Enhanced nitrobenzene adsorption in aqueous solution by surface silylated MCM-41

To improve the adsorption of nitrobenzene from aqueous solution, surface silylation of MCM-41 (hexagonal mesoporous silica) with trimethylchlorosilane was conducted. The silylated MCM-41 (CH3-MCM-41) was characterized by X-ray diffraction (XRD), transmission electron micrograph (TEM), N-2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric/differential thermalanalysis (TG/DTA) techniques. Adsorption of nitrobenzene onto CH3-MCM-41 was investigated with respect to contact time, initial nitrobenzene concentration, temperature, pH and ionic strength. The results indicated that surface modification of MCM-41 significantly enhanced its adsorption capacity for nitrobenzene. Adsorption isotherms were well described by Langmuir and Freudlich models. The maximum adsorption capacity of CH3-MCM-41 was 375.5 mu mol/g, one order of magnitude higher than that of MCM-41 (25.8 pAriolig). Negative thermodynamic constant values (Delta G(0) < 0, Delta H-0 < 0 and Delta S-0 < 0) suggested that the adsorption reaction of nitrobenzene onto CH3-MCM-41 was thermodynamically favorable, spontaneous and exothermic under the examined conditions. Moreover, adsorption of nitrobenzene by CH3-MCM-41 was independent of pH within a range of 3.0-9.5. Increasing ionic strength can apparently enhance nitrobenzene adsorption by CH3-MCM-41. Compared to other adsorbents, CH3-MCM-41 showed a relatively higher adsorption capacity and shorter equilibrium time. Therefore, surface sylilated MCM-41 has a potential and promising application in the removal of nitrobenzene from water. (C) 2016 Elsevier Inc. All rights reserved.