Superparamagnetic magnetite (Fe₃O₄) nanoparticles are prime candidates for a wide range of applications such as magnetic storage media, magnetic resonance imaging, targeted drug delivery and magnetic separation. Various methods have been reported for the synthesis of magnetite nanoparticles. Co-precipitation is the most common and convenient way to synthesize magnetite by oxidation of ferrous (Fe ²⁺ ) and ferric (Fe ³⁺ ) salt solution by a base, such as NaOH or NH₄OH in an aqueous solution. However, the size distribution of the magnetite nanoparticles produced using this method is normally very broad. Furthermore, scale-up of this method using the batch processing can be problematic as it results in inhomogeneous agitation and areas of localized pH which in turn results precipitation of non-magnetic iron oxides. In this study, we demonstrate the successful synthesis of magnetite using NH₃ gas as base source via process intensification on a rotating surface (PIRS) under scalable and continuous flow conditions. Spinning disc processing (SDP) is a milestone in process intensification modernization which in turn ensures uniform reaction conditions on the rotating disc in contrast to traditional batch technology where conditions can vary across the dimensions of the vessel. The rapid mixing and high contact area between the fluid and the atmosphere above it ensure effective mass transfer and efficient mixing. In addition, the high throughput of the system, low changeover times and wastage make this a very solvent efficient method of synthesis. The geometry and key elements of a SDP are illustrated in Figure 1.

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