A high-productivity process for mass-producing Fe3O4 nanoparticles by co-precipitation in a rotating packed bed

Abstract

Fe3O4 nanoparticles were mass-produced using a rotating packed bed (RPB) and the role of stoichiometric ratio and the effects of the FeCl2 and FeCl3 concentrations, aging temperature, and Fe2+ and Fe3+ sources on the characteristics of the obtained Fe3O4 nanoparticles were examined. A high-productivity process for mass-producing Fe3O4 nanoparticles with a rate of approximately 23 kg/day was developed with an FeSO4 concentration of 0.15 mol/L, an FeCl3 concentration of 0.3 mol/L, an NaOH concentration of 1.2 mol/L, a production temperature of 25 °C, an aging temperature of 25 °C, a rotational speed of 1800 rpm, a flow rate of aqueous FeSO4/FeCl3 of 0.5 L/min, and a flow rate of aqueous NaOH of 0.5 L/min. The thus mass-produced Fe3O4 nanoparticles had a mean diameter of 8.4 nm and exhibited superparamagnetism with a saturation magnetization of 61 emu/g. Since the RPB provides excellent micromixing and overcomes the difficulty of mass-production that is associated with traditional co-precipitation in a batch process, Fe3O4 nanoparticles that are mass-produced in an RPB are smaller than Fe3O4 nanoparticles that are batch-produced in a batch reactor, and so have a greater adsorption capacity to remove Reactive Red 2 from water. The results in this work demonstrate that an RPB can mass-produce Fe3O4 nanoparticles at a production temperature of 25 °C and an aging temperature of 25 °C with a low molar ratio of OH− to Fe2+ (8:1). Accordingly, a high-productivity process for mass-producing Fe3O4 nanoparticles can be implemented using an RPB with co-precipitation.