fig7
![Alkali pretreatment effects on acid leaching recovery of rare earth elements from coal waste of the Western Kentucky No. 13 and Fire Clay seams](https://image.oaes.cc/020683d7-f854-43cd-b83e-bde768784680/4853.fig.7.jpg)
Figure 7. BSE images of a liberated ((A and D), WAL 20), a partially encapsulated ((B and E), WAL 14), and a completely encapsulated ((C and F), WAL 15) REE-baring particle found in the Western Kentucky No. 13 material. ((A-C) and (D-F) were taken with an accelerating voltage of 20 kV and 10 kV, respectively). BSE: Backscattered electron; REE: rare earth element.