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Herein the ZIF‐67, a hydrophilic cobalt‐based zeolitic imidazolate framework is synthesized and incorporated with a poly(vinylidene fluoride) (PVDF) to fabricate hybrid ultrafiltration membranes by phase inversion method. The characteristics of PVDF/ZIF‐67 membranes are examined using different analytical techniques such as Fourier‐transform infrared spectroscopy, X‐ray diffractometer, scanning electron microscope, atomic force microscope, and contact angle analysis. The membrane performance is probed using pure water flux (PWF), bovine serum albumin (BSA), and humic acid (HA) rejection. The maximum water flux of 162.5 Lm2 h−1 with BSA and HA rejection of 97% and 98.2%, respectively, exhibited by 1.5 wt% ZIF‐67. The contact angle value is reduced from 83.5 to 58.6° indicating the increase in hydrophilic nature of PVDF membranes by the addition of ZIF‐67. The presence of ZIF‐67 in the PVDF membrane matrix showed outstanding anti‐bacterial properties against Escherichia coli and Staphylococcus aureus. Overall, the PVDF/ZIF‐67 ultrafiltration membranes demonstrate the potential for water treatment applications. [ABSTRACT FROM AUTHOR]

Highly hydrophilic and antifouling poly(vinylidene fluoride) (PVDF) ultrafiltration membranes are developed with excellent permeation using a zirconium‐based metal–organic framework (MOF‐801). MOF‐801 is synthesized by a solvothermal method using zirconium(IV) oxychloride octahydrate (ZrOCl2⋅8H2O) and fumaric acid. The chemical functionality of MOF‐801 is studied by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) whereas surface morphology and elemental composition are probed by scanning electron microscopy (SEM)/energy‐dispersive X‐ray analysis (EDX). The PVDF/MOF‐801 membranes are characterized in terms of FTIR, XRD, FESEM/EDX and atomic force microscopy. The performance of the hybrid PVDF/MOF‐801 membranes in terms of pure water flux and antifouling ability is found to be improved compared with bare PVDF membranes. The wettability of the membranes is measured by water contact angle and found to be 76.7° for bare PVDF membrane, which decreases upon the addition of MOF‐801 to 55.1° due to the increase in surface hydrophilicity. A notable increase in roughness of 226.29 nm and a porosity of 67.91% is observed for the addition of 2 wt% MOF‐801 in PVDF membrane matrix. The flux recovery ratio of the hybrid membrane is increased from 66.4% to 89.6% and from 68.3% to 85.2% for bovine serum albumin (BSA) and humic acid (HA) separation, respectively. In addition, the reversible and irreversible fouling performance during the rejection of BSA (93%) and HA (88%) indicates the enhanced antifouling property of the PVDF/MOF‐801 membranes. A zone of inhibition test evidences the outstanding antibiofouling activity of the PVDF/MOF‐801 membranes against E. coli and S. aureus. Overall results demonstrated the suitability of hybrid PVDF/MOF‐801 membranes for water and wastewater treatment. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Silver‐loaded iron‐based metal–organic frameworks (Ag@FeBTC) are synthesized and incorporated with poly (vinylidene fluoride) (PVDF) to make hybrid ultrafiltration (UF) membranes and are efficiently utilized to treat water containing macromolecular pollutants. The chemical functionality and semi‐amorphous nature of the Ag@FeBTC are validated by FT‐IR and XRD, respectively. The morphology and elemental composition of PVDF/Ag@FeBTC membranes are probed by SEM and EDX mapping. The creation of pores is visibly seen in cross‐sectional SEM images and the improvement in roughness is noticed in AFM images. Because of the improved hydrophilicity of Ag@FeBTC on the PVDF membrane matrix, the contact angle is reduced to 33.9°. The excellent dispersion of Ag@FeBTC on the PVDF membrane matrix is observed through elemental mapping. The PVDF/Ag@FeBTC hybrid membranes exhibited higher pure water flux (160 L m−2 h−1) and greater than 90% rejection as well as flux recovery ratio for foulant removal (BSA and HA). The antimicrobial property of PVDF/Ag@FeBTC hybrid membranes is probed using a zone of inhibition test against E. coli and S. aureus, and the results revealed that the hybrid membranes possess superior antibacterial behavior. The long‐term stability of MOF in hybrid membranes is confirmed by AAS. Overall characterization and performance results of the hybrid PVDF/Ag@FeBTC UF membrane clearly demonstrated its potential use for water treatment applications. [ABSTRACT FROM AUTHOR]

