Membrane separation combined with

Y.V. Plekhanova, A.N. Reshetilov, E.V. Yazynina, A.V. Zherdev, and B.B. Dzantiev, A new assay format for electrochemical immunosensors polyelectrolyte-based separation on membrane carriers combined with detection of peroxidase activity by pH-sensitive field-effect transistor. Biosens. Bioelectron. 19, 109-114(2003). 

The best strategy for acceptance in high-temperature gas/vapour separation (T > 200°C) and catalytic membrane reactors is probably its introduction in small-scale processes and/or hybrid installations which exist in two types (a) a combination of a membrane separation unit with a conventional process [4,7,12] and (b) interstage removal of component(s) by a membrane unit in between two reactors in series [15]. 

Another example of the use ofHF-SLM separation concerns the resolution of racemic ofloxacin [200]. This important drug, a fluoroquinolone antibiotic with one chiral center, was separated in chiral systems by hoUow-fiber liquid-supported membrane technology combining with countercurrent fractional extraction. The two chiral solutions contained L-dibenzoyltartaric acid and D-dibenzoyltartaric acid in 1-octanol, and flowed through the lumen side and the sheU side of fibers, respectively. The solution which Uowed through the lumen side of fibers also contained racemic ofloxacin. The waU of hoUow fibers was fiUed with an aqueous of 0.1 mol/l Na2[ ll O4/[ fd O4 buffer solution of pH 6.86 containing 2 mmol/1 of cetyltrimethylammonium bromide for 48 h. The obtained optical purity for ofloxacin enantiomers was up to 90% when 11 hoUow-fiber membrane modules of 22 cm in length in series were used. 

An analogous system can be used to generate methanesulfonic acid (MSA) eluent for the separation of cations (Fig. 1.10). In this case, the anode generates for eluent production. The cathode generates OH anion that combines with the H in the MSA electrolyte reservoir. MSA anion migrates across the anion exchange membrane to combine with the eluent cation (maintaining electric neutrality). 

U should be noted that this definition does not characterise the membrane nor the pores ot the membrane, but rather the size of the particles or molecules retained by it. "nw separation characteristics are determined by the large pores in the membrane.. Another factor of interest is the surface porosity. This is also a very important variable in determining the flux through the membrane, in combination with the thickness of the top layer or the length of the pore. Different miciofiltration membranes exhibit a wide range of surface porosity as discussed in chapter III. from about S to 70%. In contrast, the ultrafiltration membranes normally show very low surface porosities, ranging from 0.1-1. ... 

Yang, M.J. and Pawliszyn, J. Headspace membrane extraction combined with multiplex gas chromatography and mass selective detector for monitoring of volatile organic compounds. Journal of Microcolumn Separations 1996, 8 (2), 89-98. 

The efficiency of membrane separation increases with the permeability and the selectivity. Thin membranes are economic, since according to Equation (2.1) the gas flow is inverse proportional to the layer thickness. However thin polymeric films, which have favorable permeability and selectivity, are too weak to withstand the high pressure difference between permeate and retentate side. The economic breakthrough set in with the production of ultrathin compound polymeric membranes. These are designed as hollow fibres with a thick porous back-up layer for mechanical stability and a thin dense non porous membrane layer for gas separation. The porous layer only has a slight influence on gas separation. These hollow fibres are combined in a bundle, which is arranged in a cylindrical container [2.13]. Several of these bundles, also called modules, can be added to... 

The treatment of membrane separation processes in this book merits some deliberation. The most commonly used driving force in membrane separation processes is negative chemical potential gradient a few processes also employ electrical force. Figure 3.4.5 identifies the variety of feed phase-membrane type combinations with variations due to the nature of the permeate phase when negative chemical potential gradient is imposed across the membrane. Section... 

The answers to these challenges are probably given by the fabrication of MMMs, in which the novel membrane materials are loaded in a host of polymeric membranes as filler nanoparticles. Thus, high processibilty of polymeric membranes is combined with high separation performance of filler materials. Usually, separation performance of MMMs is much improved compared with the host polymeric membrane, but the improvement is not as spectacular as expected from the novel membrane materials. A flux that is orders of magnitude higher than the host polymeric membrane has never been achieved by MMMs. 

Both PSI and PSII are necessary for photosynthesis, but the systems do not operate in the implied temporal sequence. There is also considerable pooling of electrons in intermediates between the two photosystems, and the indicated photoacts seldom occur in unison. The terms PSI and PSII have come to represent two distinct, but interacting reaction centers in photosynthetic membranes (36,37) the two centers are considered in combination with the proteins and electron-transfer processes specific to the separate centers. 

Cross-flow-elec trofiltratiou (CF-EF) is the multifunctional separation process which combines the electrophoretic migration present in elec trofiltration with the particle diffusion and radial-migration forces present in cross-flow filtration (CFF) (microfiltration includes cross-flow filtration as one mode of operation in Membrane Separation Processes which appears later in this section) in order to reduce further the formation of filter cake. Cross-flow-electrofiltratiou can even eliminate the formation of filter cake entirely. This process should find application in the filtration of suspensions when there are charged particles as well as a relatively low conduc tivity in the continuous phase. Low conductivity in the continuous phase is necessary in order to minimize the amount of elec trical power necessaiy to sustain the elec tric field. Low-ionic-strength aqueous media and nonaqueous suspending media fulfill this requirement. 

The combination of diafiltration and batch concentration can be used to fractionate two macrosolutes whose retentions differ by as little as 0.2. It is possible in principle to achieve separations that are competitive with chromatography. When tanks and other equipment are considered, as well as the floor space they occupy, the economics of membrane separation of proteins may be attractive [R. van Reis, U.S. Patent 5,256,294 (1993)]. 

Membrane techniques have already been combined with two-phase liquid catalysis. The main function of this method is to perform fine separation of undesirable constituents from the catalytic system after phase decantation has already performed the coarse separation of the catalyst from the products. This technique can be applied to ionic liquid systems as a promising approach for the selective removal of volatile solutes from ionic liquids [20]. 

Dasgupta and Jacobs [29] patented a concept of using a gel layer in combination with a microporous membrane. The gel layer acts as an adhesive bridge between separator and electrodes, just as in the flat pack Zn/MnC cell [30], The microporous membrane (for example, Celgard membrane) provides excellent mechanical... 

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