Partial replacement of chlorine dioxide with ozone in prebleaching of Acacia mangium kraft pulp

The main objective of this study was to investigate the outcomes from the combined use of chlorine dioxide and ozone in the prebleaching of Acacia mangium kraft pulps. Oxygen delignified acacia pulps with two different kappa numbers, ca 12 and 8, were used. In the combined use of chlorine dioxide and ozone, (DZ) mode of application was evaluated at 15-100% replacements of chlorine dioxide with ozone in terms of oxidation equivalent. In this mode of application, 40% replacement gave the best result in terms of kappa reduction, hexenuronic acid removal and brightness gain. At 40% replacement the bleaching sequence (DZ)EopD(1) gave very similar result as reference sequence D(0)EopD(1). Brightening with (PO) instead of D(1) in the final stage produced pulp with higher brightness stability, but inferior strength properties.