Recovery of rare-earth elements from coal fly ash via enhanced leaching

ABSTRACT

Coal fly ash is regarded as a potential alternative source of rare-earth elements and has gained much attention over the past few years. However, the majority of rare-earth elements in coal fly ash are entrapped in the glassy phase, which makes the recovery of rare-earth elements from coal fly ash extremely challenging. In this paper, two pre-treatments (mechanical grinding and alkali solution treatment) were conducted to enhance the leaching recovery of rare-earth elements from coal fly ash. The best recovery of rare-earth elements by acid leaching after grinding is 79.19% at the optimal conditions. That is due to the increase of surface area, resulting in more rare-earth elements exposed from the glass phase and increase the rate of leaching. The highest rare-earth element recovery gained by acid leaching after alkali pre-treatment is 95.50% in the paper. Alkali solution destroyed the glassy aluminosilicate spheres (such as metal oxide, amorphous silicon in amorphous silica-aluminosilicate) of coal fly ash more efficiently, making it more solvable in hydrochloric acid. This research has focussed on grinding and alkali pre-treatment to provide a theoretical foundation and technology support to the extraction of rare-earth elements from coal fly ash.

KEYWORDS:

• Rare earth elements
• coal fly ash
• mechanical grinding
• alkali pre-treatment
• enhance leaching

Acknowledgments

The authors wish to acknowledge financial support from the Fundamental Research Funds for the Central Universities (2019XKQYMS30).

Disclosure Statement

The authors declare no competing financial interest.

Additional information

Funding

This work was supported by the Fundamental Research Funds for the Central Universities [2019XKQYMS30].