Solvent extraction porous membrane based

Figure 8.1.35(f) illustrates a porous membrane based solvent extraction device. Figure 8.1.13(a) illustrated the basic design of such devices in greater detail The basic principle of nondispersive contact of two immiscible liquid phases at the mouth of the pore of a membrane has been described earlier (see Figure 3.4.11, Section S.4.3.2) (Kiani et ah, 1984 Prasad and Sirkar, 1988). Large-scale devices built based on such a principle and related patents (Sirkar, 1991, 1995) are being used. One of the liquids (liquid is brought in through a central liquid distributor with circumferential perforations, which allows the liquid to flow out radially through the hollow fiber bundle. The device has a central baffle, which turns around the shell-side liquid ti, to the second half of the device, where this liquid flows radially inward in the fiber bundle to the central liquid distributor tube, which is blocked in the middle to insulate inlet liquid from exiting liquid...

It would be of interest to find out the role (if any) of backmixing in nondispersive porous membrane based solvent extraction devices. Here, only the shell-side liquid phase can encounter backmixing, or, more correctly, bypassing and channeling. Simple countercurrent devices often display such flow behavior. However, the baffled construction with radial flow illustrated in Figure 8.1.35(f) is thought to be generally free of such flow distortions. 

Several manufacturers introduced products amenable for this solid-supported LLE and for supported liquid extraction (SLE). The most common support material is high-purity diatomaceous earth. Table 1.8 lists some commercial products and their suppliers. The most widely investigated membrane-based format is the supported liquid membrane (SLM) on a polymeric (usually polypropylene) porous hollow fiber. The tubular polypropylene fiber (short length, 5 to 10 cm) is dipped into an organic solvent such as nitrophenyl octylether or 1-octanol so that the liquid diffuses into the pores on the fiber wall. This liquid serves as the extraction solvent when the coated fiber is dipped... 

Solute diffusion through porous liquid-filled membrane We consider here solute diffusion through a porous liquid-filled membrane under the condition of no convection (Figure 3.4.5(c)). Examples of separation pro-cesses/techniques where such a situation is encountered are isotonic dialysis, membrane based nondispersive gas absorption/stripping or solvent extraction, supported or... 

Consider microporous membrane-based solvent extraction using a hydrophilic porous membrane whose pores are filled with the organic solvent used to extract a product, species i, from an aqueous feed solution. The aqueous-phase pressure is maintained equal to or higher than the organic-phase pressure to maintain the aqueous-organic interface for nondispersive solvent extraction conditions. 

Almost all countercurrent extraction devices utilize dispersion of one immiscible phase as drops in another immiscible phase we will provide a brief introduction here. At the end, we will introduce porous hollow fiber membrane based nondispersive countercurrent solvent extraction devices. The dispersive devices may involve continuous agitation or no agitation at all. Dispersive devices without any agitation as such are of three types spray towers packed towers perforated plate towers. Spray towers were illustrated in Figure 8.1.2(b). 

Several processes are based on blends of UHMWPE and oil (22) where the oil acts as a diluent rather than a solvent. The UHMWPE particles imbibe the oil, swell and form gels. Unlike UHMWPE alone, the resulting gel can then be extruded on modified plastic screw extruders and fiber lines. Subsequent extraction of the oil from the formed sheets results in a porous material suitable for battery electrode plate separators or filter membranes. The majority of automotive lead acid batteries manu ctured today contain UHMWPE electrode plate separators produced in this manner. 

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