Water Flux Recovery Ratio Research Articles

Modeling and Optimization of NLDH/PVDF Ultrafiltration Nanocomposite Membrane Using Artificial Neural Network-Genetic Algorithm Hybrid.

In this research, MgAl-CO32- nanolayered double hydroxide (NLDH) was synthesized through a facile coprecipitation method, followed by a hydrothermal treatment. The prepared NLDHs were used as a hydrophilic nanofiller for improving the performance of the PVDF-based ultrafiltration membranes. The main objective of this research was to obtain the optimized formula of NLDH/PVDF nanocomposite membrane presenting the best performance using computational techniques as a cost-effective method. For this aim, an artificial neural network (ANN) model was developed for modeling and expressing the relationship between the performance of the nanocomposite membrane (pure water flux, protein flux and flux recovery ratio) and the affecting parameters including the NLDH, PVP 29000 and polymer concentrations. The effects of the mentioned parameters and the interaction between the parameters were investigated using the contour plot predicted with the developed model. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle techniques were applied to characterize the nanocomposite membranes and to interpret the predictions of the ANN model. The developed ANN model was introduced to genetic algorithm (GA) as a bioinspired optimizer to determine the optimum values of input parameters leading to high pure water flux, protein flux, and flux recovery ratio. The optimum values for NLDH, PVP 29000 and the PVDF concentration were determined to be 0.54, 1, and 18 wt %, respectively. The performance of the nanocomposite membrane prepared using the optimum values proposed by GA was investigated experimentally, in which the results were in good agreement with the values predicted by ANN model with error lower than 6%. This good agreement confirmed that the nanocomposite membranes prformance could be successfully modeled and optimized by ANN-GA system.

Excellent hydrophilic and anti-bacterial fouling PVDF membrane based on ag nanoparticle self-assembled PCBMA polymer brush

A silver nanoparticles-poly(carboxybetaine methacrylate) (AgNPs-PCBMA) nanocomposite was prepared on poly(vinylidene fluoride) (PVDF) membrane surface to improve its hydrophilicity and antifouling properties. Firstly, the PVDF membranes were grafted by PCBMA via physisorbed free radical grafting technique. Then Ag+ coordinated to the carbonyl group on PCBMA and subsequently was reduced to silver nanoparticles. The hydrophilicity of the PVDF-g-PCBMA/Ag membrane was enhanced with the increasing fixed degree (FD) of AgNPs, and the original water contact angle of membrane was reduced to 33.97°. Additionally, water flux recovery ratio (FRR) and bovine serum albumin (BSA) rejection ratio of PVDF-g-PCBMA/AgNPs membrane were improved from 52% to 93.32% and 28.12% to 91.12%, respectively. Further, the PVDF-g-PCBMA/AgNPs membranes exhibited the more pronounced inhibition zone. The study demonstrated that compared with pure AgNPs or the PCBMA polymer brush, the synergistic effect of PCBMA and AgNPs made PVDF membranes have better hydrophilicity and anti-bacterial performances.

Effect of Polyethylene glycol methyl ether blend Humic acid on poly (vinylidene fluoride-co-hexafluropropylene) PVDF-HFP membranes: pH responsiveness and antifouling behavior with optimization approach

Flat sheet asymmetric membranes were fabricated with homogeneous solution of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) using N-methyl-2-pyrrolidone (NMP) as solvent via phase inversion method. PEGME (Poly ethylene glycol methyl ether) (Mn 5000) blend Humic Acid (HA), of different mole ratio was used as additive. Characterization of the membranes was done by Field emission scanning electron microscope (FESEM), Fourier Transform Infrared (FTIR) spectroscopy, Atomic force microscopy (AFM) and Differential scanning calorimetry (DSC) studies. Liquid-liquid displacement porosimetry (LLDP) study evaluated the morphological parameters, average pore size and pore size distribution. Bovine serum albumin (BSA) (MW - 68,000 Da) was used to study the antifouling effect and pore blocking mechanism of the membranes. The pure water flux (PWF), solute rejection and flux recovery ratio drastically increases for the PEGME blended HA membranes whereas the water contact angle decreases significantly. The pH responsiveness character of the prepared membranes altered the hydraulic permeability and rejection % at different pH. Finally, optimization of the variables contributing towards the PWF and BSA rejection of the desired membrane was performed using Design expert software 9.0 TRIAL through ANOVA (analysis of variance) using the combination of response surface methodology (RSM) and central composite design (CCD).

