Efficient adsorption of Norfloxacin by Fe-MCM-41 molecular sieves: Kinetic, isotherm and thermodynamic studies

Fe-MCM-41 was prepared by a direct synthesis method and employed as an adsorbent to remove Norfloxacin (NFX) in water. The characterization results showed that Fe-MCM-41 retained the hexagonal mesoporous structure after incorporating Fe and had a large surface area ranging from 894 to 1028 m(2) g(-1). A significant relationship was found among adsorption efficiency, the surface area and the Fe content of adsorbent. The amounts of NFX absorbed increased from 52 to 117 mg g(-1) with Fe content in Fe-MCM-41. The value of constant k(2) (288 g mg(-1) h(-1)) obtained from pseudo-second-order model was much greater than that of frequently used adsorbents such as macroporous resin (58 g mg(-1) h(-1)). The results suggested that the introduction of Fe successfully enhanced hydrophobicity of MCM-41 and its adsorption efficiency. Additionally, Fe component also accelerated the formation of complex between NFX and Fe-MCM-41. Apart from the former mechanisms, electrostatic interaction and pi-pi interactions were also found in the adsorption process, and their combined effects significantly accelerated NFX adsorption. The adsorption isotherm was better fitted with Freundlich model. Thermodynamic results illustrated that the adsorption process was spontaneous and performed better at higher temperature. (C) 2015 Elsevier B.V. All rights reserved.