Chlorine dioxide bleaching of nineteen non-wood plant pulps

Abstract

Abstract Bleaching of unbleached and oxygen delignified pulps from nineteen non-wood plants has been evaluated in elemental chlorine free bleaching. Chlorine dioxide charge (kappa factor 0.15, 0.20 and 0.25) and temperature (70 and 85 °C) in the delignification stage (D) were varied. Chlorine dioxide (ClO2) charge and temperature exhibited lower kappa number and higher brightness after alkaline extraction (EP) stage. High temperature ClO2 delignification (DHT) exhibited higher final pulp brightness. The final brightness of wheat straw pulp reached to 90 % after D0/DHT(EP)D1 bleaching, while banana pseudo stem pulp showed the worst bleachability. Residual hexeneuronic acid contents in final pulp from most of the non-wood plants were lower and exhibited 1–2 % higher pulp brightness in DHT process than D0 process. Oxygen delignified pulp and DHT process discharged lower COD load.