This study deals with the making of poly(vinylidene fluoride) (PVDF) hybrid ultrafiltration (UF) membranes incorporated with zeolitic imidazolate framework‐8 (ZIF‐8) nanocrystals. The surface morphology and roughness of ZIF‐8 are explored in terms of atomic force microscopy (AFM) and scanning electron microscopy (SEM) whereas their distribution in PVDF matrix and antibacterial activity are probed by energy dispersive X‐ray (EDX) analysis and zone of inhibition test. The chemical functionality of ZIF‐8 is verified by Fourier transform infrared (FTIR) and X‐ray diffraction (XRD) spectroscopic studies. The permeability of hybrid membranes is raised to 2 wt% addition of ZIF‐8 into the PVDF matrix owing to an enhancement in hydrophilicity and porosity. The FESEM images of the top and cross‐section view make visible the formation of macrovoids with the addition of ZIF‐8. On account of high porosity and surface hydrophilicity, the pure water permeation of hybrid membranes is increased to 278.6 Lm−2 h−1. The hybrid membranes showed higher rejection and permeate flux of bovine serum albumin (BSA; 92.8 Lm−2 h−1) and humic acid (HA; 94.3 Lm−2 h−1) owing to the synergetic effect of their enhanced hydrophilicity and surface roughness. This is confirmed by the higher flux recovery ratio (FRR) and lower irreversible fouling characteristics of hybrid PVDF membranes. The atomic absorption spectroscopy (AAS) revealed the long‐standing stability of ZIF‐8 in the PVDF matrix. Among all, the PVDF hybrid membrane with 2 wt% of ZIF‐8 showed excellent permeability, antifouling, and antibiofouling ability and was found to be more effective in water treatment applications. [ABSTRACT FROM AUTHOR]

Hybrid membranes are fabricated using the blends of sulfonated poly (vinylidene fluoride‐co‐hexafluoropropylene) (SPVDF‐co‐HFP) and sulfonated octaphenyl polyhedral oligomeric silsesquioxane (SOPS) as an alternate for expensive Nafion in vanadium redox flow battery (VRFB) applications. The FT‐IR and TEM investigation indicates the successful sulfonation of OPS and uniform distribution of SOPS. The morphological study of hybrid membranes by SEM–EDX and FESEM revealed the excellent dispersing ability of SOPS on a SPVDF‐co‐HFP matrix. The physicochemical analysis of SPVDF‐co‐HFP/SOPS membranes demonstrated an increase in hydrophilic ion‐exchangeable sites. The SPVDF‐co‐HFP/SOPS (0.5 wt.%) membrane displayed a maximum proton conductivity of 6.27 × 10−3 Scm−1 at 80°C because of strong hydrogen bond formation between SPVDF‐co‐HFP and SOPS facilitates proton migration. Besides, the cage‐like structure of SOPS effectively shields vanadium‐ion permeation to 1.21 × 10−8 cm2 min−1 and thus, showed a maximum membrane selectivity of 43.05 × 104 Scm−3 min. Overall, the hybrid membranes of SPVDF‐co‐HFP/SOPS were considered to be a better substitute for Nafion in VRFBs. [ABSTRACT FROM AUTHOR]

Metal--organic frameworks (MOFs) are widely explored for advances in hybrid membranes because of their bonding and favourable attraction in polymers. In particular, hybrid polymeric ultrafiltration (UF) membranes are fabricated using engineered MOFs as fillers with the aim of long-standing water treatment. The hydrophilic MOF-199 was synthesized by a facile method at room temperature and incorporated with a polyvinylidene fluoride (PVDF) casting solution to create novel hybrid PVDF/MOF-199 UF membranes via a phase inversion method. The hybrid UF membranes showed higher pure water permeation of 187 L m-2 h-1, which is 2.8 times greater than that of a pristine PVDF membrane, and the water contact angle is decreased to 53.51. The porosity also increased due to an enhancement in hydrophilicity and also retains the rejection property for contaminants such as BSA and HA at their limits, indicating a good trade-off between permeability and rejection. The permeability results are in good agreement with the surface morphology and roughness of the membranes, as shown in the SEM and AFM images, respectively. Contact angle images and TGA studies established the hydrophilicity and thermal stability of the hybrid membranes. BSA and HA permeation studies revealed antiorganic fouling while a zone test clearly demonstrated antibiofouling by the hybrid UF membranes. Overall, the PVDF/MOF-199 hybrid membranes are found to have potential for use in industrial and domestic water treatment. [ABSTRACT FROM AUTHOR]

