Protection of Cellulose During Ozone Bleaching, 1992 Pulping Conference Proceedings
During ozone bleaching some cellulose degradation takes place. One key development of ozone bleaching is to prevent cellulose from degradation.
At low consistency ozonation, it was found that a pretreatment with EDTA at high temperature (90^0C) enhanced the rate of delignification dramatically without any adverse effect on cellulose. As a consequence selectivity, measured as loss in DP versus kappa number drop, was improved. Addition of oxalic acid alone or in combination with the EDTA pretreatment did not bring any improvement.
At high consistency, the situation was different. Both EDTA pretreatment and addition of oxalic acid improved selectivity mainly because of a lesser degradation of cellulose. The content in metal ions was measured after each of these experiments. It appeared that the improvement of selectivity can be explained by the decrease in metal ions.
Protection of Cellulose During Ozone Bleaching, 1992 Pulping Conference Proceedings
