Figure 4
Removal efficiency of methylene blue. (a) Effect of the concentration of 3D hollow porous Fe3O4 microspheres on the removal efficiency of methylene blue (2 μg/mL) in the presence of H2O2 (0.4 M) and ultrasound irradiation, pH = 5.0. (b) Effect of the concentration of H2O2 on the removal efficiency of methylene blue (2 μg/mL) in the presence of 3D hollow porous Fe3O4 microspheres (2 μg/mL), pH = 5.0.