Supported liquid membranes design

In this paper an overview of the developments in liquid membrane extraction of cephalosporin antibiotics has been presented. The principle of reactive extraction via the so-called liquid-liquid ion exchange extraction mechanism can be exploited to develop liquid membrane processes for extraction of cephalosporin antibiotics. The mathematical models that have been used to simulate experimental data have been discussed. Emulsion liquid membrane and supported liquid membrane could provide high extraction flux for cephalosporins, but stability problems need to be fully resolved for process application. Non-dispersive extraction in hollow fib er membrane is likely to offer an attractive alternative in this respect. The applicability of the liquid membrane process has been discussed from process engineering and design considerations. 

Membrane Techniques The interest in membrane techniques for sample preparation arose in the 1980s. Extraction selectivity makes membrane techniques an alternative to the typical sample enrichment methods of the 1990s. Different membrane systems were designed and introduced into analytical practice some more prominent examples are polymeric membrane extraction (PME), microporous membrane liquid-liquid extraction (MMLLE), and supported liquid membrane extraction (SEME) [106, 107]. Membrane-assisted solvent extraction (MASE) coupled with GC-MS is another example of a system that allows analysis of organic pollutants in environmental samples [108-111] ... 

We have made use of the cation-selective properties of macrocycles to design liquid membrane [6], supported liquid membrane [6], and macrocycle-bonded silica gel [7] systems for specific cation separations. The selective transport of Ag [8, 9], Pb " [8], K" [10] and Li [11] was observed in a bulk liquid membrane system using various macrocyclic ligands. In the supported liquid membrane (thin sheet and hollow fiber) systems, selective and predicted separations of Na /K , Cd " / Hg ", and others have been achieved [12, 13],... 

The design of the hollow fiber supported liquid membrane modules for the separation concentration of solute using overall permeability coefficient P centers on... 

In the next section, four chapters describe three main configurations of liquid membranes supported, emulsion, and bulk LM. Each chapter is subdivided into theory and transport mechanisms, module design and experimental techniques, and applications in different fields of chemical, biochemical, environmental, and pharmaceutical separations. 

Ultra-thin liquid membranes can be fabricated down to 1 pL in thickness. Ultra-thin liquid membranes can be formed in the skin layer of an porous asymmetric polymer membrane by methods in which the liquid is selectively deposited in the skin rather than the backing support. The wide variety of pore sizes and membrane configurations available in asymmetric membranes allows for good flexibility in the design of ultra-thin liquid membrane systems. 

The focus in the thin film research impact area is to develop a fundamental understanding of how morphology can be controlled in (1) organic thin film composites prepared by Langmuir Blodgett (LB) monolayer and multilayer techniques and (2) the molecular design of membrane systems using ionomers and selected supported liquids. Controlled structures of this nature will find immediate apphcation in several aspects of smart materials development, particularly in microsensors. 

The customary type of a liquid membrane electrode is a design in which the sensitive membrane is composed of a water-immiscible organic solvent containing the ion of interest in the form of ion associate. The membrane is interposed between a standard (internal) and a test (external) ion solution.""" In early types of liquid membrane electrodes, an organic phase as a membrane is placed between two aqueous phases in bulk or with the support of a thin, porous cellulose sheet, sintered glass, or similar lamellas. Nitrobenzene is the popular membrane solvent other organic solvents are also applied such as o-nitrotoluene, 4-ethylnitrobenzene, 4-nitro-m-xylene, and p-nitrocoumarin. 

Liquid film membranes consist of immiscible solutions held in membrane supports by capillary forces. The chemical composition of these solutions is designed to enhance transport rates of selected components through them by solubility or coupled chemical reaction. 

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