Ag-decorated Al2O3-CeO2 spherical composite as an efficient adsorbent for removal of ciprofloxacin in aqueous media

Abstract

The search for ceramic materials with chemical stability, mechanical resistance, and high adsorption capacity has led to the proposal of several structural modifications, such as combining two oxides in a single material, and surface modifications, such as incorporating metallic nanoparticles upon the surface of a ceramic material. This study presents the synthesis, characterization, and adsorption capacity of ciprofloxacin of porous spherical composites of Al₂O₃, Al₂O₃-CeO₂ and Al₂O₃-CeO₂-Ag. Polystyrene (PS) nanospheres were employed as a sacrificial template to enhance porosity, and silver nanoparticles (Ag-Nps) were used for surface decoration. The phase transformations of Al₂O₃ and CeO₂ into their stable crystalline forms were confirmed through FTIR and XRD analysis. Scanning electron microscopy (SEM) revealed a homogeneous polycrystalline morphology, while zeta potential (pζ) analysis indicated an increase in negative surface charge, reaching values of −87 mV for Ag-decorated spheres at pH 5. Adsorption studies demonstrated ciprofloxacin removal capacities of 0.25 mg g⁻¹ for Al₂O₃, 1.02 mg g⁻¹ for Al₂O₃-CeO₂ and 0.39 mg g⁻¹ for Al₂O₃-CeO₂-Ag at pH 5. Kinetic analyses fit well to pseudo-second-order and Elovich models, with determination coefficients ranging from 0.89 to 0.99, due to a mixed chemisorption mechanism. Freundlich and Temkin models confirmed the affinity of the three materials for ciprofloxacin, with Freundlich coefficients exceeding 1.0 and Temkin adsorption heats exceeding 26,000 J mol⁻¹, findings that highlight the potential of Al₂O₃, Al₂O₃-CeO₂ and Al₂O₃-CeO₂-Ag as efficient adsorbent materials for pharmaceutical contaminants, like ciprofloxacin, in water treatment applications.