Extraction of metals using supercritical fluid and chelate forming legand

• US 5,730,874 A
• Filed: 06/02/1994
• Issued: 03/24/1998
• Est. Priority Date: 06/12/1991
• Status: Expired due to Fees

• Current Assignee: Idaho Research Foundation, Inc.
• Original Assignee: Idaho Research Foundation, Inc.
• Inventors: Wai, Chien M., Laintz, Kenneth E.
• Primary Examiner(s): Drodge, Joseph W.
• Application Number:
  US08/253,000
• Time in Patent Office: 1,391 Days
• Field of Search: 210/634, 210/638, 210/674, 210/511, 210/639, 210/912, 423/21.1, 423/21.5, 252/364, 134/1
• US Class Current: 210/638
• CPC Class Codes: B01D 11/0203 with a supercritical fluid
• CPC Class Codes: B01D 11/0288 Applications, solvents
• CPC Class Codes: B01D 11/0403 with a supercritical fluid
• CPC Class Codes: B01D 11/0407 the supercritical fluid acting as solvent for the solute
• CPC Class Codes: B01D 11/0492 Applications, solvents used
• CPC Class Codes: B08B 7/0021 by liquid gases or supercritical fluids
• CPC Class Codes: B09C 1/02 Extraction using liquids, e.g. washing, leaching , flotation
• CPC Class Codes: C01F 17/17 involving a liquid-liquid extraction
• CPC Class Codes: C01F 17/276 Nitrates
• CPC Class Codes: C22B 3/1641 with ketones or aldehydes
• CPC Class Codes: C22B 3/306 Ketones or aldehydes
• CPC Class Codes: C22B 3/32 Carboxylic acids
• CPC Class Codes: C22B 3/3846 Phosphoric acid, e.g. (O)P(OH)3
• CPC Class Codes: G21F 9/125 by solvent extraction
• CPC Class Codes: Y02P 10/20 Recycling
• CPC Class Codes: Y02P 20/54 using solvents, e.g. supercritical solvents or ionic liquids
• CPC Class Codes: Y10S 210/912 Heavy metal

Abstract

A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated β-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated β-diketone and a trialkyl phosphate, or a fluorinated β-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated β-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

Claims

1. A method for extracting a metalloid or metal species from a solid or liquid, comprising exposing the solid or liquid to a supercritical carbon dioxide fluid solvent and a halogenated β

-diketone chelating agent for a sufficient period of time to form chelates between the agent and species that are solubilized in the supercritical fluid solvent.

2. The method of claim 1 further comprising the step of separating the supercritical fluid from the solid or liquid after the chelate is solubilized in the supercritical fluid.

3. The method of claim 1 wherein the halogenated β

-diketone is a fluorinated β

-diketone.

4. The method of claim 1 wherein the exposing step further comprises providing a secondary modifying solvent.

5. The method of claim 4 wherein the modifying solvent is selected from the group consisting of medium-boiling-point alcohols and esters.

6. The method of claim 5 wherein the modifying solvent is methanol.

7. The method of claim 1 wherein the β

-diketone is represented by the formula ##STR22## wherein R₁ and R₂ are independently selected from the group consisting of lower alkyl, fluorinated lower alkyl, thenoyl and fluorinated thenoyl groups.

8. The method of claim 7 wherein R₁ and R₂ each is selected from the group consisting of methyl, trifluoromethyl, ethyl, fluorinated ethyl, propyl, fluorinated propyl, butyl, and fluorinated butyl.

9. The method according to claim 1 wherein the β

-diketone is selected from the group consisting of trifluoroacetylacetone, hexafluoroacetylacetone, thenoyltrifluoroacetylacetone and heptafluorobutanoylpivaroylmethane.

10. The method according to claim 1 wherein the β

-diketone is selected from the group consisting of trifluoroacetylacetone, hexa-fluoroacetylacetone, thenoyltrifluoroacetylacetone and heptafluorobutanoylpivaroylmethane.

