Permeation lower curves

In all late-time regimes notably those represented by Eqs. (60), (62), (64) and (66) ideal kinetics is obeyed 144.15°.15i.154.159.l6l) whereas this is not so in the short-time regimes presented by Eqs. (59), (63) and (65) 150 ,51 154,163,64) (which convey essentially the same information).151 The short time behaviour of lower permeation curves represented by Eq. (61) appears to occupy an intermediate position, in the sense that ideal kinetics appears to be followed only to a first approximation151. The relation between permeation and symmetrical sorption indicated by Eq. (70) is also notable. The respective kinetics become very similar at long times154 as indicated by the relevant relations151) D2M = Ds = D7 = D8 and... 

Au nanotubule membranes with the following approximate nanotubule diameters were used to obtain the majority of the data reported here i.d. = 28 1, 7.0 0.1, 1.9 0.1, and 1.5 0.2 nm. Figure 19 shows permeation data for transport of pyridine through these various membranes. Data for membranes derivatized with both the R = -C2H4-OH (upper solid curve) and the R = -C16H33 (lower dashed curve) thiols are shown. The corresponding flux data are shown in Table 3. As would be expected [114], the flux of pyridine decreases with decreasing tubule diameter for both the... 

Enrichment of the preferred gas, helium in this case, is most productively displayed as a plot of the feed concentration of this gas relative to the remainder gases (or to a less preferred gas in the mixture) versus the equivalent ratio in the permeate. This is thus a plot of feed ratio vs. flux ratio. If this is done for several feed compositions representing a significant preferred-gas composition ran e, enrichment curves can be generated, such as those displayed in Figures 6 and 7. Here it can be seen that the lower pressure differentials are more desirable from a permeate quality standpoint. 

The chromatograms of cellulose triacetate (CTA) whole polymer (Ac w = 61.0 wt %, dotted curve) and its fractions (solid curves) are illustrated in Fig. 3. For the cellulose diacetate (CDA) and CTA fractions, the TLC becomes apparently sharp with an increase in Mw. The double-peaked form of the chromatograms is characteristic of the CTA samples, although their gel permeation chromatography (GPC) curves have been found to be single-peaked. This fact implies that the peak at the lower end of Rf corresponds to fully substituted CTA and the peak at the higher end is obviously due to the existence of not-fully substituted acetate. In this sense, real CTA is a binary mixture of ideal CTA and CDA. 

The more conventional method for studying the energetics of diffusion in membranes is to perform permeation experiments as a function of equilibrium temperature. Figure 13 illustrates the eflEect of temperature on the apparent diflEusion coeflScient calculated from the water vapor permeation time lag established by steady-state permeation with a 75 to 0% RH gradient across the membrane. The principles of the time lag permeation method are adequately discussed elsewhere (58). The lower curve corresponds to a sample which was not mechanically supported and was observed to deform into a hemispherical shape. This deformation is the combined result of a small pressure diflEerence across the membrane and a decrease in modulus of stratum corneum as the temperature is increased. The upper curve corresponds to a supported sample. Previous to the experiment, both samples had identical thermal histories. Stresses accompanying deformation of the unsupported cor-... 

A new empirical correlation was proposed and for a given permeate flow rate, the energy consumption is lower for a curved module than for a straight one... 

Figure 4.25 A typical gel permeation chromatogram. The lower trace with short vertical lines is the differential refractive index while the upper curve is an absorption plot at a fixed ultraviolet frequency. The short vertical lines are syphon dumps numbered consecutively from the time of injection of the sample. The units of the ordinate depend on the detector, while those of the abscissa can be in terms of syphon volumes (counts) or volume of solvent.

Fig. 4.5.6. An example of the combination of gel permeation (ion exchange) chromatography of metalloproteins with atomic absorption spectrometry for evaluation of fractions I96], Rat liver supernatant (0.2 ml) obtained after injection of cadmium chloride was applied to a TSK Gel SW 3000 column 600x21.5 mm, and eluted with 50 mM Tris-HCl buffer solution (pH 8.6 at 25°C). Absorbance at 280 nm (lower curves) and concentration of cadmium (A) or zinc (B) (upper curves) were continuously monitored. I and II indicate metallothionein-l and -II, respectively. This chromatogram indicates the contribution of ion exchange to TSK Gel SW gel-permeation chromatography, because both separated proteins have the same molecular weight, and the sequence of peaks emerging corresponds to the ion exchange chromatography separation.

A similar effect (increasing the fluidization gas velocity will decrease the extent of densified zones) has been found for the turbulent fluidization regime (Fig. 4.34B). However, the slopes of the curves representing the extent of the densified zones as a function of the permeation gas velocity are lower than for the bubbling regime. This means that it is preferred to operate in the turbulent fluidization regime, because with the same permeation gas velocity (i.e., membrane permeance), the extent of densified zones is much decreased. 

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