• Flat sheet polyvinylidene fluoride - polytetrafluoroethylene (PVDF - PTFE) nanocomposite membranes were fabricated. • The flux of the nanocomposite membrane was 464% higher than that of the neat PVDF membrane. • Water contact angle increased from 67.8° to 87.4° by incorporating of PTFE. • Salt rejection ratio remained unchanged when the feed temperature was increased. Supported flat sheet polyvinylidene fluoride - polytetrafluoroethylene (PVDF-PTFE) nanocomposite membranes were fabricated for this study using the phase inversion process. Several characterization methods, such as scanning electron microscopy, atomic force microscopy, attenuated total reflectance - Fourier transform infrared spectroscopy, water contact angle, and liquid entry pressure of water (LEP w) measurements, were carried out on the prepared membranes, and vacuum membrane distillation (VMD) experiments were then applied to test membrane permeabilities. The cooperation of PTFE was demonstrated to have great potential in enhancing the permeate flux of PVDF membranes while maintaining an acceptable LEP w value. At a feed temperature of 30 °C and vacuum pressure 97.54 kPa, the VMD pure water permeates flux of the prepared nanocomposite membrane embedded with 40 wt% PTFE was 5.61 kg/m2·h, while that of pure PVDF membrane was 0.71 kg/m2 h. The salt rejection results of the prepared nanocomposite membranes were all above 99.9%. These results indicate the applicability of the PVDF-PTFE nanocomposite membranes supported on non-woven polyester fiber for desalination. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Membranes with multi-walled carbon nanotubes (MWCNTs) and two additives MWCNTs/SiO 2 were fabricated. • With the MWCNTs addition, the average pore size decreases, but the finger-like pores are extended. • Hybrid nanocomposite membranes with 1% SiO 2 , integrated additive shows synergetic effects on vapor flux through membrane. • High SiO 2 content could increase liquid entry pressure of water of membrane compared with membrane blended MWCNTs only. • MWCNTs exhibits different effects on tensile properties of membrane when loading ratio of SiO 2 is different. Abstract Polyvinylidene fluoride (PVDF) was blended with multi-walled carbon nanotubes (MWCNTs) and MWCNTs/SiO 2 nano-additives to fabricate nanocomposite vacuum membrane distillation (VMD) membranes for desalination. The effects of MWCNTs and MWCNTs/SiO 2 integrated additives on the morphology and performance of the PVDF membrane were studied. When only MWCNTs were used, 2 wt% loading of MWCNTs to PVDF had the maximum effect on the improvement of VMD flux, due primarily to the enlargement and elongation of the finger-like pores. Then, one of three different SiO 2 nanoparticles (NPs) (hydrophobic, superhydrophobic and hydrophilic) was further added to the membrane that already contained 2 wt% of MWCNTs. When the amount of SiO 2 NPs was relatively low, VMD flux increased as a result of the synergistic effects between the two filler components, i.e. one is the increase of overall porosity by MWCNTs and the other is the growth of the macrovoids by SiO 2 NPs. But among those two, the effect of MWCNTs was more dominant. Compared with the pristine PVDF membrane and the nanocomposite PVDF membrane with a single filler of MWCNTs, respectively, the flux increase by the addition of SiO 2 was 292% and 55%. On the other hand, when a relatively large amount of SiO 2 NPs was added, the effect of SiO 2 NPs started to dominate. Especially, the asymmetric structure of the membrane disappeared, leading to low mechanical strength. All fabricated membranes exhibited great desalination potential with salt rejection as high as >99.97%. [ABSTRACT FROM AUTHOR]

