Microporous Poly Vinylidene Fluoride Research Articles

Printed Capacitive Immunoassay for Detecting SARS-CoV-2 Viral Particles

The key to fight against a global pandemic such as COVID-19 is to have low-cost, reliable and fast response diagnostic tools. Electronic biosensors are preferred because of their ease of integration into current centralized health care networks and integration with modern point-of-care testing (POCT) devices. Printed electronic sensors provide a sensitive and reliable diagnostic platform to aid in controlling transmissible diseases. In this work, we demonstrate a fully printed capacitive biosensor. The sensor uses coplanar electrodes, coupled with capture antibodies immobilized on microporous Polyvinylidene-fluoride (PVDF) film to detect the SARS-CoV-2 spike protein in spiked buffer solutions. Antibody immobilization on PVDF surface is confirmed with confocal fluorescent imaging microscopy. Gold nanoparticle (GNP) tagged detection antibodies are also introduced to provide increased sensitivity. The gold nanoparticles provide a reflectance layer which leads to increased capacitance. This increased capacitance can be measured directly and has demonstrated the ability to screen for spiked samples with statistical significance. This fully printed capacitive immunoassay has the potential to be used as a transmissible disease screening and vaccine efficacy assessment tool for resource-limited areas.

Uncovering the role of algal organic matter biocoating on Navicula incerta cell deposition and biofilm formation

ABSTRACTSpontaneous natural biofilm concentrates microalgal biomass on solid supports. However, the biofilm is frequently susceptible to exfoliation upon nutrient deficiency, particularly found in aged biofilm. Therefore, this study highlights a novel biofilm cultivation technique by pre-depositing the algal organic matters from marine diatom, Navicula incerta onto microporous polyvinylidene fluoride membrane to further strengthen the biofilm developed. Due to the improvement in membrane surface roughness and hydrophobicity, cells adhered most abundantly to soluble extrapolymeric substances-coated (sEPS) (76×106±16×106 cells m−2), followed by bounded EPS-coated (57.67×106±0.33×106 cells m−2), internally organic matter (IOM)-coated (39.00×106±5.19×106 cells m−2), and pristine control the least (6.22×106±0.77×106 cells m−2) at 24th h. Surprisingly, only bEPS-coated membrane demonstrated an increase in cell adhesion toward the end of the experiment at 72 h. The application of the bio-coating has successfully increased the rate of cell attachment by at least 45.3% upon inoculation and achieved as high as 89.9% faster attachment at 72 hours compared to the pristine control group. Soluble polysaccharides and proteins might be carried along by the cells adhering onto membranes hence resulting in a built up of EPS hydrophobicity (>70% in average on bio-coated membranes) over time as compared with pristine (control) that only recorded an average of approximately 50% hydrophobicity. Interestingly, cells grown on bio-coated membranes accumulated more internally bounded polysaccharides, though bio-coating had no discernible impact on the production of both externally and internally bounded protein. The collective findings of this study reveal the physiological alterations of microalgal biofilms cultured on bio-coated membranes.

Separation Mechanisms and Anti-Fouling Properties of a Microporous Polyvinylidene Fluoride-Polyacrylic Acid-Graphene Oxide (PVDF-PAA-GO) Composite Membrane with Salt and Protein Solutions.

This research demonstrates the preparation of composite membranes containing graphene oxide (GO) and investigates the separation mechanisms of various salts and bovine serum albumin (BSA) solutions. A microporous polyvinylidene fluoride-polyacrylic acid-GO (PVDF-PAA-GO) separation layer was fabricated on non-woven support. The GO-incorporating composite resulted in enlarged pore size (0.16 μm) compared with the control membrane (0.12 μm). The zeta potential of the GO composite was reduced to -31 from -19 mV. The resulting membranes with and without GO were examined for water permeability and rejection efficiency with single salt and BSA solutions. Using the non-woven/PVDF-PAA composite, the permeance values were 88-190 kg/m2hMPa, and the salt rejection coefficients were 9-28% for Na2SO4, MgCl2, MgSO4, and NaCl solutions. These salt removals were based on the Donnan exclusion mechanism considering the ion radii and membrane pore size. Incorporating GO into the separation layer exhibited limited impacts on the filtration of salt solutions, but significantly reduced BSA membrane adhesion and increased permeance. The negatively charged protein reached almost complete removal (98.4%) from the highly negatively charged GO-containing membrane. The GO additive improved the anti-fouling property of the composite membrane and enhanced BSA separation from the salt solution.

