Method for leaching rare earth elements and critical minerals from organically associated materials
A method for extracting rare earth elements and critical minerals including adding an acid to a mixture comprising organically bound rare earth elements. The mixture is maintained at a pH of 0.25 to 4 for a period of time, resulting in a liquor and a leached mixture. The liquor is removed from the leached mixture to form a dewatered cake. The dewatered cake is washed to form a washing liquid. The washing liquid is recycled to create a second slurry comprising organically bound rare earth elements.
1. A method for extracting rare earth elements, critical minerals, or a combination thereof, the method comprising:
adding an acid to a mixture comprising organically bound rare earth elements, critical minerals, or a combination thereof to maintain a pH of the mixture from 0.25 to 4 for a period of time, resulting in a liquor and a leached mixture;
removing the liquor from the leached mixture to form a dewatered cake;
washing the dewatered cake to form a washing liquid; and
recycling the washing liquid to create a second mixture comprising organically bound rare earth elements, critical minerals, or a combination thereof.
2. The method of claim 1 wherein the mixture comprises lignite coal, subbituminous coal, or bituminous coal.
3. The method of claim 2 wherein the pH is maintained between 0.5 and 2.
4. The method of claim 1 wherein the mixture comprises peat, biomass, crude oil or a combination thereof.
5. The method of claim 4 wherein the pH is maintained between 2 and 3.5.
6. The method of claim 1 wherein the acid has a concentration greater than 30 weight percent.
7. The method of claim 1 wherein the acid is a mineral acid.
8. The method of claim 1 wherein the period of time is between 10 minutes and 12 hours.
9. The method of claim 1 wherein the pH is continuously monitored.
10. The method of claim 1 wherein the liquor is removed from the leached mixture by filter press.
11. The method of claim 1 wherein the liquor is removed from the leached mixture by centrifuge.
12. The method of claim 1 wherein the dewatered cake is washed at between 40 and 150 psi.
13. The method of claim 1 wherein the dewatered cake is washed with between 1 and 5 liters of water per kilogram of dewatered cake.
14. The method of claim 1 wherein the liquor is further processed to recover the rare earth elements.
15. The method of claim 1 wherein liquor is further processed to recover critical minerals.
16. The method of claim 1 wherein the acid comprises two acids combined at a ratio between 60:40 and 95:5.
17. The method of claim 1 , wherein the mixture comprising organically bound rare earth elements comprises ore and the amount of acid added is between at least 5 kg of acid per ton of ore and no more than 100 kg of acid per ton of ore.
18. The method of claim 1 wherein the step of adding the acid is performed between at least 10° C. and no more than 90° C.
19. The method of claim 1 further comprising adding acid in the washing step to a resultant pH of between 0.75 and 2.