Papers by Keyword: Membrane

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Authors: Ye.V. Tourleigh, K.V. Shaitan, N.K. Balabaev
Abstract: The distributions and transfer energies of several molecules and atomic groups between water and a structured hydrophobic phase were calculated by the molecular dynamics method. The coefficients of oxygen diffusion in a tetradecane membrane were estimated. The transfer energy of charged atomic groups was found to correlate with changes in the Born solvation energy. The contributions of atoms to the transfer energy of functional groups were shown to be non-additive. The steered dynamics method for estimating the kinetic parameters of the penetration of molecules through interphase boundaries was developed. Heterogeneous microviscosity of a membrane was calculated for a hydrated l-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine bilayer. Effects of the chemical properties of penetrant molecule on its translocation through the membrane were studied.
Authors: K. Thoeni, A. Effeindzourou, Bruno Chareyre, A. Giacomini
Abstract: A generalised approach for the modelling of arbitrary shaped deformable structures in the framework of the discrete element method is presented. Minkowski sums of polytopes and spheres are used to describe the geometry of rounded cylinders and particle facets. In the current formulation, these new elements can be deformable. Their deformation is defined by the set of positions and orientations of their nodes. The elements can be connected to form arbitrary structures, such as grids and membranes. The constitutive behaviour of such connections is defined via an elastic perfectly plastic beam model. Contacts between other not connected structures or particles are detected based on three simple primitives: spheres, cylinders and thick rounded facets. The introduction of a virtual sphere at the contact point not only allows for straightforward contact handling but as well for the use of standard contact models based on sphere–sphere interactions. Hence, there is no need for developing new contact models. The approach is implemented into the open-source framework YADE. The capability of the newly developed approach for the modelling of soil–inclusion problems is presented.
Authors: Hendrik C. Elsenheimer, Jan Tabellion, Florian Paul, Jürgen Haußelt
Abstract: The spatially distributed local electric field strength during the electrophoretic deposition (EPD) of alumina suspensions on a membrane is within the scope of the present article. The water-based alumina suspensions were optimized in order to achieve stable suspensions, high deposition rates and maximum green densities of the deposited bodies. In-situ measurements of the local potential drop inside the EPD-cell were carried out using a computer assisted process control set-up with electronic data acquisition. The behaviour of the spatial- and time-dependent electric field distribution was calculated from measured potential drops. The influence of varrying input voltages on the output parameters, such as deposition rate and green density for EPD on membranes was investigated and is discussed. It is shown that the distribution of the local electric field depends on the applied voltage and on time for the case of higher voltages. A dependance of the local electrical fields on the deposition rate is suggested as well.
Authors: Vitor Magueijo, Viriato Semião, Maria Norberta de Pinho
Abstract: A model based on steric hindrance mechanisms [1] is used to determine the pore sizes of two ultrafiltration (UF) membranes. The lysozyme rejection coefficients of those membranes are predicted through the same model after modification of the pore size and solute radius by taking into account the development of electric double layers. Two asymmetric cellulose acetate membranes M1 and M2 were prepared and characterized. Membrane M1 has an hydraulic permeability of 2.1x10-6 m/s/bar, a molecular weight cut-off (MWCO) of 30,000 Da and an average pore radius of 2.6 nm. Membrane M2 has an hydraulic permeability of 5.9x10-6 m/s/bar, a molecular weight cut-off (MWCO) of 60,000 Da and an average pore radius of 5.3 nm. Aqueous solutions of lysozyme containing a NaCl concentration of 0.1M were ultrafiltrated through membranes M1 and M2. The predicted lysozyme rejections considering the development of electric double layers on the protein and membrane pore surfaces, are in good agreement with the experimental results.
