Surfactant-enhanced adsorption of organic compounds by layered double hydroxides

Clay-based adsorbents were synthesized by incorporating anionic surfactants, sodium octylsulfate (SOS), sodium dodecylsulfate (SDS), sodium 4-octylbenzenesulfonate (SOBS), and sodium dodecylbenzenesulfonate (SDBS), into magnesium aluminum layered double hydroxide (Mg–Al LDH) via ion exchange. Adsorption isotherms indicated the amount of surfactants intercalated decreased in the order: SDS>SOBS>SDBS>SOS. X-ray diffraction analysis of the organo-LDHs revealed that surfactant molecules could adopt various configurations within the Mg–Al LDH interlayer space, with SOS forming bilayers whereas others exhibited monolayer arrangements. Intercalation of surfactants into Mg–Al LDH resulted in a decrease in surface area as determined by BET analysis. The products were also examined for their ability to adsorb organic pollutants. The adsorption results indicated that both 1,2,4-trichlorobenzene and 1,1,1-trichloroethane could be adsorbed by all of the organo-LDHs studied, presumably due to partitioning, with adsorption affinity dependent upon the type of surfactant used. Adsorption results indicated anionic surfactants intercalated into Mg–Al LDH form a more effective partition phase than octanol.