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

The amount of pollutants (AOX, chlorinated phenols, COD, color) genera ted during kraft pulp bleaching decreases with decreasing kappa factor , unbleached pulp kappa number, and increasing level of chlorine dioxi de substitution. At 100% chlorine dioxide substitution, the formation of polychlorinated phenolic compounds is at or below the detection lim it and essentially independent of the kappa number of the unbleached p ulp and, therefore, of the use of extended or oxygen delignification. In fact, oxygen delignification may actually increase the concentratio n of catechols and guaiacols and, therefore, the concentration of thei r chlorinated derivatives.