Dispersion in oscillatory electro-osmotic flow through a parallel-plate channel with kinetic sorptive exchange at walls

Dispersion in time-oscillatory electro-osmotic flows in a slit micro-channel under the effect of kinetic sorptive exchange at walls is theoretically investigated using the homogenization method. The two walls of the channel are considered to be made up of different materials, and therefore have different zeta potentials and sorption coefficients. A general expression for the Taylor dispersion coefficient under different zeta potentials as well as various sorption conditions at the walls is derived analytically. The dispersion coefficient is found to be dependent on the oscillation frequency, the Debye parameter, the species partition coefficient, the reaction kinetics and the ratio of the wall potentials. The results demonstrate that the presence of wall sorption tends to enhance the dispersion when the oscillation frequency is low, but the effect is negligible in high-frequency oscillatory flows. Moreover, it is found that the dispersion coefficient could be significantly changed by adjusting the relative wall potentials for low-frequency flows.