Utilization of mixed anionic/cationic surfactants for styrene and ethylcyclohexane solubilization/entrapment in contaminated subsurface remediation technologies

Abstract

This research reports the studies of mixtures of anionic and cationic surfactants having single and twin head groups. The surfactant mixtures investigated were: (a) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), in mixture with the twin-head cationic surfactant pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD) adsorption was studied on silica; and (b) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfanate (SHDPDS), and the single-head cationic surfactant dodecylpyridinium chloride (DPCl) adsorption was studied on alumina. While the mixed surfactant system of SHDPDS/DPCl showed comparable adsorption on alumina to SHDPDS-alone, the mixed surfactant system of SDS/PODD showed increased adsorption on silica as compared to PODD-alone. Mixtures of SDS/PODD showed solubilization synergism when mixed at a molar ratio of 1:3; however, solubilization experiments of mixed SHDPDS/DPCI at a ratio of 3:1 did not show solubilization enhancement over SHDPDS-alone. The adsolubilization of ethylcyclohexane was greater in mixed SDS/PODD system than for PODD-alone and in mixed SHDPDS/DPCI system than for SHDPDS-alone. The experiments of organic solutes retardation through the column packed with silica adsorbent showed dramatical synergism of mixed surfactant which adsorbed on silica surface. Thus this study suggests that the adsorbent of mixed admicelles on silica can be effectively used for groundwater plume management without the contamination from the surfactants themselves.