there are few data on the pH dependence of superior surface character achieved. This study examined UF performance and cleaning efficiency of atmospheric pressure argon jet plasma (AP‐AJP) modified PES membrane in whey concentration at various operation pH compared to the plain membrane (UP020). The highest initial permeate flux for the UP020 at pH of 6.4 increased the cake layer formation and the irreversible fouling resistance. The plasma action led to greater intrinsic membrane resistance causing low water permeability compared with the UP020. This effect reduced cake layer resistance despite the fact that the irreversible fouling was more severe at all operation pH. The increase in pH caused to decrease in contribution of fouling to total resistance. For the UP020, the shift in operation pH from acidic point to neutral reduced the recovery in hydraulic permeability after chemical cleaning. The plasma action induced greater cleaning efficiency, which is the most obvious at pH of 6.4. The overall results showed that the AP‐AJP may have the potential to maintain profit‐making UF process in whey concentration at broad range of pH.Practical ApplicationsIn the industrial point of view, cost friendly, and sustainable operation in valorization of whey can be achieved by fouling resistant membranes. Atmospheric pressure argon jet plasma provides extremely hydrophilic character to poly(ether)sulfone membrane. The plasma action decreases fouling resistance and especially cake layer formation. This effect broadens the operating pH of whey without any pre‐adjustment and results in easy to clean membrane surfaces.

Novel superhydrophilic antifouling PVDF-BiOCl nanocomposite membranes fabricated via a modified blending-phase inversion method

PVDF nanocomposite membranes prepared by the widely used conventional blending-phase inversion method generally suffer from nonuniform distribution and low exposure of additive nanomaterials, resulting in unsatisfactory hydrophilicity and antifouling capability. Herein, we developed a modified blending method that incorporates the water-triggered precipitation (resembles phase inversion) of the nanomaterials into PVDF phase inversion. PVDF-bismuth oxychloride (BiOCl) nanocomposite membranes were prepared by dissolving KCl and Bi(NO3)3 in the PVDF dope solution to enable the simultaneous precipitation of PVDF and hydrophilic BiOCl in the coagulation bath. Characterizations demonstrated that the nanocomposite membranes are superhydrophilic, mainly attributed to the surface-preferential precipitation of BiOCl. Crossflow filtration results showed that the nanocomposite membrane had a pure water flux of 854 L m-2 h−1 bar−1 (LMHB) and a humic acid separation flux of 780 LMHB, much higher than 377 and 240 LMHB of the plain membrane. For bovine serum albumin (BSA) separation, the nanocomposite membrane achieved a quasi-steady state flux of 370 LMHB and a rejection ratio of ~90% during three test cycles. In contrast, the hydrophobic plain membrane was severely fouled by BSA, evidenced by a rejection ratio lower than 40%. We proposed a new mechanism that illustrated the effects of protein-membrane interactions and filtration hydrodynamics that well explained the filtration results. The nanocomposite membrane also possessed a 3-fold higher capacity for Cr (VI) adsorption than the plain membrane. These results suggest that this modified blending-phase inversion method could fabricate nanocomposite membranes with great separation and antifouling capability, and multifunctionality.

Thin film nanocomposite membranes filled with MCM-41 and SBA-15 nanoparticles for brackish water desalination via reverse osmosis

This work aimed to investigate the impact of filling MCM-41 and SBA-15 nanoparticles (NPs) on the performance of thin film nanocomposite membranes that applied in reverse osmosis, where SBA-15 is firstly reported here for this purpose. The membranes were prepared via the interfacial polymerization reaction between m -phenylenediamine (MPD) aqueous solution and trimesoyl chloride (TMC)-isooctane solution on a support sheet of polyethersulfone. The reaction time in the presence of NPs was investigated by fixing MPD contact time at 75 s; it was found that 30 s is the optimum TMC contact time. Different loading ratios in the range of 0-0.15 wt% were applied to fill the NPs inside the membranes. Scanning electron microscope (SEM), X-ray Diffractometer (XRD), Fourier-transform infrared spectroscopy (FTIR), and N 2 adsorption/desorption tests were used to study the NPs characterizations. While SEM, contact angle, mechanical strain and strength, and membrane performance tests were conducted to study the membranes properties. Results showed that in both nanoparticles (i.e. MCM-41 and SBA-15) cases, 0.1 wt% was the optimum filling percentage. When SBA-15 was loaded, water flux increased from 40 to 74.17 L.m −2 .h −1 (LMH), and NaCl rejection increased from 95.1 to 98.5% comparing with the plain membrane. While when the optimum MCM-41 ratio was loaded, water flux and NaCl rejection raised to 60 LMH and 96.9%, respectively. The performance test conditions were 15 bar, 25 °C, and 2500 NaCl feed concentration. • MCM-41 and SBA-15 NPs were filled in TFN membranes. • Both additives improved the membranes performance. • SBA-15 is firstly reported as a filler for RO application. • SBA-15 effect was higher on the membranes water flux and salt rejection.

