Effect of Magnesium and Sodium Salts on the Interfacial Characteristics of Soybean Lecithin Dispersants

One of the most widely accepted oil spill response strategies is chemical dispersant application. However, since the surfactant used in their formulation may be ionic, its interfacial characteristics may be influenced by ions present in the sea. In this work, we have examined the effect of magnesium salts (MgSO₄ and MgCl₂) and sodium salts (NaCl, Na₂SO₄, and sodium benzoate) on the interfacial characteristics of hydroxylated soybean lecithin dispersant (H-PI). The oil-in-water emulsions formed with magnesium salts were more stable than those formed with sodium salts. Magnesium salts recorded the highest interfacial tension reduction and the highest dispersion effectiveness values when compared with sodium salts. These observations were attributed to (i) the Mg²⁺ ions interconnecting the negatively charged headgroups of H-PI at the oil-droplet-water interface, thus increasing the surface elasticity and viscosity, and (ii) the smaller ionic size of Mg²⁺ allowing for easy packing between the charged head groups of H-PI.