Supported liquid membranes concentration profile

The typical concentration profile of solute in an SLM system with quaternary ammonium salt as carrier is schematically shown in Fig. 6. To model the facilitated transport within a supported liquid membrane [58,59], the following assumptions are usually made ... 

Fig. 6. Ty pical concentration profile in a supported liquid membrane system...

Figure 2.2 Concentration profiles for the transport of specie S through (A) supported liquid membrane (SLM) and (B) emulsion liquid membrane (ELM).

Figure 2.1 Concentration profiles for the transport of species S through (A) bulk liquid membrane (BLM) with hydrophobic membrane supports (B) BLM with hydrophilic or ion-exchange membrane supports (C) BLM without membrane support (layered BLM).

It is understood that the economical success of any membrane process depends primarily on the quality of the membrane, specifically on flux, selectivity and service lifetime. Consideration of only the transport mechanisms in membranes, however, will in general, lead to an overestimation of the specific permeation rates in membrane processes. Formation of a concentration boundary layer in front of the membrane surface or within the porous support structure reduces the permeation rate and, in most cases, the product quality as well. For reverse osmosis. Figure 6.1 shows how a concentration boundary layer (concentration polarization) forms as a result of membrane selectivity. At steady state conditions, the retained components must be transported back into the bulk of the liquid. As laminar flow is present near the membrane surface, this backflow is of diffusive nature, i.e., is based on a concentration gradient. At steady state conditions, the concentration profile is calculated from a mass balance as... 

Contact modalities and concentration profiles in catalytic membrane reactors for three-phase systems.The concentration of reactants is represented on the y-axis and the spatial coordinate along the membrane cross-section is represented on the x-axis. Below the scheme of each case the sequence of the mass transfer (MT) resistances and of the reaction event (R) are reported. (a)Traditional slurry reactor (b) supported thin porous catalytic layer with the liquid impregnating the porosity and the gas phase in contact with the catalytic layer (c) supported thin porous catalytic layer with the liquid impregnating the porosity and the liquid phase in contact with the catalytic layer (d) supported dense membrane which is perm-selective to the gas-phase reactant (e) dense catalytic membrane perm-selective to both reactants in the gas and liquid phases (f) forced flow of the liquid phase enriched with the gas-phase reactant through the thin catalytic membrane layer. 

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