Fabrication of blend hydrophilic polyamide imide (Torlon®)-sulfonated poly (ether ether ketone) hollow fiber membranes for oily wastewater treatment

Blend hydrophilic polyamide imide (PAI)-sulfonated poly (ether ether keton) (SPEEK) hollow fiber membranes were fabricated for oil-water emulsion separation. The structure and performance of the membranes were examined by FESEM analysis, N2 permeation, overall porosity, collapsing pressure, water contact angle, pure water flux, molecular weight cutoff (MWCO), and oil rejection tests. By studying ternary phase diagrams of polymer/solvent-additive/water system, the higher phase-inversion rate was confirmed for the solutions prepared at higher PAI/SPEEK ratio. A more open structure with larger finger-likes was observed by increasing PAI/SPEEK ratio. Mean pore size of 81 nm, overall porosity of 79% and water contact angle of 58° were obtained for the improved membrane prepared by PAI/SPEEK ratio of 85/15. Increasing SPEEK ratio resulted in lower mechanical stability in terms of collapsing pressure. Pure water flux of about 2.5 times of the plain PAI membrane was found for the improved membrane. MWCO of 460 kDa was found for the improved blend membrane. From oil rejection test, all the membranes demonstrated an oil rejection of over 95%. The improved membrane showed a lower rate of permeate flux reduction compared to the plain membrane which was related to the smaller fouling possibility. Less fouling resistance of the improved membrane was related to the higher flux recovery ratio (about 92%). For all the membranes, the dominant fouling mechanism was found to be the cake filtration. The improved PAI-SPEEK hollow fiber membranes was found to be practical for ultrafiltration of oily wastewaters.

Evaluation of polyvinyl alcohol (PVA) loading in the PVA/titanium dioxide (TiO2) thin film coating on polyvinylidene fluoride (PVDF) membrane for the removal of textile dyes

Polyvinylidene fluoride (PVDF) membrane was coated with polyvinyl alcohol (PVA)/titanium dioxide (TiO2) solution using dip-coating method. The effect of PVA loading (0–12 wt%) at a fixed TiO2 concentration (1 wt%) was investigated through physical and morphological characterization of the membranes. The experimental results showed that increasing the PVA content from 0 to 12 wt% in the coating solution increased the hydrophilicity and tensile strength as well as the young’s modulus of the coated membranes. It also increased the thickness of the thin film coating which enhanced the removal of dyes but affected the permeate flux adversely. Larger the molecular weight of the dye, higher the rejection and lower the permeate flux obtained. The antifouling performance of the membrane was studied using Bovine Serum Albumin (BSA) solution and the fouling was measured using the irreversible fouling factor. The results indicated that the PVA/TiO2 coated PVDF membrane had lower irreversible fouling factors compared to plain PVDF membrane. The PVDF membrane with a thin film coating containing 3 wt% of PVA and 1 wt% of TiO2 showed high photocatalytic degradation for the three dyes studied under UV irradiation due to uniform dispersion of TiO2 nanoparticles over the membrane surface. Further, smaller the molecular weight of the dye, larger the photodegradation that was observed.

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N 2 permeation, overall porosity, critical water entry pressure (CEP w ), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N 2 permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m −1 . CEP w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m −2 ·h −1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.

A novel stimuli-responsive and fouling resistant PVDF ultrafiltration membrane prepared by using amphiphilic copolymer of poly(vinylidene fluoride) and Poly(2-N-morpholino)ethyl methacrylate

