CHLORINE DIOXIDE BLEACHING OF PULP FROM CROP RESIDUES: BAGASSE, KASH AND CORN STALKS

This investigation describes the effect of hot chlorine dioxide delignification (D-HT) of bagasse, kash and corn stalk pulps on pulp properties and effluent quality. The pulps were subjected to D-HT at 85 degrees C for 45 min and the results were compared with those of the D-0 process carried out at 70 degrees C for 45 min. The kappa numbers after the alkaline extraction (Ep) stage in D-HT bleaching were always lower and brightness was higher, compared to the corresponding parameters in D-0 bleaching, without impacting pulp viscosity. The final brightness of the corn stalk pulp was 84.8% at a kappa factor of 0.25 in the D-0 process, while in the D-HT process, the same type of pulp reached the brightness of 87.2% at a kappa factor of 0.15, saving 40% ClO2 in the first stage. Similarly, kash pulp exhibited 90% brightness at a kappa factor of 0.15, which also saved 40% ClO2, compared to the conventional D-0 process. The brightness of bagasse pulp in D-HT and D-0 processes was almost similar. Oxygen delignified pulp had a lower effluent discharge than unbleached pulps in subsequent ECF bleaching. The COD value in D-HT was lower than that in D-0.