The adsorption of cetylpyridinium chloride (CPC) and sodium dodecylbenzenesulfonate (SDBS) onto a ceramic glaze mixture composed
of limestone, feldspar, quartz, and kaolin has been investigated. Both adsorption isotherms and the average particle zeta potential have been
studied in order to understand the suspension stability as a function of pH, ionic strength, and surfactant concentration. The adsorption of
small amounts of cationic CPC onto the primarily negatively charged surfaces of the particles at pH 7 and 9 results in strong attraction and
flocculation due to hydrophobic interactions. At higher surfactant concentrations a zeta potential of more than +60 mV results from the
bilayered adsorbed surfactant, providing stability at salt concentrations 0.01 M. At 0.1 M salt poor stability results despite substantial zeta
potential values. Three mechanisms for SDBS adsorption have been identified.When anionic SDBS monomers either adsorb by electrostatic
interactions with the few positive surface sites at high pH or adsorb onto like charged negative surface sites due to dispersion or hydrophobic
interactions, the magnitude of the negative zeta potential increases slightly. At pH 9 this increase is enough to promote stability with an
average zeta potential of more than −55 mV, whereas at pH 7 the zeta potential is lower at about −45 mV. The stability of suspensions at pH
7 is additionally due to steric repulsion caused by the adsorption of thick layers of neutrally charged Ca(DBS)2 complexes created when the
surfactant interacts with dissolved calcium ions from the calcium carbonate component.