Aluminum phosphate ceramics for waste storage
View Patent ↗The present disclosure describes solid waste forms and methods of processing waste. In one particular implementation, the invention provides a method of processing waste that may be particularly suitable for processing hazardous waste. In this method, a waste component is combined with an aluminum oxide and an acidic phosphate component in a slurry. A molar ratio of aluminum to phosphorus in the slurry is greater than one. Water in the slurry may be evaporated while mixing the slurry at a temperature of about 140-200° C. The mixed slurry may be allowed to cure into a solid waste form. This solid waste form includes an anhydrous aluminum phosphate with at least a residual portion of the waste component bound therein.
1. A method of processing waste, comprising:
combining a waste component with an aluminum oxide and an acidic phosphate component in a waste slurry comprising water, wherein the waste component comprises hazardous waste and a molar ratio of aluminum oxide to metal phosphate in the slurry is greater than one and wherein the acidic phosphate component is a phosphate of a monovalent metal;
evaporating water in the slurry while mixing the slurry at a functional temperature of about 140-200° C.; and
allowing the mixed slurry to cure into a solid waste form comprising an anhydrous compound of aluminum oxide and metal phosphate with a residual portion of the waste component bound therein,
wherein:
combining the waste component, the aluminum oxide, and the acidic phosphate component in the waste slurry comprises:
reacting at least a portion of the aluminum oxide with the acidic phosphate component in a phosphate precursor slurry;
at least partially drying the phosphate precursor slurry to form a phosphate precursor comprising a paste or a powder; and
after at least partially drying the phosphate precursor slurry, mixing the phosphate precursor with the waste component in the waste slurry, the waste slurry having more water than the phosphate precursor prior to the evaporation of the water in the waste slurry.
2. The method of claim 1 wherein the waste component comprises a heavy metal, further comprising mixing the slurry at a temperature of no greater than about 130° C. for a first time before mixing the slurry at the functional temperature.
3. The method of claim 1 wherein the aluminum oxide comprises aluminum hydroxide or anhydrous Al 2 O 3 .
4. The method of claim 1 wherein the aluminum oxide and the acidic phosphate component are combined prior to combining with the waste component.
5. The method of claim 1 further comprising terminating the mixing upon reaching a terminal consistency.
6. The method of claim 1 wherein combining in the slurry further comprises combining a CBPC precursor other than an aluminum oxide with the waste component and the acidic phosphate in the slurry and, thereafter, adding the aluminum oxide to the slurry.
7. The method of claim 1 wherein the waste component is stored in a waste storage container and wherein the waste component, aluminum oxide, and acidic phosphate component are combined in the waste storage container.
8. The method of claim 1 wherein the slurry further comprises at least one of SnCl 2 or Na 2 S.
9. The method of claim 1 wherein the waste has a first pH level, and further comprising adding a neutralizing material to the waste before allowing the mixed slurry to cure to at least partially neutralize the waste so the waste has a second pH level different from the first pH level.
10. The method of claim 9 wherein the neutralizing material is added to the waste before the waste is combined with the aluminum oxide and the acidic phosphate.
11. The method of claim 1 , further comprising adding at least one of a beta-absorptive, gamma-absorptive, alpha-absorptive, or neutron-absorptive material directly to the waste before allowing the mixed slurry to cure.
12. The method of claim 11 wherein the at least one of a beta-absorptive, gamma-absorptive, alpha-absorptive, or neutron-absorptive material is added to the waste before the waste is combined with the aluminum oxide and the acidic phosphate.
13. The method of claim 1 , further comprising dewatering the waste during or before the waste is combined with the aluminum oxide and the acidic phosphate.
14. 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 aluminum oxide and the acidic phosphate.
15. The method of claim 14 wherein the neutralizing material is added before the evaporating the water.
16. The method of claim 14 wherein the neutralizing material is added after evaporating the water, and mixing occurs after adding the neutralizing material.
17. The method of claim 14 , further comprising adding an H 2 getter agent to the waste or the slurry to reduce H 2 gas generation.
18. The method of claim 1 wherein the H 2 getter agent include MgO.
19. The method of claim 1 wherein the waste is an acidic waste, further comprising neutralizing the waste with at least one metal oxide.
20. The method of claim 1 , further comprising adding a salt to the slurry to control reaction rates during mixing of the slurry.
21. The method of claim 1 , further comprising adding at least one of a stabilizing agent or a reactant agent to the waste or the slurry.
22. The method of claim 1 , further comprising adding an exothermic agent to at least one of the waste or the slurry that reacts to create heat that heats the at least one of the waste or the slurry.
23. The method of claim 1 , further comprising adding to least one of the waste or the slurry a shielding agent for neutrons, alpha particles, beta particles, or gamma particles in the waste to provide an at least partially self-shielding waste.
24. The method of claim 1 , wherein the anhydrous compound of aluminum oxide and metal phosphate is aluminum monovalent phosphate, aluminum magnesium phosphate, aluminum cesium phosphate, aluminum potassium phosphate, aluminum sodium phosphate, aluminum lithium phosphate, aluminum strontium phosphate or aluminum zirconium phosphate.
25. The method of claim 1 , wherein the waste component is radioactive waste.