Recovery and separation of rare Earth elements using salmon milt

Yoshio Takahashi; Kazuhiro Kondo; Asami Miyaji; Yusuke Watanabe; Qiaohui Fan; Tetsuo Honma; Kazuya Tanaka

doi:10.1371/journal.pone.0114858

Recovery and separation of rare Earth elements using salmon milt

PLoS One. 2014 Dec 9;9(12):e114858. doi: 10.1371/journal.pone.0114858. eCollection 2014.

Authors

Yoshio Takahashi¹, Kazuhiro Kondo², Asami Miyaji³, Yusuke Watanabe⁴, Qiaohui Fan⁴, Tetsuo Honma⁵, Kazuya Tanaka⁶

Affiliations

¹ Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bukyo-ku, Tokyo, 113-8654, Japan; Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.
² Aisin Cosmos R&D Co., LTD., Kisarazu, Chiba, 292-0818, Japan.
³ Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.
⁴ Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bukyo-ku, Tokyo, 113-8654, Japan.
⁵ SPring-8, Japan Synchrotron Radiation Research Institute (JASRI), Sayo-cho, Hyogo, 679-5198, Japan.
⁶ Institute for Sustainable Sciences and Development, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8530, Japan.

Abstract

Recycling rare earth elements (REEs) used in advanced materials such as Nd magnets is important for the efficient use of REE resources when the supply of several REEs is limited. In this work, the feasibility of using salmon milt for REE recovery and separation was examined, along with the identification of the binding site of REEs in salmon milt. Results showed that (i) salmon milt has a sufficiently high affinity to adsorb REEs and (ii) the adsorption capacity of the milt is 1.04 mEq/g, which is comparable with that of commercial cation exchange resin. Heavier REEs have higher affinity for milt. A comparison of stability constants and adsorption patterns of REEs discussed in the literature suggests that the phosphate is responsible for the adsorption of REE in milt. The results were supported by dysprosium (Dy) and lutetium (Lu) LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. The REE-P shell was identified for the second neighboring atom, which shows the importance of the phosphate site as REE binding sites. The comparison of REE adsorption pattern and EXAFS results between the milt system and other adsorbent systems (cellulose phosphate, Ln-resin, bacteria, and DNA-filter hybrid) revealed that the coordination number of phosphate is correlated with the slope of the REE pattern. The separation column loaded with milt was tested to separate REE for the practical use of salmon milt for the recovery and separation of REE. However, water did not flow through the column possibly because of the hydrophobicity of the milt. Thus, sequential adsorption-desorption approach using a batch-type method was applied for the separation of REE. As an example of the practical applications of REE separation, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste by a batch-type method using salmon milt.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
DNA / chemistry*
Magnets
Metals, Rare Earth / chemistry*
Metals, Rare Earth / isolation & purification*
Recycling
Salmon / growth & development*
Water / chemistry
X-Ray Absorption Spectroscopy

Substances

Metals, Rare Earth
Water
DNA

Grants and funding

This work was supported by a grant-in-aid for scientific research from the Ministry of Education, Science, Sports, and Culture of Japan. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.