Abstract
In order to clarify the effect of electric double layer overlapping in the pore of microporous membrane on the measurements of streaming potential (SP) and the apparent zeta potential, ζobs, of the pore surface, the mixed cellulose ester microporous membranes having different pore sizes ranging from 0.025 to 0.8 μ m were used. The dependence of SP on KCl concentration was measured by the continuous measuring method of SP over the wide range of KCl concentration. Both the SP and the ζ obs estimated from the measured SP had the maximum negative value at a certain value of KCl concentration, which depended on the pore size. The ζ obs obtained from the different pore sizes did not coincide with each other even at the higher κγ, which is the ratio of pore radius, γ, to Debye length, κ-1, where the electric double layer overlapping was assumed to be negligible. However, it was demonstrated that the relationship between SP and KCl concentration could be evaluated from the theoretical calculation by using the fitting parameters of surface charge density and pore size. The calculated pore size of membrane tested was the same order of nominal one.
