Investigation of the electrokinetic properties of paraffin suspension. 1. In inorganic electrolyte solutions

Although electrical properties of nonionogenic hydrophobic surface (solid or liquid) in water and/or electrolyte solutions have been studied for many decades, they are still not well recognized, especially as for the nature of the charge and potential origin. Similarly, water structure at such a surface is still extensively studied. One such system is paraffin wax/water (electrolyte). The zeta potentials and the particle diameters of this system were investigated in this paper. To obtain the suspension of paraffin in water or electrolyte solution (NaCl or LaCl3), the mixture was heated to ca. 70 degrees C and then stirred during cooling. For thus obtained suspensions, the zeta potential was determined as a function of time at 20 degrees C. Also the pH effect on the zeta potentials was investigated. The zeta potentials were calculated from Henry's equation. The results obtained by us are in agreement with those obtained earlier by others. They confirm that although H+/OH- are not surface charge creating ions, OH- ions to some extent are zeta potential determining for the paraffin surface. By use of the potentials and diameters, the electric charge for a spherical particle in the shear plane was calculated. These values are small in the range of 10(-3) C/m2. On the basis of the findings of water structure near hydrophobic surface and the calculated charges, it is concluded that in fact the potential may be created by immobilized and oriented water dipoles.