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Engineer Explores Pollution-fighting Ceramic Materials

Professor Marc Anderson with photocatalytic reactor

A research associate prepares a photocatalytic reactor for operation. The reactor's UV light source photoactivates semi-conducting particles contained in the ceramic membrane, generating electron-hole pairs which can be used for reduction and oxidation work. The reactor is designed to degrade organic microcontaminants such as PCBs and trichloroethylene. It can also be used for inorganics such as chromate ions, a waste product generated by the metal plating industry. In a slightly different configuration, it also could be used for gas phase degradation. (large image)

Ceramic brings to mind the simple stuff of plates and pottery, yet it may work wonders in the complex world of environmental cleanup, from filtering pollution to degrading hazardous chemicals.

A University of Wisconsin-Madison research effort led by Professor Marc A. Anderson, civil and environmental engineering, has produced a multitude of environmental products using microporous ceramic materials. The "porous" nature of these materials would make for flawed pottery, but excels as a tool for filtering water and air, whether it be at an industrial plant or in the home.

"These materials have a lot of advantages over conventional technology," says Anderson, who discussed the environmental uses of his work during the recent American Chemical Society national meeting.

"Since they perform at low temperatures, they are feasible for use in homes and office buildings," he says. "Cleaning indoor air is really where the action is, since these materials can remove extremely fine particles."

Microporous ceramics are actually composites of tiny metal oxide particles, such as alumina or titania, that are held together in a suspension. By packing them together in a controlled manner, researchers can create materials with high surface area and microscopic pores that can trap elusive traces of pollution.

Ceramic membrane and supports

The unsupported ceramic membrane, top, is too fragile to be used on its own. Also shown are examples of supporting vehicles which yield applications including catalysis, batteries, and sensors. (large image)

In 1990, Anderson was the first academic researcher to receive federal funding to explore the basic properties of ceramic oxides, which had previously received limited interest in industry. Since then, Anderson and colleagues have generated more than 20 patents on applications for the materials.

Anderson says his latest patents may be the most commercially promising. They involve the use of high-performance porous oxides for breaking down volatile organic compounds, such as benzene, formaldehyde and industrial solvents. They work as photocatalysts, gaining their power to neutralize chemicals after being exposed to ultraviolet light. Their lab improved on existing technology by creating hybrids of different metals.

Anderson says these thin films also can be used in treating contaminated waste water and soils, and reducing air pollution in high-risk areas such as printing rooms and dry cleaning shops. His lab also has developed a prototype air filtration device for office buildings, using low-temperature photocatalysis. The device is made to fit in normal air ducts.

That line of research emerged two years ago, through a collaboration between Anderson and a UW-Madison researchers growing plants aboard the NASA space shuttle. Anderson developed an air filtering device for the plant growth chambers that removed ethylene, the chemical which triggers rotting in plants.

From that project, Anderson developed a commercial cooperative called PhotoKleen, which is working to develop devices that can reduce spoilage of produce in the shipping industry and refrigeration rooms.

The research group also has an energy program, looking at developing capacitors that can store 100 times more energy than current devices. Yet another project aims at developing extremely small, high-powered batteries for use in medical devices, micromachines, computer memories and space exploration vehicles.

In the realm of environmental cleanup, Anderson says these materials are not a cure-all, but do offer a durable, inexpensive and more palatable alternative than incineration for getting the job done.

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