Effect of solvent type on the physicochemical properties and performance of NLDH/PVDF nanocomposite ultrafiltration membranes

Abstract The effect of different solvents e.g. N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethylacetamide (DMAc) and dimethylformamide (MDF) on the physicochemical properties of Mg-Al nanolayered double hydroxide (NLDH)/PVDF nanocomposite ultrafiltration membranes was investigated. The Mg-Al NLDH was applied as a hydrophilic nanofiller with the purpose of improving PVDF-based ultrafiltration membranes. The main purpose of this study was to find which solvent could better highlight effect of the nanoparticle in the membrane preparation. Scanning microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and water contact angle techniques were used for analyzing the surface and cross-sectional morphology, the NLDH distribution in matrix of nanocomposite membrane, surface roughness and hydrophilicity of the prepared PVDF/NLDH nanocomposite membranes, respectively. The permeability and the antifouling properties of the prepared membranes were investigated via determination of pure water flux and flux recovery ratio ( FRR ), respectively. The results showed that the morphology, dispersion of NLDH in the matrix of polymer and the properties of the nanocomposite are mainly affected by the type of the solvent. This research demonstrates that when NMP is used as solvent the NLDH can significantly improve the performance of the PVDF membrane, while by using other solvent the NLDH is not able to affect the performance of the PVDF membrane significantly. Indeed, in the case of using NMP as the solvent, beside the surface porosity enhancement in the presence of NLDH, the cross sectional morphology of the membrane was significantly affected and the pores changed from sponge-like to finger-like, resulting in significant permeability improvement of this membrane.

Preparation and characterization of PVC/PAN blend ultrafiltration membranes: Effect of PAN concentration and PEG with different molecular weight

The current study investigates the effect of polyacrylonitrile (PAN) addition on morphology and antifouling properties of poly(vinyl chloride) (PVC) asymmetric flat ultrafiltration (UF) membranes. The membranes are prepared via phase inversion method induced by immersion precipitation at different PVC/PAN blending ratio up to 40 wt% PAN. Also, membranes with blending ratio of PVC/ PAN:70/30, which showed the highest water flux and flux recovery ratio, were used for membrane preparation with 4 wt% of Polyethylene glycol (PEG) addition in four different molecular weight, 600 Da, 1,000 Da, 6,000 Da and 20,000 Da, which was used as pore former and hydrophilic polymeric additive. The performance of the membranes was studied by using pure water and bovine serum albumin (BSA) as feed at operating pressure of 3 bar. The cross-sections of the fabricated membranes were studied using SEM, and the images showed remarkable changes in morphology and structure of the prepared membranes after PAN and PEG addition. PAN addition led to increment in water flux up to 30 wt% and then decreased. The similar trend was observed in the case of flux recovery ratio. Also, viscosity of polymeric solution, contact angle and porosity of the membranes, antifouling and flux recovery of the membranes were studied.

Sulfonated multiwall carbon nanotubes assisted thin-film nanocomposite membrane with enhanced water flux and anti-fouling property

