THE EFFECT OF ALUMINUM ON THE 2-STAGE PEROXIDE BLEACHING OF EUCALYPTUS-REGNANS STONE GROUNDWOOD PULP

The addition of aluminum nitrate (up to 100 ppm Al on pulp) to a two-s tage acid/alkali, hydrogen peroxide bleach of Eucalyptus regnans stone groundwood pulp enhanced the brightness gain of the pulp, over a rang e of consistencies. It is proposed that the presence of aluminum ions modifies the catalytic behaviour of the transition metal ions present in the pulp, especially manganese, reducing peroxide consumption while increasing the brightness of the pulp. The two-stage process, under o ptimized conditions at low consistency, consumes considerably less per oxide while achieving a greater brightness increase than a single-stag e alkaline peroxide bleach.