Feasibility of using a rotating packed bed in preparing Fe₃O₄ nanoparticles

Fe₃O₄ nanoparticles were prepared by continuously pumping aqueous solutions of FeCl₃/FeCl₂ and NaOH into a rotating packed bed (RPB), where 0.148mol/L of FeCl₃·6H₂O, 0.075mol/L of FeCl₂·4H₂O, and 0.888mol/L of NaOH co-precipitated. A rotational speed of 1800rpm, liquid flow rates of 500mL/min, and a temperature of 60°C were adopted. Fe₃O₄ nanoparticles that were prepared in this manner had an average diameter of 6.4nm, a maximal saturation magnetization of 50emu/g, and a BET surface area of 173m²/g. The rate of production of Fe₃O₄ nanoparticles was 17kg/day. The H₂O₂-activating capacity of Fe₃O₄ nanoparticles that were prepared using the RPB, measured using the decolorization of Rhodamine B (RhB), was related to the Fe₃O₄ dosage, the H₂O₂ concentration, and the temperature. At pH 5 and 80°C with an Fe₃O₄ dosage of 0.30g/L and an H₂O₂ concentration of 0.11mol/L, the Fe₃O₄ nanoparticles that were prepared using the RPB were observed to activate H₂O₂ and to have a decolorization efficiency of approximately 100% in 75min with an observed decolorization rate constant of 0.0592min^-1. The decolorization of RhB in the Fe₃O₄-H₂O₂ process was consistent with the pseudo-first-order kinetic model.