Ligand Assisted Chromatography for Metal Ion Separation

Patent metadata

Field	Value
Publication number	US-2017166993-A1
Application number	US-201515327041-A
Country	US
Kind code	A1
Filing date	Jul 17, 2015
Priority date	Jul 18, 2014
Publication date	Jun 15, 2017
Grant date	—

Abstract

Presented herein is a ligand-assisted elution chromatography process for the separation of metal ions using a sorbent. An inorganic sorbent, titania, for example, has three types of adsorption sites: Bronsted acid (BA), Bronsted base (BB), and Lewis acid (LA). At a high pH, the BA sites can interact with the metal ions as a cation exchanger. If a ligand with COO groups is preloaded onto the sorbent, the COO— groups of the ligand can adsorb onto the LA sites. The adsorbed. ligands become strong adsorption sites for the metal ions. If the Langmuir a value for metal ion adsorption is similar to that of metal ion complexation with the ligand in the mobile phase, the different metal ions can be eluted separately with an overall selectivity which is equal to the ratio of the ligand selectivity to the sorbent selectivity.

First claim

1 - 39 . (canceled)

40 . A process for isolating a substantially pure (95% or higher) rare earth element (REE) comprising the steps of:
a. dissolving a mixture containing REEs in a strong acid to result in a dissolved mixture of metal ions, including that of REEs; b. capturing metal ions of REEs in a first set of chromatographic columns; c. washing said first set of chromatographic columns with a salt solution to remove non-adsorbing metal ions; d. eluting metal ions of REES from said first set of chromatographic columns with a first ligand solution to result in a solution of enriched metal ions of REEs; e. loading said solution of enriched metal ions of REEs onto a second set of chromatographic columns; and f. stepwise eluting bound metal ions of REEs from said second set of chromatographic columns using a second ligand solution to afford a substantially pure REE.

41 . The process of claim 40 wherein said salt solution is a sodium or ammonium salt solution with a counter ion selected from the group consisting of chloride (Cl − ), sulfate (SO 4 2− ), bisulfate (HSO 4 − ), and nitrate (NO 3 − ).

42 . The process of claim 40 wherein said first ligand is ethylenediaminetetraacetic acid (EDTA), pentetic acid (DTPA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), N-(2-Hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA), iminodiacetic acid (IDA), citric acid, or any combination thereof.

43 . The process of claim 40 , wherein said metal ions of REEs are eluted separately by using said first ligand solution with a linear or stepwise concentration gradient of said ligand.

44 . The process of claim 40 , wherein said metal ions of REEs are eluted separately by using said first ligand solution with a linear or stepwise gradient of pH.

45 . The process of claim 40 , wherein said second ligand solution is a solution of ethylenediaminetetraacetic acid (EDTA), pentetic acid (DTPA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), N-(2-Hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA), iminodiacetic acid (IDA), citric acid, or any combination thereof.

46 . The process of claim 45 , wherein metal ions of REEs are eluted separately by using said second ligand solution with a linear or stepwise concentration gradient of said ligand.

47 . The process of claim 45 , wherein metal ions of REEs are eluted separately by using said second ligand solution with a linear or stepwise gradient of pH.

48 . The process of claim 40 , wherein said strong acid compromises one or more acids selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H 2 SO 4 ), and nitric acid (HNO 3 ).

49 . The process of claim 40 wherein said first set of chromatographic columns are packed with an ion exchange resin.

50 . The process of claim 49 , wherein said ion exchange resin is a strong acid cation exchange resin.

51 . The process of claim 40 wherein said second set of chromatographic columns are packed with an absorbent.

52 . The process of claim 51 , wherein said absorbent is modified, covalently or non-covalently, by a chelating ligand.

53 . The process of claim 51 , wherein said absorbent is a hydrous polyvalent metal oxide.

54 . The process of claim 51 , wherein said absorbent is TiO 2 , ZrO 2 , or SnO 2 .

55 . The process of claim 51 , wherein said absorbent is a chelating resin containing a chelating functional group of iminodiacetic acid.

56 . The process of claim 40 , wherein said REEs comprise at least one of praseodymium (Pr), neodymium (Nd), and samarium (Sm).

57 . The process of claim 40 , wherein said chromatographic separation process is performed at a pH from about 3 to about 11 with a said first or second ligand concentration of from about 0.001 M to about 1 M.

58 . A product of substantially pure (95% or higher) REEs of claim 40 .

59 . A product of substantially pure (95% or higher) praseodymium (Pr), neodymium (Nd), or samarium (Sm) prepared by the process of claim 40 .

Assignees

• Purdue Research Foundation

Inventors

• Wang Nien-Hwa Linda
• Ling Lei

Classifications

• B01D15/42

  characterised by the development mode, e.g. by displacement or by elution · CPC title

• C22B3/06

  in inorganic acid solutions {, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions} · CPC title

• B01D15/3828

  Ligand exchange chromatography, e.g. complexation, chelation or metal interaction chromatography · CPC title

• C22B59/00

  Obtaining rare earth metals · CPC title

• B01D15/422

  Displacement mode · CPC title