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Supported liquid membranes structures

In supported liquid membranes, a chiral liquid is immobilized in the pores of a membrane by capillary and interfacial tension forces. The immobilized film can keep apart two miscible liquids that do not wet the porous membrane. Vaidya et al. [10] reported the effects of membrane type (structure and wettability) on the stability of solvents in the pores of the membrane. Examples of chiral separation by a supported liquid membrane are extraction of chiral ammonium cations by a supported (micro-porous polypropylene film) membrane [11] and the enantiomeric separation of propranolol (2) and bupranolol (3) by a nitrate membrane with a A/ -hexadecyl-L-hydroxy proline carrier [12]. [Pg.130]

These types of separators consist of a solid matrix and a liquid phase, which is retained in the microporous structure by capillary forces. To be effective for batteries, the liquid in the microporous separator, which generally contains an organic phase, must be insoluble in the electrolyte, chemically stable, and still provide adequate ionic conductivity. Several types of polymers, such as polypropylene, polysulfone, poly(tetrafluoroethylene), and cellulose acetate, have been used for porous substrates for supported-liquid membranes. The PVdF coated polyolefin-based microporous membranes used in gel—polymer lithium-ion battery fall into this category. Gel polymer... [Pg.184]

Affinity of MIP towards the target analyte should be examined prior to fabrication of the chemosensor. Batch binding assays are used to test selectivity of suitable MIPs. Especially, affinity of MIP to compounds, which are structurally related to the target analyte, should be tested. If MIP binds similarly with these compounds as the template, then cross-reactivity is manifested [156], This effect was exploited for determination of adenine and its derivatives with the use of MIP templated with 9-ethyladenine. Nevertheless, the cross-reactivity, if undesired, can be avoided by suitable sample pretreatment, e.g. by interferant extraction with a supported liquid membrane (SLM) coupled to the MIP-PZ chemosensor. The Fluoropore membrane filter of submicrometre porosity can serve that purpose. That way, this membrane holds interferants, thus eliminating the matrix effect. The SLM-involving determination procedure is cheaper than traditional laborious sample pretreatment used to remove the interfering substances. For instance, caffeine [143] and vanillin [157] in food samples have been determined using this procedure. [Pg.228]

The range of apphcations of supported liquid membranes (SLMs) in the wastewater treatment is comparable to the ELM (Section 3), with respect to the range of chemicals that have been treated using this technology. This section, therefore, has a structure that is analogical to Section 3. [Pg.381]

In the present paper, we examine the influence of structural variation within series of crown ether carboxylic acid and crown ether phosphonic acid monoalkyl ester carriers upon the selectivity and efficiency of alkali metal transport across three types of liquid organic membranes. Structural variations within the carriers include the polyether ring size, the lipophilic group attachment site and the basicity of ethereal oxygens. The three membrane types are bulk liquid membranes, liquid surfactant (emulsion) membranes and polymer-supported liquid membranes. [Pg.87]

Polymer liquid (PL) membranes The PL membrane is a relatively new type of self-supporting liquid membrane, which resembles the SL membrane. Similarly to the SL membrane, the PL membrane incorporates a liquid extractant in the membrane polymeric structure. In some cases the incorporation of additional organic compounds (plasticizers) is required to achieve homogeneity and sufficient flexibility of the membrane. [Pg.2989]

Supported liquid membrane extraction (SLME) is emerging as a fast and efficient sample preparation technique. Aromatic aminophosphonate isolation from water samples based on SLME allowed the identification and study of the operational parameters (pEI and ionic strength of the aqueous phase, composition of the membrane phase, and concentration of analytes) as well as the structure-extraction efficiency relationship. [Pg.3601]

Depending on their structure, symmetric membranes can be catalogued as porous and non-porous or dense (polymeric swollen-network), while asymmetric membranes for desalting applications (NF and RO, basically) consist of a dense and thin active layer and a thick porous sublayer for mechanical stability (usually an UF membrane). Moreover, supported liquid membranes (SLMs), and aetivated membranes (AMs), which basically consist in the immobilization of speeifie agents (organic solvent, carrier or ionic liquid at room temperature) in the pores/structure of a support membrane, have been developed for selective separation of valuable/contaminant compoimds [8-11]. [Pg.240]

Different extraction techniques have been developed. These techniques have been classified as porous and nonporous, based on their structure, as a flat (like a paper sheet with less than 1 pm of thickness) or hollow fiber (200-500 pm i.d.) configuration. Other classification refers to the number of phases involved in the extraction (one-, two-, or three-phase extraction techniques) [186]. A distinction can be based on the nature of the acceptor phase liquid membrane extractions, where the acceptor phase is a liquid, such as supported liquid membrane (SLM) extraction, microporous membrane liquid-liquid... [Pg.639]

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. [Pg.75]

In this study, experiments on the simultaneous permeation of CO2 and CH4 through aqueous MEA, DEA and ethylenediamine hydrochloride (EDAHCl) membranes are performed and the permeation rates of CO2 are quantitatively discussed on the basis of the approximate solution of facilitated transport (77). A method is also proposed for applying the facilitated transport theory developed for a liquid membrane consisting of a liquid membrane phase alone to the analysis of facilitated transport through a supported liquid membrane prepared by impregnating a microporous polymer support having tortuous pore structure with a carrier solution. [Pg.240]

