Preparation and oxidation mechanism of iron oxide nanoparticle by use of ultrasonic sonochemial oxidation

Fe3O4 nanoparticles were prepared by ultrasonic sonochemical oxidation and the oxidation mechanism of its formation was investigated. Sonochemical oxidation of Fe2+ ion was carried out by reverse precipitation method (RPM) with and without surfactants under Air, Ar, N2 and O2 gas replacement in the solutions. The order of oxidative reactivity is Air > O2 > N2 ～ Ar. In order to reveal the mechanism of oxidation, we measured oxidants such as OH-, NO2- and NO3- under presence of various gases in the solutions after ultrasound irradiation. As the results, coexistence of N2 and O2 in the solution enhanced sonochemical oxidation since NO2- and NO3- formation took place in addition to OH- as sonochemical oxidant