Adsolubilization and solubilization using conventional and extended anionic surfactants on an aluminum oxide surface

Abstract

Adsolubilization of organic solutes by media-sorbed surfactants is an important phenomenon for surfactant-based environmental technologies. Adsolubilization is strongly influenced by the amount of adsorbed surfactant, solution pH, surface type, and surfactant molecular structure. In this research, the adsorption of two anionic extended carboxylate surfactants (C16-17-4PO-5EO-COONa and C16-18-4PO-5EO-COONa), an anionic extended sulfate surfactant (C16-17-4PO-SO4Na) and an anionic conventional surfactant (SDS) on alumina oxide surface were investigated. The results showed that the adsorption of all surfactant types onto aluminum oxide surface increased with increasing surfactant concentration. Moreover, the extended sulfate surfactant exhibited the highest maximum adsorption capacity onto the aluminum oxide surface while the extended carboxylate surfactant with C16-18 reached maximum adsorption at the lowest surfactant concentration. Two organic solutes with different the degree of polarity, styrene and phenanthrene, were evaluated in adsolubilization and solubilization studies. For styrene adsolubilization study, SDS showed a greater styrene adsolubilization capacity than the extended surfactants; however, the extended surfactants required lower surfactant amounts to form admicelles. The extended sulfate surfactant showed the highest phenanthrene adsolubilization capacity due to the maximum adsorption capacity. The adsolubilization capacity of phenanthrene was significantly influenced by the amounts of adsorbed admicelles at the plateau region. For solubilization study, the extended surfactants exhibited the higher styrene and phenanthrene solubilization capacities than the conventional surfactant. The extent of solubility of organic solutes by surfactants depended on both hydrophilic and hydrophobic of surfactant and organic solutes. In consideration of surfactant loss from the solid surface, the desorption capacity was determined to evaluate the stability of the surfactants adsorbed onto the surface. The results indicated that the extended carboxylate surfactants showed the lower desorption capacity as compared to the conventional surfactant due to the stronger lateral interaction between surfactant tails. Therefore, the use of extended surfactant adsorbed onto solid surface can reduce the surfactant losses from the surface and improved the operating characteristics of the surfactant-modified adsorbent for removal of organic pollutants.