Sono-assisted preparation of highly-efficient peroxidase-like Fe(3)O(4) magnetic nanoparticles for catalytic removal of organic pollutants with H(2)O(2).

Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4) 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 Fe(3)O(4) MNPs possessing smaller particle sizes (16.5nm), greater BET surface area (82.5m(2)g(-1)) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe(3)O(4) MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe(2+)/Fe(3+) during the preparation process. The H(2)O(2)-activating ability of Fe(3)O(4) 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 degrees C, the sonochemically synthesized Fe(3)O(4) MNPs were observed to be able to activate H(2)O(2) and remove ca. 90% of RhB (0.02mmolL(-1)) in 60min with a apparent rate constant of 0.034min(-1) for the RhB degradation, being 12.6 folds of that (0.0027min(-1)) over the Fe(3)O(4) MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe(3)O(4) MNPs were discussed to develop more efficient novel catalysts. Copyright 2009 Elsevier B.V. All rights reserved.