Investigation of the Electrokinetic Properties of Paraffin Suspension. 1. In Inorganic Electrolyte Solutions

Abstract

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.

Coalescence efficiency model including electrostatic interactions in liquid/liquid dispersions

“…Another widely used assumption is the preferred accumulation or adsorption of specific ions at the interface (especially hydroxide ions (Beattie and Djerdjev, 2004;Beattie and Gray-Weale, 2012;Beattie et al, 2005;Creux et al, 2009;Franks et al, 2005;Gray-Weale and Beattie, 2009;Marinova et al, 1996)), whether it is described by Gibbs (Lyklema, 2000) or Langmuir monolayers (Marinova et al, 1996;Tian and Shen, 2009). Other research groups doubt this concept of ion adsorption and attribute the created potential to the immobilization and orientation of water dipoles at the surface (Chibowski et al, 2005;Vacha et al, 2011) or to the deprotonation of fatty acid impurities in the oil Cabane, 2012a, 2012b). The van der Waals force is the opposing attractive force acting on particles in the same range of magnitude and distance (few tens of nanometres).…”

Effect of phospholipid and (phospho)lipase modification on interfacial properties of oil/water emulsion

“…7, 9). Most of the oil-in-water emulsions show negative zeta potentials because as we suggested in previous papers [24,25,28,29] the water (ethanol) dipoles might play a role in the zeta potential creation. H + and OH -ions were found to be potential-determining for the n-alkane/electrolyte, n-alkane/alcohol and n-alkane/protein emulsions.…”

“…present on the oil droplet surface and possibility of ordering of water dipoles. In the emulsion containing phospholipids at the oil droplets/water interface the lipids are aligned with their hydrophilic parts facing the water phase [28,29,38]. Since the concentration of phospholipid in this investigation was greater than the appropriate c.m.c., adsorption of its individual molecules rarely occurred.…”

“…Ethanol and water molecules form hydrogen bonds with the phospholipid molecules which are of comparable strength [25]. Phospholipid molecules can replace water and ethanol immobilized dipoles at the droplet surface and form hydrogen bonds with them, which appears in the change of the system zeta potential [24,25,28,29]. Furthermore, the phospholipase activity might be greater in the ethanoltreated systems, but the literature data on this effect are ambiguous [57,58].…”

“…By employing a few methods a number of lipid dispersed systems of potential biological application have been characterized. In this way, we hope to emphasize and better understand the processes occurring in biological cells [24][25][26][27][28][29][30][31][32][33][34][35][36].…”