<< Back

Materials capable of filtering mercury from wastewater are under development at Pacific Northwest National Lab (PNNL) in Richland, Wash. Within a year or two, say PNNL scientists, such materials will be capable of filtering mercury not just from wastewater, but directly from a coal-burning power plant's flue gases as the gases go up the stack.

Mercury emissions from coal-fired power plants contribute some 48 tons of mercury to the environment every year, accounting for more than one-third of the total human-caused mercury emissions in the U.S. per year. The recent developments at PNNL have potential to help reduce coal-fired plant emissions significantly.

Led by chemist and project manager Shas Mattigod, PNNL scientists have developed a synthetic material that can be tailored to filter mercury or other toxins out of wastewater by essentially locking it up within tiny pores in a special type of ceramic. The ceramic, which the researchers have likened to a honeycomb, is specially coated with a material that attracts the contaminant. Mattigod explains that two tablespoons of the material has an internal surface area equal to that of a football field.

Called SAMMS, for Self-Assembled Monolayers on Mesoporous Supports, the material has pores so small that only the contaminant ions can get in; this means that once they are in, they do not leach out. Within a year or two, Mattigod expects that a similar material capable of absorbing mercury directly from the flue gases in a smokestack will be ready for testing.

The new materials are expected to augment existing technologies for filtering mercury and particulates at power plants. Such technologies include carbon-injected filters, scrubbers on the insides of flues, and fabric screens that trap particles from escaping.

The diagram shows how a porous ceramic material developed at the Pacific Northwest National Laboratory latches on to a toxic metal molecule (top right) in order to capture it. Image: PNNL