Enhanced adsolubilization in silica-packed column by mixture of cationic and anionic surfactants

Abstract

Recently, surfactant-based processes have been widely studied for using in the area of environmental remediation. Surfactant adsorption onto solid surface is one of the interests. When undesirable, surfactant adsorption can render a design ineffective and significantly increase dosage requirements and thus adversely affect the economics of the system. The purpose of this research was to enhance the adsolubilization capacity of organic solutes in the mixed adsorbed surfactant aggregates onto silica packed column. The system of mixed anionic and cationic surfactants at 1:3 molar ratio of the conventional anionic surfactant, sodium dodecyl sulfate (SDS), and the twin-head cationic surfactant, Pentamethyloleyl alky1-1, 3-propane diammonium dichloride (PADD) and the system of single surfactant, PADD were selected for comparison study in this work. The adsorption of the surfactants onto silica from these two sytems as well as their adsolubilization were determined in order to investigate the transports of organic solutes including polar compound (styrene) and non-polar compound (ethylcyclohexane). The synergism of the mixed surfactants system could be obviously observed. The adsorption was found at 0.49 mmole/g or 2.08 molecules/nm2 and 0.23 mmole/g or 0.98 molecules/nm2, for the mixed and single surfactant systems, respectively. The adsolubilization capacity and retardation factor of both styrene and ethylcyclohexane increased in the mixed surfactants system. For styrene, the adsolubilization capacity and retardation factor in mixed surfactants system were 0.89 molecules/nm2 and 12.8, respectively. The adsolubilization capacity and retardation factor of ethylcyclohexane in mixed surfactants system were 0.89 molecules/nm2 and 12.8, respectively. The adsolubilization capacity and retardation factor of ethylcyclohexane in mixed surfactants system were 1.08 molecules/nm2 and 60.95, correspondingly. Moreover, these results showed the adsolubilization of ethylcyclohexane in surfactant admicelles was greater than styrene.