(136g) Boehmite Dissolution Model Based On Simulant Data

Boehmite is present in significant quantities in several of the Hanford waste tanks. It has been proposed that the boehmite will be dissolved through caustic leaching in the Hanford Waste Treatment and Immobilization Plant (WTP) currently under construction. Therefore, it is important to fully understand the nature of this dissolution process so that caustic leaching can be effectively deployed on the Hanford tank wastes.

This research determined the impact of primary control parameters such as temperature, hydroxide concentration, approach to solubility, and stirring rate on the boehmite dissolution rate. The impact of aluminate ion on the dissolution kinetics was also determined. In addition, other parameters that impact boehmite dissolution, such as free-hydroxide concentration and reaction temperature, were also assessed and used to develop a semi-empirical model of the boehmite dissolution process. The understanding derived from this work will be used as the basis to evaluate and improve the planned performance of aluminum leaching during waste pretreatment in preparation of waste vitrification in the WTP .

This work is the first in a series of programs aimed at demonstrating the WTP waste pretreatment leaching process . This work was used to develop a simulant of the boehmite-containing Hanford waste. That simulant is subsequently being used in laboratory- and pilot-scale testing to demonstrate the WTP pretreatment process in an integrated fashion.