Using Cu-TCPP Nanosheets as Interlayers for High-Performance Organic Solvent Nanofiltration Membranes

The development of highly permeable and selective thin-film composite (TFC) membranes is essential for organic solvent nanofiltration (OSN) applications. However, overcoming the permeability–selectivity trade-off in polymer membranes remains highly challenging owing to the difficulty in controlling the thickness and nanostructures of the selective layers. In this study, TFC OSN membranes with sandwich-like structures were developed via interfacial polymerization on Cu-TCPP nanosheet-modified microporous polyvinylidene fluoride (PVDF) substrate surface. The interfacial polymerization was done by using mixed amine (polyethyleneimine and piperazine) in the aqueous phase and the 1,3,5-benzenetricarbonyl trichloride in the hydrophobic ionic liquid phase as monomers. It was found that the Cu-TCPP nanosheets of micrometer lateral dimensions and nanometer thickness (1.5 ± 0.6 nm) can be deposited on the PVDF substrate as an interlayer to facilitate the following interfacial polymerization reaction. The Cu-TCPP interlayer also can be served as a binder between the polyamide selective layer and the microporous PVDF substrate to enhance their mechanical strength. As compared with the PVDF/PA membrane, the PVDF/t-Cu-TCPP/PA membrane exhibited higher elongation (8.0 vs. 4.6%) while ensuring slightly lower tensile strength (36.0 vs. 48.6 MPa). Under optimal synthetic conditions, the TFC membranes could achieve 2.7 L m–2 h–1 bar–1, and 98.9% and 95.0% rejection to Brilliant Blue R (826 Da) and Congo red (697 Da), respectively, in ethanol. Furthermore, the membranes showed steady performance throughout the 36 h nanofiltration of the Rose bengal/ethanol mixture and exhibited good performance in the concentration of lecithin in methanol. Accordingly, this work highlights the potential of using thin metal–organic framework nanosheets as interlayers to develop high-performance TFC membranes for OSN applications.

Algal extracellular organic matter pre-treatment enhances microalgal biofilm adhesion onto microporous substrate

Adhesive biocoating has microstructure composed of biomolecules to entrap viable cells in a stabilized matrix over exposed surfaces. Although marine benthic diatoms are a common group of algae excreting substantial amount of extracellular polymeric substances (EPS), studies regarding the utilization of these EPS are scarce. Using the soluble EPS derived from Navicula incerta and pre-deposition of it as a thin conditioning layer on microporous polyvinylidene fluoride (PVDF) membranes, the pre-coated surface was used to investigate the cell binding affinity of three marine microalgae, namely Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta. Microalgae actively engaged themselves on the pre-coated membranes which was 10 times greater than the initial cell adhesion degree. Soluble EPS is mainly comprised of polysaccharide while bounded EPS is mainly comprised of protein. On EPS pre-coated membranes, N. incerta released the least amount of bounded polysaccharides (<100 mg m−2) and vice versa for the other two because EPS production is usually maximized to assist cell adhesion onto unfavorable substrates. In stark contrast, when the adaptation period (first 6 h) ended, cells began to secrete more bounded protein for cell growth, and an increasing trend of protein content found in N. incerta has verified its optimal adaptation onto the biocoating itself. On pristine PVDF membranes, the adhesion degree was ranked in ascending order: C. fusiformis, N. incerta and A. coffeaeformis. Interestingly, after the pre-coating process, the order was reported as: A. coffeaeformis, N. incerta and C. fusiformis, but it should be noted that C. fusiformis demonstrated fluctuating cell colonization degree and bounded EPS production over time. In other words, the biofilm's susceptibility was confirmed since the cells latched loosely on the membranes rather than in a biofilm matrix. Biocoating enables uniform cell distribution and firmer biofilm growth, opening the door to vast future applications in environmental bioremediation and sensing.

