Low-Temperature Hydrothermal Synthesis of Chromian Spinel from Fe-Cr Hydroxides Using a Flow-Through Reactor

Recent studies have suggested that a chromian spinel can be formed under natural hydrothermal conditions; however, the required conditions, process, and associated redistribution of Cr are still poorly understood. Here, formation was performed by Fe-Cr hydroxides alteration with an Fe2+(aq) supply at 150, 170, 200 °C 5 MPa simulating diagenetic process. The flow-through system enabled to leached from magnetite acidic solution synthesize as starting material two reaction cells, flow lines, heaters, high-performance liquid chromatography (HPLC) pump. accuracy temperature measurement confirmed based on amorphous silica solubility. Mineralogical analysis solid samples recovered cell indicated between 150 170 through goethite simultaneous hematite formation, while Mössbauer spectra showed large quantity ferrihydrites remained after experiments probably because addition stability ferrihydrites. Cr/Fe ratio smaller than bulk equivalent Cr-rich magnetite, suggesting during transformation synthesized conditions.