Comparative Adsorption of Ibuprofen and Ciprofloxacin from Aqueous Solution Using Natural Bentonite Clay: Experimental and DFT Study

Abstract

This Study examines the adsorption characteristics of ibuprofen (IBP) and ciprofloxacin (CIP) onto bentonite (BT) in aqueous medium. To investigate surface properties, SEM, FTIR and XRD techniques were used to characterize the bentonite applied as adsorbent. The results confirmed the properties of typical bentonite clay as acceptable. Batch adsorption studies were conducted under different adsorption experimental conditions. The outcome indicated that pH, initial IBP/CIP concentration, adsorbent dosage, contact time and temperature greatly influenced IBP/CIP removal by BT in aqueous medium. Adsorption equilibrium was attained after 240 minutes of contact time for both IBP and CIP. The pseudo first order, pseudo second order, and intraparticle diffusion kinetic models were utilized to describe the kinetic data, while the Langmuir, Freundlich, and Temkin isotherm models were fitted to the equilibrium data. Results obtained from kinetic and isotherm studies showed that both the kinetic and equilibrium data were efficiently described by the pseudo second order kinetic model and Freundlich isotherm model for both pharmaceuticals respectively, as evidenced by correlation coefficients (R²) exceeding 0.98 and lower chi-square (χ²) values observed. Thermodynamic analysis indicated that the removal of IBP/CIP from aqueous solution by BT is spontaneous, endothermic, and characterized by increased disorder. Analysis from Density functional theory (DFT) was incorporated into experimental findings in other to gain clarity on distinctive characteristics of IBP/CIP adsorption. Greater chemical molecular reactivity, lower water solubility, decreased steric hindrance effects, as well as greater hydrophobicity, were factors mostly responsible for the improved ibuprofen and ciprofloxacin adsorption by bentonite.