A novel stimuli-responsive and anti fouling poly(vinylidene fluoride) (PVDF) membrane is proposed by incorporating amphiphilic copolymer, poly(vinylidene fluoride)-graft-Poly(2-N-morpholino)ethyl methacrylate (PVDF-g-PMEMA) as modifier due to presence of tertiary amine and heterocyclic oxygen (oxa-group). The prepared membrane exhibits dual responsive properties, i.e. pH responsive and temperature responsive behaviour as well as antifouling characteristics. The mechanism of the pH-responsive performance is originated from the pH-responsive swelling and shrinking of PMEMA chains embedded in the membrane and Temperature-responsive performance is attributed to the Temperature-responsive extended and collapsed state of PMEMA chains at around LCST. The antifouling property is induced owing to presence of hydrophilic PMEMA chains in the membrane. As a result, the permeability of the novel PVDF membrane was increased from 0.29 L/m2hkPa (plain membrane) to 0.77 L/m2hkPa (modified membrane) with addition of amphiphilic copolymer from 0 wt % to 3 wt %. The maximum o/w emulsion rejection percentage of about 97% was obtained through blended membrane. Thus the proposed membrane in this research work offers an approach for the treatment of oily wastewater.

Preparation and characterization of PVDF-filled MWCNT hollow fiber mixed matrix membranes for gas absorption by Al2O3 nanofluid absorbent via gas–liquid membrane contactor

Porous polyvinylidene fluoride (PVDF)-filled MWCNT hollow fiber mixed matrix membranes were fabricated and applied for carbon dioxide absorption in a gas–liquid membrane contactor with Al2O3 water-based nanofluid absorbent. The formation of MWCNTs’ nanotubes was verified through Transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FESEM) images while the resultant membranes were characterized for their morphology, gas permeation rate, pore size, porosity, surface hydrophilicity and wettability resistance. Upon the incorporation of MWCNT into the matrix, the formation of finger-like pores was facilitated and surface roughness increased. Gas permeation test results showed increasing the surface porosity and reducing the pore size. The surface contact angle also was improved from 83°±1.5 for the unfilled membrane to 103°±1.5 for the membrane containing 5wt% CNT. CO2 absorption flux also was enhanced considerably. For instance, the flux of the membrane containing 5wt% CNT as the best performing membrane at a liquid velocity of 2.5m/s and Al2O3 water-based nanofluid as absorbent was 3.85×10−3mol/m2s which was approximately 200% higher than that of the plain membrane at the same operating conditions. A long-term absorption test also revealed non-wetting tendencies of the membranes as well as the unclogged membrane pores by the nanomaterials existed in the nanofluid absorbent. Therefore, it could be hypothesized that the improved membrane structure and synthesized nanofluid absorbent considering their superior performance to several commercial and in-house made membranes can be suitable alternatives to the current polymeric membranes and commercial used absorbents, respectively.

Photocatalytic Degradation of Ampicillin Using PLA/TiO2 Hybrid Nanofibers Coated on Different Types of Fiberglass

New photocatalytic membranes based on polylactic acid (PLA)/TiO2 hybrid nanofibers deposited on fiberglass supports were prepared and tested for the removal of ampicillin from aqueous solutions. The electrospinning technique was used to obtain hybrid nanofibers that were deposited on three types of fiberglass with different structures, resulting in three distinct photocatalytic membranes namely fiberglass fabric plain woven-type membrane, fiberglass mat-type membrane, and fiberglass fabric one-fold edge-type membrane. The results of the photocatalytic tests showed that the highest efficiency of ampicillin removal from aqueous solution is obtained with the fiberglass fabric plain woven-type membrane. Although it has been shown that the rate of photocatalytic degradation of ampicillin is high, being practically eliminated within the first 30 min of photocatalysis, the degree of mineralization of the aqueous solution is low even after two hours of photocatalysis due to the degradation of PLA from the photocatalytic membrane. The instability of PLA in the reactive environment of the photocatalytic reactor, evidenced by morphological, mineralogical and spectroscopic analyzes as well as by kinetic studies, is closely related to the structure of the fiberglass membrane used as a support for PLA/TiO2 hybrid nanofibers.

Preparation of tungstic acid functionalized titanium oxide nanotubes and its effect on proton exchange membrane fuel cell

Titanium oxide nano tubes (TNT) were synthesized by hydrothermal method and tungstic acid (ion exchange group) were covalently grafted on its surface. The synthesized tungstic acid functionalized TNT (W-TNT) were characterised by SEM, TEM, XRD analysis for the nano-tubular morphology and the successful grafting of tungstic acid group was confirmed by FTIR and solid state NMR techniques. Composite membranes of different weight percentage W-TNT (2%, 4%, 6% and 8%) and sulfonated poly ether ether ketone (SPEEK) were fabricated which resulted in high ion exchange properties. The prepared composite membranes were characterised by SEM, XRD, FTIR, water uptake, ion exchange capacity and proton conductivity to ensure the aptness of the membranes to be used as electrolyte in fuel cell application. From the studies it was found that SPEEK with 6% W-TNT showed optimum electrochemical properties. Upon testing this membrane in fuel cell as an electrolyte with carbon supported platinum anode and cathode electrodes, a maximum power density of 352 mW cm−2 was achieved at 80 °C. The presence of additional ion exchange groups (tungstic acid) and hollow nature of TNT lead to the improved performance than the plain membrane.

