A NOVEL METHOD FOR THE DETERMINATION OF THE POINT OF ZERO NET PROTON CHARGE OF COLLOIDAL KAOLINITE IN AQUEOUS SOLUTIONS

摘要

In this work, a novel method to determine the point of zero net proton charge (PZNPC) of colloidal kaolinite in aqueous solutions was presented through the measurement of zeta potential of the particles in various concentrations of NaCl solution and the mathematic regression of the zeta potential versus pH curves. This method is based on the observation that there are two common intersection points (CIP) in the two curves of zeta potential versus pH of colloidal kaolinite with a low and a high NaCl concentration. The observation might be attributed to that NaCl would compress the electric double layer of kaolinite particles and affect the efficiency of the protonation/deprotonation of the HD-faces. The experimental result showed that the PZNPC of kaolinite is 5.37.