Supported liquid membranes separation

As described above, the application of classical liquid- liquid extractions often results in extreme flow ratios. To avoid this, a completely symmetrical system has been developed at Akzo Nobel in the early 1990s [64, 65]. In this system, a supported liquid-membrane separates two miscible chiral liquids containing opposite chiral selectors (Fig. 5-13). When the two liquids flow countercurrently, any desired degree of separation can be achieved. As a result of the system being symmetrical, the racemic mixture to be separated must be added in the middle. Due to the fact that enantioselectivity usually is more pronounced in a nonaqueous environment, organic liquids are used as the chiral liquids and the membrane liquid is aqueous. In this case the chiral selector molecules are lipophilic in order to avoid transport across the liquid membrane. 

Huang, D.S., Huang, K.L., Chen, S.P. et al. (2008) Rapid reaction-diffusion model for the enantioseparation of phenylalanine across hollow fiber supported liquid membrane. Separation Science and Technology, 43 (2), 259-272. 

Dreher, T.M. and Stevens, G.W. (1998) Instability mechanisms of supported liquid membranes. Separation Science and Technology, 33, 835. 

Supported Liquid Membrane Separation Technique—THE Principle... 

Dzygiel, P., Wieczorek, P., Kafarski, P. (2003). Supported liquid membrane separation of amine and amino acid derivatives with chiral esters of phosphoric acids as carriers. J. Sep. Sci., 26, 1050-6. 

El-Said, N., Rahman, N.A., Borai, E.H., Modification in Purex process using supported liquid membrane separation of cerium(III) via oxidation to cerium(IV) from fission products from nitrate medium by SLM, J. Membr. Sci. 198, 23, 2002. 

Singh, S.K., Misra, S.K., Sudersanan, M. Dakshinamoorthy, A. (2009) Studies on the recovery of uranium from phosphoric acid medium by D2EHPA/n-dodecane supported liquid membrane. Separation Science and Technology, 44 (1), 169-189. 

Kooherginsky, N.M. Yang, Q. (2007) Big carrousel mechanism of copper removal from ammoniacal wastewater through supported liquid membrane. Separation and Purification Technology, 54,104-116. 

Rathore, N.S., Sonawane, J.V Gupta, S.K. (2004) Separation of uranium and plutonium from aqueous acidic wastes using a hollow fiber supported liquid membrane. Separation Science and Technology, 39, 1295-1319. 

Liquid-liquid extraction is a basic process already applied as a large-scale method. Usually, it does not require highly sophisticated devices, being very attractive for the preparative-scale separation of enantiomers. In this case, a chiral selector must be added to one of the liquid phases. This principle is common to some of the separation techniques described previously, such as CCC, CPC or supported-liquid membranes. In all of these, partition of the enantiomers of a mixture takes place thanks to their different affinity for the chiral additive in a given system of solvents. 

In supported liquid membranes, a chiral liquid is immobilized in the pores of a membrane by capillary and interfacial tension forces. The immobilized film can keep apart two miscible liquids that do not wet the porous membrane. Vaidya et al. [10] reported the effects of membrane type (structure and wettability) on the stability of solvents in the pores of the membrane. Examples of chiral separation by a supported liquid membrane are extraction of chiral ammonium cations by a supported (micro-porous polypropylene film) membrane [11] and the enantiomeric separation of propranolol (2) and bupranolol (3) by a nitrate membrane with a A/ -hexadecyl-L-hydroxy proline carrier [12]. 

ILs, on the other hand, are uniquely suited for use as solvents for gas separations. Since they are non-volatile, they cannot evaporate to cause contamination of the gas stream. This is important when selective solvents are used in conventional absorbers, or when they are used in supported liquid membranes. For conventional absorbers, the ability to separate one gas from another depends entirely on the relative solubilities (ratio of Henry s law constants) of the gases. In addition, ILs are particularly promising for supported liquid membranes, because they have the potential to be incredibly stable. Supported liquid membranes that incorporate conventional liquids eventually deteriorate because the liquid slowly evaporates. Moreover, this finite evaporation rate limits how thin one can make the membrane. This... 

