Streaming potential measurements performed on silicate and calcium aluminate glass microspheres

Streaming potential measurements were performed on microspheres of silica, soda lime silicate and calcium aluminate glass containing silica and iron oxide. The silicate based glasses exhibited acidic surfaces with isoelectric points (IEP) around a pH of 3 while the calcium aluminates displayed more basic surfaces with IEP ranging from 8 to 9.5. The surface of the calcium aluminate microspheres containing silica reacted with background electrolyte solution during the measurement. This dynamic surface altered the measured zeta potential values and became severe enough that the formation of a solid plug inhibited electrolyte flow past the sample at ∼pH 4.