Evaluation of a modified mica and montmorillonite for the adsorption of ibuprofen from aqueous media

The goals of this work were to prepare and characterize two functional materials, a natural montmorillonite (Mt) and a synthetic mica (Na-mica-4) were modified with the cationic octadecylamine by a cation-exchange reaction between obtained C₁₈-Mt and C₁₈-mica-4, and to explore their potential uses as adsorbent of water containing emerging compounds such as ibuprofen. Both materials were characterized by X-ray diffraction (XRD), Zeta potential and thermogravimetric analysis (DSC-TG), before and after adsorption experiments. The incorporation of ibuprofen in the interlayer was demonstrated by XRD and on the external surface by Zeta potential. The adsorption equilibrium isotherm was fitted with the Langmuir, Freundlich and Dubinin-Radushkevitch mathematical models to obtain the respective parameters. Langmuir and Freundlich were the models that best fitted the experimental data (R² > 0.999). The adsorption rate of C₁₈-Mt (99.9%) was not dependent of ibuprofen concentration (0.1–80 mg/L) but it was in the case of C₁₈-mica-4 (from 99.9% at 0.1 mg/L to 67% at 80 mg/L). In addition, these values were not affected by sample pH in the range from 4 to 9. Kinetic of ibuprofen adsorption onto the organoclays was evaluated using pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich models. Pseudo-second order was the kinetic model that best described the adsorption of ibuprofen (R² > 0.993) reaching the equilibrium time (up to 100% adsorbed) in <5 min and 60 min for C₁₈-Mt and C₁₈-mica-4, respectively. The mechanistic study confirmed the validity of these materials for the uptake of ibuprofen from water.