WASHINGTON, DC, May 8, 2014 (ENS) – The U.S. military wants its members to wear clothing made of fabric that can filter out toxins and then decontaminate itself. Dr. Brandy White, a chemist at the U.S. Naval Research Laboratory Center for Biomolecular Science and Engineering, is meeting that need with self-decontaminating clothing for the combat environment.
In her lab, Dr. White is designing materials that capture entire classes of contaminants and break them down into harmless substances such as water and carbon dioxide.
“Today’s filters are carbon – like in your water pitcher at home, or in military suits and gas masks. Carbon is great at capturing and holding contaminants, but they’re still there. You still can’t take that suit and go to a populated place,” says Dr. White. “The fabrics that we’re talking about with my coating, they grab it and they hold it in just like carbon would, but then they convert it into something else.”
White has made these chemical materials into useful formats in addition to clothing – a powder that goes into gas masks and a surface coating for windows or electronics.
The materials become “covalently part of the fabric; not just a coating on the fabric,” she says.
By dipping fabric through different sorbents, layering different fabrics, or mixing multiple powders, White can screen for and break down multiple classes of toxins.
White’s materials are specific to classes of toxins. If she designs a material that binds organophosphonate pesticides, it will also bind the nerve agents sarin and VX and all compounds with a similar chemical structure.
She has made materials that bind to blister agents such as mustard gas, and others that bind to explosives like TNT.
She has also made materials for toxic industrial chemical and toxic industrial material targets, as listed by the Department of Defense Chemical and Biological Defense Program TIC/TIM Task Force and listed for first responders by the National Institute of Standards and Technology.
These materials can solve problems common in the combat environment.
White gives an example. As U.S. Marines moved in on Baghdad in 2003, they were wearing hot, unbreathable, full-body suits day and night. When they were finally able to take off their Mission Oriented Protective Posture, MOPP, gear. “You can imagine how it felt to have air circulation for the first time in weeks, and then you can just imagine the smell,” she said.
“If they’ve actually been exposed to something, then putting on their MOPP gear no longer protects them, they’re just trapping it all inside. So the idea behind this type of fabric was it could be used to give them time to get their MOPP gear on,” she said.
White’s research also complements efforts by the Defense Threat Reduction Agency to think beyond clothing to uses such as protecting heating, ventilation and air conditioning systems in buildings from the intrusion of toxins.
“If you think about air filters,” she says, “like for your HVAC system at home, you have those pleated things. That’s a fabric.” Air purification material could be placed in the ductwork of buildings. With filters to break down airborne toxins at every air intake, terrorists could not expose an entire building to toxics.
Industry could use such filters to reduce ammonia smells in hospitals or improve air quality around industrial processes. “It could be on stack gases for exhaust from industrial processes,” says White.
She has already proven, with perchlorate, that she could help industry and federal agencies monitor and clean up water pollutants.
The applications for the combat environment are so promising, in part because White’s material is washable and stable in extreme conditions whether they are dry or in water.
“You can capture the organics out of your waste stream and make your water safe,” adding, “I know that you can stick them out in a July sun at 100 degrees for a week and nothing about their performance characteristics changes. As far as I can tell, the materials are identical to when I stuck them out there.”
Because her materials break down toxic targets naturally, they do not become saturated and have to be discarded.
Chemically, White has designed a sorbent structure with porphyrin photocatalysts.
She starts with an organosilica sorbent, which has an organized, porous structure. “That means that they have solid parts and they have open air parts,” she says.
“The solid parts give you binding affinity. The open pores give lots of surface area, which means lots of binding sites.”
With colleague Brian Melde, she designs specific pockets or imprints for each target toxin into the skeleton-like structure.
To make the structure even better at capturing her target, she adds specific precursors to the sorbent. “The precursor gives you the chemical affinity that you’re looking for. So that might be a benzene group or it might be an ethane group or some mixtures of those things.”
With a process she has patented, White couples a porphyrin into the organosilica structure. “The sorbent part captures the material and pulls it in close to where we’ve immobilized the porphyrins within the material,” she says, “and the porphyrin takes light and converts the molecule into something that’s less toxic.”
“Porphyrins are all of a basic shape that’s very similar,” she says. “The porphyrins absorb light, then transfer energy to the target to break it down.
Choosing from the library of commercially available porphyrins she keeps in the lab, “I can screen 96 porphyrin variants at a time to look for affinity for the targets that I’m interested in.” Adding a coordinated metal further increases reactivity.
Without light, the system will eventually stop. But passing even a low voltage current through the materials restarts catalysis. “We’re only using 9 volt batteries,” she said.
White is working with another group at the Naval Research Lab on a portable sensor, about the size of a soda can, that quantitatively measure concentrations of a target substance.
White explains that these sensors will communicate via Wi-Fi so the perimeter of a toxin’s location and extent can be monitored.
Recently, White began a project to purify biodiesel.
“There’s been a big push recently within the Navy to switch to alternative fuels,” she says. The Navy and Marine Corps already run ships and jets on biofuel blends. But part of the expense of biofuel is due to the purification process.
White has shown she can capture nitroenergetics from water. Her idea is to do something similar to purify biodiesel by designing sorbents to capture substances out of the slurry that impact stability and cold weather performance.
Her concept would be more efficient that those currently used, and reduce waste water associated with the washing process.
By the time the project’s funding has run out in three years, White says she hopes to demonstrate that she can take unprocessed biodiesel and capture impurities so that it will pass the American Society for Testing and Materials standard.
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