Selective Removal of Naphthalene from Non-Ionic and Anionic Surfactants Using Activated Carbon

Surfactants have been widely used for extracting hydrophobic organic compounds from soils into aqueous phase. Non-ionic surfactants such as Triton X-100 and anionic surfactants such as SDS (sodium dodecyl sulphate) have been of particular interest because of their high solubilizing ability and low toxicity. However, the resulting wastewater that contains both surfactant and organic contaminants should be treated and surfactants should be recovered as much as possible in view of residual effects and economic considerations. This paper investigated the use of activated carbon for surfactant recovery in wastewater treatment. Selective adsorption of naphthalene (the simplest form of polyaromatic hydrocarbons) from Triton X-100 and SDS were observed at relatively low surfactant concentrations (i.e., slightly above respective critical micelle concentrations, CMCs), indicating that it is feasible to recover surfactant from wastewater for future reuse. Nevertheless, at high surfactant concentrations (more than two-fold of CMC values) both Triton X-100 and SDS were adsorbed along with naphthalene, while removal of naphthalene was incomplete. Thus, at these high surfactant concentrations it is difficult to either recover the surfactants or remove the organic contaminants. These results clearly showed that surfactants should be prudently applied at appropriate concentration ranges so as to allow effective wastewater treatment using activated carbon.