Method of waste stabilization with dewatered chemically bonded phosphate ceramics

• US 20060235258A1
• Filed: 02/26/2004
• Published: 10/19/2006
• Est. Priority Date: 02/26/2003
• Status: Active Grant

• Current Assignee: CH2M Hill Incorporated (CH2M Hill Companies Limited), UChicago Argonne LLC, University of Chicago
• Original Assignee: CH2M Hill Incorporated (CH2M Hill Companies Limited)
• Inventors: Wagh, Arun, Maloney, Martin D.
• Granted Patent: US 7,745,679 B2
• Time in Patent Office: Days
• US Class Current: 588/249
• CPC Class Codes: B09B 3/25 using mineral binders or matrix
• CPC Class Codes: C04B 14/304 Magnesia
• CPC Class Codes: C04B 18/04 Waste materials; Refuse
• CPC Class Codes: C04B 2103/0094 Agents for altering or buffering the pH; Ingredients characterised by their pH
• CPC Class Codes: C04B 2103/0095 Oxidising agents
• CPC Class Codes: C04B 2103/0096 Reducing agents
• CPC Class Codes: C04B 2111/00767 for waste stabilisation purposes
• CPC Class Codes: C04B 28/342 the phosphate binder being present in the starting composition as a mixture of free acid and one or more reactive oxides
• CPC Class Codes: C04B 40/0028 Aspects relating to the mixing step of the mortar preparation
• CPC Class Codes: C04B 40/0263 Hardening promoted by a rise in temperature C04B40/024 takes precedence
• CPC Class Codes: G21F 9/16 by fixation in stable solid media G21F9/305 takes precedence
• CPC Class Codes: G21F 9/302 in an inorganic matrix
• CPC Class Codes: G21F 9/304 Cement or cement-like matrix compositional aspects C04B
• CPC Class Codes: G21F 9/305 Glass or glass like matrix C03B5/005 takes precedence; compositional aspects C03C
• CPC Class Codes: Y02W 30/91 Use of waste materials as fillers for mortars or concrete

Abstract

A method of stabilizing a waste in a chemically bonded phosphate ceramic (CBPC). The method consists of preparing a slurry including the waste, water, an oxide binder, and a phosphate binder. The slurry is then allowed to cure to a solid, hydrated CBPC matrix. Next, bound water within the solid, hydrated CBPC matrix is removed. Typically, the bound water is removed by applying heat to the cured CBPC matrix. Preferably, the quantity of heat applied to the cured CBPC matrix is sufficient to drive off water bound within the hydrated CBPC matrix, but not to volatalize other non-water components of the matrix, such as metals and radioactive components. Typically, a temperature range of between 100° C.-200° C. will be sufficient. In another embodiment of the invention wherein the waste and water have been mixed prior to the preparation of the slurry, a select amount of water may be evaporated from the waste and water mixture prior to preparation of the slurry. Another aspect of the invention is a direct anyhydrous CBPC fabrication method wherein water is removed from the slurry by heating and mixing the slurry while allowing the slurry to cure. Additional aspects of the invention are ceramic matrix waste forms prepared by the methods disclosed above.

Claims

1. A method of stabilizing a waste in chemically bonded phosphate ceramic comprising:

preparing a slurry comprising the waste, water, an oxide binder and a phosphate binder;

allowing the slurry to cure to a solid hydrated chemically bonded phosphate ceramic matrix; and

removing bound water from the solid hydrated chemically bonded phosphate ceramic matrix.

3. The method of claim 1 wherein the hydrated ceramic matrix is heated to a select temperature between a lower first temperature where the bound water begins to be driven from the hydrated ceramic matrix and a higher second temperature where non-water components of the hydrated ceramic matrix are volatilized.

5. The method of claim 1 wherein the waste and the water have been mixed prior to the preparation of the slurry and further comprising removing a select amount of water from the waste and water mixture prior to preparation of the slurry.

8. The method of claim 1 further comprising removing water from the slurry while allowing the slurry to cure.

9. The method of claim 8 wherein the water is removed from the slurry through evaporation by heating, and wherein the slurry is heated to a select curing temperature between a first curing temperature where water is removed from the slurry as it cures and a second curing temperature where non-water components of the slurry are volatilized.

