The transport of hydronium and hydroxide ions through reverse osmosis membranes

Abstract

It is important to understand the fundamental behaviour of reverse osmosis membranes under a range of pH and salinity conditions. In this work, experiments and modelling are used in a complementary manner to better understand these fundamentals. We find experimentally that both pH and salinity can influence membrane charge, the fractional free volume (or pore size) and the membrane thickness. The thickness of the membrane is quantified using ellipsometry while the pore size is estimated through glucose filtration. The membrane swells marginally with increasing pH, but more so with increasing salt concentration up to 170mM. The flux of hydronium and hydroxide ions are investigated under simil..