Effect on flux

When colloidal hematite particles are present (Table 8.10) the effect of ferric chloride dosing is smaller and resistances are highest for the 100 kDa membrane. In the presence of the hematite colloids it appears as if permeation drag becomes important and pressure plays a minor role. 

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If the system is badly fouled, m - 0, and increasing or decreasing flow at constant pressure has httle effect on flux. However, raising the pressure may raise flux. For an unfouled system in laminar flow 0.33 [Pg.2041]

In a 1991 study by van Reis et al. (5), a filtration operation as applied to harvest of animal cells was optimized by the use of dimensional analysis. The fluid dynamic variables used in the scale-up work were the length of the fibers (L, per stage), the fiber diameter (D), the number of fibers per cartridge (k), the density of the culture (p), and the viscosity of the culture (p). From these variables, scale-up parameters such as wall shear rate (y ) and its effect on flux (L/m /h) were derived. Based on these calculations, an optimum wall shear rate for membrane utilization, operating time, and flux was found. However, because there is no single mathematical expression relating all of these parameters simultaneously, the optimal solution required additional experimental research. 

Similar experiments can be done on intact cells or organisms, using specific inhibitors or activators to change the activity of one enzyme while observing the effect on flux through the pathway. The amount of an... 

When the gel used as a gating membrane to control the release of solute these will have two competing effects on flux ... 

Palecek, S.P. and Zydney, A.L., Intermolecular electrostatic interactions and their effect on flux and protein deposition during protein filtration, Biotechnol. Prog., 10, 207, 1994. 

Membrane properties have been characterized and their effects on flux, retention, and fouling have been studied extensively by several authors. Some common facts can be concluded from these studies. 

The effects of pH and ionic strength on the performance of an a-alumina microfiltration membrane from U.S. Filter was evaluated by Nazzal and Wies-ner [46]. Concerning pH effect on flux, results obtained in this work perceptibly differ from the previous one. Here the membrane operated at a significantly higher permeation rate at a pH well below the isoelectric point of the membrane. This variance can be explained considering the isoelectric point of the membrane was found at pH = 8.3 in this case while it was at pH = 3.5 in the... 

It is well known that pumping of the fluid has a major effect on flux in the mass tTcinsfer controlled region for UF/MF process. Indeed agitation and mixing of the fluid near the membrane surface sweep away the accumulated solutes, thus reducing the thickness of boundary layers. This is the simplest and most effective method of controlling the effect of concentration polarization. 

Air Sparging Gas sparging or injection of air bubbles has been effectively used to reduce concentration polarization and enhance mass transfer. " The secondary flows around bubbles promote mixing and reduce the thickness of the concentration polarization boundary layer. When the bubble diameter exceeds that of the membrane (tubular or hollow fiber), slugs are then formed further increase in bubble diameter has no effect on flux improvement. Large slugs can displace most of the boundary layer and cause the pressure to pulsate. This results in enhancing the flux. 

Figure 8 shows the flux and conductivity and color rejections for a dynamic membrane at various recovery levels using mixtures of the range wash water effluents. The temperature and pressure effects on flux are pvovided in Figures 9 and 10. 

Antifoam concentration, effect on flux, tangential flow filtration, 6l,63f... 

Antifoam type, effect on flux, tangential flow filtration, 6l,62f Assays, largomycin F-II, 135,137 Axial dispersion, estimation of transfer units, 116... 

Temperature and Viscosity. The operating temperature can have a beneficial effect on flux primarily as a result of a decrease in viscosity.f There is an additional benefit for shear thinning viscoelastic fluids, where the viscosity reduces with an increase in shear (i.e., cross-flow velocity). Typical examples are clarification of fermentation broths and concentration of protein solutions. l l It must be noted that for most fermentation and biotechnology related applications, temperature control is necessary for microbial survival and/or for product stability (e.g., antibiotics, enzymes, proteins and other colloidal materials). 

In permeate return mode, permeate was recombined with retentate and recirculated. This mode was used to observe the effect on flux of increasing filter pressure (a pressure scan) or increasing transfilter flow (a flow scan). 

A typical recipe for an interfacially formed aromatic polyamide composite membrane comprised a 2.0% aqueous solution of the aromatic diamine and a 0.1% nonaqueous solution of trimesoyl chloride. This recipe was extraordinarily simple, and ran quite contrary to experience with piperazine-based membranes. For example, surfactants and acid acceptors in the aromatic diamine solution were generally not beneficial, and in many cases degraded membrane performance by lowering salt rejection. In contrast, surfactants and acid acceptors were almost always beneficial in the NS-300 membrane system. In the nonaqueous phase, use of isophthaloyl chloride as a partial replacement for trimesoyl chloride had relatively little effect on flux, but tended to decrease salt rejection and increase susceptibility to chlorine attack. 

Fixed Charge Hypothesis. According to the computation described above, the movement of an ion across the red cell membrane is governed by its concentration gradient and the transmembrane potential. It has been suggested (33) that the membrane potential is one factor that, in addition to its direct effect on flux, is a determinant of ionic permeability. For cation movements over wide ranges of membrane potential, a relatively small dependence of permeability on potential has been demonstrated (34). 

Permeate flux increases on decreasing viscosity and therefore a higher permeability is achieved at higher temperatures. A common method to account for this change with temperature is to multiply the obtained flux with the viscosity ratio with respect to a reference temperamre. If temperature effects on flux are only influenced by changes in viscosity, then the product of flux and viscosity should be constant. 

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