Diglycolamide derivatives for separation and recovery of rare earth elements from aqueous solutions
Inventors
Jansone-Popova, Santa • Popovs, Ilja • Moyer, Bruce A.
Assignees
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Publication Number
US-12398444-B2
Publication Date
2025-08-26
Expiration Date
Abstract
Rare earth extractant compounds having the following structure: wherein R1, R2, R3, and R4 are independently selected from alkyl groups containing 1-30 carbon atoms and optionally containing an ether or thioether linkage connecting between carbon atoms, provided that the total carbon atoms in R1, R2, R3, and R4 is at least 12; R5 and R6 are independently selected from hydrogen atom and alkyl groups containing 1-3 carbon atoms; and provided that at least one of the conditions (i)-(iv) apply as follows: presence of a distal branched group in at least one of R1-R4 (condition i), asymmetry in R1-R4 (condition ii), presence of amine-containing ring (condition iii), or presence of lactam ring (condition iv). Also described are hydrophobic water-insoluble solutions containing at least one extractant compound of Formula (1), as well as method for extracting rare earth elements from aqueous solution by contacting the aqueous solution with the water-insoluble solution.
Core Innovation
The invention relates to a rare earth extractant compound having a defined structure in which R1, R2, R3, and R4 are independently selected from alkyl groups containing 1-30 carbon atoms and optionally containing an ether or thioether linkage connecting between carbon atoms, with the total carbon atoms in R1, R2, R3, and R4 being at least 12. R5 and R6 are independently selected from hydrogen atom and alkyl groups containing 1-3 carbon atoms.
A key structural condition is that at least one of R1, R2, R3, and R4 is a distal branched alkyl group constructed of a linear alkyl backbone having at least four carbon atoms, with an alpha carbon atom of the linear alkyl backbone attached to a nitrogen atom shown in Formula (1). The linear alkyl backbone contains a substituting hydrocarbon group at a gamma carbon or higher positioned carbon, and the substituting hydrocarbon group contains at least two carbon atoms, with the distal branched alkyl group containing a total of up to 30 carbon atoms.
The invention further provides a liquid solution useful for extracting rare earth elements from aqueous solutions, the solution comprising the rare earth extractant compound dissolved in an aqueous-insoluble hydrophobic solvent. The same structural definition for the extractant compound applies, including the carbon-number constraints for R1-R4 and the distal branched alkyl group constructed from the linear alkyl backbone with gamma-or-higher substituting hydrocarbon placement.
Claims Coverage
The document includes two independent claims. Across these claims, the main inventive features are the specific rare-earth extractant compound structure with a distal branched alkyl condition and the use of that compound in a liquid extraction solution containing an aqueous-insoluble hydrophobic solvent.
Distal branched alkyl substituted rare earth extractant compound
A rare earth extractant compound having the defined structure wherein R1, R2, R3, and R4 are independently selected from alkyl groups containing 1-30 carbon atoms and optionally containing an ether or thioether linkage connecting between carbon atoms, with total carbon atoms in R1, R2, R3, and R4 at least 12; R5 and R6 are independently selected from hydrogen atom and alkyl groups containing 1-3 carbon atoms; and at least one of R1, R2, R3, and R4 is a distal branched alkyl group constructed of a linear alkyl backbone having at least four carbon atoms with an alpha carbon atom attached to a nitrogen atom shown in Formula (1), the linear alkyl backbone contains a substituting hydrocarbon group at a gamma carbon or higher positioned carbon, the substituting hydrocarbon group contains at least two carbon atoms, and the distal branched alkyl group contains a total of up to 30 carbon atoms.
Liquid solution for rare earth extraction with defined extractant structure
A liquid solution useful for extracting rare earth elements from aqueous solutions, comprising a rare earth extractant compound dissolved in an aqueous-insoluble hydrophobic solvent, wherein the rare earth extractant compound has the defined structure with R1, R2, R3, and R4 independently selected from alkyl groups containing 1-30 carbon atoms optionally containing an ether or thioether linkage, total carbon atoms in R1, R2, R3, and R4 at least 12; R5 and R6 independently selected from hydrogen atom and alkyl groups containing 1-3 carbon atoms; and at least one of R1, R2, R3, and R4 being the distal branched alkyl group constructed of a linear alkyl backbone having at least four carbon atoms with an alpha carbon atom attached to a nitrogen atom shown in Formula (1), with a substituting hydrocarbon group at a gamma carbon or higher positioned carbon containing at least two carbon atoms, and the distal branched alkyl group containing a total of up to 30 carbon atoms.
Claim coverage centers on a defined rare earth extractant compound characterized by multi-alkyl R1-R4 carbon-number constraints and a distal branched alkyl group built from a linear alkyl backbone with gamma-or-higher hydrocarbon substituent placement and an upper carbon total. A second independent claim covers a liquid solution for extracting rare earth elements that dissolves this extractant in an aqueous-insoluble hydrophobic solvent, while retaining the same extractant structural conditions.
Stated Advantages
Reduced/minimized third-phase gelling/precipitation at higher ligand concentrations (≤0.1 M) relative to known behavior described in the partial content.
Enables operation at lower acid (e.g., 1-8 M) as stated in the partial content.
Potential selectivity between rare earth elements as stated in the partial content.
Documented Applications
Liquid-liquid extraction for separating rare earth elements from acidified aqueous solutions using the aqueous-insoluble hydrophobic extractant solution, with optional stripping using a lower-acid inorganic acid as described in the partial content.
Comparative extraction performance context is described, including use of known diglycolamide extractants (TODGA, TEHDGA, DMDODGA) and solvent/additive comparisons, as referenced in the partial content.
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