ABSTRACT
The electrophoretic mobility of liquid drops (and air bubbles) is greater than that of rigid particles because the flow velocity of the surrounding liquid need not become zero at the drop surface and is conveyed into the drop interior.[33,39] The electrophoretic mobility of a drop thus depends on the viscosity ηd of the drop as well as on the liquid viscosity η. Here we treat the case of mercury drops, in which case the drop surface is always equipotential so that it is relatively easy to solve the electrokinetic equations. The general mobility expression for a mercury drop having a zeta potential ζ is derived by Ohshima et al.,[35]
(59)
where G(r) is given in Eq. 26. For the case where ζ is low, Eq. 59 leads to
(60)
For ηd→∞, Eq. 60 reduces to Henry’s Eq. 32 for a rigid sphere. Ohshima[38] has shown that Eq. 60 is approximated well by
(61)
with the maximum relative error of less than 1%.
