Fabrication and Characterization of Nanomagnetite/Chitosan Composite for Advanced Adsorption and Photo-Fenton Degradation of Erythromycin: Processes Optimization and Mechanism

In this work, three different solid materials namely nanomagnetite (G), chitosan (CS), and nanomagnetite/chitosan composite (CSG) were synthesized for the effective adsorption and Photo-Fenton degradation of erythromycin (ERY) as complemented mechanisms. The manufactured solids were characterized using several physicochemical methods. Nanomagnetite/chitosan composite displayed the highest surface area (878.7 m²/g), lower energy band gap (2.21 eV), average TEM particle size of 67 nm, zero surface charge at pH 5.80, and having different surface chemical functional groups. Adsorption and Fenton degradation techniques were performed under different application conditions such as the effect of pH, initial ERY concentration, time, temperature, and the incorporation of ultraviolet radiation in case of Photo-Fenton process. The maximum adsorption capacity was confirmed by CSG (230.95 mg/g) at pH 7, and the adsorption well fitted by Langmuir and Temkin as adsorption model, while the kinetic studies prove the application of pseudo-second-order models and 12 h is the suitable equilibrium adsorption time. The results of Fenton and Photo-Fenton degradation showed that CSG is more efficient than G, which might be explained by its lower energy band gap and larger surface area. Erythromycin degradation showed 99% in the presence of CSG catalyst in the presence of UV radiation after 60 min of the catalytic reaction. Thermodynamic and kinetic studies of ERY Photo-Fenton degradation verified the endothermic (average ΔH*, 47.80 kJ/mol), nonspontaneous (average ΔS*, − 0.1021 kJ mol⁻¹ K⁻¹), and pseudo-first-order (average R², 0.9785) catalytic procedure. After eight application cycles, the catalyst’s reusability showed only a 7.4% decrease in activity. The fabricated composite showed significant antibiotic adsorption capacity and degradation efficiency when the pollutant concentration was higher or lower, respectively.