Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation and Recycle of Sodium Hydroxide and Sodium Nitrate

The objective of this research is to explore new liquid-liquid extraction approaches to the selective separation of major sodium salts from alkaline high-level wastes stored in underground tanks at Hanford, Savannah River, and Oak Ridge sites. Disposal of high level waste is horrendously expensive, in large part because the actual radioactive matter in the tanks has been diluted over 1000-fold by ordinary inorganic chemicals. Since the residual bulk chemicals must still undergo expensive treatment and disposal after most of the hazardous radionuclides have been removed, large cost savings will result from processes that reduce the overall waste volume. It is proposed that major cost savings can be expected if sodium hydroxide needed for sludge washing can be obtained from the waste itself, thus avoiding the addition of yet another bulk chemical to the waste and still further increase of the waste volume and disposal cost. Secondary priority is given to separating potassium an d abundant anions, including nitrate, nitrite, aluminate, and carbonate. Salts of these ions represent possible additional value for recycle, alternative disposal, or even use as commodity chemicals. A comprehensive approach toward understanding the extractive chemistry of these salts is envisioned, involving systems of varying complexity, from use of simple solvents to new bifunctional host molecules for ion-pair recognition. These extractants will ideally require no adjustment of the waste composition and will release the extracted salt into water, thereby consuming no additional chemicals and producing no additional waste volume. The overall goal of this research is to provide a scientific foundation upon which the feasibility of new liquid-liquid extraction chemistry applicable to the bulk reduction of the volume of tank waste can be evaluated