The solubilities of the various gases in [BMIM][PFg] suggests that this IL should be an excellent candidate for a wide variety of industrially important gas separations. There is also the possibility of performing higher-temperature gas separations, thanks to the high thermal stability of the ILs. For supported liquid membranes this would require the use of ceramic or metallic membranes rather than polymeric ones. Both water vapor and CO2 should be removed easily from natural gas since the ratios of Henry s law constants at 25 °C are -9950 and 32, respectively. It should be possible to scrub CO2 from stack gases composed of N2 and O2. Since we know of no measurements of H2S, SO, or NO solubility in [BMIM][PFg], we do not loiow if it would be possible to remove these contaminants as well. Nonetheless, there appears to be ample opportunity for use of ILs for gas separations on the basis of the widely varying gas solubilities measured thus far. 

Antico, E. Masana, A. Hidalgo, M. Salvado, V. Valiente, M. New sulfur-containing reagents as carriers for the separation of palladium by solid supported liquid membranes. Hydrometallurgy 1994, 35, 343-352. 

The principle of a three-phase membrane extraction is illustrated in Figure 1.28. An organic solvent is immobilized in the pores of a porous polymeric support consisting of a flat filter disc or a hollow fiber-shaped material. This supported liquid membrane (SLM) is formed by treating the support material with an organic solvent that diffuses into its pores. The SLM separates an aqueous... 

For the sake of discussion, we have divided the separators into six types—microporous films, non-wovens, ion exchange membranes, supported liquid membranes, solid polymer electrolytes, and solid ion conductors. A brief description of each type of separator and their application in batteries are discussed below. 

These types of separators consist of a solid matrix and a liquid phase, which is retained in the microporous structure by capillary forces. To be effective for batteries, the liquid in the microporous separator, which generally contains an organic phase, must be insoluble in the electrolyte, chemically stable, and still provide adequate ionic conductivity. Several types of polymers, such as polypropylene, polysulfone, poly(tetrafluoroethylene), and cellulose acetate, have been used for porous substrates for supported-liquid membranes. The PVdF coated polyolefin-based microporous membranes used in gel—polymer lithium-ion battery fall into this category. Gel polymer... 

Nondispersive solvent extraction is a novel configuration of the conventional solvent extraction process. The term nondispersive solvent extraction arises from the fact that instead of producing a drop dispersion of one phase in the other, the phases are contacted using porous membrane modules. The module membrane separates two of the immiscible phases, one of which impregnates the membrane, thus bringing the liquid-liquid interface to one side of the membrane. This process differs from the supported liquid membrane in that the liquid impregnating the membrane is also the bulk phase at one side of the porous membrane, thus reducing the number of liquid-liquid interfaces between the bulk phases to just one. 

T0174 Commodore Separation Technologies, Inc., Supported Liquid Membrane T0178 Constructed Wetlands—General... 

T0173 Commodore Applied Technologies, Inc., Solvated Electron Technology (SET) T0174 Commodore Separation Technologies, Inc., Supported Liquid Membrane T0178 Constructed Wetlands—General... 

In order to develop the liquid membrane techniques, i.e., emulsion Hquid membrane (ELM), supported liquid membrane (SLM), non-dispersive extraction in hollow fiber membrane (HFM), etc., for practical processes, it is necessary to generate data on equilibrium and kinetics of reactive extraction. Furthermore, a prior demonstration of the phenomena of facilitated transport in a simple liquid membrane system, the so-called bulk liquid membrane (BLM), is thought to be effective. Since discovery by Li [28], the liquid membrane technique has been extensively studied for the separation of metal ion, amino acid, and carboxyHc acid, etc., from dilute aqueous solutions [29]. 

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