Membrane and Water Treatment

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Rare earth element recovery from coal ash and leaching wastewaters by ecofriendly sequential extraction

  • Siyu Chen (Civil and Environmental Engineering, Konkuk University) ;
  • Jae Wan Choe (Department of Civil Engineering, Gwangju University) ;
  • Han S. Kim (Civil and Environmental Engineering, Konkuk University)
  • Received : 2024.09.13
  • Accepted : 2024.10.08
  • Published : 2024.10.25
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Abstract

It has been reported that rare earth elements (REEs) are considerably present in coal ash. In this study, an ecofriendly sequential extraction method was developed for the effective REE recovery from coal ash and leaching wastewaters. Citrate, a weak and environmentally benign solvent that replaces acetate employed in the existing sequential extraction methods (e.g., European community bureau of reference (BCR) and Tessier methods), was found to be highly effective in leaching REEs from coal ash. Microwave-assisted thermal digestion improved the REE extraction efficiency even further, with an overall leaching rate of 70%, which is 2.54 and 3.76 times higher than the values achieved by the conventional BCR and Tessier methods, respectively. It was also confirmed that the majority of REEs was strongly bound to CaO, Al2O3, Fe2O3, and P2O5, not to SiO2. The sequential extraction method developed in this study is expected to be used as an effective and simple recovery procedure for REEs from coal ash and remaining leaching wastewaters.

Keywords

Acknowledgement

This work was financially supported by the Korean National Research Foundation (2022R1I1A1A01056866) and Konkuk University Research Support Program for the Faculty Sabbatical in 2021.

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