System and method for rare earths extraction

1. A method for recovering a rare earth element from ore including a first group of metals selected from a group consisting of at least one of iron and aluminum, and a second group of metals selected from a group consisting of at least one of the following rare earth elements: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium, the method comprising:

drying the ore at a temperature from 20° C. to 150° C.;

contacting the ore with a sub-stoichiometric amount of sulfuric acid to obtain a mixture of ore and sulfates of the first group of metals;

subjecting the mixture to a temperature between 620° C. and 750° C. to convert the sulfates of the first group of metals into a stable species and the second group of metals into sulfates, thereby obtaining a mixture of impurities and rare earth sulfates;

adding water to the mixture of impurities and rare earth sulfates, selectively dissolving the rare earth sulfates and forming a rare earth solution; and

subjecting the rare earth solution to a purification process.

2. The method according to claim 1 , wherein the ore contains monazite, bastnasite or other rare earth-bearing mineral.

3. The method according to claim 1 , further comprising increasing the grade and reducing the size of the ore prior to the contacting.

4. The method according to claim 3 , wherein the reducing of the size of the ore comprises reducing to 0.5 mm or smaller.

5. The method according to claim 1 , wherein the contacting further comprises mixing the ore with concentrated (90-98%) sulfuric acid.

6. The method, according to claim 5 , that the acid added is calculated taking into consideration all alkali and earth-alkali metals present and the rare earth elements plus an excess of 0 to 50%.

7. The method according to claim 1 , wherein the temperature of the subjecting of the mixture is applied for between 1 and 12 hours.

8. The method according to claim 1 , wherein the selectively dissolving of the rare earth elements comprises cooling to a dissolution temperature of 25° C., and wherein the rare earth solution has a pulp density of no more than 15% by weight solids.

9. The method according to claim 1 , wherein rare earth solution pH must not be higher than 5 but not lower than 1.5.

10. The method according to claim 1 , wherein the selectively dissolving has a residence time between 15 and 150 minutes.

11. The method according to claim 1 , wherein the temperature of the subjecting of the mixture is between 650° C. and 720° C.

12. The method according to claim 1 , wherein the sub-stoichiometric amount converts no more than 20% of the iron or aluminum by weight into sulfates.

13. The method according to claim 1 , wherein the sub-stoichiometric amount converts no more than 5% of iron or aluminum by weight into sulfates.

14. A method for recovering a rare earth element from ore including a first group of metals selected from a group consisting of at least one of iron and aluminum, and a second group of metals selected from a group consisting of at least one of the following rare earth elements: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium, the method comprising:

drying the ore at a temperature from 20° C. to 150° C.;

contacting the ore with a sub-stoichiometric amount of sulfuric acid to obtain a mixture of ore and sulfates of the first group of metals, wherein the sub-stoichiometric amount converts no more than 20% of iron or aluminum by weight into sulfates after heating the mixture;

subjecting the mixture a temperature between 650° C. and 750° C. to convert the sulfates of the first group of metals into a stable species and the second group of metals into sulfates, thereby obtaining a mixture of impurities and rare earth sulfates;

adding water to the mixture of impurities and rare earth sulfates, selectively dissolving the rare earth sulfates and forming a rare earth solution; and

subjecting the rare earth solution to a purification process.

15. A method for recovering a rare earth element from ore including a first group of metals selected from a group consisting of at least one of iron and aluminum, and a second group of metals selected from a group consisting of at least one of the following rare earth elements: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium, the method comprising:

drying the ore at a temperature from 20° C. to 150° C.;

contacting the ore with a sub-stoichiometric amount of sulfuric acid to obtain a mixture of ore and sulfates of the first group of metals, wherein the sub-stoichiometric amount converts no more than 20% of iron or aluminum by weight into sulfates;

subjecting the mixture a temperature sufficient to convert the sulfates of the first group of metals into a stable species and the second group of metals into sulfates, thereby obtaining a mixture of impurities and rare earth sulfates;

adding water to the mixture of impurities and rare earth sulfates, selectively dissolving the rare earth sulfates and forming a rare earth solution; and

subjecting the rare earth solution to a purification process.