Membranes osmotic

D. C. Guell, H. Brenner. Physical mechanism of membrane osmotic phenomena. Ind Eng Chem Res 55 3004, 1996. 

Osmotic pressure is another property due to dissolved substances. The presence of solute particles lowers the ability of solvent molecules to pass through a semipermeable membrane. Osmotic pressure is very important in biological systems, and an application of the theory behind osmotic pressure allows for the purification of seawater. The osmotic pressure of a solution, IT, is proportional to the molarity (the number of moles per liter) ... 

Despite its many advantages, the enclosure of nucleic acids and proteins within membranes introduced several complications. Perhaps the most significant were the effects of osmosis. Membranes are somewhat permeable to water and small nonpolar molecules, whereas they are impermeable to macromolecules such as nucleic acids. When macromolecules are concentrated inside a compartment surrounded by such a semipermeable membrane, osmotic forces drive water through the membrane into the compartment. Without counterbalancing effects, the flow of water will burst the cell (Figure 2.15). 

Membrane processes termed as osmotic distillation or membrane distillation could be shown to be applications of membrane contactor technology also. Both of these processes are based on gas membranes. Osmotic distillation, sometimes called osmotic evaporation, involves transfer of water vapor across a gas-fiUed membrane, the process is driven by a difference in water vapor pressure maintained across the membrane [58-59] by separate aqueous hquids. Membrane distillation is a process where water vapor transfer is driven solely by a temperature difference across the gas-fiUed membrane [60-61]. Water evaporates from a hot aqueous phase and condenses on a cooler surface. This process may be useful in desalinating water or producing pure water if a good natural source of warm water is available, such as in a geothermal process. 

Osmosis is the natural movement of a solvent through a semipermeable membrane into a solution of higher solute concentration, leading to equal solute concentrations on both sides of the membrane [93]. A semipermeable membrane can be crossed by solvent molecules but solute (ionic or high molecular weight compounds) permeation is impeded. Solvent migration from one side of the membrane to the opposite one takes place to render equal solute and solvent chemical potentials across the membrane. Osmotic pressure tt can be expressed by... 

Exchange of ions in membranes osmotic and electrolyte control (Na, K, Mg,... 

Consider a solvent and a solution each of practically infinite size. Suppose one mole of solvent is transferred from the pure solvent to the solution Work is done in the transfer which can be reckoned m terms of the solvent pressure The maximum woik is RT log w / ir, provided the general relation, ir (V - b) = RT, holds good, as is assumed m Tinker s treatment of the problem The gram-molecule of solvent is now removed from the solution reversibly by means of a semipeimeable membrane, osmotic woik being done upon the system The volume of one gram-molecule of the solvent is supposed to be the same, viz Vlt in the solution as it is in the solvent, since the solution is an ideal one The maximum osmotic work done upon the system is therefore PVX The gram-molecule may now be added without further work to the original solvent and the cycle is complete Since it is isothermal the total work is zero, or—... 

Binding to the receptors and insertion into the membrane Formation of pores in the membrane Osmotic disruption of the gut cell... 

Wang L., Min J. (2011), Modelling and analyses of membrane osmotic distillation nsing non-eqnilibrinm thermodynamics, J. Membrane ScL, 378,462-470. 

The understanding of the thermodynamic behaviour of PEO in aqueous solutions is important for predicting the phase behaviour of these compounds and many of polyoxyethylene derivates. PEO has a wide application in technics, surface and colloid chemistry, medicine and pharmacy. The purpose of this work is, to determine the thermodynamic functions in a large range of concentration and temperature with the aid of vapour pressure (VPO) and membrane osmotic (MO) measurements. Furthermore we have used a differential measuring technique in TO, which is a modified steady state method w e have developed [l, 2]. A similar method was introduced in the membrane osmosis by Rehage and Meys C3]. 

V = dilute solution viscosity LS = light scattering OP = membrane osmotic pressure VPO = vapour pressure osmometry F = preparative fractionation... 

Quantitative estimates of stability in multiple emulsions are complicated by the fact that the systems are not to be considered simply as water-in-oil emulsions dispersed as an oil-in-water emulsion. This approach is doomed to failure the presence of water droplets in an oil drop suspended in water leads to the oil layer acting as a semi-permeable membrane. Osmotic factors thus lead to swelling or contraction of the inner water droplets by passage of water molecules across the oil layer [153]. 

Keywords Adsorption Bilayer Hydrophobic interaction Insertion Lipid membrane Osmotic pressure Poly(ethylene glycol) Vesicle... 

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