Methods for separation and recovery of rare earth elements from aqueous solutions using diglycolamide derivatives
Inventors
Jansone-Popova, Santa • Lyon, Kevin L. • Popovs, Ilja • Moyer, Bruce A.
Assignees
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Publication Number
US-12668857-B2
Publication Date
2026-06-30
Expiration Date
Abstract
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.
Core Innovation
The invention provides a method for extracting rare earth elements from an aqueous solution by acidifying the aqueous feed with an inorganic acid and then contacting the acidified solution with an aqueous-insoluble hydrophobic solution that contains a rare earth extractant compound. The rare earth elements are selected from lanthanides, actinides, or combinations thereof, and extraction into the hydrophobic phase is achieved by binding of the rare earth extractant compound to the rare earth elements.
A key aspect is that the rare earth extractant compound is selected from diglycolamide extractant compounds and related structures, including Formula (1) and related structures (1c-1 to 1c-4), with substituent ranges and lactam ring formation of 5- or 6-membered rings. The disclosed design rationale emphasizes minimizing third-phase gelling/precipitation at higher extractant loadings and reducing acid requirements while maintaining selective separation behavior.
The disclosed extractant solution comprises a rare earth extractant compound dissolved in an aqueous-insoluble hydrophobic solvent, with the option of including additional components as described in the document. Extraction performance is characterized using distribution coefficient D and separation factor SF, and the document further describes an optional stripping step in which rare earth elements are contacted with an aqueous stripping solution containing an inorganic acid under a defined concentration relationship to the acid used in the acidifying step.
Claims Coverage
The independent claim covers an extraction method with two main inventive features: acidifying an aqueous feed with an inorganic acid at 1–12 M, then contacting it with an aqueous-insoluble hydrophobic phase containing a specified diglycolamide-based rare earth extractant. The dependent claims further narrow the inorganic acid concentration, specify hydrohalide including hydrochloric acid, add lanthanide-over-actinide selectivity, and define an optional stripping condition with linked acid concentration thresholds.
Acidified aqueous solution at 1–12 M inorganic acid
Acidifying an aqueous solution containing rare earth elements with an inorganic acid to form an acidified aqueous solution in which the inorganic acid is present at 1–12 M, wherein the rare earth elements are selected from lanthanides, actinides, or combinations thereof.
Extraction into aqueous-insoluble hydrophobic phase by binding with a defined diglycolamide extractant
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 extract one or more rare earth elements into the 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 specified structures including Formula (1) and related structures.
Narrow inorganic acid concentration for acidifying (1–8 M)
The method further specifies that the inorganic acid concentration in the acidified aqueous solution is 1–8 M.
Inorganic acid as hydrohalide including hydrochloric acid
The inorganic acid used is a hydrohalide, and in a further refinement the hydrohalide is hydrochloric acid.
Lanthanide-over-actinide extraction selectivity
Using an aqueous solution containing lanthanide and actinide elements, such that one or more lanthanide elements are extracted to a greater extent than one or more actinide elements.
Optional stripping with linked inorganic-acid concentration thresholds
Stripping one or more rare earth elements from the aqueous-insoluble hydrophobic solution by contacting it with an aqueous stripping solution containing an inorganic acid, wherein the inorganic acid concentration is no more than 4 M and at least 0.5 M less than the acid concentration in the acidifying step.
Overall, the claim set centers on extracting lanthanides and/or actinides by binding using a defined diglycolamide rare earth extractant dissolved in an aqueous-insoluble hydrophobic solvent, preceded by acidifying the aqueous feed with an inorganic acid at 1–12 M, with dependent narrowing to 1–8 M and hydrohalide such as hydrochloric acid. Dependent claims further require lanthanide-over-actinide extraction selectivity and optionally include stripping under a specified acid-concentration relationship.
Stated Advantages
Minimizing third-phase gelling/precipitation at higher extractant loadings.
Reducing acid requirements while enabling selective rare earth separation.
Selective extraction as measured by distribution coefficient D and separation factor SF.
Separation of lighter and heavier lanthanides.
Competitive extraction across a lanthanide series.
Ligand structural modifications influence extraction behavior, including steric/branching effects and third-phase formation for a specific ligand.
Documented Applications
Selective extraction and separation of rare earth elements from aqueous solutions, including lanthanide versus actinide selectivity.
Extraction of rare earth elements from an aqueous solution.
Selective extraction of lanthanides and actinides.
Separation of lighter and heavier lanthanides.
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