流動電位測定による多孔質幕評価の新展開

概要

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The applications of streaming potential (SP) measurement to the characterization of porous membranes including microfiltration (MF) and ultrafiltration (UF) membranes were discussed. The SP of the porous membranes will be affected by pore size and ionic strength in addition to the surface charge condition of pores because the thickness of electric double layer (EDL) in the pore will be almost same range as the pore sizes of MF and UF membranes. The zeta potential estimated from SP with Helmholtz -Smoluchowski (H-S) equation is widely used for the index of surface charge condition of pores although the H-S equation does not consider the overlapping of EDLs in the pore. The effect of the overlapping of EDLs in pore on the zeta potential was discussed with wide range of measurements. This behavior of EDL in pore can be used for pore size determination of the porous membranes. The pore size determinations by SP measurements with microscopic model were demonstrated and discussed for MF and UF membranes. The zeta potential can be also used for the characterization of fouling status. The responses of zeta potential to fouling configurations of MF membrane such as adsorption onto pore surface, pore blocking, and cake formation were discussed. It is shown that the change in zeta potential during filtration reflects both the local zeta potential and the location of pressure drop.