Coalescence of stable oil/water emulsion through microporous polyvinylidene fluoride membranes

This work presents the factors that determine the coalescence of the micron-sized oil droplets (<0.4 μm) and the permeation flux by using two different types of commercial flat-sheet microporous polyvinylidene fluoride (PVDF) membranes. Results show that the PVDF-Westran membrane coalesced the oil droplets up to 1.1 μm while the PVDF-Synder membrane enlarged the oil droplets to approximately 5.6 μm. The pore size distribution instead of the both casted and fibrous membrane structures influenced the coalescence of the oil droplets. The membrane feed side that comprised of the smaller pores exhibited better in the coalescence while the pore size on the membrane permeate side did not show the significant effect on the coalescence. The water permeation flux was proportional to the pore size of the membrane feed side while the permeation flux during the coalescence was inversely proportional to the membrane pore size. The oil droplets in the feed solution has reduced the permeation flux about 10 times lower. The addition of the polyacrylamide in the oily water has essentially fouled the membranes at least 1.4 times higher and the foulant has induced the cleavage effect on the oil droplets.

In-situ manipulation of gel layer fouling into gel layer membrane formation on porous supports for water treatment

The inaccessibility of clean water is one of the growing issues of this era. Indeed, cost-effective and sustainable methods for recycling wastewater are essential. Although membrane separation is an efficient technology for the recycling and purification of water, membrane fouling is still a major drawback of this technology. This work is aimed to develop a dynamic method to form gel layer membranes (GLMs) by manipulating the irreversible fouling process itself as a problem-solving approach. A microporous polyvinylidene fluoride (PVDF) support is subjected to gel layer formation by applying a supernatant of industrial aerobic sludge (containing soluble extracellular polymeric substances EPS) as a feed. Retention of polysaccharides and calcium during the filtration and the topographical analysis after the filtration show that EPS uniformly formed a gel layer on the PVDF support. No further decline in permeability is observed (i.e. remained around 27–33 L/m 2 hr) when the formed GLM is subjected to fouling under similar conditions. Moreover, the percent flux recovery ratio (FRR) of the GLM is also significant (i.e. 90.1 ± 2.71). The retention ability, hydrophilicity, porosity, and water uptake capability of the formed GLM also increased significantly. The optimal performance and stability of GLMs are observed at room temperature (RT) under neutral pH and sub-critical trance membrane pressures (TMP). Based on these results it is suggested that the in-situ manipulation of gel layer fouling is a viable approach for preparing fouling resistant GLMs with high retention efficiency, potentially applicable to wastewater treatment under normal conditions.

Comprehensive insights into performance of water gap and air gap membrane distillation modules using hollow fiber membranes

A commercially available microporous polypropylene hollow fiber membranes were employed for air gap and water gap membrane distillation (i.e., AGMD and WGMD, respectively) processes. In both configurations, the outer surface of commercially available dense polypropylene hollow fibers was used as the condensing surface of the permeate. The performance levels of the AGMD and WGMD processes utilizing microporous polyvinylidene fluoride membranes fabricated in-house were compared with those using polypropylene membranes. Under the given specific operating conditions, the maximum mean permeation flux values in AGMD and WGMD using polypropylene hollow fiber membranes were approximately 24 and 27 kg/m2h, respectively. In addition, theoretical studies on AGMD and WGMD using the designed hollow fiber module configuration were performed. The predicted results were found to well agree with the experimental results, thus verifying their validity. Moreover, parametric studies were conducted to identify the optimum evaporation-to-condensation surface area ratio (i.e., optimum numbers of hollow fiber membranes and hollow fiber condensers) in terms of specific energy consumption.

Towards a High-Flux Separation Layer from Hexagonal Lyotropic Liquid Crystals for Thin-Film Composite Membranes.

