Zeta potential of Teflon in presence of monovalent and divalent ions

In this study, the specific effects of Na+ and Ca2+ ions on natural hydrophobic Teflon particles and flat Teflon surfaces were investigated using zeta potential and contact angle measurements, respectively. The zeta potential measurements showed that the surface charge of Teflon was negative at all pH values in the absence of salt ions, and became the positive with the increased salt concentration, and obtained an iso electric point (iep) between pH 3 and 4. The results also indicated that Ca+2 ions more adsorbed on the Teflon surface compared to Na+ ions in the case of the compression of the electrical double layer. The contact angle measurements with Teflon sample showed that while the flat Teflon had a contact angle of 107° at pure water, and the contact angle considerably reduced as a function of salt concentration. This decrease was more effective in the presence of Ca2+ ions rather than Na+ ions. While calcium is a strong water structure maker cation, sodium is a weak structure maker cation, but the role of calcium is more effective at the Teflon-water interface according to zeta potential and contact angle measurements. It is revealed that the Ca+2 ions have a specific effect on Teflon surface due to low salt concentrations and ion charges. The different effects of these cations on Teflon-water interface can be attributed to use in mineral processing, especially in flotation enrichment.