This work examines the translation of a well-known production method for uniform single core magnetite nanoparticles based on the oxidative precipitation of FeSO₄ in aqueous media into a continuous-flow process, which implements complete control of operating parameters and products’ quality, managing to minimize the duration of the rate-controlling thermal aging step. Particularly, the transformation of the green rust intermediate form into Fe₃O₄ nanoparticles was carried out by heating in a microwave cavity adapted to a continuous-flow reactor. The role of reaction parameters was first investigated in batch experiments, which indicated a particle size variation in the range of 20–35 nm following the use of an iron precursor concentration from 0.02 to 0.2 M and the adjustment of reaction time from hours to minutes at a reaction temperature of 90 °C. The continuous-flow approach initially involved a vessel reactor placed into the microwave oven, continuously fed with the green rust precursor. Such an arrangement was sufficient to produce Fe₃O₄ nanoparticles with dimensions up to around 50 nm in less than 20 min of heating and significantly reduced the percentage of ethanol as solvent. Surprisingly, by using a plug-flow reactor (PFR), an extremely high heating rate was succeeded and well-defined magnetic nanoparticles with size around 30 nm were produced with a heating period of less than 30 s. Optimization of the continuous-flow procedures was assisted by the computational fluid dynamics study of the heating reactor’s thermal profile. The techno-economic and life cycle evaluation of the developed procedure was performed, indicating a total production cost of 2 € per g of dried nanoparticles and a high sustainability degree compared to other reported methods.

中文翻译：

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基于微波辅助连续流过程的更可持续的磁性纳米颗粒合成


这项工作研究了一种众所周知的基于 FeSO₄ 在水性介质中氧化沉淀的均匀单核磁铁矿纳米颗粒生产方法转化为连续流过程，该过程实现了对操作参数和产品质量的完全控制，设法最大限度地减少了速率控制热老化步骤的持续时间。特别是，通过在适用于连续流反应器的微波腔中加热，将绿锈中间形式转化为 Fe₃O₄ 纳米颗粒。首先在批量实验中研究了反应参数的作用，结果表明在 90 °C 的反应温度下，使用 0.02 至 0.2 M 的铁前驱体浓度并将反应时间从小时调整到分钟后，粒径在 20-35 nm 范围内发生变化。 连续流方法最初涉及将容器反应器放入微波炉中，连续进料绿锈前体。这种排列足以在不到 20 分钟的加热时间内产生尺寸高达 50 nm 左右的 Fe₃O₄ 纳米颗粒，并显著降低乙醇作为溶剂的百分比。令人惊讶的是，通过使用活塞流反应器 （PFR），成功实现了极高的加热速率，并在加热时间小于 30 秒的情况下产生了尺寸约为 30 nm 的清晰磁性纳米颗粒。加热反应器热剖面的计算流体动力学研究有助于优化连续流程序。 对开发的程序进行了技术经济和生命周期评估，表明与其他报道的方法相比，每克干燥纳米颗粒的总生产成本为 2 欧元，并且具有很高的可持续性。