Use of chlorine dioxide and ozone in combination in prebleaching

• (DZ)Eo prebleaching of oxygen-delignified softwood kraft pulp gave a synergistic delignification effect compared to the effect of chlorine dioxide and ozone Separately, and the (DZ)Eo process was somewhat better than (ZD)Eo prebleaching in terms of delignification. The solubilization of the lignin in chlorine dioxide and ozone bleaching seems to be governed by the large number of carboxyl groups introduced into the lignin structure. The efficient delignification obtained in (DZ)Eo prebleaching may be explained by the ability of chlorine dioxide and ozone to degrade different Apes of lignin structures. Whereas chlorine dioxide mainly degrades phenolic lignin structures, ozone is capable of degrading both phenolic and non-phenolic lignin structures. The (DZ) treatment initially allows chlorine dioxide to degrade the phenolic lignin structures, and leaves the non-phenolic and less reactive lignin structures for the ozone treatment.

Nyckelord

pretreatment

kraft pulps

softwood pulps

oxygen

delignification

bleached pulps

chlorine dioxide

ozone

performance evaluation

phenolic hydroxyl-groups

hexeneuronic acid groups

residual lignin

bleaching sequence

structural-changes

kraft cooking

wood

pulp

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)