Quickly and safely decontaminating mission-critical equipment from Chemical Warfare Agents (CWAs) is a complicated puzzle. Warfighters must piece together chemistry, equipment, resources and logistics — and it must be immediate — in order to ensure combat effectiveness. One way that the Defense Threat Reduction Agency’s Chemical and Biological Technologies Department is helping warfighters in this threat environment is by developing a sprayable slurry that can quickly and safely decontaminate CWAs.
Immediate decontamination is not the simple process of washing away the chemical agent. Current efforts require the application of the decontaminant for lengthy contact times of 30 minutes to several hours, and large amounts of water for rinsing to avoid material corrosion. This can be a logistical burden to deployed warfighters due to the copious amounts of water required.
It''s also a chemistry puzzle. CWAs can be absorbed by equipment surfaces, so a decontaminant must first chemically coax absorbed agents in a process called partitioning. Then, the agents must be detoxified, either by binding (a process called adsorption) or by chemically destroying them. The ideal decontaminant should rapidly partition, adsorb and destroy vapor and contact hazards from multiple CWAs while being logistically feasible (i.e., no rinsing), easily deployed and effective on multiple materials and surfaces. Previously, nothing like this has ever been developed to support the warfighter.
This was the challenge undertaken by a team from the Decontamination Sciences Branch at the U.S. Army Research, Development and Engineering Command Chemical and Biological Center (RDECOM – C&B Center). Funded by DTRA CB, they combined fundamental chemical principles with previous decontamination studies to successfully develop a new and effective decontaminant: the Sprayable Slurry for detoxification of CWAs.
To do this, the team first identified a solvent, sulfolane, that effectively partitioned absorbed agents from surfaces. Partitioning is important because it dissolves the agents in a solvent that supports detoxification by chemical reaction. Sulfolane also mixes efficiently with water, which supports destruction of CWAs by chemical hydrolysis.
Then the team mixed in a second ingredient, zirconium hydroxide (Zn(OH)4), that adsorbs CWAs and chemically destroys them. Zirconium hydroxide was first studied as a promising new filter material precisely because it has excellent adsorption properties and wide-ranging reactivity toward numerous types of CWAs and toxic industrial chemicals.
Lastly, the team added a third ingredient, dibromo-dimethyl hydantoin (DBDMH), used industrially for drinking water purification and treatment and paper bleaching. DBDMH oxidizes and destroys CWAs, similar to the action of bleach, but without corroding critical equipment. Once the components were selected, the research team tested multiple ingredient ratios to establish important formulation variables to optimize decontamination.
Testing at RDECOM C&B Center’s Toxic Chamber Facility confirmed that the Sprayable Slurry can reduce the amount of CWAs on military relevant materials and complex surfaces by up to 1,000-fold. The decontamination process consists of applying the Sprayable Slurry onto surfaces less than 15 minutes after a contamination incident. Partitioning, adsorption and chemical reaction begin immediately and continue with as much time as the mission allows to react with and detoxify the CWA. The research team also showed an immediate reduction in vapor hazards after spraying, which minimizes operational risk and allows warfighters to continue their mission.
Sprayable Slurry has a paint-like consistency and military-relevant pigments. Thickening agents have also been added to improve the slurry appearance and adherence of the decontaminant to multiple surfaces. Once prepared, it has a storage life of almost one month, which allows premixing for near future chemical or biological incidents.
The research team at RDECOM C&B Center’s Toxic Chamber Facility completed live-agent laboratory efficacy testing on complex surfaces mock-ups containing grooves, screw threads and curved surfaces and areas such as a HUMVEE door. Warfighters also demonstrated the application for vehicle decontamination during hands-on, operationally-relevant training scenarios.
They demonstrated that application of the non-aqueous slurry can be done in a single step. Unlike current decontaminants, the slurry requires no application brush, no scrubbing or agitation, no rinsing, and does not significantly degrade test materials. Thus, it is logistically feasible and supports both immediate and operational decontamination by individuals, crews and unit teams.
Although CWA decontamination is the primary focus of the current testing, future tests at the Naval Surface Warfare Center Dahlgren Division will establish the effectiveness of Sprayable Slurry against biological agents, such as Bacillus anthracis spores. Additional programs, managed by Glenn Lawson, Ph.D., of DTRA CB, are in progress to identify and optimize the applicator used to apply the slurry.
As a result of this innovative chemistry, the Department of Defense is one step closer to providing the warfighter with a means to rapidly and effectively defend themselves against CWAs. Its use will greatly reduce the time and resources needed to restore combat power after a chemical or biological attack.
DTRA CB POC: Glenn Lawson, Ph.D.; glenn.e.lawson8.civ@mail.mil Performer POC: Kevin Morrissey, Ph.D.; kevin.m.morrissey.civ@mail.mil