Fluoride removal in waters using ionic liquid-functionalized alumina as a novel adsorbent

A novel ionic liquid modified gamma-alumina was prepared via a modified sol-gel method, using 1-methyl-3-octylimdazolium chloride ionic liquid as multifunctional material in terms of solvent and template, and its ability for the removal of fluoride from synthetic as well as real contaminated fluoride solution was investigated through adsorption by batch and column mode. The interaction between the IL and alumina involves electrostatic affinity between imidazolium cations, and surface hydroxyl groups in alumina. The IL modified gamma-alumina acts as a good adsorbent for fluoride ions due to interesting interactions such as electrostatic interaction and ion exchange process. Characterizations of the material made by Fourier transform infrared spectroscopy, X-ray powder diffraction, Thermogravimetric analysis, N-2 adsorption desorption isotherm, Transmission electron microscopy, with Energy-dispersive X-ray spectroscopy elemental mapping, Field Emission Scanning Electron Microscopy, and X-ray photoelectron spectroscopy. Adsorption kinetic study showed that the adsorption process followed the pseudo-second-order kinetics and the maximum adsorption capacity is found to be 25.0 mg g(-1) from Langmuir adsorption isotherm. Fixed bed column study was carried out to check the role of flow rates on adsorption of fluoride ions using synthetic and contaminated aqueous solution. All of the results suggested that the alumina modified ionic liquid have a strong and specific affinity towards fluoride and can be considered as excellent adsorbent for treatment of fluoride contaminated water. (C) 2017 Elsevier Ltd. All rights reserved.