Authors: Rong Liu, Yan Wang, Jing Zhu, Zu Ming Hu, Jun Rong Yu
Abstract: The effects of Modified NanoSiO2 Agents on the morphology and performance of ultra-high-molecular weight polyethylene (UHMWPE) microporous membranes via thermally induced phase separation were investigated in this work. The NanoSiO2 was surface modified by silane coupling agent KH570 (KH570-NanoSiO2). Differential scanning calorimetry (DSC) and X-Ray Diffraction (XRD) were performed to obtain crystallization of UHMWPE/white oil/ KH570-NanoSiO2 doped system. The morphology and performance of the prepared UHMWPE microporous membranes were characterized with scanning electron microscopy (SEM) and microfiltration experiments. The results showed that the morphology of UHMWPE membrane could be disturbed by KH570-NanoSiO2. Porosity and the rejection of Bovine serum albumin (BSA) of the blend membrane increased with increasing concentration of Modified NanoSiO2, while the water flux slightly decreased.
Authors: Yu Lin, Wei Ming Xue, Yun Lu Fu, Han Yu Ren, Qing Lv, Yi Yan
Abstract: Immobilization of microencapsulated cell is a kind of membrane technology. Therefore, the characteristics of membrane have a great impact on the growth of microorganisms. This study is designed to achieve the greatest growth rate of microencapsulated cell, Escherichia coli were immobilized in AC microcapsules made with different type of chitosan and then cultured in the Luria-Bertani medium. Effect of deacetylated degree (DD), molecular weight, membrane formation time and the pH of chitosan on the swelling ratio, cell release and proliferation were investigated at 2, 4, 6, 12, 24and 48h respectively. The results showed that the DD has no obviously influence on terminal biomass concentration, but the swelling ratio of membrane reached lowest when the DD was 90%. The biomass concentration increased with the rising of chitosan Mw and membrane formation time. Especially, the terminal biomass concentration near to 6.5×106·mL in the microcapsules made with 10KDa chitosan Mw ands 15min membrane formation time. Moreover, the swelling ratio closed to lowest point as the chitosan solution pH was 6.3.
Authors: Jiu Mei Xiao
Abstract: A simple process to fabricate porous polyimide membranes (PPMs) and effect of warm-up temperature rates on morphologies of the PPMs were reported in this paper. The polymer solution layer consisting of the corresponding polyamic acid (PAA), solvent and the pore forming agents with high boiling temperature or high decomposition temperature was first treated under a lower temperature (about 150°C). The received solid membrane was further imidized by a higher temperature (about 270°C) and the pore forming agents were removed from the membrane at a temperature above their boiling temperature or decomposition temperature at last. Then a PPM was obtained. As the temperature was elevated gradually, the porosity of the received PAA membrane was lower than that of the PPM treated by a faster warm-up temperature rate.
Authors: Adanti Wido Paramadini, Prihartini Widiyanti, Djoni Izak Rudyardjo
Abstract: Traffic accident is the highest cause of head injury. In the field of neurosurgery, it is closely related to the defect of duramater (outer layer of the brain). This study aims to perform artificial duramater synthesis from bacteria cellulose that is composited with collagen in order to find the precise composition. Bacteria cellulose was synthesized by fertilizing Acetobacter xylinum bacteria into coconut water. In addition, bacteria cellulose pellicle membrane immersed into collagen solution with various concentration such as 0.4% w/v, 0.5% w/v, 0.6% w/v and 0.7% w/v. The dried sample was characterized by Fourier Transform Infra Red (FTIR), tensile tester, Scanning Electron Microscope (SEM) and swelling test procedure. Result showed that the best sample was ‘Sample A’ (bacteria cellulose-collagen 0.4% w/v) that obtained 8% elongation and 185 μm for the average thickness. Based on the entire result, the biocomposite of bacteria celluose-collagen has a high potential as a candidate of artificial duramater.
Authors: Muhamad Zaini Yunos, Zawati Harun, H. Basri, Ahmad Fauzi Ismail
Abstract: In this work, polysulfone ultrafiltration membranes were prepared via simple phase inversion with distilled water as non-solvent additive. The main reason for the addition of water in polysulfone dope solution preparation was to enhance the membranes structure. In the dope, 15 wt. % of polysulfone was used and water was varied up to 6 wt. %. The effects of water on morphology, porosity and tensile properties were investigated in detail. From the porosity test, results showed that the addition of water has improved membrane porosity up to 53 %. The FESEM images revealed that membrane morphology has also been modified. However, the tensile properties of membrane decreased as water content increased which may be due to the porosity interaction between polysulfone/NMP with water.
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