Exfoliated molybdenum disulfide (E-MoS2) nanosheets were synthesized from bulk MoS2. Poly(vinylidene fluoride) (PVDF) was incorporated into E-MoS2 to yield nanocomposite ultrafiltration (UF) membranes by the phase inversion technique. Various proportions of E-MoS2 (0.1, 0.5 and 0.8 wt%) were prepared and were characterized in terms of permeation and antifouling properties. FT-IR and XRD studies confirmed the presence of E-MoS2 in the membranes. Moreover, SEM and FESEM/EDX analysis of the membranes confirmed the increase in the porosity and presence, respectively, of E-MoS2. Atomic force microscopy (AFM) images confirmed that the membrane with 0.5 wt% E-MoS2 exhibited a uniform surface structure with (Ra = 35 nm), compared to the pure PVDF membrane (Ra = 37.6 nm). In addition, the membrane with 0.5 wt% E-MoS2, exhibited higher pure water flux (PWF) (105.1 L m−1 h−1), water content (73.7%), porosity (12.24%), bovine serum albumin (BSA) solute rejection (92.3%), least mechanical stability (1.13 MPa), hydraulic resistance (7.44 kPa L−1 m−2 h−1) and contact angle (72.8°). From all these, it is evident that the overall PVDF membrane performance was enhanced by the E-MoS2 addition, and the membrane with 0.5 wt% E-MoS2 outperformed the other counterparts due to its versatile characteristics and superior potential in the water treatment. [ABSTRACT FROM AUTHOR]

The zinc-based metal-organic frameworks (MOFs) such as MOF-5 and silver-loaded MOF-5 (Ag@MOF-5) are synthesized by facile solvothermal method and utilized to fabricate poly (vinylidenefluoride)(PVDF) hybrid ultrafiltration (UF) membranes for water treatment applications. As-synthesized MOF-5 and Ag@MOF-5 are characterized by ATR-FTIR, XRD, and SEM. The ATR-FTIR is used to validate the successful production of MOFs while the XRD pattern and SEM revealed their high crystallinity and cubical structure, respectively. The Ag@MOF-5 is verified by FTIR, XRD and SEM for its chemical functionality and morphology. From the SEM images, it is clearly seen the flaky structure of MOFs. The membranes are examined by ATR-FTIR, XRD, and SEM/EDAX. From the cross-section SEM images, macrovoids formed are visibly seen and the increase in roughness is obviously seen in AFM. The dispersion of MOF-5 and Ag@MOF-5 in the PVDF membrane matrix is validated via elemental mapping by the EDAX spectrum. The PVDF/Ag@MOF-5 hybrid membranes outperformed bare PVDF and PVDF/MOF-5 membranes in permeation and fouling properties, especially, the PVDF/Ag@MOF-0.5 (0.5 wt% of Ag@MOF-5) hybrid membrane exhibited higher pure water flux (PWF) of 236.5 Lm−2h−1 and superior hydrophilicity with contact angle of 52.3°. Besides, PVDF/Ag@MOF-0.5 membranes demonstrated the enhancement in rejection of 98.4% and 96.5% and better antifouling with flux recovery ratio (FRR) of 89.7% and 92.4% for BSA and HA respectively. Moreover, PVDF/Ag@MOF-0.5 hybrid membranes displayed excellent antibacterial properties in the zone of inhibition test against E. coli and S. aureus. The overall findings indicate that the PVDF/Ag@MOF-0.5 hybrid membrane shows potential for the treatment of water and wastewater. [Display omitted] • Zinc-based MOF-5 and Ag nanoparticles loaded MOF-5 were synthesized by facile solvothermal method. • PVDF/MOF-5 and PVDF/Ag@MOF-5 UF membranes were fabricated by phase inversion method. • PVDF/Ag@MOF-0.5 membranes displayed 98.4% and 96.5% for BSA/HA rejection. • PVDF/Ag@MOF-0.5 membrane showed high FRR of 89.7% and 92.4% for BSA and HA showed its antifouling ability. • PVDF/MOF-0.5 and PVDF/Ag@MOF-0.5 membranes were exhibited good antibacterial ability. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a promising separation technique capable of being used in the desalination of marine and brackish water. Poly(vinylidene fluoride) (PVDF) flat sheet nano-composite membranes were surface modified by coating with electro-spun PVDF nano-fibres to increase the surface hydrophobicity. For this purpose, the nano-composite membrane containing 7 wt.% superhydrophobic SiO 2 nano-particles, which showed the highest flux in our previous work, was first subjected to pore size augmentation by increasing the concentration of the pore forming agent (Di-ionized water). Then, the prepared flat sheet membranes were subjected to nanofibres coating by electro-spinning. The uncoated and coated composite fabricated membranes were characterized using contact angle, liquid entry pressure of water, and scanning electron microscopy. The membranes were further tested for 6 h desalination by direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD), with a 3.5 wt.% synthetic NaCl aq as the feed. In DCMD the feed liquid and permeate side temperature were maintained at 27.5 °C and 15 °C, respectively. For VMD, the feed liquid temperature was 27 °C and a vacuum of 94.8 kPa was applied on the permeate side. The maximum permeate flux achieved was 3.2 kg/m 2 .h for VMD and 6.5 kg/m 2 .h for DCMD. The salt rejection obtained was higher than 99.98%. The coated membranes showed a more stable flux than the uncoated membranes indicating that the double layered membranes have great potential in solving the pore wetting problem in MD. [ABSTRACT FROM AUTHOR]

