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Membranes, Volume 3, Issue 4 (December 2013), Pages 249-439

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Research

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Open AccessArticle Numerical Simulation of Particle Distribution in Capillary Membrane during Backwash
Membranes 2013, 3(4), 249-265; doi:10.3390/membranes3040249
Received: 18 July 2013 / Revised: 17 September 2013 / Accepted: 23 September 2013 / Published: 27 September 2013
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Abstract
The membrane filtration with inside-out dead-end driven UF-/MF- capillary membranes is an effective process for particle removal in water treatment. Its industrial application increased in the last decade exponentially. To date, the research activities in this field were aimed first of all at
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The membrane filtration with inside-out dead-end driven UF-/MF- capillary membranes is an effective process for particle removal in water treatment. Its industrial application increased in the last decade exponentially. To date, the research activities in this field were aimed first of all at the analysis of filtration phenomena disregarding the influence of backwash on the operation parameters of filtration plants. However, following the main hypothesis of this paper, backwash has great potential to increase the efficiency of filtration. In this paper, a numerical approach for a detailed study of fluid dynamic processes in capillary membranes during backwash is presented. The effect of particle size and inlet flux on the backwash process are investigated. The evaluation of these data concentrates on the analysis of particle behavior in the cross sectional plane and the appearance of eventually formed particle plugs inside the membrane capillary. Simulations are conducted in dead-end filtration mode and with two configurations. The first configuration includes a particle concentration of 10% homogeneously distributed within the capillary and the second configuration demonstrates a cake layer on the membrane surface with a packing density of 0:6. Analyzing the hydrodynamic forces acting on the particles shows that the lift force plays the main role in defining the particle enrichment areas. The operation parameters contribute in enhancing the lift force and the heterogeneity to anticipate the clogging of the membrane. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessArticle Performance Modeling and Cost Analysis of a Pilot-Scale Reverse Osmosis Process for the Final Purification of Olive Mill Wastewater
Membranes 2013, 3(4), 285-297; doi:10.3390/membranes3040285
Received: 6 August 2013 / Revised: 8 September 2013 / Accepted: 29 September 2013 / Published: 11 October 2013
Cited by 2 | PDF Full-text (970 KB) | HTML Full-text | XML Full-text
Abstract
A secondary treatment for olive mill wastewater coming from factories working with the two-phase olive oil production process (OMW-2) has been set-up on an industrial scale in an olive oil mill in the premises of Jaén (Spain). The secondary treatment comprises Fenton-like oxidation
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A secondary treatment for olive mill wastewater coming from factories working with the two-phase olive oil production process (OMW-2) has been set-up on an industrial scale in an olive oil mill in the premises of Jaén (Spain). The secondary treatment comprises Fenton-like oxidation followed by flocculation-sedimentation and filtration through olive stones. In this work, performance modelization and preliminary cost analysis of a final reverse osmosis (RO) process was examined on pilot scale for ulterior purification of OMW-2 with the goal of closing the loop of the industrial production process. Reduction of concentration polarization on the RO membrane equal to 26.3% was provided upon increment of the turbulence over the membrane to values of Reynolds number equal to 2.6 × 104. Medium operating pressure (25 bar) should be chosen to achieve significant steady state permeate flux (21.1 L h−1 m−2) and minimize membrane fouling, ensuring less than 14.7% flux drop and up to 90% feed recovery. Under these conditions, irreversible fouling below 0.08 L h−2 m−2 bar−1 helped increase the longevity of the membrane and reduce the costs of the treatment. For 10 m3 day−1 OMW-2 on average, 47.4 m2 required membrane area and 0.87 € m−3 total costs for the RO process were estimated. Full article
(This article belongs to the Special Issue Membranes in Process Intensification)
Open AccessArticle Interface Properties between Lithium Metal and a Composite Polymer Electrolyte of PEO18Li(CF3SO2)2N-Tetraethylene Glycol Dimethyl Ether
Membranes 2013, 3(4), 298-310; doi:10.3390/membranes3040298
