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sphere (where anthropogenic emissions are less important) the NO levels are likely to be somewhat less. Thus, reaction with NO is likely to be a major fate of the peroxy radicals generated from HFC-l34a, and so the products determined here are likely to be major products of the atmospheric oxidation of HFC-134a. To further delineate the atmospheric chemistry of HFC-l34a, additional research is needed to define the role of reactions 13 and 14 in the atmospheric oxidation of HFC-l34a, the fate of CF, radicals, and the aqueous phase chemistry of CF,COF, COF2, and HC(0)F.
Acknowledgments We thank Ole John Nielsen (Rim National Laboratory, Denmark) and Steve Japar (Ford Motor Co.) for helpful discussions. Registry No. CF3CFH2,811-97-2; CF,CHFO', 140872-97-5; 7782-44-7.
02,
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Received for review November 11,1991. Accepted February 25, 1992.
Degradation of Dibenzodioxin during Chlorine Dioxide Bleaching of Kraft Pulp Alison K. Daube, Mohammed R. Karlm, Donald R. Dlmmel, Thomas J. McDonough, and Sujlt BanerJee* Institute of Paper Science and Technology, 575 14th Street, NW, Atlanta, Georgia 30318
The degree of sorption of dibenzodioxin (DBD) to pulp varies with the lignin content of the latter. DBD is rapidly degraded by chlorine dioxide in aqueous solution but is much more stable in the presence of semibleached pulp, suggesting that sorbed DBD is far less reactive than the freely dissolved material. Degradation products include the 2-chloro derivative and products inextricably bound to pulp.
Introduction Chlorinated organic compounds are formed during the bleaching of pulp. The component that has been of greatest interest is 2,3,7,8-tetrachlorodibenzodioxin(TCDD). A potential sowce of TCDD is dibenzodioxin (DBD), which can enter the bleach plant as a contaminant in the brownstock pulp (1). The reactivity and pulp-water distribution of DBD and its derivatives under typical bleaching conditions are, therefore, essential to the understanding of TCDD formation. Furthermore, as a stable hydrophobic material, DBD serves as a model for other substrates that may undergo chlorination. We have studied the reactivity and distribution of DBD in pulpwater systems during chlorine dioxide bleaching, and in this paper we provide a broad overview of its fate. 1324
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Materials and Methods A loblolly pine Kraft pulp of K no. 40.6 (-6% lignin) and a bleached hardwood pulp of K number
