Title: Facile and Efficient Decontamination of Thorium from Rare Earths Based on Selective Selenite Crystallization

Abstract

The coexistence of radioactive contaminants (e.g., thorium, uranium, and their daughters) in rare earth minerals introduces significant environmental, economic, and technological hurdles in modern rare earth production. Capable, low cost, and green decontamination strategies are therefore desired to ameliorate this problem. In this work, we report a single-step and quantitative decontamination strategy of thorium from rare earths based on a unique periodic trend in the formation of crystalline selenite compounds across the lanthanide series, where Ce(III) is fully oxidized in situ to Ce(IV). This gives rise to a crystallization system that is highly selective to trap tetravalent f-blocks while all other trivalent lanthanides completely remain in solution when coexist. These findings are bolstered by first-principles calculations of lattice energies and an examination of bonding in these compounds. This system is contrasted with typical natural and synthetic systems, where trivalent and tetravalent f-block elements often cocrystallize. The separation factors after one round of crystallization were determined from binary systems of Th(IV)/La(III), Th(IV)/Eu(III), and Th(IV)/Yb(III) to reach 2.1 × 10⁵, 1.2 × 10⁵, and 9 × 10⁴, respectively. Selective crystallization of thorium from a simulated monazite composite yields a separation factor of 1.9 × 10³ with nearly quantitative removal of thorium.

Authors:

Wang, Yaxing  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-1842-339X"

Lu, Huangjie ^[2]; Dai, Xing ^[2]; Duan, Tao ^[3]; Bai, Xiaojing ^[4]; Cai, Yawen ^[2]; Yin, Xuemiao ^[2]; Chen, Lanhua ^[2]; Diwu, Juan ^[2]; Du, Shiyu  ^[4];

• Search DOE PAGES for author "Du, Shiyu"
• Search DOE PAGES for ORCID "0000-0001-6707-3915"

Zhou, Ruhong  ^[2];

• Search DOE PAGES for author "Zhou, Ruhong"
• Search DOE PAGES for ORCID "0000-0001-8624-5591"

Chai, Zhifang ^[2]; Albrecht-Schmitt, Thomas E.  ^[5];

• Search DOE PAGES for author "Albrecht-Schmitt, Thomas E."
• Search DOE PAGES for ORCID "0000-0002-2989-3311"

Liu, Ning ^[6]; Wang, Shuao  ^[2]

• Search DOE PAGES for author "Wang, Shuao"
• Search DOE PAGES for ORCID "0000-0002-1526-1102"

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+ Show Author Affiliations

1. Sichuan Univ., Chengdu (China); Soochow Univ., Suzhou (China)
2. Soochow Univ., Suzhou (China)
3. Southwest Univ. of Science and Technology, Mianyang (China)
4. Chinese Academy of Sciences (CAS), Ningbo (China)
5. Florida State Univ., Tallahassee, FL (United States)
6. Sichuan Univ., Chengdu (China)

Publication Date:

Fri Feb 02 00:00:00 EST 2018

Research Org.:

Florida State Univ., Tallahassee, FL (United States). Energy Frontier Research Center (EFRC) Center for Actinide Science & Technology (CAST)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1470227

Grant/Contract Number:  

SC0016568

Resource Type:

Accepted Manuscript

Journal Name:

Inorganic Chemistry

Additional Journal Information:

Journal Volume: 57; Journal Issue: 4; Journal ID: ISSN 0020-1669

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY