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Abstract : Vapor Permeation of Aqueous Ethanol through Agarose-Sericin Membrane
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Abstract: A self-standing membrane was obtained from renewable polymers, such as agarose and sericin. Differential scanning calorimetric study revealed that there were two states of water in the membrane, such as bound water and free water. The membrane preferentially transported water from aqueous ethanol mixture by vapor permeation. Preliminary study revealed that the present membrane was applicable to forward osmosis.. Keywords: Agarose, Melting Point Depression, Membranes, Vapor Permeation, Sericin.Download Full Article |
Abstract : New Concept for Dual-Layer Hydrophilic/Hydrophobic Composite Membrane for Membrane Distillation
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Abstract: This study presents a new concept of a simple method for the synthesis of dual layer hydrophilic/hydrophobic composite membranes for membrane distillation (MD). The membranes were prepared of poly(vinylidenefluoride) (PVDF) by phase inversion. The synthesis was realized by allowing a full or partial penetration of the polymer solution through one or two non-woven support (NWS) layers. This was achieved by proper selection of a thin NWS having high stiffness, high porosity and low surface tension, in combination with a runny polymer solution and sufficient time gap between casting and coagulation. The applied preparation method was effective in yielding dual layer composite membranes. The first layer atop the NWS was a hydrophilic or slightly hydrophobic one (contact angle (CA) of 88-92º), while the bottom layer beneath the NWS was highly hydrophobic (CA=132-140º). The difference in surface energy between the top and bottom layers originated from a difference in morphology. A smooth and dense top layer is formed as a result of an instantaneous demixing, while a porous and multi-scale network with some degrees of spherulitical structure was formed on the bottom by a delayed demixing mechanism. Direct contact MD (DCMD) results showed that the obtained flux was comparable to other composite MD membranes with high salt rejection. Membrane alignment inside the MD module is a critical element in determining the membrane performance and is shown to significantly increase flux when a top facing feed configuration is used. Keywords: Membrane distillation, poly(vinylidenefluoride), phase inversion, dual-layer, composite membrane.Download Full Article |
Abstract : A Review of Applications of Rotating and Vibrating Membranes Systems: Advantages and Drawbacks
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Abstract: Dynamic filtration (DF) consists in creating a high membrane shear rate by disks rotating near a fixed membrane or by rotating or vibrating membranes. The shear rate can exceed 3 105s-1 in some modules and significantly increases permeate flux and membrane selectivity as compared to cross flow (CF) devices. This paper describes several DF industrial modules and gives equations for calculating shear rates at rotating and vibrating membranes. It reviews 23 recent articles from 2008 to 2014, dealing with diverse applications: separation of microalgae from sea water by UF, clarification of rough beer, concentration of CaCO3 suspensions, treatment of dairy effluents and shipboard wastewaters, inulin extraction from chicory juice, treatment of oil field water, and separation of bovine albumin from yeast. In several applications, the maximum permeate flux at initial concentration ranged from 270 to 760 Lh-1m-2. Modules with ceramic membranes rotating around several shafts inside a housing seem to be preferable to the concept of multi-compartments modules with metal disks rotating between fixed membranes. Since the cost of DF modules is higher than that of spiral wound ones, it is better to apply DF to ”end of pipe treatment” after an initial concentration by CF. Keywords: High shear rate filtration, rotating disks, rotating or vibrating membranes.Download Full Article |
Abstract : Influence of a Microwave Irradiation on the Swelling and Permeation Properties of a Nafion Membrane
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Abstract: The effect of a microwave irradiation at 2450 MHz on the swelling and permeation properties of a Nafion membrane in water and methanol media has been studied. The influence of the irradiation power and the exposure time has been analyzed. The results found show that the irradiation hardly affects the membrane liquid uptake, but it affects the expansion properties of the membrane. The hydraulic permeability coefficient of the unmodified and the irradiated membranes has been experimentally determined. Higher hydraulic permeability has been obtained for the irradiated membranes in both water and methanol, but the degree of increment in permeability coefficient with microwave depends on kinds of permeation liquid. The results have been discussed considering the degradation effect occurring on the membrane hydrophobic matrix, which affects to the membrane elastic properties. Keywords: Nafion membrane, microwave, hydraulic permeability, swelling, liquid uptake, water, methanol. Download Full Article |
