Low-cost selective precipitation circuit for recovery of rare earth elements from acid leachate of coal waste

Patent metadata

Field	Value
Publication number	US-11155897-B2
Application number	US-201816185120-A
Country	US
Kind code	B2
Filing date	Nov 9, 2018
Priority date	Nov 9, 2017
Publication date	Oct 26, 2021
Grant date	Oct 26, 2021

Abstract

The present invention concerns a process of selective precipitation for the purpose of recovering rare earth elements from acidic media derived from coal and coal byproducts via two main steps of sequential precipitation and selective precipitation. An intermediary step of re-precipitation can be included to further increase RRE concentrations, as well as improve contaminant metal removal.

First claim

We claim:

1. A method for concentrating rare earth materials from a feed stock comprised of coal leachate and/or precipitate obtained therefrom, the method comprising:
a) mixing the feed stock with an acid of a first class in a solution;
b) increasing the pH of the solution incrementally to precipitate iron and aluminum and removing such precipitates from the solution;
c) further increasing the pH incrementally to precipitate rare earth metals and separating such from the resulting filtrate;
d) re-dissolving the precipitated rare earth metals in a smaller volume of the filtrate;
e) transferring the re-dissolved filtrate to an acid solution of a second class; and
f) incrementally increasing the pH to selectively precipitate rare earth metals.

2. The method of claim 1 , further comprising a re-precipitation step between c) and d), the step comprising re-dissolving the rare earth metals in the filtrate by lowering the pH.

3. A method for concentrating rare earth materials from a feed stock, the method comprising:
a) mixing the feed stock with an acid in a solution;
b) increasing the pH of the solution incrementally to precipitate iron and aluminum and removing the precipitated iron and aluminum from the solution;
c) further increasing the pH incrementally to precipitate rare earth metals and separating the precipitated rare earth metals from a resulting filtrate;
d) re-dissolving the precipitated rare earth metals in a smaller volume of the filtrate;
e) transferring the re-dissolved filtrate to an acid solution; and
f) incrementally increasing the pH to selectively precipitate rare earth metals.

4. A method for concentrating rare earth materials from a feed stock, the method comprising:
a) mixing the feed stock with an acid in a first solution;
b) increasing the pH of the solution incrementally to precipitate contaminants and removing the precipitated contaminants from the solution;
c) further increasing the pH incrementally to precipitate rare earth metals;
d) re-dissolving the precipitated rare earth metals in the filtrate by lowering the pH;
e) incrementally increasing the pH to gradually precipitate and remove additional contaminates and finally precipitate a rare earth metal concentrated re-precipitate;
f) re-dissolving the rare earth metal concentrate re-precipitate in a smaller volume of the filtrate;
g) acidifying the smaller volume of the filtrate including the re-dissolved rare earth metal concentrate re-precipitate; and
h) incrementally increasing the pH to selectively precipitate the rare earth metals.

5. The method of claim 4 , including using a different acid to re-dissolve the rare earth metals in the filtrate than used when mixing the feed stock.

6. The method of claim 5 , including adding CaCl 2 , MgCl 2 or CaCl 2 and MgCl 2 to the smaller volume of the filtrate prior to step e).

7. The method of claim 4 , including adding CaCl 2 , MgCl 2 or CaCl 2 and MgCl 2 to the smaller volume of the filtrate prior to step e).

8. The method of claim 4 , further including using coal leachate, a coal leachate precipitate or coal leachate and a coal leachate precipitate as the feed stock.

9. The method of claim 4 , further including using a first class of acid to mix with the feedstock in the solution and using a second, different class of acid to re-dissolve the rare earth metal concentrate re-precipitate in the smaller volume of the filtrate.

Assignees

• Univ Kentucky Res Found

Inventors

• Zhang Wencai
• Honaker Rick Q

Classifications

• C22B3/44

  by chemical processes (treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42) · CPC title

• C22B59/00 Primary

  Obtaining rare earth metals · CPC title

• C22B3/22

  by physical processes, e.g. by filtration, by magnetic means {, or by thermal decomposition} (treatment or purification of solutions by liquid-liquid extraction C22B3/26) · CPC title

• Y02P10/20

  Recycling · CPC title