Received: 22 July 2013 / Revised: 18 October 2013 / Accepted: 21 October 2013 / Published: 25 October 2013
Cited by 6 | PDF Full-text (889 KB) | HTML Full-text | XML Full-text
Abstract
The electrochemical properties of a composite solid polymer electrolyte, consisting of poly(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) was examined as a protective layer between lithium metal and a water-stable lithium ion-conducting glass ceramic of Li1+x
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The electrochemical properties of a composite solid polymer electrolyte, consisting of poly(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) was examined as a protective layer between lithium metal and a water-stable lithium ion-conducting glass ceramic of Li1+x+y(Ti,Ge)2−xAlxP3−ySiyO12 (LTAP). The lithium ion conductivity and salt diffusion coefficient of PEO18LiTFSI were dramatically enhanced by the addition of TEGDME. The water-stable lithium electrode with PEO18LiTFSI-2TEGDME, as the protective layer, exhibited a low and stable electrode resistance of 85 Ω·cm2 at 60 °C, after 28 days, and low overpotentials of 0.3 V for lithium plating and 0.4 V for lithium stripping at 4.0 mA·cm−2 and 60 °C. A Li/PEO18LiTFSI-2TEGDME/LTAP/saturated LiCl aqueous solution/Pt, air cell showed excellent cyclability up to 100 cycles at 2.0 mAh·cm−2. Full article
(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)
Open AccessArticle Testing the Chemical/Structural Stability of Proton Conducting Perovskite Ceramic Membranes by in Situ/ex Situ Autoclave Raman Microscopy
Membranes 2013, 3(4), 311-330; doi:10.3390/membranes3040311
Received: 1 August 2013 / Revised: 7 October 2013 / Accepted: 17 October 2013 / Published: 25 October 2013
Cited by 8 | PDF Full-text (1087 KB) | HTML Full-text | XML Full-text
Abstract
Ceramics, which exhibit high proton conductivity at moderate temperatures, are studied as electrolyte membranes or electrode components of fuel cells, electrolysers or CO2 converters. In severe operating conditions (high gas pressure/high temperature), the chemical activity towards potentially reactive atmospheres (water, CO2
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Ceramics, which exhibit high proton conductivity at moderate temperatures, are studied as electrolyte membranes or electrode components of fuel cells, electrolysers or CO2 converters. In severe operating conditions (high gas pressure/high temperature), the chemical activity towards potentially reactive atmospheres (water, CO2, etc.) is enhanced. This can lead to mechanical, chemical, and structural instability of the membranes and premature efficiency loss. Since the lifetime duration of a device determines its economical interest, stability/aging tests are essential. Consequently, we have developed autoclaves equipped with a sapphire window, allowing in situ Raman study in the 25–620 °C temperature region under 1–50 bar of water vapor/gas pressure, both with and without the application of an electric field. Taking examples of four widely investigated perovskites (BaZr0.9Yb0.1O3−δ, SrZr0.9Yb0.1O3−δ, BaZr0.25In0.75O3−δ, BaCe0.5Zr0.3Y0.16Zn0.04O3−δ), we demonstrate the high potential of our unique set-up to discriminate between good/stable and instable electrolytes as well as the ability to detect and monitor in situ: (i) the sample surface reaction with surrounding atmospheres and the formation of crystalline or amorphous secondary phases (carbonates, hydroxides, hydrates, etc.); and (ii) the structural modifications as a function of operating conditions. The results of these studies allow us to compare quantitatively the chemical stability versus water (corrosion rate from ~150 µm/day to less than 0.25 µm/day under 200–500 °C/15–80 bar PH2O) and to go further in comprehension of the aging mechanism of the membrane. Full article
(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)
Open AccessArticle Correlation of Gas Permeability in a Metal-Organic Framework MIL-101(Cr)–Polysulfone Mixed-Matrix Membrane with Free Volume Measurements by Positron Annihilation Lifetime Spectroscopy (PALS)
Membranes 2013, 3(4), 331-353; doi:10.3390/membranes3040331
Received: 30 August 2013 / Revised: 15 October 2013 / Accepted: 16 October 2013 / Published: 25 October 2013
Cited by 20 | PDF Full-text (2526 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hydrothermally stable particles of the metal-organic framework MIL-101(Cr) were incorporated into a polysulfone (PSF) matrix to produce mixed-matrix or composite membranes with excellent dispersion of MIL-101 particles and good adhesion within the polymer matrix. Pure gas (O2, N2, CO
