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Polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes were prepared using 16 wt% PVDF in Dimethyl acetamide (DMAc) by phase inversion technique for desalination application using Membrane Distillation (MD). In this work,...
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Polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes were prepared using 16 wt% PVDF in Dimethyl acetamide (DMAc) by phase inversion technique for desalination application using Membrane Distillation (MD). In this work, the effect of coagulation mediums such as ethanol and water as well their synergistic behavior on the fabricated PVDF membrane morphology was studied using SEM. Moreover, other characteristics required for the membrane distillation applications namely porosity, hydrophobicity and tensile strength were measured using the gravimetric method, sessile drop method and universal testing machine respectively. It was observed that the membrane morphology paradigm shifted from the finger-like structure to the sponge-like structure on increasing the ethanol concentration in coagulant. The porosity of the fabricated membrane was under the required MD range and found to be 57.3% at 16 weight % of PVDF in DMAc solvent under a pure ethanol coagulant bath. Moreover, the top surface contact angle ranges from 85° to 115° on increasing the bath concentration from CBC 0 to CBC 100 at 16 weight % of PVDF in DMAc solvent.
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The impacts of aging and chemical cleaning on the properties and performance of ultrafiltration membranes in potable water treatment were investigated using membrane samples from a full-scale water filtration plant. A range of ana...
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The impacts of aging and chemical cleaning on the properties and performance of ultrafiltration membranes in potable water treatment were investigated using membrane samples from a full-scale water filtration plant. A range of analytical tools were employed to characterize various membrane attributes, encompassing flux, tensile strength, morphology, surface resident functional groups, and both organic and inorganic foulants. The results of laboratory experiments that simulated chemical cleaning sequences were consistent with those observed in the full-scale water filtration plant, in terms of their effects on the properties of the membranes. It was revealed that aging played a significant role in the deterioration of the tensile strength of the membrane media, as well as the degradation of the intensity of surface resident functional groups, which led to the accumulation of foulants. While cleaning with hypochlorite resulted in a decrease of membrane tensile strength, identical cleaning with citric acid had no such effect. The degradation of membrane tensile strength may be correlated to a decrease in the intensities of functional groups as measured by Fourier transform infrared spectroscopy (FTIR). These results suggest that the concentration of hypochlorite and the cleaning duration should both be minimized to reduce their negative impacts on membrane properties.
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Transport numbers of sodium, nickel, and lanthanum counterions have been studied in microporous (average pore radius is r = 2-3.4 nm) and macroporous (r = 16-27 nm) magnetite-free glasses and those containing magnetite in their ma...
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Transport numbers of sodium, nickel, and lanthanum counterions have been studied in microporous (average pore radius is r = 2-3.4 nm) and macroporous (r = 16-27 nm) magnetite-free glasses and those containing magnetite in their matrices. It has been found that, in the case of microporous glasses, the relation between the transport numbers of the studied cations is primarily governed by the structure of secondary silica in pore channels. For membranes prepared from macroporous glasses, the transport numbers of the cations in the pore space depend on the surface charge magnitude and the structure of the electrical double layer.
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Fatty acids (FAs) are known to form vesicle structures, depending on the surrounding pH conditions. In this study, we prepared vesicles by mixing FAs and a cationic surfactant, and then investigated their physicochemical propertie...
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Fatty acids (FAs) are known to form vesicle structures, depending on the surrounding pH conditions. In this study, we prepared vesicles by mixing FAs and a cationic surfactant, and then investigated their physicochemical properties using fluorescence spectroscopy and dielectric dispersion analysis (DDA). The assemblies formed from oleic acid (OA) and linoleic acid (LA) were modified by adding didecyldimethylammonium bromide (DDAB). The phase state of FA/DDAB mixtures was investigated with pH titration curves and turbidity measurements. The trigonal diagram of FA/ionized FA/DDAB was successfully drawn to understand the phase behaviors of FA/DDAB systems. The analysis of fluidities in the interior of the membrane with use of 1,6-diphenyl-1,3,5-hexatriene (DPH) indicated that the membrane fluidities of OA/DDAB and LA/DDAB at pH 8.5 slightly decreased in proportion to the molar ratio of DDAB in FA/DDAB systems. The fluorescent probe 6-lauroyl-2-dimethylamino naphthalene (Laurdan) indicated that the LA vesicle possessed a dehydrated surface, while the OA vesicle surface was hydrated. Modification of LA vesicles with DDAB induced the hydration of membrane surfaces, whereas modification of OA vesicles by DDAB had the opposite effect. DDA analysis indicated that the membrane surfaces were hydrated in the presence of DDAB, suggesting that the surface properties of FA vesicles are tunable by DDAB modification.