Sulfonated multiwall carbon nanotube (SMWCNT) with pendant alkyl sulfonic acid groups was synthesized from hydroxyl-functionalized multiwall carbon nanotube (MWCNT-OH). Small changes in microstructure, due to nucleophilic substitution reaction, were confirmed by X-ray photoelectron spectroscopy, transmission electron microscopy, and N2 adsorption-desorption measurements. Prepared SMWCNT exhibited excellent water dispersity, which facilitated interfacial polymerization to prepare novel poly(piperazine amide) thin-film nanocomposite (TFN) membranes. Water flux and salt rejections of the TFN membranes were readily adjusted by optimizing the SMWCNT content, to get most optimum separation performance. TFN-0.01% showed high water flux of 13.2Lm−2h−1bar−1, 1.6 times more than the pristine thin-film composite (TFC) membrane, maintaining reasonably high rejection of 96.8% to Na2SO4. TFN-0.01% membrane, with enhanced surface hydrophilicity exhibited better anti-fouling ability to bovine serum albumin with water flux recovery ratio as high as 91.2%, even after two “fouling-washing” cycles, compared to 82.0% for TFC membrane.

Application of sulfonic acid group functionalized graphene oxide to improve hydrophilicity, permeability, and antifouling of PVDF nanocomposite ultrafiltration membranes

A novel, highly hydrophilic nanocomposite additive, sulfonated graphene oxide (SGO), was synthesized from graphene oxides (GO), and characterized using a range of techniques. To examine the effects of the sulfonic acid groups of the filler particles on the polyvinylidene fluoride (PVDF) membrane performance, the PVDF-GO/SGO modified membranes were obtained through phase inversion by dispersing GO and different concentrations of SGO (0.4–1.2wt%). The surface of the prepared membranes was analyzed by scanning electron microscopy and atomic force microscopy. The addition of GO and SGO caused by an increase in surface roughness, porosity, and pore size of the membranes compared to the PVDF membrane. The P-SGO and P-GO blend membranes showed a 146.6% and 53.3% enhancement of the water permeation flux, respectively. The presence of additional sulfonic groups (-SO3H) on SGO supports hold a thicker water hydrogen layer and improve the water flux. The anchored –SO3H group in SGO is a stronger hydrogen-bonding group compared to the -COOH/-OH groups present in GO. From the antifouling test, P-SGO with the 0.8wt% blend membranes exhibited a high water flux recovery ratio (FRR) of 88.7% and low irreversible fouling (Rir) Of 11.2% compared to the GO nanocomposite membrane (75% and 24%, respectively). This was recognized to the high hydrogen bonding forces and electrostatic repulsion of SGO against the fouling proteins. Overall, the induced SGO nanoparticle opens a novel path to enhance the hydrophilicity, water flux, antifouling, and mechanical performance of PVDF ultrafiltration membranes.

An effective approach to fabrication of antifouling ultrafiltration membrane based on zwitterionic polyimide

In this study, a new kind of membrane material, an aromatic zwitterionic polyimide (PI) copolymer, was synthesized through a one-pot polymerization reaction by precise variation of the molar ratios of different monomers with specific groups. The zwitterionic PI ultrafiltration (UF) membrane was prepared through an immersion precipitation phase inversion method and thoroughly characterized by scanning electron microscopy, water contact angle measurement, protein adsorption measurement, and UF experiment. The zwitterionic PI membrane showed significantly improved hydrophilicity and permeability and stable antifouling property. The amount of bovine serum albumin adsorbed on the zwitterionic PI membrane was considerably lower compared with the reference PI membrane. According to the cycle UF experiment for protein solution, the zwitterionic PI membrane had a water flux recovery ratio of 86.7%, compared with only 61.1% for the reference PI membrane. Moreover, the irreversible fouling of the zwitterionic PI membrane was significantly decreased, suggesting superior antifouling property. This new approach to the preparation of a zwitterionic polymer seems promising for potential applications in separation membrane.

