Liquid Membrane Method

Both requirements of a high specific interfacial area and a direct spectroscopic observation of the interface were attained by the CLM method shown in Fig. 2 [12]. Two-phase system containing about 100 pi volumes of organic and aqueous phases is introduced into a cylindrical glass cell with a diameter of 19mm. The cell is rotated at the speed of 7000-10,000 rpm. By this procedure, a stacked two-liquid membrane each with thickness of 50-100 pm is produced inside the cell wall, which attains the specific interfacial area over 100 cm-1. UV-Vis spectrometry was used in the original work for the measurement of the interfacial species as well as those in the bulk phases. This method can be excellently applied for the measurement of interfacial reaction rate as fast as the order of seconds. 

The study of interfacial aggregation also has been developed by this technique, since this method is very advantageous for measuring the formation of interfacial aggregates of dyes and metal complexes, which are formed only at the interface and usually exhibit unique spectral changes. 

CLM method can also be combined with various kinds of spectroscopic methods. Fluorescence lifetime of an interfacially adsorbed zinc-tetra-phenylporphyrin complex was observed by a nanosecond time-resolved laser induced fluorescence method [25]. Microscopic resonance Raman spectrometry was also combined with the CLM. This combination was highly advantageous to measure the concentration profile at the interface and a bulk phase [14]. Furthermore, circular dichroic spectra of the liquid-liquid interface in the CLM could be measured [19]. 

Analogous to the stopped flow method used in studies of solution kinetics, rapid stopped flow mixing of organic and aqueous phases is an effective way to produce dispersed condition within a few milliseconds. The specific interfacial 

By the TIR condition at the liquid-liquid interface, one can observe interfacial reaction in the evanescent layer with a thickness of ca. 100 nm calculated by 

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Lazarova Z and Boyadzhiev L. Liquid film pertraction—a liquid membrane method for recovery and preconcentration of aromatic amines from their dilute aqueous solutions. Int J Environ Anal Chem, 1992 46(4) 233-244. 

Tbe extraction of phenol has been used by Schlosser and Kossaczky11 and Halwachs et al.16 as a model for studying liquid-membrane transport. The former group compared the liquid-membrane method to a conventional liquid-liquid double extraction process. They concluded thet liquid membranes have disliact economic ndvsmages in cases where type I or type 2 facilitation methods can be used (e.g., phanel or metal ion extractions). However, where one must rely on simple differential permeation (bydrocarbon seperations) rhe ndvantage is less clear-cut. 

A new technique referred to as the liquid membrane method has been developed (69). Immobilized Hquid membranes are expected to become... 

Most studies of the surface wettability of fibers by the Wilhelmy balance method use relatively short specimens because of the difficulty of immersing long fibers vertically in the liquid. In an effort to overcome this disadvantage of the bulk immersion method, TRI has developed the liquid membrane method for the scanning of long filaments (23). The experimental arrangement for this method is shown schematically in Figure 8. 

H. Nagatani and H. Watarai, Direct spectrophotometric measurement of demetallation kinetics of tetraphenylporphyrinato zinc(II) at the liquid-liquid interface by a centrifugal liquid membrane method. Anal. Chem., 70, 2860-2865 (1998). 

Y.K. Kamath, C.J. Dansizer, S. Homby, H.D. Weigmann, Surface wettability scanning of long filaments by a liquid membrane method. Text Res J 57 (1987) 205. 

Table 8.1. Structural formulae of some of the organic extractants used for U extraction by liquid membrane methods. 

Bhattacharyya, A., Mohapatra, P. K., Roy, A., Gadly, T., Ghosh, V. K., and Manchanda, V. K. 2009. Ethyl-bis-triazinylpyridine (Et-BTP) for the separation of Americium(lll) from trivalent lanthanides using solvent extraction and supported liquid membrane methods. Hydrometallurgy 99 18-24. 

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