On the importance of radical species in TCF bleaching.
1995 (English)In: Proceedings 8th Int. Symp. Wood Pulp. Chem., 1995, 301-307 p.Conference paper (Refereed)
The present paper addresses the reasons behind the lack of selectivity in ozone bleaching of pulp. The main cause for this is concluded to be a superoxide mediated chain reaction forming hydroxyl radicals in the fiber. Therefore, a strategy to improve the selectivity must focus on possibilities to eliminate superoxide. This may be achieved with efficient superoxide scavengers, in themselves stable under ozone bleaching conditions, or by performing ozone bleaching in the absence of oxygen, which seems to be a realistic alternative. A preliminary study shows that phenolic compds. with α-carbonyl groups are particularly efficient in forming radicals in their reactions with ozone. Therefore, measures to remove α-carbonyl groups before the ozone stage may be expedient. The cellulose model Me-β-D-glucopyranoside does not produce radicals in its reactions with ozone. Thermo-labile structures are formed in the pulp as a result of ozone bleaching. This indicates that an ozone bleached pulp may undergo faster aging than pulp bleached conventionally. However, this can be prevented if the ozone bleached pulp is treated with alkali or acid sulfite.
Place, publisher, year, edition, pages
1995. 301-307 p.
Polymer Technologies Polymer Chemistry
IdentifiersURN: urn:nbn:se:kth:diva-79815OAI: oai:DiVA.org:kth-79815DiVA: diva2:497947
International Symposium on Wood and Pulping Chemistry, 8th, Helsinki, June 6-9, 1995 (1995), 1, 301-307
NR 201408052012-02-112012-02-092012-02-11Bibliographically approved