Preparation and Characterization of the Sol-Gel Silica Containing Ionic Liquids as a Potential Adsorbent for the Removal of Cr(VI) Ions from Aqueous Solutions

Abstract

In this study ionic liquid mediated sol-gel silica adsorbents were prepared and characterized to investigate the sorption of Cr (VI) ions from aqueous solutions. For this purpose silica based adsorbents containing ionic liquids (ILs) were synthesized by following the sol-gel method in ionic liquid media. Thus the high extracting ability of ILs were combined with the surface properties of silica substances. Commercial (Aliquat 336® and EMIMTf2N) and synthesized ([A336][NO3]) ionic liquids were incorporated directly by sol-gel process. Silica based adsorbents were being initiated with silica precursor (TEOS), water, alcohol and ionic liquid hydrolysis in the presence of an acid catalyst then completed with a condensation reaction. Chemical and morphological characterization of prepared adsorbents have been investigated by FTIR, SEM and BET analysis. The materials exhibited average pore diameter of 2 nm, pore volume of 0.3 cm3/g and BET surface area of 300–600 m2/g. The sorption behaviors of adsorbents have been investigated by using a series of batch sorption studies. Cr(VI) sorption percentages of the adsorbents were enhanced by containing ILs up to 99% with the adsorption capacity of 31.74 mg/g. It can be concluded that sorption of Cr(VI) ions from aqueous solution by sol-gel silica based adsorbents containing Aliquat 336 takes place favorably and these type of adsorbents are promising agents in the adsorption processes.