Permeation data filtration

While the calibration curves presented in Figure 1 provide an adequate treatment of gel permeation calibration data, they are nonlinear in the extremes of the useful calibration regions. Two methods of data treatment may be used to provide linear representations of gel filtration results. These methods substantially increase the usefulness of the technique. The equations for these methods, developed by Porath (8) and Ackers (9), are as follows ... 

It may be possible to do a membrane autopsy to identify the foulant(s) and fouling mechanism. For microporous membranes the blocking law analysis [1], which uses permeate volume (V) vs. time (t) data, can supplement the observations. The generalized relationship at constant pressure and in dead-end filtration mode gives,... 

Protein transmission data (Fig. 8) indicate nearly 100% transmission of protein initially, but the fraction of protein transmitted decreased rapidly for forward filtration of a BSA-only solution and appeared to reach a steady value of only 35% transmission after 10,000 s. When a secondary membrane of yeast was deposited at the beginning of each cycle, and then filtration of a BSA solution was carried out, the protein transmission values remained at nearly 100% for about 4000 s and subsequently decreased gradually to about 60% after 18,000 s of filtration. With SMY, the amount of protein recovered in the permeate is more than two times that recovered after filtration of the BSA-only solution after 18,000 s. 

Wai and Fumeaux [1990] applied CFD to crossflow membrane filtration to provide an array of data such as local pressures and fluid velocities on both sides of a membrane, shear stresses on the membrane surface and local concentrations of retentate species. This type of information is useful for designing the membrane unit as a separator or a reactor. With a commercial CFD code, the authors simulated the fluid flow, on both the feed and permeate sides, along the membrane channel and through the membrane. Frictional effects between the fluid and membrane surfaces depend on the nature of the fluid flow. For flow parallel to the essentially flat membrane surface, standard wall friction expressions based on logarithmic velocity profiles adjacent to the wall arc used. 

Nanostructured polymers, in particular block copolymers, have immense potential in areas ranging from templating inorganic materials to permeation/ filtration media, nano-assaying, nanolithography and high density data storage media. 

The filtration experiments were conducted in cross-flow mode at pressure 0.25-0.5 MPa in the system. In that pressure range for filtration of water, permeate flux was 26-85 L/m. AU process parameters were recorded with data acquisition system periodically the samples of permeate and retentate were collected for chemical analysis. 

Membrane Pore Diameter or Molecular Weight Cutoff. The value of membrane pore diameter will have a major influence on the permeation and separation characteristics for most process filtration applications. The intrinsic membrane permeability is related to the pore diameter for many microfiltration membranes whereas, for ultrafiltration membranes, it is typically indicative of the solute retention properties. Tables 8 and 9 provide typical permeability and retention data for many common MF and UF membranes, respectively.f t ... 

To investigate (ii), we obtained data for toluene in a crossflow filtration cell, and for two different large organic molecules at concentrations > 1 wt%. The experimental data can be described using a combined solution-diffusion-film-the-ory model, since the data suggest that at these high concentrations, concentration polarization becomes significant. Careful attention was paid to the role of the activity coefficients of the solute and the solvent, which seem to markedly affect the permeate flux. 

A serious limitation in the data collected by these researchers was the ct that a was measured in permeation rather than in filtration conditions the packing (porosity) and the resistance of newly formed filter cake under the dynamic ccmditions obtaining during filtration may be e ected (in general) to be different fi om those applying after prolonged rotation The latter results in the densest packing and hipest a values. 

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