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New foam tames an asbestos.

Ever since the carcinogenicity of asbestos came to light, regulators have been pushing building owners to rid their structures of the mineral or to seal it in place so that it cannot escape. Yet removing or treating asbestos, a material widely used from at least the 1940s through the 1960s for fireproofing and thermal insulation, can release mineral fibers into the air, creating a carcinogenic dust.

Now, chemists from W.R. Grace & Co. of Boca Raton, Fla., and the Energy Department's Brookhaven National Laboratory (BNL) in Upton, N.Y., have developed a chemical foam that lets building owners treat asbestos-containing fireproofing material without removing it. As the foam seeps into the fireproofing, it initiates chemical reactions that "digest" any asbestos, say Grace and BNL scientists. Within 24 hours, more than 99 percent of the fibers present undergo a transformation that makes them less toxic by altering their chemistry and their shape, notes BNL chemist Leon Petrakis.

Almost all of the asbestos used for fireproofing is chrysotile. Its fibers have a hollow, "jelly-roll' structure" of chemically bound sheets of magnesium oxide and silicon oxide, explains foam project manager David F. Myers, a chemical engineer in Grace's Cambridge, Mass., office.

"Because of the differences in the atomic radii of silicon and magnesium, when the sheets fall one atop the other they grow into a hollow tube," Petrakis says.

The foam contains both an acid, which attacks the magnesium oxide, and a tiny amount of fluoride ions. Together, they "synergistically unbind the sheets and selectively remove some [positively charged materials]," Petrakis explains. "What remains is a hard material--globs of minerals bound together."

In animal tests, the treated material proved nontoxic. In fire tests, it retained its ability to protect metal structures used in buildings.

Seven patents on the foam are pending, and Grace hopes to begin marketing it in the next few months. Meanwhile, Petrakis' team continues to work on adapting the technology for other types of asbestos and applications, such as thermal insulation.
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Title Annotation:chemical foam treats asbestos-containing fireproofing materials
Author:Raloff, Janet
Publication:Science News
Article Type:Brief Article
Date:Jan 3, 1998
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