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White paper - with less dioxin.

White paper--with less dioxin

Last year's finding that chlorine bleaching of wood pulp generte some 250 different chlorinated contaminants, including the most toxic dioxin, sent paper mills scurrying to modify or redesign their bleaching operations (SN: 8/5/89, p.94). One new technology promises not only to reduce these toxic residues in pulp and its wastes by more than 90 percent, but also to cut costs and bleaching time, reports I.J. Wilk, a consulting chemist in Menlo Park, Calif.

His system passes an electric current through a saltwater bath containing 10 percent wood pulp. As the briny solution decomposes, oxygen, chlorine and ozone are generated at the positive electrode. Wilk observes that this "very potent" bleaching combo takes only 4 to 15 minutes to accomplish the same degree of whitening obtained after 1 hour or more with conventional pulp-bleaching mixes.

Moreover, in 15-minute test runs, his electrolytic system produced only 0.6 to 0.8 percent as much chlorinated organic pollution as conventional chlorine bleaching and only 8 percent as much as chlorine-dioxide bleaching. "By adjusting ozone levels, we think we might be able to totally eliminate any chlorinated [organic contaminants]," Wilk told SCIENCE NEWS. However, he adds, because the test data show that this system can also destroy chlorinated organic chemicals, any contaminants that do form might be purged by simply recycling the contaminated wastewater -- minus the pulp -- through the electrolytic cell. Though his team has not yet assayed for dioxin in the pulp and waste, Wilk says, "we don't expect to find any dioxin" because the process generates such a low overall level of chlorinated contaminants.

Last week the U.S. government added impetus to the search for cleaner pulp-bleaching techniques when EPA and FDA announced plans to formally regulate dioxin levels in pulp wastewater, sludges and possibly paper products. Said EPA Deputy Administrator Henry F. Habicht, "Even though dioxin levels in paper products are small enough to be no cause for alarm, our intention is to reduce those levels even more."
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Title Annotation:paper mills redesign their bleaching operations to produce fewer contaminants
Author:Raloff, Janet
Publication:Science News
Date:May 12, 1990
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