Production of ferrihydrite and schwertmannite using a microjet mixer device

•The application of a microjet mixer for precipitation reactions was studied.•Influencing parameters on product properties were identified.•Nanostructured particles at the μm-scale were produced. Scope of this work was the production of nanostructured ferric oxide particles from ferric sulphate solution and ammonia by fast precipitation in a microjet mixer. Therefore, the main influencing factors on the chemical composition as well as the physical properties were identified. The chemical composition was determined by the pH value during mixing resulting in the formation of ferrihydrite or schwertmannite. Primary particle size as well as agglomerate particle size were mainly influenced by reactant concentrations, fluid velocity and the application of an additional gas stream for product discharge. Further investigations showed possibilities for the directed formation of nanostructured ferrihydrite particles in the range of 8.5 to 53μm.