Methods for the recovery of rare earth elements
Provided herein are methods recovering rare earth elements (REEs) from a solution containing one or more REEs. These methods can comprise contacting an aqueous solution comprising one or more rare earth elements (REEs) with a solid sequestration media (e.g., a stabilized flue gas desulfurization (sFGD) material, or a sludge by-product from a water treatment process) to provide a REE-containing solid feedstock; and contacting the solid feedstock with an extraction solution to generate a rare earth element (REE) solution.
1 . A method comprising:
contacting an aqueous solution comprising one or more rare earth elements (REEs) with a solid sequestration media to provide an REE-containing solid feedstock; and
contacting the solid feedstock with an extraction solution to generate a rare earth element (REE) solution;
wherein the extraction solution comprises a chelating agent and a dithionite reducing agent.
2 . The method of claim 1 , wherein the aqueous solution comprises acid mine drainage (AMD).
3 . The method of claim 1 , wherein contacting the aqueous solution with the solid sequestration media comprises flowing the aqueous solution through a fixed bed comprising the solid sequestration media.
4 . The method of claim 3 , wherein the method further comprises constructing a fixed bed comprising the solid sequestration media in proximity to a mine emitting AMD, and fluidly connecting the fixed bed to the mine such that AMD emitted from the mine flows through the fixed bed.
5 . The method of claim 1 , wherein the chelating agent comprises a polydentate carboxylate ligand such as citrate.
6 . The method of claim 1 , wherein the method further comprises concentrating the REE solution.
7 . The method of claim 1 , wherein the method further comprises separating the REEs from the REE solution to form a rare earth oxide (REO) feedstock.
8 . The method of claim 7 , wherein the concentration of REEs in the REO feedstock is at least twenty times greater than the concentration of REEs in the solid feedstock.
9 . The method of claim 7 , wherein the ratio of the concentration of REEs in the REO feedstock to the to the concentration of REEs of the solid feedstock is from 20:1 to 100:1.
10 . The method of claim 1 , wherein the concentration of REEs in the aqueous solution is less than 1,000 ppm.
11 . The method of claim 1 , wherein the concentration of REEs in the solid feedstock is less than 1000 ppm.
12 . The method of claim 1 , wherein the concentration of REEs in the REE solution is at least ten times greater than the concentration of REEs in the solid feedstock.
13 . The method of claim 1 , wherein the solid sequestration media comprises an inorganic industrial waste material.
14 . The method of claim 1 , wherein the solid sequestration media comprises calcium sulfate, calcium sulfite, calcium carbonate, calcium hydroxide, aluminium silicate, iron oxide, or a combination thereof.
15 . The method of claim 1 , wherein the solid sequestration media comprises a stabilized flue gas desulfurization (sFGD) material.
16 . The method of claim 1 , wherein the solid sequestration media comprises a sludge by-product from a water treatment process, such as lime sludge.
17 . A method for remediating an abandoned mine site, the method comprising:
constructing a fixed bed comprising a solid sequestration media in proximity to a mine emitting acid mine drainage (AMD)
fluidly connecting the fixed bed to the mine such that AMD emitted from the mine flows through the fixed bed;
burying the fixed bed;
allowing the AMD to contact the solid sequestration media within the fixed bed to provide a rare earth element-containing (REE-containing) solid feedstock within the fixed bed;
removing the REE-containing solid feedstock from the fixed bed; and
contacting the REE-containing solid feedstock with an extraction solution to generate a rare earth element (REE) solution; and
separating the REEs from the REE solution to form a rare earth oxide (REO) feedstock.
18 . The method of claim 17 , wherein the solid sequestration media comprises an inorganic industrial waste material, calcium sulfate, calcium sulfite, calcium carbonate, calcium hydroxide, aluminium silicate, iron oxide, stabilized flue gas desulfurization (sFGD) material, a sludge by-product from a water treatment process, such as lime sludge, or a combination thereof.
19 . The method of claim 17 , wherein the fixed bed comprises a geotextile drainage system that fluidly connects the fixed bed to the mine.