Osmotic water transfer coefficient

Equation (20-80) requires a mass transfer coefficient k to calculate Cu, and a relation between protein concentration and osmotic pressure. Pure water flux obtained from a plot of flux versus pressure is used to calculate membrane resistance (t ically small). The LMH/psi slope is referred to as the NWP (normal water permeability). The membrane plus fouling resistances are determined after removing the reversible polarization layer through a buffer flush. To illustrate the components of the osmotic flux model. Fig. 20-63 shows flux versus TMP curves corresponding to just the membrane in buffer (Rfouimg = 0, = 0),... 

Because EY5 is equal to k the mass transfer coefficient, is strongly dete. There are two other effects that influences the performance of the process as well, i) osmotic flow and ii) less effective Donnan exclusion. Osmotic flow is inherently part of the process and can not be avoided. Since ions are transferred from one compartment to another an osmotic pressure difference is generated and this drives the osmotic transport of water from the diluate to the concentrated side. Secondly, in case of high ionic concentrations the Donnan exclusion becomes less effective. This effect and the less favoured energy consumption at high concentrations makes the process of electrodialysis mote competitive at relatively low concentrations. 

The first term on the right side of Eq. (1.46) is the stoichiometric flux of water due to the ORR. The second term is the electro-osmotic flux of water through the membrane, where is the effective transfer coefficient of water molecules through the MEA. ... 

Osmotic transfer of water through the membranes may be presented in the fonn of Eq. (25) coefficients. Example of data is shown in Table 6.4. 

Harris FE, Rice SA (1954) A chain model for polyelectrolytes. Int J Phys Chem 58 725-732 Heller GT, Marcus Y, Waghorne WE (2002) Enthalpies and entropies of transfer of electrolytes and ions from water to mixed aqueous organic solvents. Chem Rev 102 2773-2836 Helgeson HC, Kirkham DH, Flowers GC (1981) Theoretical prediction of the thermodynamic behavior of aqueous electrolytes at high pressures tmd temperatures IV. Calculation of activity coefficients, osmotic coefficients, and apparent moled and standard and relative partial moM properties to 600 °C and 5 kb. Am J Sci 281 1249-1516 HeplerLG, Hovey JK (1996) Standard state heat capacities ofaqueous electrolytes and some related undissociated species. Can J Chem 74 639-649... 

K) 2 is the electron transfer number for each H2O molecule produced by a 4-electron ORR F is the Faraday constant (96,487 A s moP ) and m is the amount of water osmotically dragged per proton transfer from the anode to the cathode (m is also called the osmotic drag coefficient). For a water-vapor-equilibrated system, the value of m is likely to be a constant number over a broad range of water content values, from a nearly dry membrane (--2H2O per SO3) to a fully hydrated membrane (with water vapor -14H20 per SO. The... 

A vesicle system prepared with purified soybean lecithin in 1 mM KCl has an inner radius of 15 nm. The system is then diluted with a large excess of distilled water. Estimate the time required for the encapsulated ions to transfer into the outer continuous phase given that the permeability coefficient for both ions is 10 cm/s and that the dimensions of the vesicles do not change despite the change in osmotic pressure. 

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