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Hydrothermally stable particles of the metal-organic framework MIL-101(Cr) were incorporated into a polysulfone (PSF) matrix to produce mixed-matrix or composite membranes with excellent dispersion of MIL-101 particles and good adhesion within the polymer matrix. Pure gas (O2, N2, CO2 and CH4) permeation tests showed a significant increase of gas permeabilities of the mixed-matrix membranes without any loss in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that the increased gas permeability is due to the free volume in the PSF polymer and the added large free volume inside the MIL-101 particles. The trend of the gas transport properties of the composite membranes could be reproduced by a Maxwell model. Full article
Open AccessArticle Gypsum (CaSO4·2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis
Membranes 2013, 3(4), 354-374; doi:10.3390/membranes3040354
Received: 12 October 2013 / Revised: 29 October 2013 / Accepted: 1 November 2013 / Published: 8 November 2013
Cited by 9 | PDF Full-text (2588 KB) | HTML Full-text | XML Full-text
Abstract
We have examined the gypsum (CaSO4·2H2O) scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO) processes. Three hollow fiber membranes made of (1) cellulose acetate (CA), (2) polybenzimidazole (PBI)/polyethersulfone (PES) and (3) PBI-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile
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We have examined the gypsum (CaSO4·2H2O) scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO) processes. Three hollow fiber membranes made of (1) cellulose acetate (CA), (2) polybenzimidazole (PBI)/polyethersulfone (PES) and (3) PBI-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) were studied. For the first time in FO processes, we have found that surface ionic interactions dominate gypsum scaling on the membrane surface. A 70% flux reduction was observed on negatively charged CA and PBI membrane surfaces, due to strong attractive forces. The PBI membrane surface also showed a slightly positive charge at a low pH value of 3 and exhibited a 30% flux reduction. The atomic force microscopy (AFM) force measurements confirmed a strong repulsive force between gypsum and PBI at a pH value of 3. The newly developed PBI-POSS/PAN membrane had ridge morphology and a contact angle of 51.42° ± 14.85° after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 °C. Minimal scaling and an only 1.3% flux reduction were observed at a pH value of 3. Such a ridge structure may reduce scaling by not providing a locally flat surface to the crystallite at a pH value of 3; thus, gypsum would be easily washed away from the surface. Full article
Open AccessArticle Study of Hydrophilic Electrospun Nanofiber Membranes for Filtration of Micro and Nanosize Suspended Particles
Membranes 2013, 3(4), 375-388; doi:10.3390/membranes3040375
Received: 24 July 2013 / Revised: 18 October 2013 / Accepted: 21 October 2013 / Published: 14 November 2013
Cited by 4 | PDF Full-text (1218 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric nanofiber membranes of polyvinyl chloride (PVC) blended with polyvinylpyrrolidone (PVP) were fabricated using an electrospinning process at different conditions and used for the filtration of three different liquid suspensions to determine the efficiency of the filter membranes. The three liquid suspensions included
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Polymeric nanofiber membranes of polyvinyl chloride (PVC) blended with polyvinylpyrrolidone (PVP) were fabricated using an electrospinning process at different conditions and used for the filtration of three different liquid suspensions to determine the efficiency of the filter membranes. The three liquid suspensions included lake water, abrasive particles from a water jet cutter, and suspended magnetite nanoparticles. The major goal of this research work was to create highly hydrophilic nanofiber membranes and utilize them to filter the suspended liquids at an optimal level of purification (i.e., drinkable level). In order to overcome the fouling/biofouling/blocking problems of the membrane, a coagulation process, which enhances the membrane’s efficiency for removing colloidal particles, was used as a pre-treatment process. Two chemical agents, Tanfloc (organic) and Alum (inorganic), were chosen for the flocculation/coagulation process. The removal efficiency of the suspended particles in the liquids was measured in terms of turbidity, pH, and total dissolved solids (TDS). It was observed that the coagulation/filtration experiments were more efficient at removing turbidity, compared to the direct filtration process performed without any coagulation and filter media. Full article
(This article belongs to the Special Issue Nanocomposite Membranes)
Open AccessArticle Effect of Preparation Methods on Crystallization Behavior and Tensile Strength of Poly(vinylidene fluoride) Membranes