Fabrication and characterization of amphiphilic PVDF copolymer ultrafiltration membrane with high anti-fouling property

Novel anti-fouling poly(vinylidene fluoride) (PVDF) membranes were fabricated via phase inversion method, directly using amphiphilic copolymers, which were synthesized from PVDFs with three different molecular weight grafted poly(ethylene glycol) methyl ether methacrylate (POEM) (PVDF-g-POEM), as membrane materials. Atom transfer radical polymerization (ATRP) method was employed to synthesize the amphiphilic PVDF copolymers. The membranes were characterized by scanning electron microscopy (SEM), pure water flux, contact angle measurement and BSA solution filtration experiments, etc. The permeability of the PVDF copolymer membrane reached to 567.8Lm−2h−1bar−1 with molecular weight cut off (MWCO) of about 40.0kDa. In addition, the stable state flux of the PVDF copolymer membranes was much higher than that of PVDF homopolymer membranes when BSA solution was filtrated, and after cleaning, the pure water flux recovery ratio of the copolymer membrane reached to 98.1%. These results indicate that the prepared PVDF membrane possesses good performance and anti-fouling property.

One-step fabricated bionic PVDF ultrafiltration membranes exhibiting innovative antifouling ability to the cake fouling

In view of the excellent application properties of the bionic materials, a novel polyvinylidene fluoride (PVDF) ultrafiltration membrane with regular nanoscale papillae on the membrane surface imitating the mosquito eye structures was fabricated by one-step molding method. The amphiphilic wetting agent (EW-326) was used in the membrane preparation process for the generation of numerous papillae with the diameter of 200–300nm by adjusting the phase separation process during the membrane formation. The test results of filtration fouling showed that the bionic PVDF membrane exhibited different fouling resistances between the adhesive pollutants (e.g. bovine serum albumin, BSA) and the cake layer pollutants (e.g. sodium alginate, SA) due to the different fouling layers formed on top of the papillae structure. The water flux recovery ratio (FRR) value of bionic PVDF membrane was still higher than 90% even after three fouling cycles with the SA pollutant solution. Meanwhile, this novel modified PVDF membrane also exhibited expected antifouling performance to the sewage. The novel preparation method of bionic membrane exhibits a significant effect for enhancing the antifouling performance of ultrafiltration process with cake layer formed, and can provide new insight into the formation of separation membranes with regulated surface structure.

Antifouling and High Flux Sulfonated Polyamide Thin-Film Composite Membrane for Nanofiltration

A new sulfonated aromatic diamine monomer, potassium 2,5-bis(4-aminophenoxy)benzenesulfonate (BAPBS), was synthesized and employed to develop a series of thin-film composite (TFC) nanofiltration membranes with trimesoyl chloride (TMC) on a polysulfone (PSF) substrate by an interfacial polymerization (IP) technique. The TFC membrane performed a high water flux of 72.8 L m–2 h–1 and a rejection of 92.5% to Na2SO4 at 0.6 MPa. The surface hydrophilicity of the as-prepared sulfonated polyamide (SPA) membrane was greatly improved by the introduction of sulfonic acid groups, as confirmed by the much reduced contact angle value. Moreover, the membrane also exhibited good antifouling ability with water flux recovery ratio (FRR) and total flux decline ratio (DRt) of about 88% and 18%, respectively. Molecular dynamics simulation was investigated to obtain an in-depth understanding of the transport behaviors of water molecules through the SPA polymers. The results clearly illustrated that the diffusion coefficient of...

Enhanced antifouling performance of hybrid PVDF ultrafiltration membrane with the dual-mode SiO2-g-PDMS nanoparticles

Abstract The polydimethylsiloxane modified silica (SiO2-g-PDMS) nanoparticles with hydrophilic core and hydrophobic shell are employed for the hybridization modification of PVDF ultrafiltration membrane to improve the separation and antifouling performances. The results suggest the modified SiO2-g-PDMS nanoparticles exhibit improved dispersion and significant amphiphilic characteristics, and the wetting properties of membrane surface and mimetic matrix of hybrid PVDF membranes are distinctly different with the contact angle values at 105° and 15°, respectively. In addition, the added SiO2-g-PDMS nanoparticles significantly improve the fouling repulsion and fouling release properties of hybrid PVDF membranes, the anti-adsorption ability and water flux recovery ratio (FRR-W) of hybrid PVDF membranes to the two typical pollutants of bovine serum albumin (BSA) and humic acid (HA) have been significantly improved. This article aims to provide a simple way to improve the antifouling performance of PVDF ultrafiltration membrane with dual-mode multi-functional modifier.

