Chitosan-Based Nanocomposite for Tetracycline Removal

The presence of antibiotic residues in aquatic environments poses a significant risk to water quality and public health, creating a need for effective and sustainable treatment technologies. In this study, a chitosan-based nanocomposite containing silver, cobalt, and iron (CS-HNC) was synthesized under mild conditions without a calcination step and evaluated for the removal of tetracycline (TC) from aqueous solutions. Attention was given to TC removal at an initial concentration of 10 mg L−1. Although this concentration exceeds those typically reported for natural surface waters, it is lower than the concentrations frequently employed in adsorption studies and therefore provides a useful basis for evaluating the performance of the developed adsorbent under controlled laboratory conditions. The material was characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Fourier transform infrared spectroscopy (FTIR). The characterization results confirmed the successful formation of the nanocomposite and the incorporation of metal-containing phases within the chitosan matrix. The effects of key sorption parameters were investigated, showing that TC removal was only weakly influenced by pH and ionic strength. The maximum sorption capacity reached 45.7 mg g−1, while removal efficiencies of 94.3% and 98.4% were achieved after 30 and 120 min, respectively, at an initial TC concentration of 10 mg L−1. Sorption kinetics were best described by the pseudo-second-order model, whereas equilibrium data were better fitted by the Freundlich isotherm model. No detectable leaching of Ag, Co, or Fe was observed after soaking the material in deionized water and in a solution adjusted to pH 2 for 24 h, indicating good stability of the synthesized material under the investigated conditions. These findings suggest that the developed CS-HNC nanocomposite is a promising sorbent for the removal of TC.