title: A comparative study and evaluation of sulfamethoxazole adsorption onto organo-montmorillonites.
abstract: Three organo-montmorillonites were prepared using surfactants, and their adsorption behaviors toward sulfamethoxazole (SMX) were investigated. The surfactants used were cetyltrimethyl ammonium bromide (CTMAB), 3-(N,N-dimethylhexadecylammonio) propane sulfonate (HDAPS) and 1,3-bis(hexadecyldimethylammonio)-propane dibromide (BHDAP). The properties of the organo-montmorillonites were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption-desorption isotherm measurements. Results showed that the interlayer spacing of montmorillonite was increased and the surface area as well as the morphology were changed. Batch adsorption experiments showed that the surfactant loading amount had a great effect on the adsorption of SMX. The adsorption process was pH dependent and the maximum adsorption capacity was obtained at pH3 for HDAPS-Mt, while CTMAB-Mt and BHDAP-Mt showed a high removal efficiency at 3-11. The adsorption capacity increased with the initial SMX concentration and contact time but decreased with increasing solution ionic strength. Kinetic data were best described by the pseudo second-order model. Equilibrium data were best represented by the Langmuir model, and the Freundlich constant (n) indicated a favorable adsorption process. The maximum adsorption capacity of SMX was 235.29 mg/g for CTMAB-Mt, 155.28 mg/g for HDAPS-Mt and 242.72 mg/g for BHDAP-Mt. Thermodynamic parameters were calculated to evaluate the spontaneity and endothermic or exothermic nature. The adsorption mechanism was found to be dominated by electrostatic interaction, while hydrophobic interaction played a secondary role.
authors.affiliation: State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China. Electronic address: lulaifu87@163.com.
authors.forename: Laifu
authors.initials: L
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China. Electronic address: mlgao@cup.edu.cn.
authors.forename: Manglai
authors.initials: M
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Gu
authors.affiliation: State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China.
authors.forename: Senfeng
authors.initials: S
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China.
authors.forename: Yuening
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D013420:Sulfamethoxazole / Q000302:isolation & purification*; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D001546:Bentonite; D013420:Sulfamethoxazole
keywords: Adsorption; Cetyltrimethyl ammonium bromide; Gemini surfactant; Organo-montmorillonite; Sulfamethoxazole; Zwitterionic surfactant