Bulk liquid surfactant membrane

Figure 7. Simplified representation of a bulk liquid surfactant membrane in which the membrane is composed of a surfactant-containing organic solvent.

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

Actinides, in nitric acid waste, 182 Advancing-front model, ELMs, 18,68 Alkali metal cations transport across bulk liquid membranes, 89-92 transport across liquid surfactant membranes, 93-95 transport across polymer-supported liquid, 95-96... 

Svobodova E, Cibulka R, Hampl I, Smidrkal J, Liska F. Metal ion transport through bulk liquid membrane mediated by cationic ligand surfactants. Collection Czechoslovak Chem Commun 2005 70 441-465. 

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. 

Apart from the above effect on dissolution rate, surfactant micelles also affect the membrane permeability of the solute [8j. Solubilization can, under certain circumstances, help the transport of an insoluble chemical across a membrane. The driving force for transporting the substance through an aqueous system is always the difference in its cdiemical potential (or to a first approximation the difference in its relative saturation) between the starting point and its destination. The principal steps involved are dissolution, diffusion or convection in bulk liquid and crossing of a membrane. As mentioned above, solubilization will enhance the diffusion rate by affecting transport away from the boundary layer adjacent to the crystal [8j. However, to enhance transport the solution should remain saturated, i.e. excess solid particles must be present since an unsaturated solution has a lower activity. 

The biological efficiency of an insoluble pesticide will be significantly affected by the presence of micelles, due in part to improved solution of the a.i. In addition, surfactant micelles influence the rate of dissolution of a solute as well as its membrane permeability. The driving force for transportation across a membrane may involve dissolution, diffusion, or convection in bulk liquid and crossing of the membrane. Diffusion in bulk liquid obeys Pick s law ... 

We recently synthesized several reasonably surface-active crown-ether-based ionophores. This type of ionophore in fact gave Nernstian slopes for corresponding primary ions with its ionophore of one order or less concentrations than the lowest allowable concentrations for Nernstian slopes with conventional counterpart ionophores. Furthermore, the detection limit was relatively improved with increased offset potentials due to the efficient and increased primary ion uptake into the vicinity of the membrane interface by surfactant ionophores selectively located there. These results were again well explained by the derived model essentially based on the Gouy-Chapman theory. Just like other interfacial phenomena, the surface and bulk phase of the ionophore incorporated liquid membrane may naturally be speculated to be more or less different. The SHG results presented here is one of strong evidence indicating that this is in fact true rather than speculation. 

The foregoing interpretation of the mechanism, although necessarily somewhat speculative, provides a useful kinetic model [10]. Let X, Y, and Z be the concentrations of the key chemicals Xj, the concentration of surfactant at and/or near the interface Yi the concentration of alcohol near the interface Zj the concentration of the aggregate or complex of surfactant and alcohol at and/or near the interface. Scheme 1 can be considered as a possible explanation for the mechanism of oscillation in a liquid membrane. Xb and Yb are the concentration of the surfactant and alcohol, respectively, in the bulk aqueous phase. 

This paper presents an emulsion liquid membrane (ELM) system capable of extracting both Se(IV) and Se(VI) from an aqueous waste stream containing large amounts of innocuous anions like sulfate. In an emulsion liquid membrane, small drops of an aqueous stripping phase are contained (emulsified) inside an organic hydrocarbon (oil) drop, llie surfactant-stabilized oil acts as a membrane separating the wastewater (the continuous, bulk phase solution) from encapsulated droplets of aqueous solution (the internal phase) as shown in Figure 3. 

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