Air gap membrane distillation of MEG solution using PDMS coated polysulfone hollow fiber membrane

Surface modified porous polysulfone (PSF) hollow fiber membrane was prepared by dip-coating of polydimethylsiloxane (PDMS). The prepared membranes were used in an air gap membrane distillation (AGMD) process for dehydration of MEG-water mixtures. The membranes were characterized in terms of Field Emission Scanning Electronic Microscopy (FESEM), N2 permeation, contact angle measurement and wetting pressure. From FESEM images, the prepared membrane showed a porous structure with finger-like cavities. In addition, formation of ultra-thin coating layer on the inner and outer surface was confirmed by FESEM. From N2 permeation test, the modified membrane showed smaller mean pore size (9 nm) and lower surface porosity compared to the plain membrane. The modified membrane showed a good hydrophobicity with water contact angle of 118° and wetting pressure of 800 kPa. The permeate flux of about 26 kg/m2h was obtained for the modified membrane at MEG concentration of 20 wt%, feed temperature of 90 °C and feed velocity of 0.66 m/s. Due to the improved structure, the modified membrane showed a stable AGMD operation for 80 h compared to the plain membrane.

Incorporation of cross-linked poly(AA-co-ACMO) copolymer with pH responsive and hydrophilic properties to polysulfone ultrafiltration membrane for the mitigation of fouling behaviour

N-acryloylmorpholine (ACMO), a promising fouling resistant additive with good hydrophilicity, was used to synthesize novel pH responsive hydrophilic cross-linked poly(acrylic acid-co-acryloylmorpholine) (poly(AA-co-ACMO)) copolymer via precipitation polymerization. The copolymer was directly used as an additive into the casting solution for fabrication of modified PSF membranes by phase inversion method. The successful synthesis of copolymer and membranes were confirmed by FTIR-ATR spectroscopy. The thermodynamics of the membrane formation was analysed by plotting the ternary phase diagram of poly(AA-co-ACMO)/PEG6000/PSF/NMP/H2O system. The gradual increase in dose of copolymer from 0 wt% to 1.5 wt% supports in finger-like structure and uniform pore formation mechanism in the membrane. The modified membrane showed maximum porosity, pore density and permeability with 1.5 wt% of copolymer. The CA and quantity of adsorbed BSA were decreased significantly from 59.3° and 0.12 mg/cm2 for plain membrane (M1–0.0) to 44.4° and 0.03 mg/cm2, respectively for modified membrane (M1–2.0). The modified membranes also exhibited sign of pH sensitivity and IEC compared to plain membrane. The modified membranes expressed enhanced rejection against BSA and oil-in-water (o/w) emulsion with improved fouling resistance property. Moreover, the content of acrylic acid (AA) and ACMO during synthesis of cross-linked copolymer influence the permeation behaviour of the membrane. The flux recovery ratio was increased from 0.61 (M1–0.0) to 0.92 (M1–2.0) with increase in dose of copolymer (wt%) and from 0.86 (M3–1.5) to 0.93 (M2–1.5) with increase in ACMO content in the copolymer. In general, poly(AA-co-ACMO)/PEG6000/PSF membrane may provide a potential application in separation against protein solution and o/w emulsion separation system.

Thermal conductivity of deca-nanometric patterned Si membranes by multiscale simulations

The hollowing of silicon membranes to form a lattice of cylindrical holes, also called phononic crystal, has been used by several experimental groups willing to fabricate efficient thermoelectric modules. The idea is to reduce the thermal conductivity without impacting the electronic conductivity. For several a priori identical materials, i.e. thin films containing periodic cylindrical holes, drastically different levels of thermal conductivity reduction have been reported in the literature: from 1–2 W K−1 m−1 to 15–40 W K−1 m−1, i. e. half the thermal conductivity of the plain membrane. These differences may be due to variations in the geometrical patterns, or to the technological processes specific to each group. It is therefore highly desirable to understand which level of reduction can be expected from the basic concept. In this work, we address the question by applying a fully atomistic framework, the approach-to-equilibrium molecular dynamics (AEMD), to study two deca-nanometric patterns used in the literature and reported respectively with a high and low level of thermal conductivity reduction. For both patterns, the thermal conductivity roughly decreases by a factor 2 only compared to the plain membrane. Thanks to Monte Carlo simulations, in agreement with AEMD for the two patterns, we propose that the origin of stronger reductions could be an increase of the surface roughness during the step of hole fabrication.