Hexagonal lyotropic liquid crystals (HLLC) with uniform pore size in the range of 1~5 nm are highly sought after as promising active separation layers of thin-film composite (TFC) membranes, which have been confirmed to be efficient for water purification. The potential interaction between an amphiphile-based HLLC layer and the substrate surface, however, has not been fully explored. In this research, hydrophilic and hydrophobic microporous polyvinylidene fluoride (PVDF) substrates were chosen, respectively, to prepare TFC membranes with the active layers templated from HLLC, consisting of dodecyl trimethylammonium bromide, water, and a mixture of poly (ethylene glycol) diacrylate and 2-hydroxyethyl methacrylate. The pore size of the active layer was found to decrease by about 1.6 Å compared to that of the free-standing HLLC after polymerization, but no significant difference was observable by using either hydrophilic or hydrophobic substrates (26.9 Å vs. 27.1 Å). The water flux of the TFC membrane with the hydrophobic substrate, however, was higher than that with the hydrophilic one. A further investigation confirmed that the increase in water flux originated from a much higher porosity was due to the synergistic effect of the hydrophilic HLLC nanoporous material and the hydrophobic substrate.

Separation of Carbon Dioxide by Potassium Carbonate based Supported Deep Eutectic Liquid Membranes: Influence of Hydrogen Bond Donor

This article focuses on the study of potassium carbonate (PC) based deep eutectic solvents based supported liquid membranes (DES-SLMs) for CO2 capture. A new class of green solvent was impregnated into microporous polyvinylidene fluoride (PVDF) membrane for the separation of CO2. Two types of DESs were synthesized by mixing and heating PC with glycerol or ethylene glycol separately. The novelty of this study lies in the exploitation of PC-DESs in the PVDF membrane. The mechanism of interaction was inferred from the spectral analysis (FTIR) whereas thermal analysis (TGA) was performed to analyze the stability of the prepared membrane. Experiments were performed to analyze the permeability and selectivity of the membranes. The results showed that PC-Glycerol based SLM exhibited permeability of 34.55 Barrer and ideal selectivity of 59.57 while PC-Ethylene Glycol based SLM exhibited permeability of 20.23 Barrer and ideal selectivity of 34.29 under similar operating conditions. Systematic analysis was made for some of the important operating parameters affecting the separation performance such as temperature and feed composition. Comparison was made between the performance of PC-DES-SLMs and conventional imidazolium based SILMs on the well-known Robeson’s upper bound plot. The current efforts of exploitation of PC-DES membrane will lead to new prospective for the efficient removal of CO2 from the industrial gas mixture.

Photothermal Sweeping Gas Membrane Distillation and Reverse Electrodialysis for light-to-heat-to-power conversion

Water and energy are two intimately interconnected issues of strategic relevance for a sustainable industrial development. Herein, we integrated light-harvesting/self-heating membranes and salinity gradient technology with the aim to implement the innovative concept of light-to-heat-to-power conversion.Novel photothermal membranes, prepared by immobilizing silver nanoparticles (AgNPs) on the top layer of microporous polyvinylidene fluoride (PVDF) matrix, were tested – for the first time – in a Sweep Gas Membrane Distillation (SGMD) unit applied to the desalination of synthetic seawater solution (0.5M NaCl). As a result of the ability of noble metal nanofillers to act as localized thermoplasmonic nano-heaters at membrane-feed interface for efficient water evaporation, an increase of transmembrane flux under UV radiation by about 10-fold with respect to unloaded PVDF membrane was observed.The SGMD retentate, consisting in hypersaline brine (progressively concentrated up to 4M NaCl and rejected at about 40°C) was fed to a Reverse Electrodialysis unit with the aim to harvest electrochemical energy. The maximum power density, measured for a retentate concentration increasing from 1M to 4M, raised from 0.13 to 0.9 W/m2MP (MP: RED membrane pair). Overall, the proposed integrated membrane system allowed to extract about 10% of the energy not employed for water evaporation.

