Microscale Environmental Chemistry

The determination of the point of zero charge (pzc) for different oxides is important for the prediction of the dependence of various properties with pH. Thus, the pzc can be used to study and characterize the specific adsorption of acids, bases, cations and anions at the water/oxide interface. There are many techniques available for the determination of the pzc, although most of them are somewhat complex. In this work we present a fast and simple pzc determination for some naturally occurring oxides (TiO2, MgO, ZnO, Al2O3, and SiO2), based on a potentiometric procedure. Here, the intersection between a titration curve of the suspended solid oxide (at constant ionic strength) and that of a blank solution (i.e., without the solid) corresponds to the pzc. The values thus obtained are comparable to those reported in the literature.