Comparison on performance of different Kappa number wheat straw pulps under ozone-TCF bleaching

Under different cooking conditions a variety of wheat straw pulps G-1, G-2, G-3 and L-1, by Kappa number of 29.0, 18.6, 14.0 and 7.8 respectively, were prepared with the removal of metal ions from the slurry to eliminate the consequential effect to the ozone bleaching by acidic and chelant pre-treatments. Results showed high Kappa number was inclined to result in poor delignification selectivity and low pulp brightness. However in case of L-1, the one-stage ozone bleaching reduced Kappa number about 70% with the viscosity still maintaining 1123 mL/g. Meanwhile a comparison of xylose changeover was carried out on the four pulps of various different Kappa numbers, revealing more hemicelluloses kept in L-I protected the cellulose to some extent during the ozone bleaching, the experimental findings implied low Kappa numbers played an extremely important role in realizing the TCF bleaching.