Protic ionic liquid/functionalized graphene oxide hybrid membranes for high temperature proton exchange membrane fuel cell applications

The 1-(3-aminopropyl)-3-methylimidazolium bromide ([APMIm][Br]) functionalized graphene oxide ([APMIm][Br]-GO) and 1-methylimidazolium trifluoromethanesulfonate ([MIm][TfO]) are prepared and used as fillers and proton carrier in the preparation of high temperature hybrid proton exchange membranes (PEMs), respectively. The PEMs are obtained via photo-initiated polymerization of a mixture containing polymerizable oil (styrene/acrylonitrile and divinylbenzene), protic ionic liquid (PIL, [MIm][TfO]), and different content of [APMIm][Br]-GO. The resultant membranes show good thermal stability and excellent mechanical properties. Incorporation of proper amount of [APMIm][Br]-GO significantly increases the proton conductivity of the hybrid membranes, and the membranes with 1.0 wt% [APMIm][Br]-GO shows the highest conductivity (up to 1.48 × 10−2 S cm−1 at 160 °C). Compared with the plain membrane without [APMIm][Br]-GO, the hybrid membranes with [APMIm][Br]-GO show much better PIL retention ability. These properties make this type of PIL-based hybrid membranes suitable for the application of high-temperature proton exchange membrane fuel cells (PEMFCs).

Mitigation of HA, BSA and oil/water emulsion fouling of PVDF Ultrafiltration Membranes by SiO2-g-PEGMA nanoparticles

In this work antifouling poly(vinylidene fluoride) (PVDF) ultrafiltration membranes were synthesized with direct blending of Poly(ethylene glycol) methyl ether methacrylate (PEGMA)-grafted SiO2 (SiO2-g-PEGMA) nanoparticles (NPs) in the casting solution by phase inversion method. Chemical structure of the SiO2-g-PEGMA NPs was analyzed by Fourier transform infrared (FTIR) spectroscopy. Effect of different wt.% of SiO2-g-PEGMA NPs on the structure and performance of prepared membranes were examined by Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, Field emission scanning electron microscope (FESEM), Liquid–liquid displacement porosimetry (LLDP), pure water flux (PWF), hydraulic permeability, solute rejection study, water contact angle, water uptake, porosity and bovine serum albumin (BSA) adsorption. Modified membranes have higher solute rejection than plain PVDF membrane. Also, modified membrane with 0.5 wt% of SiO2-g-PEGMA NPs showed enhanced porosity, pore density, pore area, PWF and permeability. Water contact angle and amount of adsorbed BSA for the modified membrane with 1 wt.% of SiO2-g-PEGMA NPs were 50.7° and 0.05 mg/cm2 compared to 68.7° and 0.17 mg/cm2 respectively, for the plain membrane. Furthermore, antifouling property and rejection performance of modified PVDF membranes were investigated by humic acid (HA), BSA and oil-in-water (o/w) emulsion ultrafiltration experiment. It was observed from ultrafiltration study that the irreversible fouling and total fouling were decreased and achieved high flux recovery ratio for modified membrane.

Performance enhancement of ultrafiltration in apple juice clarification via low-pressure oxygen plasma: A comparative evaluation versus pre-flocculation treatment

The aim of this study was to improve ultrafiltration (UF) performance during clarification of raw apple juice through surface modification of commercial polysulfone membranes (US100) by low-pressure oxygen plasma treatment (LP-OPlsT). A Plasma power of 90 W and exposure time of 10 min were determined as the most effective parameters enabling an increase in the ΔGiwi value of the plain membrane from (−) 25 ± 2 mN m−1 to (+) 30 ± 1 mN m−1. Improved hydrophilicity achieved by LP-OPlsT remarkably enhanced the performance of US100 throughout the clarification of raw apple juice without the need of an additional pre-flocculation step. While Rfrev (86%) was the dominant resistance controlling the fouling during UF of raw apple juice through the plain membrane, the contribution of Rfrev to Rt decreased to 56% after pre-flocculation step. LP-OPlsT further decreased this ratio, up to 46%, confirming the charge repulsion between the modified membrane and the foulant particles.