FORMATION OF POLYCHLORINATED PHENOLIC-COMPOUNDS DURING HIGH CHLORINE DIOXIDE SUBSTITUTION BLEACHING .1. LABORATORY INVESTIGATION

The amount of pollutants (AOX, chlorinated phenols, COD, color) generated during kraft pulp bleaching decreases with decreasing kappa factor, unbleached pulp kappa number, and increasing level of chlorine dioxide substitution. At 100% chlorine dioxide substitution, the formation of polychlorinated phenolic compounds is at or below the detection limit and essentially independent of the kappa number of the unbleached pulp and, therefore, of the use of extended or oxygen delignification. In fact, oxygen delignification may actually increase the concentration of catechols and guaiacols and, therefore, the concentration of their chlorinated derivatives.