Preparation and Characterization of Chitosan/Ag2O NP Biocomposites for Tetracycline Adsorption

The large-scale contamination of water resources by antibiotics, particularly tetracycline (TC), represents a massive threat. In the present study, the synthesis, characterization, and application of chitosan/Ag2O NP biocomposites as efficient adsorbents for the elimination of TC from aqueous solutions were investigated. Silver oxide nanoparticles (Ag2O NPs) were synthesized using the co-precipitation method and incorporated into a chitosan matrix to enhance adsorption capacity. The resulting biocomposite was characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM) to evaluate its structural, morphological, and functional properties. Adsorption parameters such as adsorbent mass, contact time, initial concentration, and temperature were systematically studied. The maximum adsorption capacity of 51.422 mg/g was achieved at 303 K after 60min using 0.08g of the synthesized composite. Adsorption isotherm data were analyzed using the Freundlich, Temkin, and Langmuir models, with the results showing better agreement with the Temkin and Freundlich models. Furthermore, temperature played a significant role, as the removal efficiency decreased with increasing temperature, confirming the exothermic nature of the adsorption process. Thermodynamic analysis further supported this observation, with negative ΔH° (–23.75 kJ/mol) indicating an exothermic process, positive ΔG° values (+4.08 to +5.93kJ/mol) indicate non-spontaneity under the studied conditions, and negative ΔS° values (–90 to –92J/mol.K) reflecting decreased randomness at the solid–liquid interface during adsorption.