Sulfonic nanohydrogelled surface-modified microporous polyvinylidene fluoride membrane with excellent antifouling performance for treating water-oil separation of kitchen wastewater

Kitchen wastewater containing high concentration of suspended solids, salt and oil is a comprehensive wastewater that requires urgent treatment. Organic fouling limits the use of membranes for treating kitchen wastewater. Herein, we propose a novel sulfonic nanohydrogel membrane with superhydrophilicity and underwater-superoleophobicity. A 32-nm-diameter sulfonic nanohydrogel Poly(SPP-co-MA-co-FLUORAL-P), developed by the polymerization technique in an aqueous medium, was grafted onto the polyvinylidene difluoride (PVDF) microfiltration membranes. The developed PVDF-g-Poly(SPP-co-MA-co-FLUORAL-P) membrane exhibited excellent antifouling properties for treating kitchen wastewater. The influence of organics (edible oil, surfactant, protein and humic acid) and salts on the membrane filtration was thoroughly investigated. The Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy techniques were used to confirm the successful surface modification. The experimental results revealed that the pure water flux was 2161 L m−2 h−1. A high oil rejection rate was achieved when the fabricated membrane was used for treating the simulated kitchen wastewater (˃99.7%). The excellent antifouling properties of the membrane significantly improved the circulation stability of the simulated kitchen wastewater filtration. The recovery rate of permeation flux was up to 100%. The chemical oxygen demand removal rate of the real kitchen wastewater was 61% and the flux recovery rate arrived at 98%. The PVDF-g-Poly(SPP-co-MA-co-FLUORAL-P) membrane can be potentially used for treating kitchen wastewater.

A Janus facilitated transport membrane with asymmetric surface wettability and dense/porous structure: Enabling high stability and separation efficiency

Facilitated transport membranes have been extensively applied in a myriad of industrial fields, in view of their distinctive capabilities of selective separation of target species (e.g., ions/small molecules). Despite much progress, it remains challenging to tackle the trade-off relationship between the stability and separation efficiency of these membranes. Herein, we propose a Janus facilitated transport membrane with asymmetric surface wettability and dense/porous structure by decorating a hydrophilic and dense polymer inclusion membrane (PIM) skin layer on the surface of a hydrophobic and microporous polyvinylidene fluoride (PVDF) membrane to achieve a notable balance between separation efficiency and leakage-resistance. With the hydrophilic PIM skin layer facing aqueous solutions whilst the hydrophobic PVDF membrane towards organic solution during separation process, the Janus facilitated transport membrane remarkably prevents the leakage of the liquids from 66.7% (using the plain PVDF membrane) to negligible. Through a rapid transformation of the transport mechanism from a short-term hopping in the dense PIM skin layer to an unobstructed motion in the microporous PVDF membrane matrix, the separation efficiency of the Janus facilitated transport membrane has been considerably enhanced from 25% (using the PIM) to about 70%. Investigation of the influencing factors on the structures, properties and separation performance of the Janus facilitated transport membrane suggests that the concentration of the PIM casting solution is of particular importance to the formation of the PIM skin layer and the asymmetric dense/porous structure of the membrane. In addition, the Janus facilitated transport membrane exhibits extraordinary mechanical properties and selectivity. Our work demonstrates that the Janus facilitated transport membrane holds great promise and a wide scope in versatile applications in water treatment, water-oil separation, and recovery of metal ions/small molecules in complex systems (e.g., water-oil-metal ions and water-oil-small molecules).

Multifunctional filtration membrane with anti-viscous-oils-fouling capacity and selective dyes adsorption ability for complex wastewater remediation

Multifunctional filtration membranes (MFMs), which can both effectively separate oil and selectively remove dyes from polluted aquatic system with robust anti-viscous-oil-fouling capacity, strong chemical/physical resistance, and long cycled stability, are highly required but still a challenge to be realized. Herein, a simple route has been demonstrated to address this challenge aforementioned by decorating both halloysite nanotubes (HNTs) and zwitterionic poly (sulfobetaine methyl methacrylate) (PSBMA) on the microporous polyvinylidene fluoride (PVDF) membrane surface via modified polydopamine (PDA) coating route. The as-prepared membrane exhibits super-hydrophilic/underwater super-oleophobic performance and high water permeation flux (32529 ± 278 L m−2 h−1 at 0.85 bar) to purify the diverse viscous oil-in-water emulsions from oily wastewater accompanying with good cycled stability (the recovery rate of permeate flux is close to 100% after 5 cycles). Moreover, the as-prepared MFM possesses not only strong chemical resistance under wide range of pH value (from 1 to 12) and high saline (NaCl: 10 wt%) environment, but also physical resistance against ultrasound bath for 30 min. Given the presence of HNTs, PDA, and PSBMA, our MFM shows enough active sites to adsorb the soluble dyes and metallic ions in wastewater. These excellent properties endow our MFM with great potential for the remediation of complex wastewater.

