Waste site reclamation with recovery of radionuclides and metals

• US 5,292,456 A
• Filed: 03/20/1992
• Issued: 03/08/1994
• Est. Priority Date: 03/20/1992
• Status: Expired due to Term

• Current Assignee: Brookhaven Science Associates, LLC (Government of the United States of America)
• Original Assignee: Associated Universities, Inc.
• Inventors: Francis, Arokiasamy J., Dodge, Cleveland J.
• Primary Examiner(s): Walsh, Donald P.
• Assistant Examiner(s): MAI, NGOCLAN THI
• Application Number:
  US07/855,096
• Time in Patent Office: 718 Days
• Field of Search: 252/626, 252/628, 210/682, 210/611, 210/710, 210/748
• US Class Current: 588/18
• CPC Class Codes: C02F 1/30 by irradiation
• CPC Class Codes: C02F 1/32 with ultraviolet light
• CPC Class Codes: C02F 1/683 by addition of complex-forming compounds
• CPC Class Codes: C02F 3/34 characterised by the microorganisms used
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage
• CPC Class Codes: C12N 1/205 Bacterial isolates
• CPC Class Codes: C12R 2001/39 Pseudomonas fluorescens
• CPC Class Codes: G21F 9/002 Decontamination of the surface of objects with chemical or electrochemical processes
• CPC Class Codes: G21F 9/18 by biological processes
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

A method for decontaminating radionuclides and other toxic metal-contaminate

The U.S. government has certain rights in this invention pursuant to Contract Number DE-AC02-76CH00016 between the U.S. Department of Energy and Associated Universities, Inc.

Claims

1. A method for decontamination and reclamation of materials contaminated with radionuclides, metals, or mixtures thereof comprising:

(i) contacting the material with an organic complexing agent comprising citric acid, a citrate salt or mixture thereof in an aqueous solution to remove said radionuclides, metals or mixtures thereof from the material and yield a radionuclide and/or metal-citrate complex-containing solution;

(ii) treating the radionuclide and/or metal-citrate complex-containing solution with a bacterial culture containing Pseudomonas fluorescens ATCC No. 55241 wherein a nutrient carbon source for the bacteria consists substantially of citrate in the form of the radionuclide and/or metal-citrate complexes, said treatment resulting in the precipitation or incorporation into biomass of the radionuclides and/or metals; and

(iii) if the material being decontaminated and reclamated contains the radionuclide uranium, exposing the uranium citrate complex-containing solution to light resulting in the breakdown of the complex and precipitation of uranium as a polymer;

so that the radionuclides and/or metals are recovered in a concentrated form.

2. The method of claim 1 wherein the material is selected from a group consisting of soil, sediment, sludge and aquatic environments.

3. The method of claim 1 wherein the step (ii) treating is at a temperature of from about 18°

C. to about 32°

C., at an initial pH of from about 4 to about 8.

4. The method of claim 1 wherein citric acid, a citrate salt or mixture thereof is added in a concentration in excess of the concentration of the radionuclides and/or metals in the contaminated material.

5. The method of claim 1 wherein the concentration of the citric acid, citrate salt or mixture thereof is from about 0.01M to about 1.0M.

6. The method of claim 1 further comprising adding a supplemental carbon source in step (ii).

7. The method of claim 6 wherein the supplemental carbon source is glucose.

8. The method of claim 1 wherein the solution in step (iii) has an initial pH of from about 2 to about 8, and is exposed to daylight for a time of at least 12 hours.

9. The method of claim 1 further comprising adding supplemental photoreactive compound to the solution of step (iii).

10. The method of claim 9 wherein the photoreactive compound is ferric iron.

11. The method of claim 1 wherein the solution in step (iii) is exposed to sunlight.

12. The method of claim 1 wherein step (ii) is carried out after step (iii).

13. The method of claim 1 wherein step (ii) is carried out concurrently with step (iii).