Ultrafiltration using graphene oxide surface-embedded polysulfone membranes

Abstract The effect of a hydrophilic layer of graphene oxide on polysulfone membranes was investigated to improve the antifouling properties of the membrane in ultrafiltration. Polysulfone membranes were obtained by the phase inversion method. Polyvinylpyrrolidone was added to generate pores in the membranes, and then a layer of graphene oxide was deposited on the prepared membranes using a vacuum-assisted filtration technique. This study investigated the cross-section/surface morphology, the water-contact angle, and the chemical structure of the prepared polysulfone/graphene oxide membranes. Due to the highly oxygenated structure of the graphene oxide, the surface hydrophilicity of the polysulfone membrane was significantly increased by applying a layer of graphene oxide. Moreover, the antifouling abilities of the membranes were evaluated by comparing the water-flux recovery ratio between the pure water flux before and after ultrafiltration.

Design of PVDF/PEGMA-b-PS-b-PEGMA membranes by VIPS for improved biofouling mitigation

Literature on the design of efficient nonfouling membranes by in-situ modification is poor, which can be explained by the difficulty to control membrane formation mechanisms when a third material is added to the casting solution, or by the lack of stability of matrix polymers with surface-modifiers. We present polyvinylidene fluoride membranes formed by vapor-induced phase separation and modified with a tri-block copolymer of poly(styrene) and poly(ethylene glycol) methacrylate moieties (PEGMA124-b-PS54-b-PEGMA124). After characterizing the copolymer, we move onto membrane formation mechanisms. Membrane formation is well controlled and leads to structure close to bi-continuous. Considering the formulation chosen, PVDF/PEGMA124-b-PS54-b-PEGMA124 solutions are less viscous and more hydrophilic than virgin PVDF solutions. Both effects promote non-solvent transfer, thus decreasing the chances for crystallization. Hydrophilic capability of membranes is increased from about 59mg/cm3 to 650mg/cm3, leading to a severe drop of non-specific protein adsorption, up to 85–90%, also depending on its nature. Biofouling at the micro-scale by modified Escherichia coli and Streptococcus mutans is almost totally inhibited. Finally, biofouling is importantly reduced in dynamic conditions, as measured from the water flux recovery ratio of 69.4%, after 3 water-BSA filtration cycles, much higher than with a commercial hydrophilic PVDF membrane (47.3%). These membranes hold promise as novel materials for water-treatment or blood filtration.

Antifouling ultrafiltration membrane fabricated from poly (arylene ether ketone) bearing hydrophilic hydroxyl groups

ABSTRACTA new kind of membrane formation polymer, cardo poly(arylene ether ketone) bearing hydrophilic hydroxyl groups (PEK‐OH) was synthesized from the biphenol monomer 2‐(2‐hydroxyethyl)‐3, 3‐bis (4‐hydroxyphenyl)‐isoindolin‐1‐one (PPH‐OH), and 4, 4′‐difluorodiphenylketone. PEK‐OH asymmetric ultrafiltration membranes were prepared using the immersion coagulation phase inversion method. The PEK‐OH membrane prepared using the optimized conditions exhibited a pure water flux of 516 ± 18 L·m−2·h−1 and a 99.1 ± 1.4% rejection of bovine serum albumin (BSA) at an operating pressure of 0.1 MPa. The contact angle of PEK‐OH membrane was 66.0 ± 2.4 lower than these of the PEK‐C membrane (87.0 ± 2.8°, prepared from polymer PEK‐C under the same membrane formation condition as PEK‐OH membrane) and the UE50 membrane (84.0 ± 1.6°, a commercial PES ultrafiltration membrane). The amount of BSA protein adsorbed to the PEK‐OH membrane under static condition was measured to be 3.12 μg·cm−2, which was greatly lower than that of 88.71 μg·cm−2 and 74.40 μg·cm−2 for the PEK‐C and the UE50 ultrafiltration membranes, respectively. Under dynamic filtration of BSA experiments, the PEK‐OH ultrafiltration membrane showed a 78.3% water flux recovery ratio, while only a 39.7% for the PEK‐C membrane and 46.5% for UE50 membrane were detected in the first cycle. After three cycles of BSA and LYZ filtration, the flux recovery ratio of PEK‐OH ultrafiltration membrane changed to be stable at 75% and 73%, while that of PEK‐C and UE50 ultrafiltration membranes remained declining gradually. Thus, hydrophilic PEK‐OH improves antifouling membrane property. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42809.

