30-3 Experimental Determination of the Solubility of Al(OH)3 in Alkaline Solutions: Applications to Hanford Tank Waste Sludge and to Extraction of Aluminium from Gibbsitic Bauxite Ores

Session: Geological and Geochemical Investigations of Critical Minerals in New Mexico and Beyond, and Technological Advances in Extraction of Critical Minerals

Presenting Author:

Authors:

Abstract:

The Hanford waste site contains an estimated 54 million gallons of radioactive waste, with aluminum being a significant component in the sludge phase, approximately 4,140 metric tons.  Among the various aluminum-bearing solid phases, gibbsite (a-Al(OH)₃) is of particular importance.  The tank waste contains high concentrations of NaOH, NaNO₂, and NaNO₃, necessitating an understanding of the interactions between aluminum and these solutions.  In addition, gibbsite is a dominant phase in gibbsitic bauxite ores, and alkaline solutions are used for extraction of aluminum.

To further investigate the interactions of aluminum under alkaline conditions, we have conducted solubility measurements at 60°C to develop a thermodynamic model.  This work reports the results of experiments regarding the dissolution of gibbsite in the presence of NaOH and NaNO₂.  Our experiments indicate that solubilities of gibbsite in mixed solutions of NaOH and NaNO₂ are higher than those in pure NaOH solutions.  Data from this research contributes to understanding of dissolution behavior of aluminum in alkaline solutions dominated with hydroxyl and nitrite ions and are applicable to tank waste pretreatment strategies and extraction of aluminum from gibbsitic bauxite ores.

Sandia National Laboratories is a multi-mission laboratory operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. This work was supported by the U.S. Department of Energy (DOE) Office of Environmental Management (EM) through the Laboratory Policy Office Hanford Tank Waste R&D Program. SAND2026-15796A

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