Process development for the recovery of rare earth elements and critical metals from an acid mine leachate

Wencai Zhang, Rick Honaker

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Acid mine leachate (AML) may be a significant source of rare earth and other critical elements needed for the manufacturing of advanced electronics and renewable energy technologies. A systematic study was performed on a natural leachate collected from a coal preparation plant that treated bituminous coal containing elevated amounts of pyrite. The leachate contained 1.96 ppm total REEs, 2.52 ppm Zn, 2.15 ppm Ni, 1.22 ppm Cu, 0.77 ppm Co, and 25 ppm Mn. Sequential precipitation using simple pH control generated a pre-concentrate containing 0.82% total REEs, 1.08% Zn, 0.91% Ni, 0.50% Cu, 0.34% Co, 7.1% Mn. The pre-concentrate was further treated by re-dissolution using a 10 M HNO3 solution, which resulted in a solution pH of 1.5. The addition of oxalic acid to selectively precipitate the REEs followed by roasting of the precipitate generated a product containing >98% rare earth oxides. More than 95% of the Cu and Zn were recovered from the residual liquid using Na2S at pH 2 and 3, respectively. The CuS and ZnS contents in the corresponding concentrates were 60% and 58%, respectively. The majority of the Co and Ni remained in the residual liquid. Based on these findings, a process flowsheet was developed to recover the REEs and critical metals from AML.

Original languageEnglish
Article number106382
JournalMinerals Engineering
Volume153
DOIs
StatePublished - Jul 1 2020

Bibliographical note

Funding Information:
This material was based upon work supported by the Department of Energy under Award Number DE-FE0027035 . Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Funding Information:
The experimental data provided in the previous sections indicate that REEs, Cu and Zn can be effectively recovered from a mine acid leachate by the precipitation and dissolution processing steps. After these steps, the residual liquid still contained valuable elements such as Co, Ni and Mn. Furthermore, the residual liquid was acidic with a pH value of around 3, which ultimately needed to be neutralized for environmental purposes. As such, sequential precipitation tests were performed on the remaining solution to evaluate the potential of recovering and concentrating the aforementioned elements.This material was based upon work supported by the Department of Energy under Award Number DE-FE0027035. Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Publisher Copyright:
© 2020 Elsevier Ltd

Keywords

  • Acid mine leachate
  • Coal
  • Critical metals
  • Dissolution
  • Rare earth elements
  • Selective precipitation

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Chemistry (all)
  • Geotechnical Engineering and Engineering Geology
  • Mechanical Engineering

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