Removal of Cationic Surfactants from Aqueous Solutions by Modified Cotton as a Novel High Capacity and Low Cost Adsorbent

Abstract

Direct and indirect releases of large quantities of surfactants to the environment may result in serious health and environmental problems. Therefore, surfactants should be removed from water before release to the environment or delivery for public use. Using cotton-based adsorbent may be an effective technique to remove surfactants. In this study, the removal of cationic surfactants by modified cotton was investigated. N-Cetyl-N,N,N-trimethylammonium bromide (CTAB) was selected as a cationic surfactant for the experiments. The results revealed that the modified cotton has a high affinity toward the cationic surfactants. Experiments were conducted to examine the effects of applied adsorbent dosage, initial concentration of adsorbate, pH, temperature, salt concentration on the removal efficiency. By increasing the salt concentration, removal efficiency was decreased slightly. The temperature had an adverse effect on removal efficiency. The adsorption of the CTAB increases with increasing pH of the solution. A series of batch experiments were performed to determine the sorption isotherms of modified cotton. Surfactant equilibrium data fitted very well to the Langmuir model. The Langmuir model showed that the maximum adsorption was 909 mg/g which is higher than the capacity of other adsorbents reported until now. The pseudo first-, second- order and corresponding rate equation kinetic models were investigated. Adsorption complies with a pseudo-second-order rate equation.