Removal of anionic surfactants from aqueous solutions by adsorption onto high area activated carbon cloth studied by in situ UV spectroscopy

The removal of anionic surfactants, benzene sulfonate (BS), p-toluene sulfonate (TS), 4-octylbenzene sulfonate (OBS) and 4-dodecylbenzene sulfonate (DBS) from water and 0.01 M H2SO4 solutions by adsorption onto high area activated carbon cloth (ACC) were studied by in situ UV-spectroscopic technique. The various properties of the ACC were given and the in situ UV-spectroscopic technique was described. Both kinetic and isotherm data were obtained for the adsorption of surfactants. Kinetic data were treated according to intraparticle diffusion, pseudo-first-order, pseudo-second-order and Elovich models. They were found to fit the pseudo-second-order model best. Isotherm data were treated according to well-known Langmuir and Freundlich models. The regression analysis of the data showed that Freundlich model represents the isotherm data of the surfactants better. The rate and extent of adsorption of surfactants were found to increase in the order BS < TS < OBS ∼ DBS. The main type of interaction between the ACC surface and surfactants was found to be of hydrophobic origin in H2O solutions. The adsorption was found to be enhanced by the presence of 0.01 M H2SO4 in the surfactant solution due to electrostatic attractions between the negatively charged surfactant molecules and the ACC surface which acquired a net positive charge in acidic medium. An inert electrolyte such as NaCl was found to decrease the adsorption capacity of the ACC for the anionic surfactants.