EXPERIMENTAL DETERMINATION OF BARITE SOLUBILITY IN CONCENTRATED ELECTROLYTE SOLUTIONS: IMPLICATIONS FOR CRITICAL MINERAL EXTRACTIONS AND FOR BARITE-BASED WASTEFORM DEVELOPMENT

Barite (BaSO₄) is a critical mineral, according to the definition of U.S. Geological Survey. Geologically, barite deposits occur in bedded-sedimentary rock formations, and bedded-volcanic rock formations. Addionally, there are vein, cavity-filling and metasomatic barite deposits, and residual barite deposits in weathered rock formations because barite is resistent to weathering owing to its low solubility and stable structure. In the field of nuclear waste management, barite is a wasteform for radioactive radium (Ra), as radioactive Ra(II) can substitute of Ba(II) in the structure of barite. All isotopes of radium are radioactive. Among them, Ra-226 is the most stable one, and has a half life of 1,599 years. Radioactive radium is primarily produced during operation of nuclear reactors. In addition, barite-based cements and concretes are used for immobilization of high-sulfate radioactive waste solutions, and for radiation shielding in various environments such as hospitals and nuclear facilities.

In this work, we present the solubility measurements of barite in citric acid solutions at a room temperature and elevated temperatures up to 70^oC. We choose citric acid solutions because citric acid solutions are a potential leaching agent for barite recovery. Citrate is also present in nuclear waste streams, as citric acid is used in decommissioning processes for nuclear facilities. The supporting solutions include 0.10 mol•kg^–1, 0.25 mol•kg^–1, 0.25 mol•kg^–1, 0.50 mol•kg^–1, 0.75 mol•kg^–1, and 1.0 mol•kg^‑1 citric acid. All experimnets approached the equilibrium/steady state from the direction of undersaturation.

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 research is funded by the US DOE FECM via FWP-23-025668, and the SFWST programs administered by the Office of Nuclear Energy (NE) of the U.S. Department of Energy. SAND2024-07729A.