Efficient Preparation of Super Antifouling PVDF Ultrafiltration Membrane with One Step Fabricated Zwitterionic Surface.

On the basis of the excellent fouling resistance of zwitterionic materials, the super antifouling polyvinylidene fluoride (PVDF) membrane was efficiently prepared though one-step sulfonation of PVDF and polyaniline blend membrane in situ. The self-doped sulfonated polyaniline (SPANI) was generated as a novel zwitterionic polymer to improve the antifouling property of PVDF ultrafiltration membrane used in sewage treatment. Surface attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface zeta potential, and water contact angle demonstrated the successful fabrication of zwitterionic interface by convenient sulfonation modification. The static adsorption fouling test showed the quantified adsorption mass of bovine serum albumin (BSA) pollutant on the PVDF/SPANI membrane surface decreases to 3(±2) μg/cm(2), and the water flux recovery ratio (FRR) values were no less than 95% for the three model pollutants of BSA, sodium alginate (SA), and humic acid (HA), which were corresponding hydrophobic, hydrophilic, and natural pollutants in sewage, respectively. This Research Article demonstrated the antifouling advantages of zwitterionic SPANI and aimed to provide a simple method for the large scale preparation of zwitterionic antifouling ultrafiltration membranes.

Preparation and characterization of superior antifouling PVDF membrane with extremely ordered and hydrophilic surface layer

Polyvinylidene fluoride (PVDF) membranes with ordered and super hydrophilic surface were prepared though the self-assembly of anionic polyelectrolyte sodium alginate and amino functionalized SiO2 nanoparticles, which were employed to tune the antifouling property of PVDF membrane though ordered and hydrophilic nanoscale surface. The assembly sites were introduced though the reaction between trimesoyl chloride and the reactive groups on plasma treated membrane surface. The physical and chemical properties of the membrane surface were closely related to the assembly number, since the assembled layer could effectively reduce the probability of absorption on membrane surface and entering membrane pores of pollutants to minimize the irreversible fouling at the maximum level. The modified PVDF membranes exhibited excellent hydrophilicity with obviously decreased surface contact angle, which distinctly enhanced the antifouling properties for humic acids and bovine serum albumin with secondary water flux recovery ratio (FRR) of nearly 100%. This paper aimed to provide an effective method to take the advantage of hydrophilic and ordered nanoscale surface to optimize the separation efficiency and antifouling performance of hydrophobic separation membrane.

Improving the fouling resistance of brackish water membranes via surface modification with graphene oxide functionalized chitosan

Fouling of reverse osmosis (RO) membrane is a challenging and restricting aspect in membrane filtration performance, therefore new methods are required to enhance membrane antifouling properties. In this study, a novel surface modification technique for commercial brackish water (BW30LE) thin-film composite (TFC) membrane was applied by using graphene oxide (low GO1 and high GO2) functionalized chitosan (GO/f-Cs). All the membranes including the unmodified one were treated with 200ppm of sodium hypochlorite and were further characterized by contact angle, scanning electron microscope, atomic force microscopy, UV spectrophotometer and ATR-FTIR. The obtained GO/f-Cs/polyamide (PA) composite membranes showed a superior performance compared to the unmodified PA (TFC) membrane in terms of hydrophilicity, surface smoothness, NaCl rejection, water flux and antifouling property. The unmodified membrane, GO1/f-Cs/PA (M1) and GO2/f-Cs/PA (M2), exhibited permeation fluxes of 56.1, 48.5 and 61.5L/m2h and salt rejections of 88.7%, 95.4% and 95.6%, respectively, using 1500mg/L NaCl concentration as a feed solution under 14bar. To examine the membrane's dynamic fouling resistance, cross-flow filtration tests were conducted using bovine serum albumin (BSA). M2 membrane had less flux decline than the unmodified one, and achieved 97% water flux recovery ratio by only water cleaning.

