Continuous Preparation of Fe₃O₄ Nanoparticles with Narrow Size Distribution by Partial Oxidation Coprecipitation of Fe²⁺ Ions in Microchannels

This study achieves the continuous synthesis of Fe3O4 nanoparticles by coprecipitation in a microchannel, capitalizing on strong mixing in the gas-liquid segmented flow and using oxygen to partially oxidizeFe(2+) to Fe3+ before the coprecipitation phase. The optimum conditions for nucleating agent addition, partial oxidation time, acid additive source, and H+:Fe2+ and OH-:Fe2+ ratios were determined through different experiments. X-ray diffraction and transmission electron microscopy were employed to evaluate the product. The results indicate that adding a nucleating agent to the NaOH solution and HCl to the FeCl2 solution, with an oxidation time of 19.2 s and a H+:OH-:Fe2+ ratio of 0.67:8.5:1, yields Fe3O4 nanoparticles with diameters of approximately 8 nm and a narrow size distribution range of 5-13 nm. These findings have implications for the industrial production of Fe(3)O(4)nanoparticles and contribute to the understanding of microreactor systems.