Efficient Removal of Tetracycline Hydrochloride via Adsorption onto Modified Bentonite: Study Kinetics and Equilibrium Dynamics

Pharmaceutical contamination of water sources has become a critical environmental challenge. This study explores the potential of bentonite (BN), a natural clay mineral, and its acid-treated form (BA1) as effective adsorbents for the removal of tetracycline hydrochloride (TC) from aqueous solutions. Comprehensive characterization of BN and BA1 was performed using analytical techniques, including XRF, XRD, SEM/TEM, XPS, TG/DTG, CO2 and N2 adsorption-desorption isotherms. Results indicated that BA1 is a mesoporous material with a surface area exceeding 165 m².g⁻¹, exhibiting exceptional adsorption performance. The optimal adsorption pH of the drug was 5.0. The adsorption process adhered to a pseudo-second-order kinetic model, suggesting a chemisorption mechanism. BA1 achieved a maximum adsorption capacity of 40.98 mg.g⁻¹ and removal efficiencies of up to 99% within just 30 minutes. Equilibrium isotherm calculations for BA1 showed the best fit for the Freundlich model R² > 0.9923, indicating a favorable adsorption process. These findings underscore the effectiveness, cost-effectiveness, and environmental sustainability of bentonite as a promising material for addressing pharmaceutical pollutants in water treatment applications. The tetracycline-loaded adsorbents were applied for desorption and reuse studies in consecutive seven cycles for evaluating the regeneration ability of the clay mineral materials.