Liquid permeation

The permachor method is an empirical method for predicting the permeabiUties of oxygen, nitrogen, and carbon dioxide in polymers (29). In this method a numerical value is assigned to each constituent part of the polymer. An average number is derived for the polymer, and a simple equation converts the value into a permeabiUty. This method has been shown to be related to the cohesive energy density and the free volume of the polymer (2). The model has been modified to liquid permeation with some success. 

Air Backflush A configuration unique to microfiltration feeds the process stream on the shell side of a capillaiw module with the permeate exiting the tube side. The device is rim as an intermittent deadend filter. Eveiw few minutes, the permeate side is pressurized with air. First displacing the liquid permeate, a blast of air pushed back-... 

Estimations of Liquid-Permeation Rates from Absorption Testing... 

Unlike high-resolution NMR spectra of bulk solutions where NMR linewidths well below 1 Hz can be obtained routinely, NMR spectra of liquids permeating porous solids in most cases will not exhibit such a high spectral resolution. First of all, the interaction of liquid phase molecules with pore walls of the catalyst and rapid diffusion-driven intrapore transport will lead to a pronounced homogeneous broadening of the observed NMR lines. Smaller pore sizes and the presence of paramagnetic impurities in the solid material usually aggravate the situation and thus should be avoided. Another reason why NMR spectra of liquids in porous... 

The concept of cross-flow microfiltration, described by Bertera, Steven and Metcalfe(4), is shown in Figure 8.4 which represents a cross-section through a rectangular or tubular membrane module. The particle-containing fluid to be filtered is pumped at a velocity in the range 1-8 m/s parallel to the face of the membrane and with a pressure difference of 0.1-0.5 MN/m2 (MPa) across the membrane. The liquid permeates through the membrane and the feed emerges in a more concentrated form at the exit of the module. 

Park, Lee, and Popov [136] used a similar technique to determine the liquid permeation in different diffusion layers. Feser, Prasad, and Advani [214] used the same method explained in Section 4.4.S.2 to measure the liquid in-plane permeability of DLs. When water was used, flow was forced from a pressurized tank (0-200 kPa) through the apparatus (and the sample), and the outlet water was then collected with a graduated cylinder. 

Beda (B3), 1961 Minimum residence time in agreement with Brauer s (B14) effective surface velocity results up to Nbm = 400. Distribution function agrees with theory in presence of surfactants. Theoretical treatment of film flow of liquid permeating through porous wall, with heat transfer. 

In the process designs shown in Figures 9.1 and 9.7, the permeate vapor is condensed to yield a single liquid permeate condensate. A simple improvement... 

The separation of non-volatile products from ionic liquid solutions using nanofiltration was suggested by Krockel and Kragl [136]. It was shown for both bromophe-nol blue and lactose, each in ionic liquid, that the product was rejected while the ionic liquid permeated. It should be noted that in such cases the products are not isolated. Instead, concentrated ionic liquid solutions are produced. However, depending on the solubility, phase separation might occur. 

The particle size and surface area distributions of pharmaceutical powders can be obtained by microcomputerized mercury porosimetry. Mercury porosimetry gives the volume of the pores of a powder, which is penetrated by mercury at each successive pressure the pore volume is converted into a pore size distribution. Two other methods, adsorption and air permeability, are also available that permit direct calculation of surface area. In the adsorption method, the amount of a gas or liquid solute that is adsorbed onto the sample of powder to form a monolayer is a direct function of the surface area of the sample. The air permeability method depends on the fact that the rate at which a gas or liquid permeates a bed of powder is related, among other factors, to the surface area exposed to the permeant. The determination of surface area is well described by the BET (Brunauer, Emmett, and Teller) equation. 

Descriptive model and its division into parts. The first steps in the model construction are related to Fig. 3.7. The pump PA assures simultaneously the suspension transport and the necessary transmembrane pressure. The excessive accumulation of the solid in the retentate is controlled by its permanent removal as a concentrated suspension from the reservoir RZ. The clear liquid (permeate) flow rate and the solid concentration in the exit suspension are permanently measured and these values are transferred to the control and command computer CE. The instantaneous values of the operation pressure and input rate of fresh suspension are established by the computer (this works with software based on the mathematical model of the process) and corrected with the command execution system CSE. 

Long RB. Liquid permeation through plastic films. Ind. Eng. Chem. Fund. 1965 4 445 51. 

McGuire, K.S., Lawson, K.W., and Lloyd, D.R. Pore size distribution determination from liquid permeation through microporous membranes, J. Membr. Sci., 99, 127, 1995. 

Gas, vapor, and organic liquid permeation Dialysis Electrodialysis... 

Pressure Effect Rapid pressure changes can also cause problems with both materials. Under operating conditions, liquid permeates.into the brickwork. If the pressure inside a vessel decreases suddenly, the liquid trapped within the brick may try to expand. This rapid expansion can generate critical stresses, and... 

The characteristic feature of flow FFF is the superimposition of a second stream of liquid perpendicular to the axis of separation. This cross-flow drives the injected sample plug toward a semipermeable membrane that acts as the accumulation wall. The cross-flow liquid permeates across the membrane and exits the channel, whereas the sample is retained inside the channel in the vicinity of the membrane surface. Sample displacement by the cross-flow is countered by diffusion away from the membrane wall. At equilibrium, the net flux is zero and sample clouds of various thicknesses are formed for different sample species. As with other FFF techniques, a larger diffusion coefficient D leads to a thicker equilibrium sample cloud that, on average, occupies a faster streamline of the parabolic flow profile and subsequently elutes at a shorter retention time t,. For well-retained samples analyzed by flow FFF, t, can be related to D and the hydrodynamic diameter d by... 

In cross-flow flltration, the wastewater flows under pressure at a fairly high velocity tangentially or across the filter medium. A thin layer of solids form on the surface of the medium, but the high liquid velocity keeps the layer from building up. At the same time, the liquid permeates the membrane producing a clear filtrate. Filter media may be ceramic, metal (e.g., sintered stainless steel or porous alumina), or a polymer membrane (cellulose acetate, polyamide, and polyacrylonitrile) with pores small enough to exclude most suspended particles. Examples of cross filtration are microfiltration with pore sizes ranging from 0.1 to 5 pm and ultrafiltration with pore sizes from 1 pm down to about 0,001 pm. 

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