Ionic liquid functionalized nanoporous silica for removal of anionic dye

Nanoporous silica (NPS), with an average pore diameter of 2.4 nm and a surface area of 949 m(2) g(-1), was synthesized by using nonyl phenol ethoxylated decylether (NP-10) and ethyl silicate 40% (ETS-40) under acidic condition. Ionic liquid functionalized adsorbent was prepared by grafting of N-methyl-N'-propyltrimethoxysilylimidazolium chloride onto NPS for removal of methyl orange. The adsorbent was characterized by means of small-angle X-ray scattering, scanning electron microscopy, N-2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) and Raman spectroscopy. The kinetic data revealed that the adsorption process is consistent with the pseudo-second-order model. The Langmuir isotherm showed better correlation with the experimental data. The monolayer adsorption capacity of adsorbent was found to be 135 mg g(-1). Thermodynamic parameters such as enthalpy change (Delta H degrees = +61.72 kJ mol(-1)), free energy change (Delta G degrees < 0) and entropy change (Delta S degrees = +222 J mol(-1) K-1) indicate the endothermic and the spontaneous nature of the adsorption. (C) 2013 Elsevier B.V. All rights reserved.