Ionic Liquids as Clay Swelling Inhibitors: Adsorption Study

This study investigates the inhibition performance of ionic liquids (ILs) on clay (montmorillonite) swelling and the possible inhibition mechanism. The adsorption of various types of ILs in swelling clay was studied by adsorption isotherms, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Experiments were conducted at different concentrations for different types of ILs. Moreover, the adsorption isotherms were modeled using Langmuir, Freundlich, Sips, Redlich-Peterson, and Fritz-Schlunder models. The type of model fitting was used to evaluate the clay stability in terms of monolayer and multilayer adsorption. The experimental results revealed that the ILs' adsorption strongly depends on the IL structures and concentrations. The results showed that in aqueous solutions, IL molecules have a strong interaction with swelling clay minerals, causing the intercalation between the interlayer of the clay minerals and ILs. XRD results revealed that the intercalation of ILs between the layers of clay is related to the enlargement in basal (d) spacing. The efficacy of the adsorption process was also demonstrated by the specific bands of the ILs on the infrared spectra. The relative amount of the IL adsorbed on the clay surface was in the order of 1A3MI-CN < 1B1MP-Br < TBP-MS < TEA-TFMS. Error metrics consisting of the coefficient of determination (R²), mean square error (MSE), and mean absolute error (MAE) was employed as a criterion for a better fit of the adsorption model of ILs. Sips and Redlich-Peterson adsorption models show a reasonable fitting for all ILs in this study.