Assessing the Zeta Potential at High Salinity

We present an experimental method for the reliable extrapolation of the zeta potential at low and medium ionic strength to estimate the membrane charge at high salinity conditions.

For the analysis of a membrane's surface charge we make use of the zeta potential at the membrane-water interface. The corresponding measuring parameters of streaming potential, Ustr, and streaming current, Istr, limit the analysis of the zeta potential to low and me-dium ionic strength. On the other hand, we want to understand the behavior of a membrane and its sur-face charge at high salinity conditions, especially for membranes used in seawater desalination and related processes, such as reverse osmosis and forward os-mosis membranes. We are therefore facing a discrepancy in the ionic strength between measuring condi-tions and membrane operating conditions.

The aim of this report is to examine the correlation between the zeta potential and the ionic strength, and to find a reliable procedure for an extrapolation of experimental data - obtained at low and medium ionic strength - to high salinity conditions.

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