Molecularly grafted PVDF membranes with in-air superamphiphilicity and underwater superoleophobicity for oil/water separation

Microporous polyvinylidene fluoride (PVDF) based membranes are widely used in separation and purification applications, including oil/water separation. However, due to hydrophobic nature, these membranes are prone to high fouling and wetting by low surface tension liquids and substances, thereby limiting its full potential in many important applications such as oil/water separation. Herein, we present a simple and straight forward method to modify and produce in-air superamphiphilic and under-water superoleophobic PVDF membranes by molecular grafting using three different amino silanes. The molecular grafting imparted novel properties due to the combined effect of chemistry, nanostructuring, and roughness. After grafting, the membranes exhibited in-air superamphiphilicity in both dry and wet conditions. In water, the membrane does not allow the attachment of oil droplets, making it superoleophobic. However, when placed under oil, the membrane showed superhydrophobicity but still allowed the adhesion of water droplets. After thorough characterization for structure, modification, and physicochemical properties, the membranes were tested for oil/water mixture separation. The functionalized membranes showed > 99% oil rejection and flux recovery. These results showed great promise for molecular grafting of membranes for separation and purification applications.

Novel Poly Deep Eutectic Solvents Based Supported Liquid Membranes for CO2 Capture

The poly deep eutectic solvents (PDESs), a potential substituent to ionic liquids, have emerged as relatively new material and have been successfully applied in catalysis, nanotechnology, and, more importantly, in gas separation. Herein, the PDESs were incorporated for the first time in the CO2 capturing membranes to exploit their inherent advantages in acid gas capture. The PDESs were synthesized by mixing choline chloride (hydrogen bond acceptor-HBA) and two hydrogen bond donors-HBDs (polyacrylic acid &amp; polyacrylamide) separately in different molar ratios. The physical changes of the resulting homogeneous mixture along with the FTIR confirmed the successful synthesis of the PDESs. Afterward, these PDESs were impregnated into microporous polyvinylidene fluoride (PVDF) membrane support to fabricate supported liquid membranes (SLMs). The gas performance of the prepared PDES-SLMs was tested under pure and mixed-gas conditions for CO2, CH4, and N2. The factors affecting the practical application of SLMs, such as the effect of composition of the PDESs, temperature, and volume fraction of the CO2 in the feed gas, were investigated systematically. The prepared PDES-SLMs showed significant CO2 permeabilities up to 27 Barrer as well as remarkably high CO2/CH4 and CO2/N2 selectivities of the order of 55.5 and 60, respectively. It was observed that by increasing the choline content and the temperature, the activation energy required for CO2 capture decreased, which enhanced the membrane performance (permeability and selectivity). This can be ascribed to the basicity, molar free volume, and the H-bonding strength of the synthesized PDESs. The green potential, low cost, and the significant gas separation performance make theses PDESs a favorable alternative to the competing PILs in capturing the greenhouse acid gases.

Effect of Different Pore-Forming Additives on the Formation of PVDF Microporous Membranes for Bucky-Gel Actuator

The microporous polyvinylidene fluoride (PVDF) membranes were prepared by the solvent evaporation method using 50 wt.% of different pore-forming additives: poly(1-ethyl-3-vinylimidazolium tetrafluoroborate) (PIL-BF4), polyethylene glycol 3000 (PEG-3K) and 40000 (PEG-40K), dibutyl phthalate (DBP). The influence of used additive on morphology, porosity, degree of crystallinity, tensile properties, electrolyte uptake and ionic conductivity of the membranes were investigated. The maximum electrolyte uptake of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) was 184 wt.% for the membrane prepared with PEG-40K, however, the membrane was fragile and unsuitable for practical use. The remaining membranes showed approximately the same porosity (45‒48%) and electrolyte uptakes (169‒175%). At the same time, the membranes significantly differed in mechanical properties and ionic conductivity. The membrane prepared with PIL-BF4, unlike others, has a sponge-like structure and demonstrated high mechanical properties, namely tensile strength is 17.7 MPa and fracture strain is 132.5%. Bucky gel actuators were fabricated using membranes prepared with different additives. The blocking force of the actuators based on membranes with different additives decreased in the sequence of PIL-BF4, DBP and PEG. The actuator based on the membrane prepared with PIL-BF4 demonstrates a blocking force of 5.7 mN and a deformation of 1.35 % at 3 V DC.

