Abstract
Electric conductivity (λ) dependency of streaming potential (SP) was measured to estimate the pore size and the
surface charge density of the commercial ultrafiltration (UF) membranes having different nominal molecular weight
cut-off (NMWCO). At the same λ value the absolute value of SP decreased with the decrease in NMWCO in the
range of λ＞1×10–2 S/m. The pore size and surface charge density of UF membrane could be determined by the
analysis of λ dependence of streaming potential in the range of λ＞1×10–2 S/m applying a mathematical equation
of space charge model. In order to obtain the relation between two pore sizes estimated by SP measurement and the
actual separation performance of UF membrane, the MWCO of the UF membrane was measured with 0.03wt% PEG
solution. The pore size estimated by SP measurement showed a good linear relation with the Stokes diameter of
PEG which has the molecular weight corresponding to MWCO of UF membrane tested. These observations mean
the pore size estimated by SP measurement is correlated with the separation performance of UF membrane.