Membranes 2013, 3(4), 389-405; doi:10.3390/membranes3040389
Received: 12 October 2013 / Revised: 9 November 2013 / Accepted: 13 November 2013 / Published: 21 November 2013
Cited by 5 | PDF Full-text (685 KB) | HTML Full-text | XML Full-text
Abstract
Poly(vinylidene fluoride) (PVDF) membranes were prepared by non solvent induced phase separation (NIPS), melt spinning and the solution-cast method. The effect of preparation methods with different membrane formation mechanisms on crystallization behavior and tensile strength of PVDF membranes was investigated. Fourier transform infrared
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Poly(vinylidene fluoride) (PVDF) membranes were prepared by non solvent induced phase separation (NIPS), melt spinning and the solution-cast method. The effect of preparation methods with different membrane formation mechanisms on crystallization behavior and tensile strength of PVDF membranes was investigated. Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and X-ray diffraction (XRD) were employed to examine the crystal form of the surface layers and the overall membranes, respectively. Spherulite morphologies and thermal behavior of the membranes were studied by polarized light optical microscopy (PLO) and differential scanning calorimetry (DSC) separately. It was found that the crystallization behavior of PVDF membranes was closely related to the preparation methods. For membranes prepared by the NIPS method, the skin layers had a mixture of α and β phases, the overall membranes were predominantly α phase, and the total crystallinity was 60.0% with no spherulite. For melt spinning membranes, the surface layers also showed a mixture of α and β phases, the overall membranes were predominantly α phase. The total crystallinity was 48.7% with perfect spherulites. Whereas the crystallization behavior of solution-cast membranes was related to the evaporation temperature and the additive, when the evaporation temperature was 140 °C with a soluble additive in the dope solution, obvious spherulites appeared. The crystalline morphology of PVDF exerted a great influence on the tensile strength of the membranes, which was much higher with perfect spherulites. Full article
(This article belongs to the Special Issue Selected Papers from AMS8 Conference (July 2013, Xi’an, China))
Open AccessArticle Al2O3 Disk Supported Si3N4 Hydrogen Purification Membrane for Low Temperature Polymer Electrolyte Membrane Fuel Cells
Membranes 2013, 3(4), 406-414; doi:10.3390/membranes3040406
Received: 26 November 2013 / Accepted: 2 December 2013 / Published: 5 December 2013
Cited by 2 | PDF Full-text (775 KB) | HTML Full-text | XML Full-text
Abstract
Reformate gas, a commonly employed fuel for polymer electrolyte membrane fuel cells (PEMFCs), contains carbon monoxide, which poisons Pt-containing anodes in such devices. A novel, low-cost mesoporous Si3N4 selective gas separation material was tested as a hydrogen clean-up membrane to
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Reformate gas, a commonly employed fuel for polymer electrolyte membrane fuel cells (PEMFCs), contains carbon monoxide, which poisons Pt-containing anodes in such devices. A novel, low-cost mesoporous Si3N4 selective gas separation material was tested as a hydrogen clean-up membrane to remove CO from simulated feed gas to single-cell PEMFC, employing Nafion as the polymer electrolyte membrane. Polarization and power density measurements and gas chromatography showed a clear effect of separating the CO from the gas mixture; the performance and durability of the fuel cell was thereby significantly improved. Full article
(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)
Open AccessArticle The Fouling of Zirconium(IV) Hydrous Oxide–Polyacrylate Dynamically Formed Membranes during the Nanofiltration of Lactic Acid Solutions
Membranes 2013, 3(4), 415-423; doi:10.3390/membranes3040415
Received: 15 November 2013 / Revised: 22 November 2013 / Accepted: 25 November 2013 / Published: 10 December 2013
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Abstract
The results of investigations of flux decline during nanofiltration (NF) of lactic acid solutions using dynamically formed zirconium(IV) hydrous oxide/polyacrylate membranes (Zr(IV)/PAA) under conditions resulting in low and high lactic acid rejection are reported. The experimental permeate flux versus time curves were analyzed
