Magnetically separable Cu2O/chitosan–Fe3O4 nanocomposites: Preparation, characterization and visible-light photocatalytic performance

•A novel magnetically-separable Cu2O/CS–Fe3O4 photocatalyst was in situ prepared.•Cu2O/CS–Fe3O4 NCs had rough and porous chitosan surface layer embedded with Fe3O4 NPs.•Cu2O/CS–Fe3O4 NCs showed large surface areas and special dimodal pore structure.•Cu2O/CS–Fe3O4 NCs showed superparamagnetism and could be easily magnetic separated.•Cu2O/CS–Fe3O4 NCs exhibited good visible-light photocatalytic activity and stability. A novel magnetically-separable visible-light-induced photocatalyst, Cu2O/chitosan–Fe3O4 nanocomposite (Cu2O/CS–Fe3O4 NC), was prepared via a facile one-step precipitation–reduction process by using magnetic chitosan chelating copper ions as precursor. The structure and properties of Cu2O/CS–Fe3O4 NCs were characterized by XRD, FT-IR, SEM, HRTEM, SAED, EDS, BET, VSM, XPS and UV–vis/DRS. The photocatalytic activity of Cu2O/CS–Fe3O4 NCs was evaluated by decolorization of reactive brilliant red X-3B (X-3B) under visible light irradiation. The characterization results indicated that Cu2O/CS–Fe3O4 NCs exhibited relatively large specific surface areas and special dimodal pore structure because Cu2O was wrapped in chitosan matrix embedded with Fe3O4 nanoparticles. The tight combination of magnetic Fe3O4 and semiconductor Cu2O through chitosan made the nanocomposites show good superparamagnetism and photocatalytic activity. It was found that X-3B could be decolorized more efficiently in acidic media than in neutral or alkaline media. The decolorization of X-3B was ascribed to the synergistic effect of photocatalysis and adsorption. Cu2O/CS–Fe3O4 NCs could be easily separated from the solution by an external magnet, and the decolorization rates of X-3B were still above 87% after five reaction cycles, indicating that Cu2O/CS–Fe3O4 NCs had excellent reusability and stability.