11. The method of claim 1 wherein the metal or metalloid ions are extracted from an aqueous acidic solution.

12. A method for extracting a metalloid or metal species from a solid or liquid, comprising exposing the solid or liquid to a supercritical fluid solvent containing a β

-diketone chelating agent and a trialkyl phosphate or a trialkylphosphine oxide for a sufficient period of time to form chelates between the agent and species that are solubilized in the supercritical fluid solvent.

13. The method of claim 12 wherein the trialkyl phosphate, if present, is represented by the formula ##STR23## the trialkylphosphine oxide, if present, is represented by the formula ##STR24## and wherein R₃ -R₈ are independently selected from the group consisting of lower alkyl groups.

14. The method of claim 13 wherein R₃ =R₄ =R₅.

15. The method of claim 13 wherein R₃, R₄ and R₅ are selected from the group consisting of n-butyl and n-octyl, and wherein R₆ -R₈ are n-octyl.

16. The method according to claim 12 wherein the β

-diketone is represented by the formula ##STR25## wherein R₁ and R₂ are independently selected from the group consisting of fluorinated lower alkyl, and fluorinated thenoyl groups, the trialkyl phosphate, if present, is represented by the formula ##STR26## wherein R₃, R₄ and R₅ are independently selected from the group consisting of lower alkyl groups, and wherein the trialkylphosphine oxide, if present, is represented by the formula ##STR27## R₆ -R₈ being selected from the group consisting of lower alkyl groups.

17. The method of claim 16 wherein the β

-diketone is selected from the group consisting of trifluoroacetylacetone, hexa-fluoroacetylacetone, thenoyltrifluoro-acetylacetone and heptafluorobutanoylpivaroylmethane.

18. The method of claim 16 wherein R₃, R₄ and R₅ are selected from the group consisting of n-butyl, n-octyl, and mixtures thereof.

19. A method for extracting metalloid or metal species from a solid or liquid comprising exposing the solid or liquid to supercritical carbon dioxide and ligand selected from the group consisting of fluorinated β

-diketones, trialkyl phosphates, trialkylphosphine oxides, and mixtures thereof, the ligand forming chelates with the metal or metalloid species, the chelates being soluble in the carbon dioxide.

20. The method of claim 19 wherein the metalloid or metal species is dissolved in an acidic aqueous solution.

21. The method according to claim 19 wherein the group from which the ligand is selected comprises fluorinated β

-diketones which are represented by the formula ##STR28## wherein R₁ and R₂ are independently selected from the group consisting of fluorinated lower alkyl and fluorinated thenoyl groups.

22. The method according to claim 19, wherein the group from which the ligand is selected comprises trialkyl phosphates which are represented by the formula ##STR29## wherein R₃, R₄ and R₅ are independently selected from the group consisting of lower alkyl groups, and trialkylphosphine oxides which are represented by the formula ##STR30## R₆ -R₈ are independently selected from the group consisting of lower alkyl groups.

23. The method according to claim 19 wherein the group from which the ligand is selected comprises fluorinated β

-diketones which are represented by the formula ##STR31## wherein R₁ and R₂ are independently selected from the group consisting of fluorinated lower alkyl and fluorinated thenoyl groups, trialkyl phosphates which are represented by the formula ##STR32## wherein R₃, R₄ and R₅ are independently selected from the group consisting of lower alkyl groups, and trialkylphosphine oxides which are represented by the formula ##STR33## wherein R₆ -R₈ are independently selected from the group consisting of lower alkyl groups.

24. The method of claim 23 wherein R₁ and R₂ are selected from the group consisting of fluorinated lower alkyl groups, and wherein R₃ -R₈ are independently selected from the group consisting of lower alkyl groups.

25. The method according to claim 24 wherein the group from which the ligand is selected comprises β

-diketones which are selected from the group consisting of trifluoroacetylacetone, hexafluoroacetylacetone, thenoyl-trifluoroacetylacetone and heptafluorobutanoylpivaroylmethane, and wherein R₃ =R₄ =R₅.

26. The method of claim 25 wherein R₃, R₄ and R₅ are selected from the group consisting of n-butyl and n-octyl, and wherein R₆ -R₈ are n-octyl.

