Permeation through Solids

Properties A diatomic gas. D 0.08999 g/L, d 0.0694 (air = 1.0), specific volume 193 cu ft/lb (21.1C), fp -259C, bp -252C, autoign temp 1075F (580C). Very slightly soluble in water, alcohol, and ether Noncorrosive can exist in crystalline state at from 4—1 K classed as an asphyxiant gas rate of permeation through solids is approximately four times that of air. 

It is well known that hydrogen isotopes, hydrogen, deuterium, and tritium, permeate through solid metals. Tritium produced in the reactor core tends to permeate through heat transfer tubes of IHX and the reaction tubes of the chemical reactor. Further, it is probable that the tritium will mix with the product hydrogen. Therefore, estimation of tritium permeation should be done, and a countermeasure to reduce tritium permeation, if necessary. 

The high specificity required for the analysis of physiological fluids often necessitates the incorporation of permselective membranes between the sample and the sensor. A typical configuration is presented in Fig. 7, where the membrane system comprises three distinct layers. The outer membrane. A, which encounters the sample solution is indicated by the dashed lines. It most commonly serves to eliminate high molecular weight interferences, such as other enzymes and proteins. The substrate, S, and other small molecules are allowed to enter the enzyme layer, B, which typically consist of a gelatinous material or a porous solid support. The immobilized enzyme catalyzes the conversion of substrate, S, to product, P. The substrate, product or a cofactor may be the species detected electrochemically. In many cases the electrochemical sensor may be prone to interferences and a permselective membrane, C, is required. The response time and sensitivity of the enzyme electrode will depend on the rate of permeation through layers A, B and C the kinetics of enzymatic conversion as well as the charac-... 

The EPOC microfiltration process is based on the ability of a proprietary woven polyester filter to retain particles and allow water to permeate through the filter. The technology uses a three-step process in which (1) reagents are added to the wastewater to precipitate metals and/or sorb other contaminants (2) the microfiltration unit (known as EXXFLOW) removes and concentrates the precipitates, while allowing water (permeate) to pass and (3) the concentrated precipitate is dewatered (by a module called EXXPRESS) to produce a semidry filter cake containing the metal precipitates and other filtered solids. 

There are many causes of low, particularly oral, bioavailability, F. Some of these occur in the gastrointestinal lumen, affecting the dissolution of a solid or its stability by changing, for example, pH so that only a fraction (FA) of the administered dose reaches the epithelial absorption sites. However, only a fraction of this dose may permeate through the intestinal wall into the portal blood (Fq), and then only another fractionfFn) escapes the liver and enters the systemic circulation. Accordingly, because these sites of loss are arranged in series, it follows that the overall systemic oral bioavailability F is... 

Permeation through liquids is orders of magnitude faster than that through solid polymers of comparable thickness. This rate advantage is exploited for some separations by using an immiscible liquid film as the membrane to mediate the transport of selected substances. Two somewhat different separation technologies have evolved based on... 

Lin, Y. S., Wang, W., and Han, J. (1994). Oxygen permeation through thin mixed-conducting solid oxide membranes, AIChE J. 40(5), 786. 

Many important phenomena in solid state ionics, such as ionic conduction, gas permeation through dense solids, solid state reactions, high temperature corrosion, or sintering of polycrystals, involve mobile ionic charge carriers. In most crystalline... 

The selection of diffusion equation solutions included here are diffusion from films or sheets (hollow bodies) into liquids and solids as well as diffusion in the reverse direction, diffusion controlled evaporation from a surface, influence of barrier layers and diffusion through laminates, influence of swelling and heterogeneity of packaging materials, coupling of diffusion and chemical reactions in filled products as well as permeation through packaging. 

The De Smet extractor (Figure 23) has one moving part the blet. The belt is set on a slight incline and carries the solids up the incline, throughout the extractor. This helps to ensure a more effective countercurrent flow of miscella through the solids. As a result of the incline, the miscella washes tend to permeate through the solids slanted toward the feed end (countercurrent to the solids flow). Rakes scrape... 

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