Research Offers Promising Solution To Worsening Mercury Pollution

August 20, 2003

GAINESVILLE, Fla. — Efforts to reduce mercury pollution from coal-fired power plants and other industrial sources may benefit from a new approach to removing the deadly metal — pioneered as part of research for the space program.

A team of environmental engineers at the University of Florida has found a way to use ultraviolet light and silica to sponge mercury from smokestack emissions. Developed as part of a NASA-sponsored project to engineer a better way to treat and reuse water aboard the International Space Station, the process is potentially more efficient and less costly than the current technology, which relies on activated carbon.

“The system we developed for the space station was working well, so we started to question if it would serve other applications,” said David Mazyck, an assistant professor of environmental engineering. “That’s when we discovered the application for mercury.”

Mazyck and two UF colleagues have authored a paper on their innovation, which has been accepted for publication in the Journal of Nanoparticle Research. A publication date is not yet set.

The development comes at a time of increasing public concern about mercury pollution. Released into the atmosphere by volcanoes, forest fires, coal combustion and other sources, the metal settles in lakes and rivers, where it accumulates in fish. As a result of the contamination, the Food and Drug Administration and states including Florida warn consumers against eating certain species of fish and urge limited consumption of others. The FDA plans to meet in September to consider revising its standards, which some environmental and health groups believe are insufficient.

The nation’s 1,140 coal-fired power plants, among the biggest mercury polluters, are expected to release as much as 60 tons a year of the toxic metal by 2010 unless more stringent regulations restrict their emissions. Those regulations currently are being developed by the Environmental Protection Agency, which expects to begin implementing them in 2007, Mazyck said. President Bush’s Clear Sky Initiative seeks to cut annual emissions to 28 tons by 2008, according to the initiative. Environmental advocates would like to see that number reduced further.

Mazyck said all coal contains small amounts of mercury, which is released when the coal is burned. The best existing technology to remove the mercury revolves around injecting tiny particles of activated carbon, an absorbent material used in a wide range of pollution filters, into the smokestack.

The process has several drawbacks, Mazyck said. One is that it requires 3 kilograms of activated carbon, or roughly 6.6 pounds, to capture each gram, or .03 ounces, of mercury. That means thousands of tons, costing an estimated $2 billion to $5 billion annually, would be needed to clean emissions for all power plants, straining current manufacturing limits and industry economics, Mazyck said. Not only that, the process contaminates a coal combustion byproduct called fly ash, used in concrete and wallboard. The result: Power companies could not continue to sell the ash, cutting into their profits.

Three years ago, Mazyck and Chang-Yu Wu, an assistant professor of environmental engineering, received a grant from NASA to develop technology to treat and reuse water aboard the International Space Station (the project also received support from the Environmental Protection Agency). NASA wanted the technology so it could combine it with existing hardware to regenerate water for consumption in space, which would reduce or eliminate the need for resupply from Earth.

The technology relies on silica particles implanted with a photocatalyst, a chemical that reacts with ultraviolet light. When the light shines on the catalyst, it causes a chemical reaction that produces molecules called hydroxyl radicals. These molecules “clean” the water and regenerate the silica. That allows reuse of the silica to remove more toxins, which can be used again several more times.

Tests of a small, experimental mercury control system show the technology also works to cut mercury pollution in airborne emissions, Mazyck said. The tests have revealed that silica adsorbs 10 times more mercury than activated carbon. Mazyck and Wu have teamed up with Kevin Powers, associate director of UF’s Particle Engineering Research Center, to further tweak the particles to push the capacity even further.

Mazyck said the process has a number of potential benefits. Although the silica produced by the current laboratory method costs more than activated carbon, far less is needed to perform the same job. The silica can be reused, further lowering the cost. Furthermore, the mercury cleansed from the silica during regeneration can be recycled for use in products such as fluorescent light bulbs. Last but not least, power companies could continue to sell the fly ash byproduct of the combustion process to generate revenue.

Mazyck, Powers, and Wu have a patent pending on the process and are continuing to experiment on ways to understand the science and to further enhance the performance. As part of that effort, a Maryland-based company, Microenergy Systems, has begun building a larger prototype of the system to gauge its effectiveness at the industrial scale.

“If it works, the potential is extraordinary because of the problems associated with making cheap activated carbon,” said Rich Sheahan, vice president of Microenergy Systems.

The UF researchers have formed a company, Sol-gel Power Technologies, to develop the technology.