Synthesis and characterization of imidazolium based ionic liquid modified montmorillonite for the adsorption of Orange II dye: Effect of chain length

Abstract In this study, two different imidazole-based ionic liquids (ILs) with different alkyl chain lengths were synthesized and modification of montmorillonite (MMT) clay was performed by using these ILs [N-methylimidazolium tetrafluoroborate (MIM) and N-butylimidazolium tetrafluoroborate (BIM)]. The adsorption efficiency of the IL modified MMT clays for removal of Orange II (O-II) anionic dye from aqueous solutions was studied systematically. MMT and IL modified MMT samples (MIM-MMT and BIM-MMT) were characterized by FTIR, SEM, TGA, DTG and XRD analysis. In addition, surface area, particle size and zeta potential measurements were carried out for prediction of adsorption ability. The specific surface areas of IL modified adsorbents were rather high (88.2 and 80.9 m2 g−1 for MIM-MMT and BIM-MMT respectively) comparing pristine MMT (53.6 m2 g−1). Batch studies were materialized to analyze the effect of different parameter on O-II adsorption, such as pH, contact time, solid/liquid ratio and temperature. Maximum adsorption capacities were obtained at pH 2 and the kinetic data revealed that O-II adsorption was greatest defined by pseudo-second order kinetic model. The adsorption capacities were found as 1.26 mg g−1 (75%), 2.29 mg g−1 (90%) and 1.70 mg g−1 (84%) at pH 2 for MMT, MIM-MMT and BIM-MMT, respectively. Also, isotherm data were well described Freundlich isotherm model. The thermodynamic data showed that the O-II adsorption occurred endothermic and spontaneously nature. As a result of the adsorption processes, it was observed that MIM-MMT sample with short alkyl chain length can be an alternative as an effective, innovative and cheap adsorbent for removal of harmful O-II dye pollutants.