Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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Fundamental study on ore sorting of rare-earth-rich mud by magneto-Archimedes method

  • Satoshi Nishikawa (Graduate School of Engineering, The University of Osaka) ;
  • Yoko Akiyama (Graduate School of Engineering, The University of Osaka) ;
  • Tatsuya Mori (Graduate School of Engineering, The University of Osaka) ;
  • Yuichiro Manabe (Graduate School of Engineering, The University of Osaka) ;
  • Fuminobu Sato (Graduate School of Engineering, The University of Osaka)
  • Received : 2025.06.30
  • Accepted : 2025.09.17
  • Published : 2025.09.30
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Abstract

In 2013, highly concentrated rare-earth-rich mud (REE-rich mud) was discovered around Minami-Torishima Island, presenting an opportunity to develop a new source of rare-earth elements (REEs). This study proposes a new method for selectively removing non-REE components using magnetic separation. First, we calculated the theoretical levitation positions of the target minerals using the magneto-Archimedes method, considering the mineral density, magnetic susceptibility, and magnetic field distribution of a high-temperature superconducting (HTS) bulk magnet. Next, we conducted separation experiments to selectively isolate REE-adsorbed apatite from a simulated mud sample consisting of a mixture of apatite, montmorillonite, quartz, and zeolite. The results demonstrated that non-apatite minerals were successfully removed using magnetic levitation method. Based on these results, we applied the method to actual core samples (REE-rich mud) from the coast of Minami-Torishima Island. These experiments showed that phillipsite could be selectively separated from the core sample using magnetic levitation. However, the overall weight reduction was less significant than that achieved with the simulated REE-rich mud. This discrepancy was attributed to the inability to separate the paramagnetic mineral montmorillonite into the levitated fraction, because of its swelling property and cation exchange capacity, and location-dependent variability in the mineral composition of the core samples. Possible solutions to this problem include improving the sample dispersion and combining this method with other separation techniques.

Keywords

Acknowledgement

We are grateful to the Kochi Institute for Core Sample Research of JAMSTEC for providing core samples used in this study. They would like to thank Dr. Katsuhiko Suzuki and Dr. Takayuki Tomiyama of JAMSTEC for their cooperation in the sampling process. This research was partly supported by the Cabinet Office, Government of Japan, through the Next-generation Technology for Ocean Resources Exploration (known as Zipanguin-the-ocean project) in the Cross-ministerial Strategic Innovation Promotion Program (SIP), and JSPS KAKENHI Grant Number 23H03575.

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