Effects of hydrophilic silica nanoparticles and Non-Woven Fabric (NWF) backing material on the properties and performance of the Polyvinylidene Fluoride (PVDF) membrane have been studied in this work. The nanocomposite membranes were prepared by the phase inversion method and characterized in terms of surface pore size, cross-sectional morphology, thickness, porosity, surface roughness and hydrophobicity. The fabricated membranes were subjected to Vacuum Membrane Distillation (VMD) experiments and their performance was evaluated through measuring the pure water flux and salt rejection. According to the results, effects of the hydrophilic nano-additives and NWF polyester enabled much higher VMD flux than the neat PVDF membrane when an appropriate amount of the nano-filler was added, possibly due to increase in the surface pore size and the reduction of the sponge-like layer thickness. The supported nanocomposite membranes possessed appropriate Liquid Entry Pressure (LEP w ) and mechanical strength, which make the membrane applicable in VMD process. When 7.0 wt.% of the silica nanoparticles was incorporated in a NWF supported membrane, the pure water flux became 12749.6 g/m 2 h at feed temperature of 27.5 °C and permeate side pressure of 1.2 kPa, representing a 2456% increase from the neat PVDF membrane. Almost complete NaCl rejection was also achieved when tested with 35 g/L NaCl aqueous solution. [ABSTRACT FROM AUTHOR]

The structure and performance of modified poly(vinylidene fluoride- co-hexafluoropropylene) (PVdF- co-HFP) ultra-filtration membranes prepared from casting solutions with different concentrations of poly(vinyl pyrrolidone) (PVP) were investigated in this study. Membrane properties were studied in terms of membrane compaction, pure water flux (PWF), water content (WC), membrane hydraulic resistance ( Rm), protein rejection, molecular weight cut-off (MWCO), average pore size, and porosity. PWF, WC, and thermal stability of the blend membranes increased whereas the crystalline nature and mechanical strength of the blend membranes decreased when PVP additive concentration was increased. The contact angle (CA) decreased as the PVP concentration increased in the casting solution, which indicates that the hydro-philicity of the surface increased upon addition of PVP. The average pore size and porosity of the PVdF- co-HFP membrane increased to 42.82 Å and 25.12%, respectively, when 7.5 wt% PVP was blended in the casting solution. The MWCO increased from 20 to 45 kDa with an increase in PVP concentration from 0 to 7.5 wt%. The protein separation study revealed that the rejection increased as the protein molecular weight increased. The PVdF- co-HFP/PVP blended membrane prepared from a 7.5 wt% PVP solution had a maximum flux recovery ratio of 74.3%, which explains its better antifouling properties as compared to the neat PVdF- co-HFP membrane. POLYM. ENG. SCI., 55:2482-2492, 2015. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Membranes were prepared from three poly(vinylidene fluoride) (PVDF) of different molecular weights by the phase inversion process. The membranes were characterized by scanning electron microscopy, gas permeation tests, contact angle (CA) and liquid entry pressure of water (LEPw) measurements, and further subjected to the test of flux for vacuum membrane distillation (VMD) in a scenario that is applicable for cooling processes. The results showed that the increase in PVDF molecular weight increased the viscosity and thermodynamic instability of the casting solution significantly. Regarding characterization and performance testing, the membrane prepared from the intermediate molecular weight of Kynar® MG 15 polymer showed the highest VMD flux (325 g/m 2 h) at the feed temperature of 27 °C and the lowest LEPw (622 kPa) due to the largest pore size (49.8 nm) observed among all the tested membranes. The highest flux of this particular membrane seems also due to the thinnest finger-like and sponge-like layer. [ABSTRACT FROM AUTHOR]

