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Research Highlights

Nothing but green fields ahead
Cost-effective mercury treatment wins environmental award

Results:

Like little molecular sponges, SAMMS® particles can absorb more than half their weight in mercury, and can be chemically tailored to go after other heavy metals. Little wonder why SAMMS has been named Grand Award winner for Green Technologies in Popular Science's prestigious Best of What's New (BOWN) awards for 2009. SAMMS, developed by Pacific Northwest National Laboratory and licensed by Steward Advanced Materials, Inc., is now being used to solve global environmental challenges.

Why it matters:

Mercury pollution is widely recognized as a growing risk to both the environment and human health. "There are a number of places around the country where serious heavy metal contamination in soil and groundwater is a reality," said Glen Fryxell, the Pacific Northwest National Laboratory scientist who has led the development of SAMMS. "SAMMS provides a way to treat mercury in groundwater to make it usable for drinking water, agriculture and other uses that it simply could not be used for right now."

Methods:

SAMMS, short for self-assembled monolayers on mesoporous supports, is an ordinary- looking white powder that has been engineered to suck up mercury-one teaspoonful of SAMMS contains a surface area the size of a football field. SAMMS' design holds the key to its ability to selectively and cost-effectively remove heavy metals from waste streams. Made of silica molecules arranged into a pattern of holes, SAMMS resembles a honeycomb. The inside surfaces of the tiny, cylindrical holes are coated with sulfur- containing molecules. When a mercury-contaminated liquid passes through SAMMS particles, the mercury is bound by the sulfur, creating a powder stable enough for landfills.

The beauty of SAMMS's design is that only one end of the sulfur-containing molecule is anchored to the silica base, allowing the free end to bind heavy metals like mercury, cadmium or lead. These anchor molecules can be chemically tailored to sequester other heavy metals, such as arsenic, by using other types of binding sites on the free end of the molecule. SAMMS can also be designed to recover precious metals, such as gold, silver, platinum and palladium. In addition, SAMMS has been tailored to selectively capture a variety of radionuclides important to nuclear waste clean-up.

SAMMS has been used successfully to clean waste water in a range of settings, including contaminated mining operations, coal-fired power plants, chemical manufacturing, and offshore oil drilling. At commonly encountered mercury concentrations, a 40-pound load of SAMMS can absorb the mercury from about one million gallons of water.

What's next?

Scientists at Pacific Northwest National Laboratory are developing a pharmaceutical version of SAMMS that can be delivered orally to absorb radionuclides and heavy metals from the body. "Existing chelation therapies rely on the kidneys to excrete heavy metals, placing a severe burden on the kidneys," said Fryxell. "With the SAMMS approach, the insoluble silica particles pass through the intestines, placing zero burden on the kidneys."

Acknowledgements:

The initial development of SAMMS was funded through a variety of programs, including:

  • Department of Energy, Office of Biological & Environmental Research, Environmental Management Science Program (EMSP)
  • DOE, Environmental Management, Office of Science and Technology
  • Pacific Northwest National Laboratory's (PNNL) Laboratory Directed Research & Development (LDRD)
  • DOE, Office of Basic Energy Sciences

For more information on SAMMS, see the Steward Advanced Materials, Inc. Web site at www.sammsadsorbents.com. Also see PNNL's SAMMS's site at http://samms.pnl.gov.

PNNL-SA-69773

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