Hollow-fiber liquid membrane modules

A hollow-fiber liquid membrane was used in a separation of D,L-lactic acid and D,L-alanine resolution [196]. In this case, the enantioselective transport of solutes performed in one module was facihtated by N-3,5-dinitrobenzoyl-L-alanine octylester chiral selector, dissolved in toluene. The maximum D,L-lactic acid separation factor achieved was 2.00 and that for the D,L-alanine was 1.75. In both cases, the D-enantiomer flux was preferred. These values correspond to the enantiomeric excess 33.5% ee and 27.2% ee, respectively, and are not as good as in the first example. However, note that in this case, only one separation step took place and feed phase was circulated in the module. 

Dispersion free extraction in hollow fiber (HF) membrane utilizes immobilized liquid-liquid interface at the pore mouth of a microporous membrane to effect phase to phase contact and the mass transfer process. HF module can be con-... 

Dai, X.P., Yang, Z.F., Luo, R.G. and Sirkar, K.K. (2000) Lipase-facilitated separation of organic-acids in a hollow-fiber contained liquid membrane module. Journal of Membrane Science, 171, 183. 

The design of the hollow fiber supported liquid membrane modules for the separation concentration of solute using overall permeability coefficient P centers on... 

Fig. 5-12. Separation of d,1-leucine in hollow-fiber membrane extraction using a Al- -dodecyl-l-hydrox-yproline solution in octanol as the enantioselective extraction liquid. The modules used were 32 cm long and contained 96 Celgard X-20 polypropylene fibers [57].

High-pressure gas separation, hollow-fiber membrane modules for, 15 823 High pressure liquid chromatography (hplc), 9 234 21 275 in herbicide analysis, 13 312 polymer analysis using, 19 566 High-pressure methanol, production process, 16 300-301 High pressure methods, specialized, 13 430-431... 

In the supported liquid membrane process, the liquid membrane phase impregnates a microporous solid support placed between the two bulk phases (Figure 15.1c). The liquid membrane is stabilized by capillary forces making unnecessary the addition of stabilizers to the membrane phase. Two types of support configurations are used hollow fiber or flat sheet membrane modules. These two types of liquid membrane configuration will be discussed in the following sections. 

The method of impregnating liquid membranes has become more and more popular. By impregnating fine-pore polymer films with a suitable membrane liquid, relatively stable heterogeneous solid-liquid membranes are obtained. These membranes are shaped as thin, flat barriers or hollow fibers. Usually they are manufactured from oleophilic polymers, wettable by membrane liquid. The two interfaces, F/M and M/R, have equal or close areas which can be made very large by employing modules of spirally wounded flat membrane or bundles of hollow fibers. 

The effect of concentration polarization on specific membrane processes is discussed in the individual application chapters. However, a brief comparison of the magnitude of concentration polarization is given in Table 4.1 for processes involving liquid feed solutions. The key simplifying assumption is that the boundary layer thickness is 20 p.m for all processes. This boundary layer thickness is typical of values calculated for separation of solutions with spiral-wound modules in reverse osmosis, pervaporation, and ultrafiltration. Tubular, plate-and-ffame, and bore-side feed hollow fiber modules, because of their better flow velocities, generally have lower calculated boundary layer thicknesses. Hollow fiber modules with shell-side feed generally have larger calculated boundary layer thicknesses because of their poor fluid flow patterns. 

If we consider a gas-liquid transfer for the species i in a hollow-fiber module with the liquid phase in the shell side and the gas phase in the lumen side of hydrophobic membranes, the interface is established at the outer diameter of the fibers and the overall mass-transfer coefficient can be calculated by [1] ... 

O. Shell side of microporous hollow fiber module for solvent extraction Na, = V[dha-)/L]N%N°s M Nsh- D Nlt = K = overall mass-transfer coefficient (3 = 5.8 for hydrophobic membrane. (3 = 6.1 for hydrophilic membrane. [E] Use with logarithmic mean concentration difference. dh = hydraulic diameter 4 x cross-sectional area of flow wetted perimeter (p = packing fraction of shell side. L = module length. Based on area of contact according to inside or outside diameter of tubes depending on location of interface between aqueous and organic phases. Can also be applied to gas-liquid systems with liquid on shell side. [118]... 

Much effort has been expended in attempting to use membranes for separations. Reverse osmosis membranes are used worldwide for water purification. These membranes are based on size selectivity depending on the pores used. They do not have the ability to selectively separate target species other than by size. Incorporation of carrier molecules into liquid membrane systems of various types has resulted in achievement of highly selective separations on a laboratory scale. Reviews of the extensive literature on the use of liquid membrane systems for carrier-mediated ion separations have been published [15-20]. A variety of liquid membranes has been studied including bulk (BLM), emulsion (ELM), thin sheet supported (TSSLM), hollow fiber supported (HFSLM), and two module hollow fiber supported (TMHFSLM) types. Of these liquid membranes, only the ELM and TMHFSLM types are likely to be commercialized. Inadequacies of the remaining... 

---