In this study, composite membranes of hydrophilic CuO and CaCO 3 nanoparticles and polyvinylidene fluoride (PVDF) were developed by phase inversion method. The fabricated membranes were subjected to different characterizations including morphology study, pore size, porosity, and thickness measurement, wettability and surface roughness analysis. The membrane performance was examined in terms of pure water flux in vacuum membrane distillation (VMD), salt rejection, and liquid entry pressure of water (LEP w ). It was found that the membrane performance was optimized when 1.0 to 2.0 wt.% of CuO nanoparticles were embedded into the PVDF matrix via enhancing the membrane structure through enlarging surface pores and thickening the finger-like layer (in other words, thinning of the sponge-like layer). As a result, flux increased by 153.4% at the feed temperature of 27.5 °C and vacuum pressure of 1.2 kPa, when 2.0 wt.% of the CuO nanoparticles were embedded in PVDF. Membrane selectivity did not drop as a result of the CuO nanoparticles incorporation and was more than 99.99%. All the nanocomposite membranes showed reasonable contact angle and LEP w, which proved appropriateness of the fabricated membranes for VMD application. Regarding the type of hydrophilic nanomaterials, CuO demonstrated better performance than CaCO 3 in terms of membrane permeability improvement. [ABSTRACT FROM AUTHOR]

In this study membranes were fabricated from the blend of high (H) and low (L) molecular weights poly(vinylidene fluoride) by the phase inversion process. The membranes so fabricated were characterized by scanning electron microscopy, gas permeation tests, contact angle (CA) and liquid entry pressure of water (LEPw) measurement, and further subjected to vacuum membrane distillation (VMD) in a scenario that was applicable for cooling processes, where the feed water temperature was maintained at 27 °C. It was found that the H:L mixing ratio did not affect the membrane surface hydrophobicity (as reflected by the CA) significantly. The water vapor flux of VMD was found to be the highest at the intermediate range of H:L ratio, i.e., 4:6, at which the thickness of the sponge-like layer showed a minimum, the pore size showed a maximum, the finger-like macro-voids formed a more orderly single-layer structure, and the LEPw showed a minimum. [ABSTRACT FROM AUTHOR]

Abstract: Nanofiber membranes were fabricated by electrospinning poly(vinylidene fluoride). The electrospun nanofiber membranes were further modified by grafting of acrylic acid (AA) and methacrylic acid (MAA) over the surfaces of the membranes. Plasma AA graft was attempted only, and the results indicated the partial membrane pore filling with grafted AA. For MAA grafting, chemically induced polymerization using benzoyl peroxide and hydrogen peroxide was attempted. The combination of plasma and chemically induced MAA graft polymerization was also attempted. The membranes were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and static contact angle (SCA) measurement. SEM surface analysis indicated partial pore narrowing of grafted membranes. The average pore size was reduced from 0.97μm for the untreated membrane to 0.15μm for the two step plasma and chemically induced grafted membranes. XPS analysis confirmed that grafting has taken place on the top surface of the membranes. The surfaces of the grafted membrane were significantly hydrophilic as observed by SCA. It was also found that the combination of plasma and chemically induced grafting using hydrogen peroxide was the most effective in terms of flux and selectivity. The grafting reduced the pore size by filling the pores of the original membranes by the graft polymers. This practice resulted in producing tight micro-filtration (MF) membranes from loose MF ones. An impressive high water flux of 150kg/hm2 at an operating pressure of 4 psig, and a 79% removal of polyethylene oxide (molecular weight 400kilo-Daltons) were achieved. [Copyright &y& Elsevier]

Sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVDF-co-HFP) based nanocomposite proton exchange membranes (PEM) are fabricated by simple solution casting method using polydopamine coated exfoliated molybdenum disulfide (PDA-MoS 2) nanosheets as an alternative for Nafion® in vanadium redox flow batteries (VRFBs). PDA-MoS 2 is synthesized by the etching of exfoliated MoS 2 nanosheets with dopamine molecule by self-polymerization method. Various characteristic results clearly demonstrated that the incorporated PDA-MoS 2 nanosheets homogeneously distributed into the SPVDF-co-HFP matrix and the presence of NH/NH 2 group electrostatically interacts with SPVDF-co-HFP to form a strong acid-base pair and thus enhances the proton transport via Grotthuss type mechanism. Besides, the improvement in surface hydrophilicity provides the vehicle type conduction also. As a result, SPVDF-co-HFP/PM nanocomposite membranes showed higher proton conductivity in comparison with the pristine membrane. Especially SPVDF-co-HFP/PM-1 membrane demonstrated the excellent proton conductivity of 5.24 × 10−3 Scm−1 at 25 °C, lower vanadium-ion permeability of 1.05 × 10−8 cm2min−1 and highest membrane selectivity of 49.9 × 104 Scm−3min. On the other hand, vanadium-ion stability of the membrane increased by adding the PD-MoS 2 content is attributed to their strong electrostatic attraction towards the polymer matrix. Overall results suggested that the SPVDF-co-HFP/PM-1 nanocomposite membrane is found to be a better alternative for commercially costly Nafion in VRFB applications. Image 1 • Bio-inspired polydopamine coated exfoliated molybenum disulfide (PDA-MoS 2) nanosheets are successfully synthesized. • PDA-MoS 2 nanosheets effectively block the vanadium-ion permeation via SPVDF-co-HFP membranes up to 1.05 × 10−8 cm2min−1. • Acid-base pair formation between SPVDF-co-HFP with PDA-MoS 2 offers a new proton conduction pathway. • SPVDF-co-HFP/PDA-MoS 2 membranes showed higher chemical stability and found appropriate for use in VRFBs. • SPVDF-co-HFP/PDA-MoS 2 membranes are superior to bare SPVDF-co-HFP and Nafion membranes. [ABSTRACT FROM AUTHOR]

• Nanocomposite membranes with various nanoparticles (NPs) were fabricated for a vacuum membrane distillation (VMD) process. • Able to achieve higher VMD flux using a continuous flow cell than that with a static cell. • With increasing temperature, the continuous flow cell yielded higher VMD flux than that of the static cell. • Incorporation of NPs of larger size showed better performance than that of smaller size. • Finger-like voids reached the bottom of the nanocomposite membrane when the cast film thickness was the lowest. In this study, the effects of incorporation of nanoparticles (NPs), including 7 nm TiO 2 , 200 nm TiO 2 , and hydrophilic and hydrophobic SiO 2 with a mean diameter in the range of 15–20 nm, and their concentrations on the membrane properties and vacuum membrane distillation (VMD) performance were evaluated. The effect of membrane thickness and support materials were also investigated. The membranes were characterized extensively in terms of water contact angle, liquid entrance pressure of water (LEP w), scanning electron microscopy, surface roughness, and pore size. While the best polyvinylidene fluoride (PVDF) nanocomposite membranes with 200 nm TiO 2 NPs were obtained at 2 wt% NPs concentration, the optimal NPs concentration was 5% when 7 nm TiO 2 was integrated. Using a nanocomposite membrane containing 2 wt% TiO 2 − 200 nm NPs, a VMD flux of 3.2 kg/m2h and a LEP w of 34 psi were obtained with 99.99% salt rejection. Furthermore, it was observed that decreasing the membrane thickness would increase the portion of the finger-like layer in the membrane and reduce the spongy-like layer when hydrophilic NPs were used. Using continuous flow VMD, a flux of 3.1 kg/m2h was obtained with neat PVDF membranes, which was higher than the flux obtained by the static VMD with the same membrane at the same temperature and vacuum pressure. The fluxes of both static and continuous flow cells VMD increased with temperature. Furthermore, it was evident that the continuous flow cell VMD at 2 L per minute yielded higher flux than the static cell VMD at any given temperature, indicating strong effects of turbulence provided in the continuous flow cell VMD. [ABSTRACT FROM AUTHOR]

