Mass transfer surfactants

Carrier mediation Mass transfer Surfactant-based separations Pore accessibility... 

Although the adsorption of surfactants tends to reduce mass-transfer coefficients by suppressing drop circulation, a sharp increase in mass transfer... 

As mentioned earlier, surfactants and ionic solutions significantly affect mass transfer. Normally, surface affects act to retard coalescence and thus increase the mass transfer. For example, Hikata et al. [Chem. Eng. J., 22, 61-69 (1981)] have studied the effect of KCl on mass transfer in water. As KCI concentration increased, the mass transfer increased up to about 35 percent at an ionic strength of 6 gi7i/l. Other investigators have found similar increases for hquid mixtures. 

Mendes-Tatsis, M.A., Agble, D., Mass transfer with interfacial convection and added surfactants, Int. Solvent Extraction Conf (ISEC 96) Value adding through solvent extraction, Ed. Shallcross, D.C., Paimin, R. Prvcic, L.M., Melbourne, Australia, pp.267-272, 1996. 

A summary of a number of correlations proposed for volumetric mass-transfer coefficients and specific interfacial area is presented in Table II, which includes data additional to those of Westerterp et al. (W4). It is apparent that disagreement exists as to the numerical values for the exponents. This is due, in part, to the lack of geometric similarity in the equipment used. In addition, variation in operating factors such as the purity of the system (surfactants), kind of chemical system, temperature, etc., also contribute to the discrepancies. To summarize Table II ... 

The proposed technique will be used here to illustrate the case of interfacial heat and multicomponent mass transfer in a perfectly mixed gas-liquid disperser. Since in this case the holding time is also the average residence time, the gas and liquid phases spend the same time on the average. If xc = zd = f, then for small values of t, the local residence times tc and td of adjacent elements of the continuous and dispersed phases are nearly of the same order of magnitude, and hence these two elements remain in the disperser for nearly equal times. One may conclude from this that the local relative velocity between them is negligibly small, at least for small average residence times. Gal-Or and Walatka (G9) have recently shown that this is justified especially in dispersions of high <6 values and relatively small bubbles in actual practice where surfactants are present. Under this domain, Eqs. (66), (68), (69) show that as the bubble size decreases, the quantity of surfactants necessary to make a bubble behave like a solid particle becomes smaller. Under these circumstances (pd + y) - oo and Eq. (69) reduces to... 

The effect may be reduced by the introduction of surfactants which tend to concentrate at the interface where they exert a stabilising influence, although they may introduce an interface resistance and substantially reduce the mass transfer rate. Thus, for instance, hexadecanol when added to open ponds of water will collect at the interface and substantially reduce the rate of evaporation. 

Wang BX, Peng XF (1994) Experimental investigation of liquid forced-convection heat transfer through micro-channels. Int J Heat Mass Transfer 37 73-82 Wasekar VM, Manglik RM (2002) The influence of additive molecular weight and ionic nature on the pool boiling performance of aqueous surfactant solutions. Int J Heat Mass Transfer 45 483-493... 

Hetsroni G, Gurevich M, Mosyak A, Rozenblit R (2004) Drag reduction and heat transfer of surfactants flowing in a capillary tube. Int J Heat Mass Transfer 47 3797-3869... 

Hetsroni G, Zakin JL, Lin Z, Mosyak A, Pancallo EA, Rozenblit R (2001) The effect of surfactants on bubble grows, wall thermal patterns and heat transfer in pool boiling. Int J Heat Mass Transfer 44 485-497... 

Hetsroni G, Gurevich M, Mosyak A, Rozenblit R (2003) Surface temperature measurement of a heated capillary tube by means of an infrared technique. Meas Sci Technol 14 807-814 Hetsroni G, Gurevich M, Mosyak A, RozenbUt R (2004) Drag reduction and heat transfer of surfactants flowing in a capillary tube. Int J Heat Mass Transfer 47 3797-3809 Hetsroni G, Mosyak A, Pogrebnyak E, Yaiin LP (2005) Eluid flow in micro-channels Int J Heat Mass Transfer 48 1982-1998... 

Klein D, Hetsroni G, Mosyak A (2005) Heat transfer characteristics of water and APG surfactant solution in a micro-channel heat sink. Int J Multiphase Flow 31 393 15 Kosar, A, Kuo, CJ, Peles, Y (2005) Boiling heat transfer with reentrant cavities. Int. J. Heat Mass Transfer 48 4867-4886... 

Here we also consider sorption kinetics as the mass-transfer barrier to surfactant migration to and from the interface, and we follow the Levich framework. However, our analysis does not confine all surface-tension gradients to the constant thickness film. Rather, we treat the bubble shape and the surfactant distribution along the interface in a consistent fashion. 

If the supply of surfactant to and from the interface is very fast compared to surface convection, then adsorption equilibrium is attained along the entire bubble. In this case the bubble achieves a constant surface tension, and the formal results of Bretherton apply, only now for a bubble with an equilibrium surface excess concentration of surfactant. The net mass-transfer rate of surfactant to the interface is controlled by the slower of the adsorption-desorption kinetics and the diffusion of surfactant from the bulk solution. The characteris-... 

E is one of several elasticity numbers characterizing the stabilizing effect which adsorbed surfactant molecules have on an interface during mass-transfer processes (22). Note that E is inversely proportional to the capillary radius so that the effect of soluble surfactants on the bubble-flow resistance is larger for smaller capillary radii. 

Krznaric [799] studied the influence of surfactants (EDTA, NTA) on measurements of copper and cadmium in seawater by differential pulse ASV. Adsorption of surfactants onto the electrode surface were shown to change the kinetics of the overall electrode charge and mass transfer, resulting in altered detection limits. Possible implications for studies on metal speciation in polluted seawater with high surfactant contents are outlined. 

Liquid/liquid (L/L) interface, adsorption of surfactants at, 24 133-138 Liquid-liquid mass transfer, 15 670, 714-717... 

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