Sono-assisted preparation of highly-efficient peroxidase-like Fe3O4 magnetic nanoparticles for catalytic removal of organic pollutants with H2O2

Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) with much improved peroxidase-like activity were successfully prepared through an advanced reverse co-precipitation method under the assistance of ultrasound irradiation. The characterizations with XRD, BET and SEM indicated that the ultrasound irradiation in the preparation induced the production of Fe3O4 MNPs possessing smaller particle sizes (16.5 nm), greater BET surface area (82.5 m2 g−1) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe3O4 MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe2+/Fe3+ during the preparation process. The H2O2-activating ability of Fe3O4 MNPs was evaluated by using Rhodamine B (RhB) as a model compound of organic pollutants to be degraded. At pH 5.4 and temperature 40 °C, the sonochemically synthesized Fe3O4 MNPs were observed to be able to activate H2O2 and remove ca. 90% of RhB (0.02 mmol L−1) in 60 min with a apparent rate constant of 0.034 min−1 for the RhB degradation, being 12.6 folds of that (0.0027 min−1) over the Fe3O4 MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe3O4 MNPs were discussed to develop more efficient novel catalysts.