Permeation efficiency

Permeation efficiency Reduction factor for latent heat exchange through clothing. 

The effect of these peptides on skin permeation efficiency was determined by diffusion experiments of Na-DFC through porcine skin using Franz diffusion cells. All systems were composed of Hn mesophases loaded with 1 wt% Na-DFC and 1 wt% of each CPP (the control was a system with Na-DFC and no CPP). These experiments indicated that all three peptides increased significantly the diffusion of Na-DFC through the skin. 

To enhance the permeation efficiency and selectivity of the polymeric membrane separation, a novel polymeric plasticizer membrane which is composed of cellulose triacetate (CTA) as a membrane support, o-nitrophenyl octyl ether (NPOE) as a membrane plasticizer, and trioctylmethylammonium chloride (TOMAC) as an anion-exchange carrier has been developed. Compared with the poly (vinyl chloride) plasticizer membrane which is widely used for ion-selective electrode, the CTA membrane can contain a larger amount of plasticizer due to a high affinity between CTA and NPOE (25). Thus the plasticizer (NPOE) solubilized in the membrane acts effectively as an organic medium for the carrier mediated membrane separation (25-29). 

Using the Maxwell-Stefan theory, we will closer investigate the influence of isotherm inflection on the diffusivity. When we assume that the Maxwell-Stefan diffusion coefficient (sometimes also called the corrected diffusion coefficient) is independent of the loading, the loading dependence of the conventional Pick diffusion coefficient will be completely determined by the adsorption isotherm. We will demonstrate that on the basis of mixture isotherms we can predict the membrane permeation efficiency without having to know the diffusion coefficients exactly. 

In applying quantum mechanics to real chemical problems, one is usually faced with a Schrodinger differential equation for which, to date, no one has found an analytical solution. This is equally true for electronic and nuclear-motion problems. It has therefore proven essential to develop and efficiently implement mathematical methods which can provide approximate solutions to such eigenvalue equations. Two methods are widely used in this context- the variational method and perturbation theory. These tools, whose use permeates virtually all areas of theoretical chemistry, are briefly outlined here, and the details of perturbation theory are amplified in Appendix D. 

Flux is maximized when the upstream concentration is minimized. For any specific task, therefore, the most efficient (minimum membrane area) configuration is an open-loop system where retentate is returned to the feed tank (Fig. 8). When the objective is concentration (eg, enzyme), a batch system is employed. If the object is to produce a constant stream of uniform-quahty permeate, the system may be operated continuously (eg, electrocoating). 

Constant-volume batch diafiltration is the most efficient process mode. Eor species that freely permeate the membrane. 

Layered Structures. Whenever a barrier polymer lacks the necessary mechanical properties for an appHcation or the barrier would be adequate with only a small amount of the more expensive barrier polymer, a multilayer stmcture via coextmsion or lamination is appropriate. Whenever the barrier polymer is difficult to melt process or a particular traditional substrate such as paper or cellophane [9005-81-6] is necessary, a coating either from latex or a solvent is appropriate. A layered stmcture uses the barrier polymer most efficiently since permeation must occur through the barrier polymer and not around the barrier polymer. No short cuts are allowed for a permeant. The barrier properties of these stmctures are described by the permeance which is described in equation 16 where and L are the permeabiUties and thicknesses of the layers. 

Diafiltration If a batch process is run so that the permeate is replaced by an equal volume of fresh solvent, unretained solutes are flushed through the system more efficiently. A major use of UF is fractionation, where a solvent, a retained solute and an unretained solute are present. An example is whey, containing water, protein, and lactose. If the retention of protein is I and the retention of lactose is 0, the concentration of protein in the retentate rises during UF. The ratio of protein to lac tose rises, but the feed concentration of lactose is unchanged in retentate and permeate. Diafiltration dilutes the feed, and permits the concentration of lactose to be reduced. Diafiltration is used to produce high-purity products, and is used to fractionate high-value products. R is always 0 for eveiy component. 

The ability of the gas stream to permeate the filter is also affected by the shrinking and elongation of the fabric. Elongation of the fibers results in increased pore space, and conversely shrinkage decreases the pore volume. Fabrics of good dimensional qualities are essential to fabric life and efficiency. 

It is becoming common practice to have the cross-section of a plastic moulding made up of several different materials. This may be done to provide a permeation barrier whilst retaining attractive economics by having a less expensive material making up the bulk of the cross-section. To perform stress analysis in such cases, it is often convenient to convert the cross-section into an equivalent section consisting of only one material. This new section will behave in exactly the same way as the multi-layer material when the loads are applied. A very common example of this type of situation is where a solid skin and a foamed core are moulded to provide a very efficient stiffness/weight ratio. This type of situation may be analysed as follows ... 

Owing to the low dielectric constant of organic vehicles, these pigments can ionise only after water has permeated the film, consequently their efficiency is associated with the nature of the vehicle in which they are dispersed, a point which is sometimes overlooked when comparing the relative merits of chromate pigments. 

Brackish water. Usually associated with salty water, brackish water TDS levels range from 2,000 to 20,000 ppm or more. Most industrial sources of RW supply may be well water, surface waters, or the like, but do not specifically have to contain high levels of sodium chloride. The RO applied pressure required is from 250 to 600 psig, and the permeate recovery rates are typically 60% down to perhaps 40%. There is a tremendous variety in so-called brackish water sources, and correct membrane selection and other design criteria are critical to manufacturing an efficient RO plant. 

A reliable chromatographic method has been developed for the quantitative aneilysis of hydrophobic impurities in water-soluble polymeric dyes. The method utilizes both the molecular sieve effect of normal gel permeation chromatography and solute-column packing interaction, modified by solvent composition. This method eliminates the need to extract the impurities from the polymeric dye with 100 extraction efficiency, as would be required for an ordinary liquid chromatographic analysis. 

The efficiency of a membrane module is characterized by the recovery or conversion ratio CR = permeate flow rate/feed flow rate. Low conversion means that fluid has to be repeatedly cycled past the TFF module to generate permeate. High-efficienCT NFF has CR = 1. 

Complementary to the passage, one can also consider the retention of a component as R = 1 - S (also called rejection). Retention can also be either an observed or an intrinsic measurement. Retention is useful in considering retained products during concentration mode operation. Other component separation characterizations include the log reduction value LRV =- logS which is used to characterize high-efficiency separations with permeate products (sterilization). The beta ratio P = I/S is sometimes used in NFF for clarification applications. 

Sample size may influence the analytical approach, e.g. 0.1 L of milk is easily obtained and extracted, but 10 mL of blood should be sufficient for monitoring purposes, and 5 g of fat is already the upper limit for an efficient fat cleanup by partition or gel permeation chromatography (GPC). 

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