Chemical leaching of rare earth elements from highly REY-rich mud

Yutaro Takaya*, Koichiro Fujinaga, Naoya Yamagata, Syuhei Araki, Ryota Maki, Kentaro Nakamura, Koichi Iijima, Yasuhiro Kato

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Seafloor sediment rich in rare earth elements and Y (REY-rich mud) has received attention as a new resource for REY. During research cruise KR13-02 of R/V Kairei, mud containing more than 5,000 ppm total REY was collected near Minamitorishima Island, northwestern Pacific Ocean. We conducted a series of chemical leaching experiments on this material, varying the acid concentrations, leaching times, and temperature to determine the optimum conditions of REY leaching from REY-rich mud. The highest extraction efficiency of REY other than Ce was 95.1% using hydrochloric acid and 81.3% using sulfuric acid. Extraction efficiency of REY was highest under conditions of relatively low acid concentrations (0.25-0.5 mol/L), short leaching times (2-5 min), and room temperature (25°C). REY extraction amount decreased with increasing acid concentration, leaching time (only in the case of sulfuric acid), and temperature, apparently because of precipitation of calcium sulfate, rare earth phosphate, and rare earth-Na double sulfate. Although further research is needed, the leaching properties we determined are generally favorable for industrial exploitation of REY-rich mud.

Original languageEnglish
Pages (from-to)637-652
Number of pages16
Issue number6
Publication statusPublished - 2015
Externally publishedYes


  • Chemical leaching
  • Deep-sea mineral resource
  • REY-rich mud
  • Rare earth elements

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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