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Membranes, Volume 1, Issue 2 (June 2011), Pages 91-148

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Research

Open AccessArticle Membrane Characterization by Microscopic and Scattering Methods: Multiscale Structure
Membranes 2011, 1(2), 91-97; doi:10.3390/membranes1020091
Received: 3 March 2011 / Revised: 22 March 2011 / Accepted: 23 March 2011 / Published: 13 April 2011
Cited by 4 | PDF Full-text (1348 KB) | HTML Full-text | XML Full-text
Abstract
Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic) were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES) membranes (10, 30, 100 and 300 kDa) and new 100 kDa hollow fibers (PVDF). [...] Read more.
Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic) were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES) membranes (10, 30, 100 and 300 kDa) and new 100 kDa hollow fibers (PVDF). Scanning Electron Microscopy (SEM) with “in lens” detection was used to obtain information on the pore sizes of the skin layers at the atomic scale. White Light Interferometry (WLI) and Atomic Force Microscopy (AFM) using different scales (for WLI: windows: 900 × 900 µm2 and 360 × 360 µm2; number of points: 1024; for AFM: windows: 50 × 50 µm2 and 5 × 5 µm2; number of points: 512) showed that the membrane roughness increases markedly with the observation scale and that there is a continuity between the different scan sizes for the determination of the RMS roughness. High angular resolution ellipsometric measurements were used to obtain the signature of each cut-off and the origin of the scattering was identified as coming from the membrane bulk. Full article
(This article belongs to the Special Issue Selected Papers from the AMS6/IMSTEC10 Conference)
Open AccessArticle Effect of Ammonium- and Phosphonium-Based Ionic Liquids on the Separation of Lactic Acid by Supported Ionic Liquid Membranes (SILMs)
Membranes 2011, 1(2), 98-108; doi:10.3390/membranes1020098
Received: 14 March 2011 / Revised: 26 April 2011 / Accepted: 6 May 2011 / Published: 13 May 2011
Cited by 9 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
Biodegradable polymers have attracted much attention from an environmental point of view. Optically pure lactic acid that can be prepared by fermentation is one of the important raw materials for biodegradable polymer. The separation and purification of lactic acid from the fermentation [...] Read more.
Biodegradable polymers have attracted much attention from an environmental point of view. Optically pure lactic acid that can be prepared by fermentation is one of the important raw materials for biodegradable polymer. The separation and purification of lactic acid from the fermentation broth are the major portions of the production costs. We proposed the application of supported ionic liquid membranes to recovering lactic acid. In this paper, the effect of ionic liquids, such as Aliquat 336, CYPHOS IL-101, CYPHOS IL-102, CYPHOS IL-104, CYPHOS IL-109 and CYPHOS IL-111 on the lactic acid permeation have been studied. Aliquat 336, CYPHOS IL-101 and CYPHOS IL-102 were found to be the best membrane solvents as far as membrane stability and permeation of lactic acid are concerned. CYPHOS IL-109 and CYPHOS IL-111 were found to be unsuitable, as they leak out from the pores of the supported liquid membrane (SLM), thereby allowing free transport of lactic acid as well as hydrochloric acid. CYPHOS IL-102 was found to be the most adequate (Permeation rate = 60.41%) among these ionic liquids as far as the separation of lactic acid is concerned. The permeation mechanisms, by which ionic liquid-water complexes act as the carrier of lactate and hydrochloric acid, were proposed. The experimental permeation results have been obtained as opposed to the expected values from the solution-diffusion mechanism. Full article
(This article belongs to the Special Issue Liquid Membranes)
Open AccessArticle Electroformation of Giant Vesicles on Indium Tin Oxide (ITO)-Coated Poly(ethylene terephthalate) (PET) Electrodes
Membranes 2011, 1(2), 109-118; doi:10.3390/membranes1020109
Received: 12 April 2011 / Revised: 17 May 2011 / Accepted: 19 May 2011 / Published: 26 May 2011
Cited by 4 | PDF Full-text (672 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Electroformation of cell-sized lipid membrane vesicles (giant vesicles, GVs) from egg yolk phosphatidylcholine was examined using a poly(ethylene terephthalate) sheet coated with indium tin oxide (ITO-PET) as the electrode material. With sinusoidal ac voltage, GV formation occurred in a similar manner to [...] Read more.
Electroformation of cell-sized lipid membrane vesicles (giant vesicles, GVs) from egg yolk phosphatidylcholine was examined using a poly(ethylene terephthalate) sheet coated with indium tin oxide (ITO-PET) as the electrode material. With sinusoidal ac voltage, GV formation occurred in a similar manner to that on an ITO-glass electrode widely used in electroformation. Difference in the specific electrical resistance of ITO-PET did not significantly affect electroformation. The present results indicate that ITO-PET may be used as more flexible and less expensive electrode material in electroformation. In order to obtain insights into electroformation, other electric voltage forms, static dc and dc pulses, were also tested in place of commonly used sinusoidal ac. Under the present conditions, the best GV formation was observed with dc pulses of negative polarity. The result with static dc demonstrated that the mechanical vibration of swelling lipid seen with sinusoidal ac voltage was not essential for GV formation. On the positive electrode, the electroswelling of lipid mainly yielded non-spherical membranous objects. Pre-application of positive dc voltage on lipid hindered GV formation in electroswelling of the lipid with ac. Full article
Figures

Open AccessArticle Experimental Study of Fouling and Cleaning of Sintered Stainless Steel Membrane in Electro-Microfiltration of Calcium Salt Particles
Membranes 2011, 1(2), 119-131; doi:10.3390/membranes1020119
Received: 8 February 2011 / Revised: 30 April 2011 / Accepted: 11 May 2011 / Published: 30 May 2011
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Abstract
Sintered stainless steel (SSS) microfiltration membranes, which served as electrode directly, were used for the experiment of separating Alamin, a calcium salt and protein containing particles, found in dairy processing. Fouling and cleaning of the SSS membranes under the application of an [...] Read more.
Sintered stainless steel (SSS) microfiltration membranes, which served as electrode directly, were used for the experiment of separating Alamin, a calcium salt and protein containing particles, found in dairy processing. Fouling and cleaning of the SSS membranes under the application of an external electric field were studied. The imposed electric field was found, diverging the pH of permeate and retentate. This in turn altered the solubility of the calcium salt and impacted the performance of electro microfiltration membrane. Using electric field as an enhanced cleaning-in-place (CIP) method in back flushing SSS membrane was also studied. Full article
Open AccessArticle Electrochemical Impedance Spectroscopy—A Simple Method for the Characterization of Polymer Inclusion Membranes Containing Aliquat 336
Membranes 2011, 1(2), 132-148; doi:10.3390/membranes1020132
Received: 6 April 2011 / Revised: 3 June 2011 / Accepted: 16 June 2011 / Published: 23 June 2011
Cited by 11 | PDF Full-text (336 KB) | HTML Full-text | XML Full-text
Abstract
Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with [...] Read more.
Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon. Full article
(This article belongs to the Special Issue Liquid Membranes)

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