Nanofiber Filters Eliminate Contaminants
- Sunday, 01 November 2009
Originating Technology/NASA Contribution
Water, an increasingly precious commodity on Earth, has always been priceless in space; but “priceless” is a figure of speech—water in space does have a price, and it is an expensive one. A single gallon of water costs over $83,000 to launch just into low-Earth orbit. Despite recent NASA innovations that allow astronauts to derive potable water from their own sweat and urine and technologies that may one day extract water from buried glaciers on Mars, the availability of water in space is not likely to exceed its necessity. This means methods for recycling and purifying water remain a top concern for the Space Program.
NASA’s Johnson Space Center awarded Argonide Corporation, a nanomaterials company, headquartered in Sanford, Florida, a Phase I Small Business Innovation Research (SBIR) contract in 2000 and a Phase II SBIR contract in 2002. Argonide had developed unique filtration media with the potential to revolutionize water purification and provide methods for sanitizing recycled water in space. Working toward a basic tool for water recirculation during long-term space flight, Argonide used its Phase I research to build on its proprietary technology, initially developing laboratory filter discs and syringes. During Phase II, it researched and tested the nanofiber media’s virus filtration properties and its ability to absorb DNA and RNA. Argonide also developed NanoCeram cartridges providing superior purification for drinking water applications. The NanoCeram water filter was an R&D Magazine “R&D 100” award-winning technology in 2002 and was inducted into the Space Foundation’s Space Technology Hall of Fame in 2005.
The special ingredients of Argonide’s nonwoven filtration media are nanoalumina fibers made up of the mineral boehmite. The NanoCeram fibers—each 2 nanometers in diameter and 200–300 nanometers in length (for comparison, a sheet of paper is roughly 100,000 nanometers thick)—are attached to microglass strands. The result looks like nanosize mascara brushes. With a surface area of as much as 500 square meters per gram, the fibers produce an electropositive charge when water flows through them. Many impurities carry a slight negative charge and are thus absorbed by the nanoalumina. A single layer of the resulting media, though it has a pore size of about 2 microns, is capable of removing greater than 99.99 percent of 0.025 micron particles, thanks to this property. (Three layers remove up to 99.9999 percent.) Some of the many impurities the filter media remove are bacteria, viruses, cysts, organic debris, parasites, and dissolved and particulate metals such as iron and lead. Its large pore size relative to the particles it eliminates means the filter achieves the grail of filtration media: high flow with high dirt-holding capacity and low pressure drop.
“Our NASA-funded research provided us with information, know-how, and techniques that enabled us to develop our current technology,” says Fred Tepper, Argonide’s founder and president.