13. The method of claim 1 further comprising adding a select amount of one of a reducing agent and an oxidizing agent to the slurry prior to allowing the slurry to cure.

38. The method of claim 1 wherein the waste is a high salt content waste that has a first pH level, and further comprising adding a neutralizing material to the waste before allowing the slurry to cure to at least partially neutralize the waste so the waste has a second pH level different from the first pH level.

39. The method of claim 1, further comprising adding a beta-absorptive, gamma-absorptive, alpha-absorptive, or neutron-absorptive material directly to the waste before allowing the mixed slurry to cure.

40. The method of claim 1, further comprising dewatering the waste during or before the waste is combined with the oxide binder and the phosphate binder.

41. The method of claim 1, further comprising adding a neutralizing material to the waste to at least partially neutralize the waste before the waste is combined with the oxide binder and the phosphate binder.

42. The method of claim 1 further comprising at least partially de-watering the waste before allowing the slurry to cure.

43. The method of claim 1, further comprising adding an H₂ getter agent to the waste or the slurry to reduce H₂ gas generation.

44. The method of claim 1 wherein the waste is an acidic waste, further comprising neutralizing the waste with at least one metal oxide.

45. The method of claim 1 wherein the waste is a basic waste, having a pH level further comprising reducing the pH level by adding a neutralizing agent.

46. The method of claim 1, further comprising adding a salt to the slurry to control reaction rates during mixing of the slurry.

47. The method of claim 1, further comprising adding at least one of a stabilizing agent and a reducing agent to the waste or the slurry to decrease solubility of constituents of the waste.

48. The method of claim 1, further comprising adding an exothermic agent to at least one of the waste and the slurry that reacts and heats the at least one of the waste and the slurry.

49. The method of claim 1, further comprising adding to least one of the waste and the slurry a shielding agent for neutrons, alpha particles, beta particles, or gama particles in the waste to provide an at least partially self-shielding waste.

2. (canceled)

4. (canceled)

6-7. -7. (canceled)

10-12. -12. (canceled)

14-15. -15. (canceled)

16. A method of stabilizing a waste in chemically bonded phosphate ceramic comprising:

providing a mixture of the waste and water;

removing a select amount of water from the waste and water mixture to form a residual waste and water mixture;

preparing a slurry comprising the residual waste and water mixture, an oxide binder and a phosphate binder; and

allowing the slurry to cure to a solid chemically bonded phosphate ceramic matrix.

17. The method of claim 16 wherein the select amount of water is removed from the waste and water mixture through evaporation by heating.

18. The method of claim 16 wherein the quantity of water removed from the waste and water mixture is selected to result in a solids content within the waste and water mixture, after the removal step, of equal to or less than 90% measured by weight.

22. The method of claim 16 wherein the oxide binder is a divalent metal oxide and the phosphate binder is KH₂PO₄.

23. The method of claim 22 wherein the oxide binder is MgO.

24. The method of claim 16 further comprising adding a select amount of one of a reducing agent and an oxidizing agent to the slurry prior to allowing the slurry to cure.

19-21. -21. (canceled)

25-26. -26. (canceled)

27. A method of stabilizing a waste in a chemically bonded phosphate ceramic comprising:

preparing a slurry comprising the waste, water, an oxide binder and a phosphate binder; and

removing water from the slurry while allowing the slurry to cure.

28. The method of claim 27 wherein the water is removed from the slurry through evaporation by heating, and wherein the slurry is heated to a select curing temperature between a first curing temperature where water is removed from the slurry as it cures and a second curing temperature where non-water components of the slurry are volatilized.

30. The method of claim 27 wherein the oxide binder is a divalent metal oxide and the phosphate binder is KH₂PO₄.

32. The method of claim 27 further comprising adding a select amount of one of a reducing agent and an oxidizing agent to the slurry prior to allowing the slurry to cure.

33. The method of claim 27 further comprising adding H₃PO₄ to the slurry to reduce the slurry pH.

34. The method of claim 27 further comprising adding a metal oxide to the slurry to increase the slurry pH.

29. (canceled)

31. (canceled)

35-37. -37. (canceled)