Dynamic membrane formation

Examples of such plots can be found in Figure 8, for three different dynamic membrane formation conditions. As predicted by equation (16), the data yields good straight line plots, and the values of Rj jj calculated from the intercepts are given in Table 1. One sees that the salt rejection increases from 2%% to 33% when the formation pressure is increased from 10 to 15 psi. Thus the corresponding decrease in Lp (c.f. 

Z.S. Li, Investigation of the dynamics membrane formation by of polyfether snlfone) membrane formation by precipitation immersion, Journal of Polymer Science Part B Polymer Physics 43(5) (2005) 498-510. 

Generally, the effectiveness of the separation is determined not by the membrane itself, but rather by the formation of a secondary or dynamic membrane caused by interactions of the solutes and particles with the membrane. The buildup of a gel layer on the surface of an ultrafiltration membrane owing to rejection of macromolecules can provide the primary separation characteristics of the membrane. Similarly, with colloidal suspensions, pore blocking and bridging of... 

SCF models typically make use of lattice approximations. As dynamics are not an issue, it is not necessary to specify all the potentials in equal detail. Therefore there are many differences between the SCF and simulation methods. Comparing and contrasting both methods remains of interest, because this will give insight into essential and less essential aspects of membrane formation. 

Determination of Phase Diagrams and Composition Paths The dynamics of the membrane formation process is predicted by combining the kinetics and thermody-... 

Cholesterol affects a large variety of membrane properties in animal cells (39). It is involved in modifying dynamical membrane properties by reducing passive permeation, slowing down the lateral diffusion of molecules in fluid-like membranes, and speeding up diffusion in gel-phase membranes. It also affects bilayer properties by condensing the bilayer, which changes its elastic properties and promotes the order of phospholipid acyl chains in the hydrophobic membrane core. In this manner, cholesterol develops the formation of the liquid-ordered... 

There is another type of membrane that is conceptually different from the membranes prepared according to the above methods. It is called dynamic membranes. They are formed, during application, on microporous carriers or supports by deposition of the colloidal particles or solute components that are present in the feed solution. This in-situ formation characteristic makes it possible to tailor them for specific applications in ultrafiltration and reverse osmosis (hyperfiltration). 

Dependence of Dynamic Membrane Performance on Formation Materials and Procedures... 

Dynamic membranes are formed on microporous supports under appropriate pressure and cross-flow conditions by deposition of solute components contained in a feed solution. The formation steps are ... 

The properties of dynamic membranes can be influenced at each step in the formation by altering the materials and procedures. Hence, dynamic membranes are expecially suited for tailoring to optimize a membrane s performance in a specific application, and a variety of experimental and commercial membranes have been formed. 

This paper reviews some recent developments in dynamic membrane research, describes properties and applications of commercial membranes, and reports properties of dynamic polyblend membranes. Formation of Dynamic Membranes... 

The poineering research and subsequent development of useful dynamic membranes was accomplished by Johnson and co-workers at the Oak Ridge National Laboratory. This very extensive research has been reported in a series of reports and in numerous publications and patents. Papers of special interest are the detailed report of the initial process for forming dynamic membranes with attractive hyperfiltration properties by Marcinkowsky, et al. (1 ), an early review of the research properties by Johnson ( ), and a subsequent review of hyperfiltration models and the development of hyperflltra-tion membranes by Dresner and Johnson ( ). These reviews cite the major references related to the formation, theory, properties, and applications of dynamic membranes. 

Two useful membranes developed by the group at the Oak Ridge National Laboratory have dominated the application of dynamic membranes the hydrous zirconium oxide ultrafilter and the hydrous zirconium oxide-poly(acrylic acid) hyperfilter. The technology of formation and utilization of zirconium oxide-poly(acrylic acid) dynamic membranes has been described in detail by Thomas ( ). The effects of molecular weight of the poly(acrylic acid), pore diameter of the porous support, formation cross-flow velocity, formation pressure, and pH of poly(acrylic acid) solution during initial deposition of the polyacid on the hyperfiltration performance are described and discussed. 

Hang (10) has prepared and characterized cross-linked poly-(vinyl alcohol) dynamic membranes on porous ceramic tubes. The post-formation cross-linking with a solution containing oxalic acid, boric acid, and KCr(804)2 produced membranes with good stability in both acidic and basic solutions. 

An examination of the data for dynamic membranes formed under various conditions suggests that a combination of higher pressure and cross-flow rate yields both the highest product flux and lowest oil extraction values. However, the overall impression is that the TOC or extractables level of the product is far less sensitive to formation conditions than the hydraulic permeability or even the intrinsic salt rejection toward 10 3m Na2S0ij solutions. Further evi-... 

SM Dzekunov, YN Antonenko. Dynamics of formation and dissipation of local pH gradients in the unstirred layers near bilayer lipid membranes. Bio-electrochem Bioenerg 41 187-190, 1996. 

Autofiltration The formation of a secondary or a dynamic membrane hy retention of solutes or particles on the membrane surface affects separation or fractionation in UF. The higher the pressure, the more severe the polarisation. 

Tang Yuan-hui, He Yan-dong, and Wang Xiao-lin. Investigation on the membrane formation process of polymer-diluent system via thermally induced phase separation accompanied with mass transfer across the interface Dissipative particle dynamics simulation and its experimental verification. J. Membr. Sci. 474 (2015) 196—206. 

CH2 Cheng, L.-P., Dwan, A.-H., and Giyte, C.C., Membrane formation by isothermal precipitation in polyamide-formic acid-water systems 11. Precipitation dynamics, J. Polym. Sci. Part B Polym. Phys., 33, 223, 1995. 

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