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In this work, experimental investigations were carried out for the identification of optimal membrane morphological parameters (pore size distribution, average pore size and porosity) during microfiltration (MF) of mosambi juice u...
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In this work, experimental investigations were carried out for the identification of optimal membrane morphological parameters (pore size distribution, average pore size and porosity) during microfiltration (MF) of mosambi juice using low cost ceramic membranes. Four different low cost ceramic membranes with different pore diameters (dm) and porosities ( epsilon) were subjected to MF studies to evaluate the effect of dm and epsilon on permeation characteristics (permeate flux and juice quality) of centrifuged mosambi juice (CJ) and enzyme treated centrifuged mosambi juice (ETCJ). Subsequently, a convenient factor namely effective permeable area factor ( epsilonmdm2) was evaluated to provide greater insights in the fouling phenomena. Various physio-chemical properties such as colour, clarity, pH, citric acid content, density, total soluble solid (TSS) and alcohol insoluble solids (AIS) were measured for both feed and permeate juice samples to evaluate the effect of epsilonmdm2 on juice quality. Typical permeate fluxes were observed to vary from 5.78 x 10-6 to 13.45 x 10-6m3/m2s for CJ and 14.07 x 10-6 to 60.64 x 10-6m3/m2s for ETCJ at 82.7kPa ( DeltaP) for different membranes whose epsilonmdm2 varied from 0.249 to 0.783 mum2. Among different membrane pore blocking models, flux decline by cake filtration was found to be the best fitted model. The cake filtration model constant (kc) was found to vary with DeltaP and epsilonmdm2 and was empirically correlated. Phenomenological models were proposed to illustrate the dependency of total hydraulic resistance of membrane on epsilonmdm2, DeltaP and time (t). Based on experimental as well as theoretical investigations, membranes with epsilonmdm2 up to 0.443 mum2 for CJ and 0.294 mum2 for ETCJ and a DeltaP of 82.7kPa were recommended for MF of mosambi juice.
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Electrospun nanofibers have attracted tremendous attention because of their similar structure with extracellular matrix. In this work, the polydopamine (PDA) coating layer was first applied to modify hydroxyapatite (HA) nanopartic...
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Electrospun nanofibers have attracted tremendous attention because of their similar structure with extracellular matrix. In this work, the polydopamine (PDA) coating layer was first applied to modify hydroxyapatite (HA) nanoparticles and obtain functional HA@PDA nanoparticles. Subsequently, the polylactic acid (PLA)/HA@PDA composite nanofibers were prepared via electrospinning. The hydrophilicity and water absorption of PLA/HA@PDA composite nanofibers were larger than those of PLA and PLA/HA composite nanofibers. The thermal stability, static and dynamic mechanical properties of PLA/HA@PDA composite nanofibers significantly increased because the PDA coating layer on the surface of the HA nanoparticles acted like a glue-like transition layer, which led to an increase in interfacial adhesion between HA@PDA nanoparticles and the PLA matrix. The attachment and viability of mouse embryonic osteoblast cells (MC3T3-E1) cultured on the PLA/HA@PDA composite nanofibers were significantly increased compared with those cultured on the PLA and PLA/HA composite nanofibers. These results suggested that the PLA/HA@PDA composite nanofibers have superior mechanical and biological properties, which makes it potentially useful for tissue engineering scaffolds.
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In order to investigate for anion exchange membranes (AEMs) with improved properties, four series of polyethersulfone-based composite AEMs are fabricated by incorporating pristine and three functionalized silica nanoparticles cont...
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In order to investigate for anion exchange membranes (AEMs) with improved properties, four series of polyethersulfone-based composite AEMs are fabricated by incorporating pristine and three functionalized silica nanoparticles containing propylamine, trimethylpropylamine, and melamine-based dendrimer amine groups. The results show that by choosing appropriate functional agent, anion exchange membranes with improved parameters can be achieved. The polymeric matrix of the membranes is synthesized by chloromethylation of polyethersulfone using thionyl chloride followed by amination with trimethylamine (TMA). The effectiveness of chloromethylation process is confirmed by H-1 NMR analysis. The effects of functional groups on characteristic and transport properties of the prepared composite membranes i.e., SEM, IEC, water uptake, porosity transport properties, and conductivity are investigated. The scanning electron microscope images illustrates that the synthesized membranes possess dense structures. Ion exchange capacity (IEC), water uptake, transport properties, and conductivity of the composite membranes are measured. In addition, the morphology and thermal stability are characterized. IECs and ion conductivities of up to 1.45 meq g(-1) and 45.46 mS cm(-)1 and moderate transport characteristics are obtained from the modified membranes which confirm that these membranes are appropriate for applying in electro-membrane processes. (C) 2016 Wiley Periodicals, Inc.
