Permeation solution-diffusion

Using this simplified model, CP simulations can be performed easily as a function of solution and such operating variables as pressure, temperature, and flow rate, usiag software packages such as Mathcad. Solution of the CP equation (eq. 8) along with the solution—diffusion transport equations (eqs. 5 and 6) allow the prediction of CP, rejection, and permeate flux as a function of the Reynolds number, Ke. To faciUtate these calculations, the foUowiag data and correlations can be used (/) for mass-transfer correlation, the Sherwood number, Sb, is defined as Sh = 0.04 S c , where Sc is the Schmidt... 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

Some of the polymeric membranes are suitable for bulk separation of hydrogen from impurities to enrich a dilute hydrogen stream. Dense polymers permeate gases by solution diffusion mechanism. The permeation rate of a gas species through a polymer membrane... 

The success of the Potts-Guy equation led many authors to advocate a single mechanism as the rate determining step for permeation through the skin barrier for all or at least a wide range of solutes diffusion was assumed to occur primarily via the interkeratinocyte lipids of the stratum corneum, a mixture of ceramides, fatty acids, and sterols. While from a macroscopic point of view these lipids may be modeled as a bulk solvent, on a microscopic scale they... 

Concentration in the permeate is expressed by that in the feed as Equation (5), using solution-diffusion model assuming no concentration polarization. 

Feed water (Cp, Qp) is allowed to enter into the module from its left side. Permeated water at each membrane section is expressed simply by Solution Diffusion model (Eq (1), (2) in Table 3) Concentrated water (Cg, Qg) is discharged from the right side of the module. Summation of product water at each membrane section results in total product water (Cp, Qp). At each membrane section, material balance is taken on each component (Eq (7), (8) in Table 3). 

We may conclude that our findings support independent water and salt permeation processes, and suggest that the salt permeation is governed by a solution-diffusion transport mechanism. 

The mechanism of transport of GPG using SLM has been studied at the authors laboratory [56]. GPG could be permeated from alkaUne feed of carbonate buffer into an acidic stripping solution of acetate buffer across the membrane comprising Aliquat-336 in -butyl acetate immobiUzed in a polypropylene (Gelgard 2400) support. The transport mechanism is a case of counter transport exhibiting overall rate dependence on solute diffusion in the membrane phase as well as the mass transfer across the aqueous boundary films. 

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