Refining methods and agents for rare earth production
Hydrometallurgical systems, methods, and compositions are described in which organic amine-based lixiviants are utilized in the selective recovery of rare earth elements. The lixiviant can be regenerated in situ, permitting the organic amine to be used in substoichiometric amounts.
1. A method for extracting a rare earth element, comprising:
contacting a sample comprising a first rare earth element with a first lixiviant, the first lixiviant comprising a first organic amine cation and a first counterion;
forming a first supernatant comprising an uncharged first organic amine, and a first complex comprising a cation of the first rare earth element and the first counterion;
transferring the first rare earth element cation from the first supernatant; and
regenerating the first organic amine cation,
wherein the first organic amine cation is provided in substoichiometric amounts relative to the first rare earth element.
2. The method of claim 1 , wherein the first organic amine cation is regenerated by the addition of an acid form of the first counterion while the sample is in contact with the first lixiviant.
3. The method of claim 1 , further comprising the step of removing the first complex from the supernatant.
4. The method of claim 3 , wherein the first complex is removed by forming a precipitate.
5. The method of claim 1 , wherein the first organic amine cation has a pKa of 8 to 14.
6. The method of claim 5 , wherein the first organic amine cation is obtained from a biological source.
7. The method of claim 1 , wherein the first counterion has a pKa of 1 to 6.
8. The method of claim 1 , wherein the first lixiviant is formed by adding an acid to the uncharged first organic amine that is in contact with the sample.
9. The method of claim 1 , wherein the first rare earth element cation is transferred by forming a precipitate.
10. The method of claim 1 , wherein the sample further comprises a second rare earth element, and further comprising the steps of:
transferring the first supernatant from the sample to form a depleted sample;
contacting the depleted sample with a second lixiviant, the second lixiviant comprising a second organic amine cation and a second counterion;
forming a second supernatant comprising an uncharged second organic amine and a second complex comprising a second rare earth element cation and the second counterion
transferring the second rare earth element cation from the second supernatant; and,
regenerating the second organic amine cation.
11. The method of claim 10 , wherein the second organic amine cation is regenerated by addition of an acid form of the second counterion while the sample is in contact with the second lixiviant.
12. The method of claim 10 , wherein the second rare earth element cation is transferred by forming a precipitate.
13. A method for extracting rare earth elements, comprising:
contacting a sample comprising a first rare earth element and a second rare earth element with a lixiviant, the lixiviant comprising an first organic amine cation, a second organic amine cation, and a counterion;
forming a first supernatant comprising an uncharged first organic amine, an uncharged second organic amine, a first complex comprising a first rare earth metal cation and the counterion, and a second complex comprising a second rare earth metal cation and the counterion;
transferring the first rare earth metal cation from the first supernatant to form a second supernatant;
transferring the second rare earth metal cation from the second supernatant and,
regenerating the first organic amine cation and the second organic amine cation from the second supernatant,
wherein the first organic amine cation is provided in substoichiometric amounts relative to the first rare earth metal.
14. The method of claim 13 , wherein the first organic amine cation has a pKa of 8 to 14.
15. The method of claim 13 , wherein the second organic amine has a pKa of 8 to 14.
16. The method of claim 13 , wherein the first organic amine cation and the second organic amine cation are identical chemical species.
17. The method of claim 13 wherein the first organic amine cation and the second organic amine cation are different species.
18. The method of claim 13 , wherein the first organic amine cation is regenerated by the addition of an acid form of the counterion while the sample is in contact with the lixiviant.
19. The method of claim 13 , wherein the first rare earth element is transferred from the first supernatant by the addition of a first precipitant.
20. The method of claim 19 , wherein the first precipitant is a base comprising a hydroxide.
21. The method of claim 19 , wherein the second rare earth element is transferred from the second supernatant by addition of a second precipitant.
22. The method of claim 21 , wherein the first precipitant and the second precipitant are identical chemical species applied to give a first concentration of the species in the first supernatant and a second concentration of the species in the second supernatant.