Emulsion membranes

Use of w/o-MEs for transport in liquid emulsion membrane separations Perforated rotating disk contactor Spray column Packed column... 

In the early 1970s Li [13] proposed a method that is now called Emulsion (surfactant) Liquid Membrane (ELM) or Double Emulsion Membrane (DEM) (Fig. 3). The name reveals that the three liquid system is stabilized by an emulsifier, the amount of which reaches as much as 5 % or more with respect to the membrane liquid. The receiving phase R, which usually has a smaller volume than the donor solution, F of similar nature, is finally dispersed in the intermediate phase, M. In the next step the donor solution F is contacted with the emulsion. For this purpose, the emulsion is dispersed in the donor solution F by gentle mixing typically in a mixer-settler device. After this step, the emulsion is separated and broken. The enriched acceptor solution is further processed and the membrane liquid M is fed back for reuse. 

Coupled transport with emulsion membranes demonstrated by Cussler -1972... 

A form of liquid membrane that received a great deal of attention in the 1970s and 1980s was the bubble or emulsion membrane, first developed by Li at Exxon [11-13], Figure 11.14 is a schematic illustration of an emulsion liquid membrane process, which comprises four main operations. First, fresh product solution is emulsified in the liquid organic membrane phase. This water/oil emulsion then enters a large mixer vessel, where it is again emulsified to form a water/oil/water emulsion. Metal ions in the feed solution permeate by coupled... 

Figure 11.14 Flow diagram of a liquid emulsion membrane process...

Figure 11.15 Copper extraction by a liquid emulsion membrane process [52]. Feed, 200 ml, pH 2.0, 300 ppm Cu2+ membrane, 15 mL LIX 64N in kerosene, 3% Span 80 stripping solution, 15 mL H2S04. Reprinted from J. Membr. Sci. 6, W. Volkel, W. Halwachs and K. SchUgerl, Copper Extraction by Means of a Liquid Surfactant Membrane Process, p. 19, Copyright 1980, with permission from Elsevier...

FIGURE 19 Liquid membrane extraction, (a) Emulsion membrane extraction, (b) supported membrane extraction. 

In addition to this, that an interesting novel emulsion membrane reactor concept overcomes the difficulties of the large solvent volume otherwise required for the reduction of poorly soluble ketones [30]. 2-Octanone was reduced by a carbonyl reductase from Candida parapsilosis to (S)-2-octanol with > 99.5 % ee and total turnover number of 124 - the 9-fold value of that obtained in a classical enzyme reactor. 

Mikulaj, V., Ffiatky, J., Vasekova, L. An emulsion membrane extraction of strontium and its separation from calcium utilizing crowns and picric acid. J. Radioanal. Nucl. Chem. 101(1), 51-57 (1986)... 

Boyadzhiev L, Bezenshek E, and Lazarova Z. Removal of phenol from waste water by double emulsion membranes and creeping film pertraction. J Mem Sci, 1984 21(2) 137-144. 

The concept of emulsion liquid membranes (ELM) was first proposed by Li in 1968 [1]. Since their inception in the late 1960s they have been referred to as surfactant liquid membranes, double emulsion membranes or ELM. Regardless of the terminology used, the workings of such systems are as follows they consist of an emulsion formed by an organic solvent and water, which can be stabilized by the addition of surfactant. This emulsion is then contacted with a continuous phase containing the desired solute, stirred to yield globules, and transported across the extremely thin membrane layer that separates internal phase droplets... 

Gadekar PT, Mukkolath AV, and Tiwari KK. Recovery of nitrophenols from aqueous solutions by a liquid emulsion membrane system. Sep Sci Technol 1992 27 427 55. 

Mok YS, Lee KH, and Lee WK. Control of swelling in hquid emulsion membranes employed for lactic acid separation. J Chem Technol Biotechnol 1996 65 309-316. 

Itoh H, Thien MP, Hatton TA, and Wang DIC. Water transport mechanism in bquid emulsion membrane process for the separation of amino acids. J Membr Sci 1990 51 309-322. 

Thien MP and Hatton TA. Liquid emulsion membranes and their applications in biochemical processing. Sep Sci Technol 1988 23 819-853. 

El-Reefy SA, El-Souroughy MR, El-Sherif EA, and Aly HF. Europium permeation and separation from americium using liquid emulsion membrane. Analyt Sci 1995 11 329-331. 

