Photocatalytic degradation performance of a chitosan/ZnO–Fe3O4 nanocomposite over cationic and anionic dyes under visible-light irradiation

Abstract

The sonochemical synthesis of a chitosan–ZnO/Fe₃O₄ nanocomposite yielded a highly porous structure and large surface area for enhancing the photocatalytic degradation of cationic (rhodamine B, RhB) and anionic (methyl orange, MO) dyes in aqueous solution. Chitosan–ZnO/Fe₃O₄ demonstrated a significant enhancement in photodegradation efficiency 99.49% for MO (C₀ = 5.32 mg L⁻¹, t = 150 min) and 90.73% for RhB (C₀ = 5.03 mg L⁻¹, t = 150 min) under visible light due to its narrow bandgap of 2.84 eV. The photocatalytic performance was investigated by varying the pH, dye concentration, reaction time, and catalyst dose. The photocatalytic reaction obeyed the Langmuir–Hinshelwood kinetic model owing to a high rate constant of 0.031 (min⁻¹) and 0.013 (min⁻¹) for the degradation of MO and RhB, respectively. The photocatalytic activity of the chitosan–ZnO/Fe₃O₄ nanocomposite lost 18.37% (MO degradation) and 11.08% (RhB degradation) of its performance after the first four cycles. The presented results highlight the degradation efficiency of the chitosan–ZnO/Fe₃O₄ nanocomposite under visible light irradiation with reusable and magnetically retrievable abilities.