Development of hydrogen selective microporous PVDF membrane

Hydrogen is a sustainable clean and green energy source used to eliminate the problem of greenhouse effect. In the present work, the feasibility of gas permeability in separation of H2 from CO2 and N2 have been examined using polyvinylidene fluoride (PVDF) membranes synthesised in our laboratory by the phase inversion process. Effect of various non-solvent additives, such as lithium chloride (LiCl) and Tetraethoxysilane (TEOS) in the PVDF dope solution, have been studied. The resulted asymmetric flat sheet microporous hydrophobic membrane, shows higher hydrogen permeability and selectivity over other gases (CO2 & N2). It has been observed that the MT5 membrane has shown the highest selectivity for hydrogen in comparison to CO2 and N2. The highest value of selectivity was obtained as 4.8 and 3.7 in case of H2/CO2 and H2/N2 respectively. The permeability of membrane has been obtained in the range of 2.3–4.2 mega barrer. SEM analysis is used for the investigation of membrane surface morphology.

Coupling visible light sono-photocatalysis and sono-enhanced ultrafiltration processes for continuous flow degradation of dyestuff using N-doped titania nanoparticles

Sono-photocatalysis has potential to increase the efficiency of both sonolysis and photocatalysis processes. On the other hand, in the sono-enhanced membrane separation processes the ultrasonic waves are able to clean the membrane surface, inhibit its fouling and enhance the separation efficiency. In this work, visible-light sono-photocatalysis and sono-enhanced membrane separation processes were coupled in a one pot/hybrid reactor for continuous flow removal of a dyestuff from water. First, N-doped titania sono-photocatalyst and microporous polyvinylidene fluoride membrane were prepared and characterized. Then, the hybrid reactor was set for the dyestuff degradation. The effect of operational variables including N-doped titania dosage, pH, retention time, visible-light power, radical scavengers and inorganic oxidants on the degradation efficiency was investigated. An enhancement in the degradation efficiency was observed by adding inorganic oxidants and increasing the retention time and visible light power. However, the degradation efficiency was decreased by increasing pH and adding organic and inorganic radical scavengers. 750 mg/L was the optimum N-doped titania dosage. The efficiency of the hybrid process was higher than other probable processes and the synergistic effect between photocatalysis and sonolysis was 23.51%. Main intermediates of dyestuff degradation were identified and a plausible degradation pathway was proposed using GC-MS analysis.

Preparation and characterisation of new microporous Elvaloy4170 coated PVDF membrane for desalination by air gap membrane distillation

The demand to fabricate membranes much cheaper than usual expensive methods creates an opportunity to find low-cost and more available modifying agents for synthesising an appropriate membrane for membrane distillation (MD) process. In this work, reactive ethylene terpolymer was applied to modify a commercial polyvinylidene fluoride (PVDF) membrane for using in the desalination process. Elvaloy4170 with a hydrophobic structure containing three different functional groups was coated (different contents of 0.5, 1, 1.5 and 2 wt%) on the top surface of the microporous commercial PVDF membrane and the resultant membranes were analysed under air-gap MD process. The fabricated membrane structures were determined by scanning electron microscopy and atomic force microscopy to investigate their elemental and topographical properties. After experiments, the membrane with 1.5 wt% of Elvaloy4170 showed water vapour flux of 1.93 kg/m 2 h and salt rejection of >99.7 which confirmed its suitability to be used in the desalination process. Moreover, to assess the anti-fouling properties of the membranes, real seawater was used as feed solution, and as a result the membrane with 1.5 wt% of Elvaloy4170 presented flux recovery of 87% indicating its enhanced anti-fouling properties compared with the commercial PVDF membrane (flux recovery of 71%).