Novel polyethersulfone hybrid ultrafiltration membrane prepared with SiO2-g-(PDMAEMA-co-PDMAPS) and its antifouling performances in oil-in-water emulsion application

To avoid the agglomeration of nanoparticles (NPs) in hybrid membranes and alleviate the leakage of NPs during the oily wastewater treatment process, poly(2-(dimethylamino)ethylmethacrylate-co-3-dimethyl(methacryloyloxyethyl)ammoniumpropanesulfonate) (PDMAEMA-co-PDMAPS) grafted silica (SiO2) [SiO2-g-(PDMAEMA-co-PDMAPS)] NPs were prepared by grafting PDMAEMA brushes onto SiO2 NPs surface via the surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (Si-ARGET ATRP). Subsequently, the quaternization of the tertiary amine groups in PDMAEMA and 1,3-propanesultone was performed to get [SiO2-g-(PDMAEMA-co-PDMAPS)] NPs. Then, the organic–inorganic hybrid polyethersulfone (PES) membranes with different ratios of SiO2 NPs (m membranes) and SiO2-g-(PDMAEMA-co-PDMAPS) NPs (M membranes) were fabricated via the non-solvent induced phase separation (NIPS) process. Transmission electron microscopy (TEM) images demonstrated that the modification of SiO2 NPs with PDMAEMA-co-PDMAPS was favorable for their homogeneous dispersion in organic solvents. The results of scanning electron microscopy (SEM) images indicated that the surface porosity and mean pore size of hybrid membranes were increased compared to the neat PES membrane. Furthermore, the M membranes exhibited better hydrophilicity, pure water flux and oil flux than neat PES membrane and m membranes. It was found from filtration results that the total fouling (Rt) and irreversible fouling (Rir) were significantly reduced due to higher hydrophilicity of hybrid membranes. In addition, after oil-in-water emulsion filtration, M membranes exhibited higher water flux recovery ratio (FRR) value than that of m membranes and neat PES membrane.

Effect of reduced graphene oxide/TiO2 nanocomposite with different molar ratios on the performance of PVDF ultrafiltration membranes

A partially reduced graphene oxide (rGO)/TiO2 nanocomposite with five different molar ratios (rGO/TiO2: 3/97, 30/70, 50/50, 70/30 and 90/10) were synthesized and characterized using X-ray diffraction and scanning electron microscopy (SEM) techniques. The polyvinylidene fluoride (PVDF) mixed matrix membranes containing 0.05wt.% of the nanocomposites were prepared by phase inversion method. The effect of rGO/TiO2 additive on the morphology and performance of prepared blended membranes was studied by atomic force microscopy (AFM), SEM, energy dispersive X-ray (EDX), FTIR, water contact angle, porosity and permeation measurements, rejection tests and antifouling parameters. The SEM images revealed finger-like structure of the membranes and EDX analysis confirmed well distribution of rGO/TiO2 nanocomposite in the polymer matrix. The rGO/TiO2/PVDF membranes showed enhanced hydrophilicity, higher pure water flux and flux recovery ratio compared to the bare PVDF. A comparison of pure water flux of TiO2 and rGO/TiO2 containing membranes showed that dispersion of inorganic TiO2 nanoparticles on the GO surface decreased the aggregation of the nanoparticles and improved the characteristics of the resulted mixed matrix membrane. The blended membrane containing 0.05wt.% rGO/TiO2 nanocomposite with GO to TiO2 ratio of 70/30 showed improved permeability and antifouling performance.