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

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Title: Low-Temperature Hydrothermal Synthesis of Chromian Spinel from Fe-Cr Hydroxides Using a Flow-Through Reactor
Authors: Ohtomo, Yoko Browse this author →KAKEN DB
Yang, Jeehyun Browse this author
Nishikata, Miu Browse this author
Kawamoto, Daisuke Browse this author
Kimura, Yuki Browse this author →KAKEN DB
Otake, Tsubasa Browse this author →KAKEN DB
Sato, Tsutomu Browse this author →KAKEN DB
Keywords: chromian spinel
hydrothermal alteration
flow-through reactor
Issue Date: Sep-2022
Publisher: MDPI
Journal Title: Minerals
Volume: 12
Issue: 9
Start Page: 1110
Publisher DOI: 10.3390/min12091110
Abstract: 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, chromian spinel formation was performed by Fe-Cr hydroxides alteration with an Fe-(aq)(2+) supply at 150, 170, and 200 degrees C and 5 MPa simulating the diagenetic process. The flow-through system enabled the Fe-(aq)(2+) supply to be leached from the magnetite by an acidic solution to synthesize Fe-Cr hydroxides as the starting material with two reaction cells, flow lines, heaters, and a high-performance liquid chromatography (HPLC) pump. The accuracy of the temperature measurement was confirmed based on the amorphous silica solubility. Mineralogical analysis of solid samples recovered from the reaction cell indicated that the chromian spinel was formed between 150 and 170 degrees C from Fe-Cr hydroxides through goethite with a simultaneous hematite formation, while Mossbauer spectra showed that a large quantity of Fe-Cr ferrihydrites still remained after the experiments probably because of the Cr addition to the stability of ferrihydrites. The Cr/Fe ratio of the chromian spinel was smaller than that of the bulk of the Fe-Cr ferrihydrites and equivalent to Cr-rich magnetite, suggesting a redistribution of Cr during the transformation from goethite to synthesized spinel under the hydrothermal conditions.
Rights: © 2022 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution License (
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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