In supported liquid membranes (SLMs), the transport of potassium salts is always dependent on the difhision coefiScient of the complex through the membrane with the only exception for the derivative (12p), in the partial cone structure, wliere the rate limiting step is the release of the salt in the receiving phase. Both in transport (SLM) and in detection with ion selective field-effect transistors (ISFETs) the derivative in the 1,3-alternate structure (12a) shows higher selectivity than valinomycin. ... [Pg.72]

In Section 5.4.4, we studied a variety of chemical reaction facilitated separation where the reaction was taking place in a thin liquid layer acting as the liquid membrane Figure 5.4.4 illustrated a variety of liquid membrane permeation mechnisms. Here we will identify first the structural configuration of the liquid membranes as they are used in separators with countercurrent flow pattern (as well as for the cocurrent flow pattern). There are three general classes of liquid membrane structures emulsion liquid membrane (ELM) supported liquid membrane (SLM) or immobilized liquid membrane (ILM) hollow fiber contained liquid membrane (HFCLM). Each will be described very briefly. [Pg.767]

Abstract. The synthesis of 1,2- and l,3-calix[4]-Z w-crowns, double calix[4]arenes and double calixcrowns have been shown to depend on the reaction conditions (nature of the base, structure of the ditosylates, and the stoichiometry of the reactants). The 1,3-altemate conformation of the 1,3-calix[4]- w-crowns was shown to be favourable to the selective complexation of cesium cation. The observed Na /Cs selectivity was exploited in separation processes using them as carriers in transport through supported liquid membranes (SLMs). The best Na "/Cs selectivity (1/45 000) was observed for the naphthyl derivative 7. Calix(aza)crowns and 1,3-calix[4]-/ w-(aza)-crowns were also produced through the preliminary formation of the Schiff base-calixarenes, which were further hydrogenated. The syntheses consisted of the 1,3-selective alkylation of calixarenes followed by cyclization into a 1,3-bridged calixarene or by the direct 1,3-capping of the calixarene with appropriate ditosylates. Soft metal complexation by these ligands is also presented. [Pg.137]

Enantioselective transport processes can be achieved either with solid or liquid membranes (Fig. 1-5). In this latter case, the liquid membrane can be supported by a porous rigid structure, or it can simply be an immiscible liquid phase between two solutions with the same character (aqueous or nonaqueous), origin and destination... [Pg.13]

Membrane conformational changes are observed on exposure to anesthetics, further supporting the importance of physical interactions that lead to perturbation of membrane macromolecules. For example, exposure of membranes to clinically relevant concentrations of anesthetics causes membranes to expand beyond a critical volume (critical volume hypothesis) associated with normal cellular function. Additionally, membrane structure becomes disorganized, so that the insertion of anesthetic molecules into the lipid membrane causes an increase in the mobility of the fatty acid chains in the phospholipid bilayer (membrane fluidization theory) or prevent the interconversion of membrane lipids from a gel to a liquid form, a process that is assumed necessary for normal neuronal function (lateral phase separation hypothesis). [Pg.306]

In this chapter membrane preparation techniques are organized by membrane structure isotropic membranes, anisotropic membranes, ceramic and metal membranes, and liquid membranes. Isotropic membranes have a uniform composition and structure throughout such membranes can be porous or dense. Anisotropic (or asymmetric) membranes, on the other hand, consist of a number of layers each with different structures and permeabilities. A typical anisotropic membrane has a relatively dense, thin surface layer supported on an open, much thicker micro-porous substrate. The surface layer performs the separation and is the principal barrier to flow through the membrane. The open support layer provides mechanical strength. Ceramic and metal membranes can be either isotropic or anisotropic. [Pg.89]

Yet another approach to stabilizing facilitated transport membranes is to form multilayer structures in which the supported liquid-selective membrane is encapsulated between thin layers of very permeable but nonselective dense polymer layers. The coating layers must be very permeable to avoid reducing the gas flux through the membrane materials such as silicone rubber or poly(trimethylsilox-ane) are usually used [26],... [Pg.451]

In these systems, the interface between two phases is located at the high-throughput membrane porous matrix level. Physicochemical, structural and geometrical properties of porous meso- and microporous membranes are exploited to facilitate mass transfer between two contacting immiscible phases, e.g., gas-liquid, vapor-liquid, liquid-liquid, liquid-supercritical fluid, etc., without dispersing one phase in the other (except for membrane emulsification, where two phases are contacted and then dispersed drop by drop one into another under precise controlled conditions). Separation depends primarily on phase equilibrium. Membrane-based absorbers and strippers, extractors and back extractors, supported gas membrane-based processes and osmotic distillation are examples of such processes that have already been in some cases commercialized. Membrane distillation, membrane... [Pg.447]


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See also in sourсe #XX -- [ Pg.406 ]




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