Adsorption of Aspirin from Aqueous Solution onto Expanded Vermiculite: Preparation, Characterization, and Adsorption Behavior

This study investigates the adsorption of aspirin from aqueous solution using expanded vermiculite as a low-cost adsorbent. Expanded vermiculite was prepared via hydrogen peroxide-assisted treatment combined with microwave irradiation, resulting in an exfoliated structure with enhanced surface area. Characterization by SEM, XRD, FT-IR, and BET confirmed significant structural and textural modifications after expansion. Batch adsorption experiments showed that the equilibrium data are well described by the Langmuir isotherm model, with a maximum adsorption capacity of 42.84 mg/g, indicating monolayer adsorption on relatively homogeneous active sites. Kinetic analysis revealed that the adsorption process follows the pseudo-second-order model, suggesting that chemisorption may play an important role. Intraparticle diffusion analysis further indicated that the adsorption proceeds through multiple steps. These findings demonstrate that expanded vermiculite is a promising and cost-effective adsorbent for the removal of aspirin from aqueous environments.