Abstract: In submerged circulative impinging stream reactor,Fe₃O₄ nanoparticles were prepared by co-precipitation method,with FeSO₄•7H₂O and FeCl₃•6H₂O as raw materials,and ammonia as precipitator.Effects of stirring rate,amount-of-substance ratio of Fe²⁺ to Fe³⁺,reaction temperature,and pH on dispersion and particle size of Fe₃O₄ nanoparticles were investigated.Structure and performance of Fe₃O₄ nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR),transmission electron microscopy (TEM),and X-ray diffraction (XRD).Results showed that Fe₃O₄ nanoparticles with good dispersion,high purity,and mean particle size of 10 nm could be prepared under following optimum technological conditions:amount-of-substance ratio of Fe²⁺ to Fe³⁺ was 1 ∶1,reaction temperature was 40 ℃,stirring rate was1 600 r/min,pH was about 11.0 in the presence of ammonia as precipitant.

Key words: Fe₃O₄nanoparticles, co-precipitation method, impinging stream reactor