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Magnetic Fe2O3/Fe3O4 heterogeneous nanoparticles were prepared through an alcohol-assisted combustion process. The composition, morphology and magnetic properties of the nanomaterials were characterized by XRD, TEM and VSM techniques. The magnetic Fe2O3/Fe3O4 heterogeneous nanomaterials were soft magnetic nanoparticles with a saturation magnetization of 38.6 emu g−1 and an average particle size of approximate 29 nm. The adsorption behavior of Congo red (CR) onto Fe2O3/Fe3O4 heterogeneous nanoparticles was examined by UV-visible absorption spectroscopy, and the data for the kinetics and the isotherm of CR adsorption onto Fe2O3/Fe3O4 heterogeneous nanoparticles were in good agreement with the pseudo-second-order model and Langmuir model, respectively, which suggested that the adsorption mechanism of CR onto Fe2O3/Fe3O4 heterogeneous nanoparticles was the chemical and monolayer adsorption. Moreover, the influence of pH on the adsorption process was investigated, and when pH was equal to and less than 7, there would be larger adsorbances.

Magnetic Fe2O3/Fe3O4@SiO2 nanocomposites were prepared via the citric-alcohol solution combustion process. The obtained nanocomposites were characterized with SEM, XRD, VSM, TEM, EDS, HRTEM, and FTIR techniques. The results revealed that the magnetic Fe2O3/Fe3O4@SiO2 nanocomposites were successfully obtained with the average grain size of 87 nm and the saturation magnetization of 36 emu/g. After the surface of magnetic Fe2O3/Fe3O4@SiO2 nanocomposites was functionalized by amino group, the amino-functionalized Fe2O3/Fe3O4@SiO2-NH2 nanocomposites were loaded onto graphene oxide based on Mitsunobu reaction. Subsequently, the cellulase was immobilized onto Fe2O3/Fe3O4@SiO2-NH-GO nanocomposites by a glutaraldehyde-mediated Schiff base reaction. The immobilization conditions were optimized by adjusting the pH, temperature, and cellulase dose. The results revealed that optimized immobilization conditions were determined to be temperature of 50 °C, pH of 5, and cellulase solution of 0.1 mL. 97.3% cellulase were successfully immobilized under the optimal conditions. The catalytic performances of the immobilized cellulase were also evaluated. The maximum activity was achieved at pH 4, and 50 °C with cellulase solution of 0.4 mL.

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