Superfund Research Program
The Brown University (BU) Superfund Research Program's (SRP) team of researchers, led by Dr. Robert Hurt, senior engineering student Natalie Johnson, and graduate student Love Sarin, discovered that a variant of a substance called nano-selenium can absorb most of the mercury emitted from broken and spent compact fluorescent lamps (CFLs).
The study grew out of Johnson's undergraduate award-winning poster displayed in the environmental section of the American Institute of Chemical Engineers, National Meeting at Salt Lake City in November 2007. The poster presented results of an SRP-funded, independent project titled, "The Characterization and Capture of Mercury Released from Broken Fluorescent Bulbs." Johnson's latest findings and research is now in press for publication, "Mercury Vapor Release from Broken Compact Fluorescent Lamps and In Situ Capture by New Nanomaterial Sorbents" (Environmental Science and Technology). Additional authors for this study include Hurt (corresponding author); Love Sarin, who helped author and lead in the development of the nano-selenium sorbent; and undergraduate student Shawn Manchester, and Senior Research Engineers, Indrek Kulaots, Ph.D., and Yuming Gao (laboratory co-authors).
Johnson and colleagues (Hurt Lab) tested vapor release and capture using nanoscale sorbents, including sulfur, selenium, copper, nickel, zinc, silver, and tungsten disulfide. The adsorption capacities of these elements and compounds varied over a range of more than seven orders of magnitude, from zinc micropowder to unstabilized nano-selenium, depending on sorbent chemistry and particle size.
After testing 28 substances of possible variants that might absorb mercury vapor(s), a form of amorphous nano-selenium (without the conventional protein coat) was found to be the most efficient and effective variant. 99% of mercury vapor from CFLs absorbed nano-selenium, with concentrations ranging from one to five milligrams (within a sealed chamber). The nano-selenium "just loves mercury and bonds to form stable mercury selenide nanoparticles,"comments Hurt.
From these results, i.e., the combined ingenuity of Brown's engineers, scientists, and associate professor of environmental studies, Steven Hamburg, the team is using the nano-selenium compound to create products for commercial use. Thus far, BU constructed two prototypes for incorporating the mercury-absorption properties into CFL products:
Mercury absorbent lining in store-bought CFL packages: this is a three-layered cloth attached to the inside package/box that holds the CFL. The coated nano-selenium layer is inside the package between cardboard and cloth; as a result, the compound is not exposed to users.
Plastic bags with mercury-absorbent linings: these linings would use the same layering method as described above (packages/boxes), but would be placed in small, sealed plastic bags that absorb mercury, and also prevent vapors from escaping.
There are currently federals patents pending for these new mercury-absorption packaging concepts, and the mercury absorbent material, uncoated nano-selenium. BU hopes to begin discussion with companies, in the near future, with regard to manufacturing both prototypes.
The projected market growth for energy efficient products, with the motivation to develop safe methods to manage mercury exposure and release, is on the rise. As a result, Hurt's lab continues to study methods to improve mercury vapor capture in various scenarios that arise during CFL shipping, retail, use, and recycle.
Clyde Briant, vice president for Brown University research, commented on the potential implications that these patents could have on Brown University and consumers: "these patents represent how Brown University translates fundamental research into an application that can have an impact on society, in this case, a technology that could protect households from mercury exposure and that could also energize green business growth."