Acidithiobacillus ferrooxidans: A Natural Substitute for Nitric Acid Leaching of Copper *

Many target components used in plasma physics experiments performed at the Omega Laser Facility (Omega) and the National Ignition Facility (NIF) require the use of nitric acid leaching. These components, specifically gold hohlraums and plastic spools with embedded aluminum layers, are fabricated by machining copper mandrels to the required internal shape and plating or casting the final material onto the mandrel. The final part is then nitric acid leached to remove the copper mandrel. Unfortunately, the optimized leaching process for spools leaves trace amounts of copper. Furthermore, leaching with nitric acid to remove the copper degrades the epoxy and it can begin to attack the embedded aluminum layer, which is critical to the experiment. In this study, a natural bioleaching microorganism, Acidithiobacillus ferrooxidans, was used to augment the current nitric acid leaching process. After the primary leaching process, spools containing small amounts of remaining copper contamination were exposed to a culture of A. ferrooxidans and monitored to test its effectiveness in removing the remaining copper from the spools. This presentation will give an overview of the leaching process and a detailed discussion of the bacteria and bioleaching strategies and challenges. LA-UR-21-26779