Abstract
The Sr-ferrite nanoparticle preparation process was intensified using supercritical hydrothermal conditions by employing mineral SrSO4 and acidic Fe3+ solution. The new approach consists of two unit operations: the mineral (SrSO4) dissolution in a mild alkaline NaOH solution; and the Sr/Fe hydroxide coprecipitation using a Fe3+ acid solution. In the first stage, a Sr-Fe gel colloid (Sr/Fe = 0.5) prepared by mixing acid Fe3+ and alkaline Sr2+ liquors (obtained from SrSO4 feedstock) was treated under supercritical hydrothermal conditions at 400 °C for 10 min at 30 MPa, resulting in Sr-ferrite particle crystallization. The second stage comprises increasing the production efficiency by reducing the Sr/Fe ratio to 0.2 coupled with Sr-Fe gel dehydration. The intensified processing proposed has demonstrated high efficiency through continuous flow preparation, which proceeded at a feeding rate of 50 g/L at 400 °C for a 40 s residence time.
Published Version
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