THE CHEMISTRY OF OZONE DURING PULP BLEACHING

Using competition kinetics in the presence of various OH . radical sca vengers, viscosity losses in ozonized pulp were shown to be caused by the cellulose reacting with both OH . radicals and ozone. The source o f the OH . radicals was concluded to be the reaction between ozone. an d lignin, where OH formation was similar to 0.5-3%. In the presence of ozone and oxygen, a chain reaction occurs in which OH ., O-2(-)., and cellulose-based radicals all function as chain carriers. At kappa num bers >2, the cellulose was degraded almost exclusively by OH . radical s. At the final kappa number of 2, similar to 50% of the viscosity los s was from direct attack of ozone on the cellulose.