Film mass transfer coefficient expressions for electroosmotic flows

Expressions are developed and presented that could be used to determine the film mass transfer coefficient of a solute in electroosmotic flows. In con trast to pressure-driven flows at low Reynolds numbers where the film mass transfer coefficient is independent of the linear characteristic dimension of the channel for how in electroosmotically driven flows at low Reynolds n umbers the film mass transfer coefficient is shown to be a function of the ratio R/lambda, where R is the channel radius and lambda is the Debye lengt h. This result implies that for electroosmotically driven flows in a packed bed or porous monolith with channels for flow having similar geometry but different sizes, the film mass transfer coefficient would vary with the siz e of the interstitial channels for bulk flow while in pressure-driven hows the film mass transfer coefficient would be the same for all interstitial c hannels. From the expressions presented in this work, one can show that for the same volumetric flow rate the film mass transfer coefficient of electr oosmotically driven flows is proportional to that for pressure-driven flows , (C) 2000 Academic Press.