Ion size effects on the streaming potential of narrow charged pores

The effects of ion size on the streaming potential of fixed charge membranes with narrow pores are studied theoretically as a function of the ratio between the ionic and the pore radii, and the ratio between the external concentration acid the membrane fixed charge concentration. To this end, the radial distributions of the ionic concentrations, space charge density, pressure and electric potential are obtained for finite size and point ions using a generalised Poisson-Boltzmann equation. It is found that the streaming potential increases significantly with increasing ion size. The results are presented in terms of experimentally controlled parameters in order to stimulate targeted experimental work with well defined ionic species and membranes.