Abou-Nemeh I and Van Peteghem AP. Extraction of cobalt and manganese from an industrial effluent by liquid emulsion membranes. In Baird MHI, Vijayan S, eds. Proceedings of the Second International Conference on Separation Science and Technology, Volume 2. Ottawa, Ontario Canadian Society of Chemical Engineering, 1989 416 23. 

Christensen JJ, Christensen SP, Biehl MP, Lowe SA, Lamb JD, and Izatt RM. Effect of receiving phase anion on macrocycle-mediated cation transport rates and selectivities in water-toluene-water emulsion membranes. Sep Sci Technol 1983 18 363-373. 

Mok YS, Lee SC, and Lee WK. Water transport in water-in-oil-in-water liquid emulsion membrane system for the separation of lactic acid. Sep Sci Techrwl 1994 29 743-764. 

Hong S A, Choi HI, and Nam SW. Concentration of amino acids by a hquid emulsion membrane with a cationic extractant. J Membr Sci 1992 70 225-235. 

Nilsen DN, Hundley GL, Galvan GJ, and Wright JB. Field testing of a liquid-emulsion membrane system for copper recovery from mine solutions. In Bartsch RA, Way JD, eds. Chemical separations with liquid membranes, Washington, DC American Chemical Society, ACS symposium series 642, 1996 329-341. 

Table 31.3 gives a few typical examples on recovery of actinides by ELM. Myriad literature reports exist on the use of HDEHP for metal extraction involve ELMs. Comparative studies between column and batch liquid emulsion membrane techniques based on HDEHP/HCl system were carried out to develop a system for the isolation of Th from natural uranium, which showed that, kineticaUy, the equilibrium for thorium separation using batch technique is faster than the continuous column system [37]. The effective separation of Th from natural uranium was found to be independent of time. El-Sherif studied... 

El-Reefy, S.A., El-Sherif, E.A., and Aly, H.F., Recovery of Th from natural uranium using liquid emulsion membrane based on HDEHP-HCl system. J. Radioanal. Nucl. Chem., 1996, 207 129-136. 

KuUtami, P.S., Mukhopadhyay, S., Bellary, M.P., and Ghosh, S.K., Studies on membrane stability and recovery of uranium (VI) from aqueous solutions using a liquid emulsion membrane process. Hydrometallurgy, 2002, 64 49-58. 

Affinity) Filtration Reverse-Micelle Liquid Emulsion Membrane... 

Kitagawa, T. Nishikawa, Y. Frankenfeld, J. W. Li, N. N. "Wastewater Treatment by Liquid Membrane Process" Environ. Sci. Tech. 1977,11, pp 602-605. Thien, M. P. Hatton, T. A. Wang, D. I. C. "Liquid Emulsion Membranes and Their Applications in Biochemical Separations" In Separation, Recovery, and Purification in Biotechnology ACS Symposium Series 314, 1986, pp 67-77. 

Thien, M. P. " Separation and Concentration of Amino Acids Using Liquid Emulsion Membranes", Doc. of Sci. Thesis, M.I.T., 1988. 

The application of liquid emulsion membrane based on trioctylphosphine oxide extractant for the separation of thorium and uranium was described [3]. Thoron I was used to determine Th in aqueous phase. 

A liquid emulsion membrane based on trioctylphosphine oxide extractant was applied for separation of uranium and thorium from Ce, Cu and Cd [2]. Highly selective U02 imprinted polymer (synthesized using uranium vinylbenzoate, divinylbenzene in styrene and 2,2 -azobisisobutyronitrile) was proposed for purification, preconcentration and determination of the uranyl ion [3]. Dibenzoylmethane was used as a colorimetric reagent. The detection limit of 160 ppt was achieved. 

Olsher U, Hankins MG, Kim YD, Bartsch RA, Anion effect on selectivity in crown ether extraction of alkah metal cations. J. Am. Chem. Soc. 1993 115 3370-3371. Christensen JJ, Christensen SP, Biehl MP, Lowe SA, Lamb LD, Izatt RM, Effect of receiving phase anion on macrocycle-mediated cation transport rates and selectivities in water-toluene-water emulsion membranes. Sep. Sci. Technol. 1983 18 363-373. Deblay P, Delepine S, Minier M, Renon H, Selection of organic phases for optimal stabihty and efficiency of flat-sheet supported hquid membranes. Sep. Sci. Technol. 1991 26 97-116. 

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