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The results of investigations of flux decline during nanofiltration (NF) of lactic acid solutions using dynamically formed zirconium(IV) hydrous oxide/polyacrylate membranes (Zr(IV)/PAA) under conditions resulting in low and high lactic acid rejection are reported. The experimental permeate flux versus time curves were analyzed in the frame of resistance in a series model with the aim of developing the characteristic of resistances. Analysis of experimental data and results of calculations showed that the reduction of fouling effects in the investigated system could be achieved due to appropriate hydrodynamic process conditions and regular rinsing with deionized water. Full article
(This article belongs to the Special Issue Membrane Processes and Energy)
Open AccessArticle Insights on the Study of Nafion Nanoscale Morphology by Transmission Electron Microscopy
Membranes 2013, 3(4), 424-439; doi:10.3390/membranes3040424
Received: 9 November 2013 / Revised: 4 December 2013 / Accepted: 9 December 2013 / Published: 16 December 2013
Cited by 4 | PDF Full-text (2033 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nafion is one of the most common materials used for polyelectrolyte membranes and is the standard to which novel materials are compared. In spite of great interest in Nafion’s nanostructure, it is still a subject of controversy. While multiple research efforts have addressed
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Nafion is one of the most common materials used for polyelectrolyte membranes and is the standard to which novel materials are compared. In spite of great interest in Nafion’s nanostructure, it is still a subject of controversy. While multiple research efforts have addressed Nafion’s morphology with Transmission Electron Microscopy, the results of these efforts have often been inconsistent and cannot satisfactorily describe the membrane structure. One of the reasons for differences in the reported results is the lack of sufficient control over the damage caused by electron beam irradiation. In this work, we describe some aspects of damage in the material that have a strong influence on the results. We show that irradiation causes mass loss and phase separation in the material and that the morphologies that have been observed are, in many cases, artifacts caused by damage. We study the effect of the sample temperature on damage and show that, while working at low temperature does not prevent damage and mass loss, it slows formation of damage-induced artifacts to the point where informative low-dose images of almost undamaged material may be collected. We find that charging of the sample has a substantial effect on the damage, and the importance of charge neutralization under irradiation is also seen by the large reduction of beam induced movement with the use of an objective aperture or a conductive support film. To help interpret the low-dose images, we can apply slightly higher exposures to etch away the hydrophobic phase with the electron beam and reveal the network formed by the hydrophilic phase. Energy loss spectroscopy shows evidence that fluorine removal governs the beam damage process. Full article
(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

Review

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Open AccessReview Advancement in Electrospun Nanofibrous Membranes Modification and Their Application in Water Treatment
Membranes 2013, 3(4), 266-284; doi:10.3390/membranes3040266
Received: 3 September 2013 / Accepted: 13 September 2013 / Published: 30 September 2013
Cited by 16 | PDF Full-text (949 KB) | HTML Full-text | XML Full-text
Abstract
Water, among the most valuable natural resources available on earth, is under serious threat as a result of undesirable human activities: for example, marine dumping, atmospheric deposition, domestic, industrial and agricultural practices. Optimizing current methodologies and developing new and effective techniques to remove
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Water, among the most valuable natural resources available on earth, is under serious threat as a result of undesirable human activities: for example, marine dumping, atmospheric deposition, domestic, industrial and agricultural practices. Optimizing current methodologies and developing new and effective techniques to remove contaminants from water is the current focus of interest, in order to renew the available water resources. Materials like nanoparticles, polymers, and simple organic compounds, inorganic clay materials in the form of thin film, membrane or powder have been employed for water treatment. Among these materials, membrane technology plays a vital role in removal of contaminants due to its easy handling and high efficiency. Though many materials are under investigation, nanofibers driven membrane are more valuable and reliable. Synthetic methodologies applied over the modification of membrane and its applications in water treatment have been reviewed in this article. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)

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