Liquid emulsion membrane concept

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... 

In the biomedical applications outlined by Ward et al. (7 ), more so than in any other separation application of synthetic polymeric membranes, the goal is to mimic natural membranes. Similarly, the development of liquid membranes and biofunctional membranes represent attempts by man to imitate nature. Liquid membranes were first proposed for liquid separation applications by Li (46-48). These liquid membranes were comprised of a thin liquid film stabilized by a surfactant in an emulsion-type mixture. Wtille these membranes never attained widespread commercial success, the concept did lead to immobilized or supported liquid membranes. In... 

The liquid membrane (LM) concept combines solvent extraction (SX) and membrane-based technologies, enabling both extraction and back-extraction in a single step with reduced consumption of extractants and diluents. For these reasons, separation based on LMs can be viewed as a promising alternative to traditional SX. The LM separation approach involves mass transfer of a target chemical species between two solutions (i.e., feed and receiver solutions) separated by an immiscible LM [1]. The main types of LMs are bulk liquid membranes (BLMs), emulsion liquid membranes (ELMs), supported liquid membranes (SLMs), and polymer inclusion membranes (PIMs). 

However, liquid-liquid extraction can form emulsions, and the extractant is usually expensive and sometimes toxic to the cell culture (Diirre, 1998). To solve these problems, the perstraction technique was developed based on the liquid-liquid extraction concept. In the perstraction separation process, the fermentation broth and the extractant are separated by a membrane, where two immiscible phases can exchange butanol. In this process, butanol can diffuse preferentially across the membrane, while other components (substrates, cell culture, and other fermentation products) are retained in the fermentation broth. This strategy effectively avoids the potential problems in the liquid-liquid extraction system, but it needs to point out that... 

Takahashi et al. [261] have used, with some success, intratumour injection of multiple emulsions of bleomycin and mitomycin in cases of inoperable carcinoma in human patients. Some of the impetus for the increased interest in multiple emulsions has come from the concept of liquid membranes for detoxification. Liquid membranes exist as part of large multiple oil droplets containing many internal dispersed droplets. The system was devised by Exxon Research and Engineering and they have coined the term liquid membrane capsule (LMC) (see Fig. 8.50). For use in vivo the LMCs must survive transit in the gut following oral administration. Asher et al. [262] have studied the mobility of LMCs through the... 

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