Shape-Dependent Fenton-Like Catalytic Activity of Fe3O4 Nanoparticles

Octahedral and spherical Fe3O4 nanoparticles (NPs) were synthesized and used as heterogeneous Fenton-like catalysts to degrade methylene blue (MB). Their catalytic activities were investigated by evaluating the effects of pH, catalyst dosage, H2O2, and MB concentration on the removal efficiency of MB and total organic carbon (TOC). Nearly complete color removal was achieved in 20 min at pH 3.0 in both Fenton-like systems with a low H2O2 concentration of 1.0 mmol L-1. Removal of >90% MB was achieved in the fifth and third runs by octahedral and spherical Fe3O4 NPs, respectively, and the two catalysts eliminated 77.1% and 62.9% of TOC in solution in 30 min of the first cycle. The removal rates of MB as a function of surface area were slower in the presence of spherical than octahedral Fe3O4 NPs, indicating shape-dependence of the NPs' Fenton-like catalytic activity. The catalytic activity and reusability of octahedral Fe3O4 NPs were superior to that of spherical NPs. HO center dot was found to be the main active species in the Fenton-like system.