Methods for separation and recovery of rare earth elements from aqueous solutions using diglycolamide derivatives
A method for extracting rare earth elements from aqueous solution, comprising: (i) acidifying an aqueous solution containing said rare earth elements with an inorganic acid to result in an acidified aqueous solution containing said rare earth elements and containing the inorganic acid in a concentration of 1-12 M, wherein said rare earth elements are selected from lanthanides, actinides, or combination thereof, and (ii) contacting the acidified aqueous solution with an aqueous-insoluble hydrophobic solution comprising a rare earth extractant compound dissolved in an aqueous-insoluble hydrophobic solvent to result in extraction of one or more of the rare earth elements into the aqueous-insoluble hydrophobic solution by binding of the rare earth extractant compound to the one or more rare earth elements, wherein the rare earth extractant compound has the following structure: provided that at least one of the conditions (a)-(d) applies.
1 . A method for extracting rare earth elements from aqueous solution, the method comprising:
(i) acidifying an aqueous solution containing said rare earth elements with an inorganic acid to result in an acidified aqueous solution containing said rare earth elements and containing the inorganic acid in a concentration of 1-12 M, wherein said rare earth elements are selected from lanthanides, actinides, or combination thereof; and
(ii) contacting the acidified aqueous solution with an aqueous-insoluble hydrophobic solution comprising a rare earth extractant compound dissolved in an aqueous-insoluble hydrophobic solvent, to result in extraction of one or more of the rare earth elements into the aqueous-insoluble hydrophobic solution by binding of the rare earth extractant compound to the one or more rare earth elements, wherein the rare earth extractant compound is selected from the group consisting of the following structures:
2 . The method of claim 1 , wherein the acidified aqueous solution contains the inorganic acid in a concentration of 1-8 M.
3 . The method of claim 1 , wherein the acidified aqueous solution contains the inorganic acid in a concentration of 2-6 M.
4 . The method of claim 1 , wherein the inorganic acid is a hydrohalide.
5 . The method of claim 4 , wherein the hydrohalide is hydrochloric acid.
6 . The method of claim 1 , wherein the aqueous solution contains at least one lanthanide element and at least one actinide element, and the method extracts one or more lanthanide elements to a greater extent than one or more actinide elements.
7 . The method of claim 6 , wherein said one or more actinide elements are at least one of thorium and uranium.
8 . The method of claim 1 , wherein said method further comprises:
(iii) stripping one or more rare earth elements from the aqueous-insoluble hydrophobic solution by contacting the aqueous-insoluble hydrophobic solution with an aqueous stripping solution containing an inorganic acid in a concentration of no more than 4 M, and provided that the concentration of inorganic acid in the aqueous stripping solution is at least 0.5 M less than the concentration of inorganic acid in the aqueous solution in step (i).
9 . The method of claim 8 , wherein step (iii) strips one or more lighter lanthanide elements from the aqueous-insoluble hydrophobic solution to a greater extent than one or more heavier lanthanide elements.