Electrokinetic properties of n-tetradecane/lecithin solution emulsions

Properties of surface of hydrophobic liquid (e.g. n-alkane) in aqueous solutions are very important for stability of dispersed systems, i.e. emulsions and suspensions, as well as in many biochemical processes including living organisms. Application of natural stabilizers it is a key aspect of wide-ranging investigations of emulsion. One of such systems is oil/lecithin solution. The adsorbed lecithin layer at the oil droplets determines the structural and dynamic properties of oil/water emulsions. It changes the interfacial free energy and the zeta potential. The zeta potentials determined in this paper as a function of time and pH confirm that H+/OH− ions are potential determining and the largest effect of OH− is visible at alkaline pHs. The decrease in absolute value of the zeta potential was accompanied by a growth in the effective diameter of emulsion droplets. Using both the potential and diameters electric charge at the shear plane for spherical particle was calculated. In these systems the zeta potential may be created by immobilized and oriented water dipoles and acid–base interactions. However, on the basis of the results it is concluded that the main stabilizing mechanism is the double layers repulsion, besides possible stabilizing effect of lecithin liposomes and other aggregates.