Permeation also

The stationary phase in gel permeation (also called size exclusion) chromatography contains cavities of a defined size distribution, called pores. Analytes larger than the pores are excluded from the pores and pass through the column more rapidly than smaller analytes. There may be secondary effects due to hydrophobic adsorption, ionic interaction, or other interactions between the stationary phase and analyte. Gel permeation and non-ideal interactions in gel permeation are described more fully in Chapter 6. 

Whey permeate may also be fermented anaerobically to fuel gas. Studies have also been reported on the production of ammonium lactate by continuous fermentation of deproteinized whey to lactic acid followed by neutralization with ammonia. Conversion of whey and whey permeate to oil and single-cell protein with strains of Candida curvata and Trichosporon cutaneum have been examined. Production of the solvents n-butanol and acetone by Clostridium acetobutylicum or C. butyricum is under investigation in New Zealand. Whey permeate also has potential for citric acid and acrylic acid manufacture. Extracellular microbial polysaccharide production from whey permeate has... 

Increasing the pervaporation temperature is quite often useful in order to improve the flux and separation efficiency of a membrane. This also holds for polyelectrolyte multilayer membranes [66]. For 2-propanol/water pervaporation across PVA/PVS membranes it was found, for example, that the total flux increases by a factor of ten upon changing the pervaporation temperature from 25 to 60 °C, whereas the water content of the permeate also increased slightly. The reason is that increasing the temperature mainly increases the flux of water across the membrane, which is favorable for the separation characteristics. For an optimum separation all pervaporation measurements were thus carried out at about 60 °C, the highest temperature technically available with our apparatus. 

The slow passage of liquid through a POROUS MEDIUM. Capable of being PERMEATED also having PORES or openings that permit liquids or gases to pass through. 

Figures 2 and 3 show the toluene concentration In the feed, permeate and process tank, respectively, as functions of time. The data scatter Is more pronounced at higher toluene concentrations because the Internal standard method of calculation used the relative response factors which were developed at dilute toluene concentrations (l.e., toluene concentration In permeate). Also, this data scatter could Indicate that the gas chromatograph detector response Is not linear over the wide range of toluene concentrations examined.

Figure 4.41 illustrates the water immersion period and polymer-cement ratio vs. water absorption of latex-modified mortars. The water absorption increases with additional water immersion period, and at lower polymer-cement ratios becomes nearly constant at 48 hours regardless of polymer type. Figures 4.42l l shows the 48-hour water absorption and the amount of water permeation (under a water pressure of 1 kgf/cm ) of the latex-modified mortars. Generally, the water absorption and the amount of water permeation are considerably reduced with an increase in polymer-cement ratio. In all cases, except PVAC-modified mortar, as the resistance to water absorption increases, the resistance to water permeation also increases. The waterproofness of PVAC-modified mortar is low. Polyvinyl acetate swells due to water absorption, and is partially hydrolyzed under alkaline conditions as expressed by the following equation t l i J... 

A gas on the higher pressure side of a membrane dissolves in the membrane and permeates through it to reach the side with the lower pressure. Permeation also takes place in the absence of macroscopic pores, in fact, by exchanging sites with the membrane material. If the gas is of sufficiently low solubility in the membrane, the difference in concentration Ac is, according to Henry s law, proportional to the difference in pressure Ap ... 

The integrated process was also adopted for the production of vanillin (Augugliaro et al, 2011 Camera-Roda et al., 2011b), the most important aroma for industrial use, which is photocatalyticaUy synthesized starting from an aqueous solution of feruhc acid or other aromatic precursors, and selectively and continuously recovered utilizing a PEBAX 2533 membrane prepared by solvent casting. A significant purification of the product in the permeate (also thanks to the fractional condensation of the permeate with a deposition of part of the permeated vanillin as virtually pure crystals) and an enhancement of the yield were observed. 

A plot of log K versus 1000/r for helium permeation through various glasses is shown in Fig. 5.38. Note that the permeation also follows Arrhenius behavior quite well, and that the more open-struetured glasses are the more permeable. Permeability decreases rapidly with increasing size of the permeating atom. 

Various models for composite permeability as they relate to nanocomposites have been reviewed and different models have been proposed [41—44]. The simplest way to model any composite property is to use a rule of mixtures approach. Polymer nanocomposite properties, however, do not generally follow this rule. Instead, fillers with high aspect ratio particles will influence the permeability of gases through the matrix more than filler particles with lower aspect ratios. Alignment/orientation of the filler particles (with respect to the axis of gas permeation) also plays a significant role in bulk permeability. Five models are briefly described in Sections 8.5.1-8.5.5. Predictions from these models are later compared to experimental mass loss rates. 

From the study of X-ray diffraction it is not evident if the degree of crystallization can be closely correlated to the permeability of the membrane. This could mean that the degree of crystallization is low and that the properties for gas permeation also are determined by the state of the amorphous material in the polymer, which can have a certain degree of order. 

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