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N-methyl-N-propyl-piperidin-bis(trifluoromethylsulfonyl)imide/bis(trifluoromethylsulfonyl) imide lithium base/polymethyl methacrylate(PP13TFSI/LiTFSI/PMMA) gel polymer electrolyte (GPE) membrane was prepared by in situ polymerizat...
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N-methyl-N-propyl-piperidin-bis(trifluoromethylsulfonyl)imide/bis(trifluoromethylsulfonyl) imide lithium base/polymethyl methacrylate(PP13TFSI/LiTFSI/PMMA) gel polymer electrolyte (GPE) membrane was prepared by in situ polymerization. The physical and chemical properties were comprehensively discussed. The decomposition characteristics were emphasized by thermogravimetric (TG-DTG) method in the nitrogen atmosphere at the different heating rates of 5, 10, 15 and 20 degrees C min(-1), respectively. The activation energy was calculated with the iso-conversional methods of Ozawa and Kissinger, Friedman, respectively, and the Coats-Redfern methods were adopted to employ the detailed mechanism of the electrolyte membrane. The equation f(alpha)=3/2[(1-alpha)(1/3)-1] was quite an appropriate kinetic mechanisms to describe the thermal decomposition process with an activation energy (E-alpha) of 184 kJ/mol and a pre-exponential factor (A) of 1.894 x 10(11) were obtained. (C) 2016 Elsevier Ltd. All rights reserved.
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Titania-coated carbon nanotubes (TCNTs) were obtained by a simple sol-gel method. Then chitosan/TCNT (CS/TCNT) composite membranes were prepared by stirring chitosan/acetic acid and a TCNT/ethanol suspension. The morphology, therm...
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Titania-coated carbon nanotubes (TCNTs) were obtained by a simple sol-gel method. Then chitosan/TCNT (CS/TCNT) composite membranes were prepared by stirring chitosan/acetic acid and a TCNT/ethanol suspension. The morphology, thermal and oxidative stabilities, water uptake and proton conductivity, and mechanical properties of CS/TCNT composite membranes were investigated. The CNTs coated with an insulated and hydrophilic titania layer eliminated the risk of electronic short-circuiting. Moreover, the titania layer enhanced the interaction between TCNTs and chitosan to ensure the homogenous dispersion of TCNTs in the chitosan matrix. The water uptake of CS/TCNT composite membranes was reduced owing to the decrease of the effective number of the NH2 functional groups of chitosan. However, the CS/TCNT composite membranes exhibited better performance than a pure CS membrane in thermal and oxidative stability, proton conductivity, and mechanical properties. These results suggest that CS/TCNT composite membranes are promising materials for new proton-exchange membranes. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43365.
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A series of hyperbranched polysiloxane (HBPSi)-based hyperbranched polyimide (HBPI) films with low dielectric permittivity and multiple branched structures are fabricated by copolymerizing 2,4,6-triaminopyrimidine (TAP) with 4,4-(...
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A series of hyperbranched polysiloxane (HBPSi)-based hyperbranched polyimide (HBPI) films with low dielectric permittivity and multiple branched structures are fabricated by copolymerizing 2,4,6-triaminopyrimidine (TAP) with 4,4-(hexafluoroisopropylidene)diphthalic anhydride, 4,4-diaminodiphenyl ether, and HBPSi via the two-step polymerization method. The dielectric permittivity of HBPSi hyperbranched polyimide films decreases with increasing TAP fraction, namely, from 3.28 for sample PI-1 to 2.80 for PI-4, mainly owing to the enlarged free volume created by the incorporation of multiple branched structures. Moreover, HBPSi HBPI possesses desirable solubility and good mechanical properties and thermal stability. PI-4 not only has low dielectric permittivity (2.80, 1 MHz), excellent solubility (soluble in several common organic solvents), and remarkable thermal properties (glass-transition temperature of 273 degrees C, 5% weight loss temperature of 498 degrees C in N-2 and 486 degrees C in O-2), but it also demonstrates admirable mechanical properties with a tensile strength of 103 MPa, elongation at break of 7.3%, and a tensile modulus of 2.16 GPa. HBPSi HBPI might have potential applications in interlayer dielectrics and other microelectronics fields. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47771.
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