Bulk liquid membrane

The carrier should not dissolve in the feed liquid or receptor phase in order to avoid leakage from the liquid membrane. In order to achieve sufficient selectivity, minimization of nonselective transport through the bulk of the membrane liquid is required. Liquid membranes can be divided into three basic types [6] emulsion supported and bulk liquid membranes, respectively (Fig. 5-2). 

Fig. 5-2. Three types of the liquid membrane eonfiguration (a) emulsion liquid membrane (b) supported liquid membrane (e) elassieal bulk liquid membrane set-up.

In the classical set-up of bulk liquid membranes, the membrane phase is a well-mixed bulk phase instead of an immobilized phase within a pore or film. The principle comprises enantioselective extraction from the feed phase to the carrier phase, and subsequently the carrier releases the enantiomer into the receiving phase. As formation and dissociation of the chiral complex occur at different locations, suitable conditions for absorption and desorption can be established. In order to allow for effective mass transport between the different liquid phases involved, hollow fiber... 

Liquid-liquid extraction Bulk liquid membrane transport Liquid surfactant membrane transport... 

Bulk Liquid Membrane. . . Emulsion Liquid Membrane. Supported Liquid Membrane Dispersion Free Extraction. ... 

Figure 1 shows several types of mass transfer or diffusion cells, which are of the simplest design for performing bulk liquid membrane (BLM) processes. Each of the devices is divided into two parts a common part containing the membrane liquid, M and a second part in which the donor solution F and acceptor solution R are separated by a solid impermeable barrier. The liquid, M contacts with the two other liquids and affects the transfer between them. All three liquids are stirred with an appropriate intensity avoiding mixing of the donor and acceptor solutions. For a liquid-ion exchange in a BLM system. Fig. 2 shows the transfer mechanism of cephalosporin anions, P , from donor (F) to acceptor (R) solution... 

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]. 

In 1982, /Mert-butyl-cal i x n larenes were studied by Izatt et al. for their capacity to transport cesium from an alkaline medium ([MOH] = 1M) through bulk liquid membranes made of a mixture of diluents able to dissolve these compounds methylene chloride, carbon tetrachloride, and dichloromethane. Experiments were carried out using p-tert-calix[8]arene to measure the rate of cesium transport under conditions of varying source pH. The values of the transport rate, small below a pH of 12, rise rapidly beyond this value, hence confirming that a proton is removed from the ligand in the complexation process. Under such conditions, tetramer, hexamer, and octamer (n = 4, 6, and 8, respectively) display a high selectivity for cesium over the other... 

Kirch and Lehn have studied selective alkali metal transport through a liquid membrane using [2.2.2], [3.2.2], [3.3.3], and [2.2.C8] (146, 150). Various cryptated alkali metal picrates were transported from an in to an out aqueous phase through a bulk liquid chloroform membrane. While carrier cation pairs which form very stable complexes display efficient extraction of the salt into the organic phase, the relative rates of cation transport were not proportional to extraction efficiency and complex stability (in contrast to antibiotic-mediated transport across a bulk liquid membrane). Thus it is [2.2.Ca] which functions as a specific potassium ion carrier, while [2.2.2] is a specific potassium ion receptor (Table VI). 

Mass transfer occurs from the feed films into the stripping solution films through the bulk liquid membrane. Pertraction in RD contactors has been widely studied in the Boyadzhiev group for recovery of organic acids [50-53], antibiotics [54], alkaloids [55-58], biosurfactant [59] and metals [60-64],... 

Schlosser, ., Rothova, I. and Frianova, H. (1993) Hollow-fiber pertractor with bulk liquid membrane. Journal of Membrane Science, 80, 99. 

Carrier-facilitated transport is used successfully to extract various organic and inorganic substances from a feed mixture in liquid membranes. Liquid membranes are employed as bulk liquid membranes, emulsion liquid membranes, and supported liquid membranes. 

Alkali metal ions Phenoxy compounds Bulk liquid membrane TR + R Rankumar et al. (1999)... 

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