Nanocomposite membranes were prepared for vacuum membrane distillation (VMD) by casting the dope suspension on top of a nonwoven polyester backing material. The dope consisted of 7.0 wt % hydrophilic SiO2 nanoparticles and a polyvinylidene fluoride (PVDF) blend of high molecular weight (H) and low molecular weight (L). The effects of the blend ratio (H:L) and the penetration time (τ), defined as the period between the completion of membrane casting and the immersion in the coagulation bath, on the membrane properties and performance were studied. It was found that the VMD flux is governed by the pore size and thickness of the top layer (defined as the layer formed above the backing material), both of which are affected by the H:L ratio and the penetration time. Results indicate that the VMD flux increased as the portion of L in the casting dope increased at constant τ, while a maximum flux was observed at τ = 2 min when the penetration time was changed at constant H:L ratio. It was also observed that the liquid entry pressure of water (LEPw) of membranes changed with the PVDF blend ratio and penetration time due to alteration of the maximum pore size. Considering all the data collected, the combination of H:L = 2:8 and penetration time of 3 min was identified as the best condition for the preparation of nanocomposite membranes, achieving one of the highest VMD fluxes, 12.1 kg/m² h at 27.5 °C and 1.2 kPa, an improved LEPw of 27.0 psig, and a near complete NaCl rejection. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF)/SiO 2 flat sheet composite membranes were prepared for vacuum membrane distillation (VMD) by the phase inversion immersion precipitation process. The effect of blending superhydrophobic SiO 2 nanoparticles into the PVDF dope solution was studied. The concentration of the nanoparticles in the dope solution was varied at different wt.% (1, 2, 4, 6, 7, 8 and 10 wt.%). The prepared membranes were characterized by scanning electron microscopy, water contact angle, porosity, liquid entry pressure of water, Fourier transformed infrared spectroscopy, and VMD at feed temperature of 27 °C. The nanoparticles enhanced the membrane performance through a reduction in the sponge-like layer thickness and an increase in surface pore size, leading to increased vapour flux with a maximum at 7 wt.%. The salt rejection was greater than 99.98% when a 35 g/L NaCl solution was used as feed. At this concentration, the smallest thickness of the sponge-like layer and largest macro-voids were also achieved. Beyond 7 wt.%, the sponge-like layer became predominant and the flux was reduced. With a vapour flux increase of up to 4 times (from 0.7 to 2.9 kg/m 2 h) when compared to the neat membrane, this nanocomposite membrane could be of great potential in the desalination process through VMD. [ABSTRACT FROM AUTHOR]

Through nanochannels are fabricated in poly(vinylidene fluoride-co-hexafluoro propylene) films by bombarding swift heavy ions ( SHI ) of energy 80 MeV and thereby creating latent tracks in the ion passage followed by chemical etching of the amorphous track. The dimension of the nanochannel is varied from 34 to 65 nm using different fluences and by dispersing organically modified nanoclay in polymer matrix. The nanochannels are grafted with polystyrene using the free radicals caused by SHI irradiation followed by their sulfonation. Nanoclay nucleates piezoelectric β -phase in copolymer whose extent gets enhanced after irradiation, grafting and sulfonation leading to a better material. The efficiency of functionalized nanochannel conduction is studied through dc conductivity of the bulk film in the semiconducting range against the insulating nature of the pristine copolymer. Current-voltage (I–V) characteristic of the membrane exhibits strong fluence dependency and shows superior conduction in functionalized nanohybrid. Proton conductivity of the functionalized nanohybrid is 6.2 × 10 −2 S cm −1 , while methanol permeability drastically reduces indicating higher values of the selective parameter of the developed membrane as compared to Nafion. Membrane electrode assembly studies of functionalized nanohybrid show 0.63 V as open circuit voltage leading to power density of 30.8 mW/cm 2 , considerably higher than the functionalized copolymer. [ABSTRACT FROM AUTHOR]

Functionalization of poly(vinylidene fluoride) ( PVDF ) nanohybrid has been performed in template system using two-dimensional layered silicate and superior fuel cell membrane has been demonstrated. Sulfonation of nanohybrid has been carried out at control condition to maintain the mechanical stiffness and toughness of the membrane using chlorosulfonic acid and the results have been compared with pure PVDF . The sulfonation and its relative extent have been confirmed through NMR , FTIR and UV–vis measurements showing greater degree of functionalization in nanohybrid which arises from the specific arrangement of polymer chains on top of nanoplatelets. The structural change over from common crystallized form α - to piezoelectric β -phase in nanohybrid has been established and the amount of β -phase has been enhanced after sulfonation as evident from deconvoluted XRD patterns and DSC measurement. A plausible mechanism has been proposed for this improvement which led to the formation of smart membrane. Essential criteria of an ideal membrane have been verified through high water uptake, low permeability and hydrophilic nature by measuring contact angle. The molecular level clustering due to the attachment of sulfonate group in main chain has been explored which in turn explain the higher barrier property both for gas and liquid (fuel). Proton conductivity of functionalized nanohybrid has been found to be quite high along with significantly low methanol cross over as compared to standard Nafion membrane. I – V characteristics of the nanohybrid membrane show high potential at low current density with considerably lower value of slope. Membrane electrode assembly using functionalized nanohybrid exhibit significantly high value of current density and prove its worth for superior fuel cell membrane using common thermoplastic polymer. [ABSTRACT FROM AUTHOR]