pH-dependent surface charging and points of zero charge II. Update

Abstract

Recently published PZC (points of zero charge) of metal oxides and related materials are compiled to update the previous compilations (M. Kosmulski, Chemical Properties of Material Surfaces, Dekker, New York, 2001; J. Colloid Interface Sci. 253 (2002) 77). The electroacoustic method has been widely used; it has become a standard tool, and it has proved to produce IEP (isoelectric points) comparable with those obtained by means of classical electrokinetic methods. The recently published numerical values of PZC/IEP of various materials corroborate the old results, with one exception: the PZC of magnetite found at pH 8 is substantially higher than the values reported in the old literature. New approaches to the electrokinetics of sparingly soluble salts have recently been proposed; e.g., the hysteresis in electrokinetic curves of (nominally) BaTiO3 has been interpreted in terms of changes in the surface stoichiometry caused by leaching.