ELECTROKINETIC STUDIES OF MINERALS IN AQUEOUS SOLUTIONS THROUGH ELECTROACOUSTIC MEASUREMENT

Electrokinetic property of various minerals in aqueous solutions has been studied through electroacoustic measurement in the present work. This study was carried out on the particles of calcite (CaCO3), magnetite (Fe3O4), quartz (SiO2), and galena (PbS) in an aqueous NaCl solution. Electrophoretic measurement was also applied to magnetite and quartz particles for the comparison of the two methods. The experimental results have shown that the point of zero charges (PZCs) of calcite, magnetite, and galena were at pH 12.5, 3.8 and 2.8, respectively, while no PZC for quartz appeared in the pH range of 1.5–11. The electroacoustic and electrophoretic measurements have obtained the same PZC and similar curves of zeta potential vs pH for magnetite and quartz particles in aqueous solutions. In addition, it has been found that a specific adsorption of Na+ cation was applied to magnetite surfaces in aqueous solutions if the electrolyte (NaCl) concentration in the solution is high enough, leading the isoelectric point to shift rightward. This observation might be more remarkable in electroacoustic measurement than electrophoretic measurement.