27. The method according to claim 19 wherein the supercritical carbon dioxide includes a modifying solvent selected from the group consisting of lower alkyl alcohols.

28. The method according to claim 27 wherein the modifying solvent is methanol.

29. The method of claim 19 wherein the exposing step comprises continuously flowing the supercritical carbon dioxide through the solid or liquid.

30. A method for extracting metals or metalloids from an acidic aqueous solution comprising exposing the acidic aqueous solution to carbon dioxide and ligand selected from the group consisting of fluorinated β

-diketones, trialkyl phosphates, trialkylphosphine oxides, and mixtures thereof, the ligand forming chelates with the species, the chelates being soluble in the carbon dioxide.

31. The method according to claim 30 wherein the carbon dioxide is subcritical.

32. The method according to claim 30 wherein the carbon dioxide is supercritical.

33. The method of claim 32 wherein the group from which the ligand is selected comprises fluorinated β

-diketones which are represented by the formula ##STR34## wherein R₁ and R₂ are independently selected from the group consisting of fluorinated lower alkyl and fluorinated thenoyl groups, trialkyl phosphates which are represented by the formula ##STR35## wherein R₃, R₄ and R₅ are independently selected from the group consisting of lower alkyl groups, and trialkylphosphine oxides which are represented by the formula ##STR36## wherein R₆ -R₈ are independently selected from the group consisting of lower alkyl groups.

34. The method according to claim 33 wherein the group from which the ligand is selected comprises β

-diketones which are selected from the group consisting of trifluoroacetylacetone, hexafluoroacetylacetone, thenoyltrifluoroacetylacetone and heptafluorobutanoylpivaroylmethane, and wherein R₃ =R₄ =R₅.

35. The method of claim 34 wherein R₃, R₄ and R₅ are selected from the group consisting of n-butyl and n-octyl, and wherein R₆ -R₈ are n-octyl.

36. The method of claim 32 wherein the exposing step comprises continuously flowing the supercritical carbon dioxide through the aqueous solution.

37. An extraction solvent comprising a supercritical fluid and a halogenated β

-diketone chelating agent.

38. The solvent of claim 37 wherein the supercritical fluid is supercritical carbon dioxide.

39. The solvent of claim 38 wherein the fluid further includes a trialkyl phosphate or a trialkylphosphine oxide chelating agent.

40. The solvent of claim 39 wherein the β

-diketone chelating agent is fluorinated.

41. The solvent of claim 39 wherein the supercritical fluid is supercritical carbon dioxide, the halogenated β

-diketone chelating agent is represented by the formula ##STR37## wherein R₁ and R₂ are independently selected from the group consisting of fluorinated lower alkyl and fluorinated thenoyl groups, the trialkyl phosphate, if present, is represented by the formula ##STR38## wherein R₃, R₄ and R₅ are independently selected from the group consisting of lower alkyl groups, and wherein the trialkylphosphine oxide, if present, is represented by the formula ##STR39## wherein R₆ -R₈ are independently selected from the group consisting of lower alkyl groups.

42. The solvent of claim 37 wherein the β

-diketone is selected from the group consisting of trifluoroacetylacetone, hexafluoroacetylacetone, thenoyltrifluoro-acetylacetone and heptafluorobutanoylpivaroylmethane, R₃, R₄ and R₅ are selected from the group consisting of n-butyl, n-octyl, and mixtures thereof, and wherein R₆ -R₈ are n-octyl.

43. A method for treating acidic waste material containing metalloid and metal waste species, comprising the steps of:

providing a container of the acidic waste material;

exposing the waste material in the container to carbon dioxide and a ligand selected from the group consisting of fluorinated β

-diketones, trialkyl phosphates, trialkylphosphine oxides and mixtures thereof, the waste species being soluble in the carbon dioxide such that the carbon dioxide solubilizes the waste species; and

removing the carbon dioxide and solubilized waste species from the container.

45. The method according to claim 43 wherein the carbon dioxide is supercritical.

44. The method according to 43 wherein the carbon dioxide is subcritical.