Effect of pH on the electrokinetic properties of hydrophilic quartz and quartz made hydrophobic with petroleum

A study was made of the electrokinetic properties of quartz sand having a hydrophilic surface and a surface made hydrophobic by petroleum. The electrokinetic or zeta potential was calculated from the Helmholtz-Smoluchowski equation. It was shown that the effect of the pH on the wetting contact angle and on the zeta potential of quartz with a gel layer is determined by the surface area and not by the electrokinetic charge of the quartz. If the surface charge of quartz having a gel layer due to hydrophobization by petroleum decreases, the decrease is insignificant and the effect of the pH on the wetting by water should persist.