Reactive Strippable Coatings for Visualization and Remediation of Mercury Contaminated Surfaces - 21292

Mercury (Hg) has been identified as a high priority contaminant at the Y-12 National Security Complex (Y-12) by the U.S. Department of Energy (DOE). The cleanup of this site specifically requires techniques and technologies for safe and cost-effective facility demolition, soil remediation, and on-site treatment and disposal of mercury bearing wastes. The technology development (TD) needs and timelines to characterize buildings during pre-demolition were scheduled to run through FY 2020, followed by demolition of four large buildings contaminated with mercury (FY 2021-FY 2043). Oak Ridge Office of Environmental Management (OREM) has specifically identified material/debris decontamination as a TD. The broader goal for Y-12 specifies a reactive strippable coating for targeted pre-demolition and decontamination to limit volume of debris requiring treatment for disposal and Hg mobilization. Toward this, InnoSense LLC (ISL) has developed a water-based reactive strippable coating (Trap and See-Hg^TMa) to sequester, visually locate the contaminant through color changes, and thus to remediate contaminated surfaces. The work is being funded through a Small Business Innovation Research grant from DOE's Office of Environmental Management (EM). The coating uses water borne polymeric dispersions with wetting aids, chemochromic chelators, reactive and passive sorbents to capture elemental mercury (Hg0) and mercuric Hg(II) species. The formulation is optimized for manual or robotic spray application, ambient cure to result in a coating that sequesters and indicates Hg presence and can be stripped from the surface when dry. Soil and brick/rubble samples containing a range of Hg concentrations were collected from the Y-12 site and characterized by the Oak Ridge National Laboratory (ORNL) team. Radioactive material-free samples were provided to ISL for laboratory testing. ORNL measured the Hg concentration by head space analysis. Speciation of the Hg in these samples was evaluated using Hg0 analyzer and chemical sequential extraction following techniques developed at ORNL. Coatings were applied to the Y-12 soil and brick/rubble samples at ISL and characterized by headspace analysis for Hg0 concentrations. The peeled paints from both soil and brick/rubble samples were shipped to ORNL and extracted for total mercury analysis via atomic absorption spectroscopy. The visible detection capabilities for known Hg-contaminated (soluble and insoluble species) surfaces was established on drywall and concrete surfaces through pink color formation in regions where they were present. Specific color detection was also noted for 1:500 excess of co-existing interferents, e.g., copper (Cu), nickel (Ni), lithium (Li) and iron (Fe). The coating is compatible with manual and robotic spray application and can be peeled after curing. The production of the custom formulation was scaled-up at a contract manufacturer and sprayed on 16-foot custom walls (metal, wood, and smooth and porous concrete) using International Climbing Machine's (ICM) wall climbing robot with an adjustable spray head. Trap and See-Hg was used successfully in a small scale in-situ trial at Y-12 by the ORNL collaborator. Small areas of the alpha-2 basement wall, beam and floor were manually sprayed with the paint after establishing Hg-vapors were present. The dried paint was peeled and analyzed indicating that Hg0 vapors were sequestered in the paint from two different locations. In another test carried out at ORNL, the coating suppressed Hg vapors from metal and concrete samples from the Y-12 site. Total Hg analysis of the peeled paints indicated the paints have a high sorption capacity for Hg. Toxicity characteristic leaching procedure (TCLP) and Environmental Protection Agency (EPA) SW-846 Method 1030 Ignitability of Paints tests have also been completed. A suitable test site and target date for the technology demonstration are being identified presently, with the help of a site contractor, OREM and ORNL. In summary, the Trap and See-Hg attributes of high Hg uptake and color indication offer great value to identify Hg hazards and seal them in place to enhance worker safety and downstream waste disposal considerations at Y-12. (authors)