Chemical characteristics and stability of eucalyptus kraft pulps bleached with tertiary amine catalyzed hypochlorous acid

Ghazaleh Afsahi*, Tatu Rojalin, Tapani Vuorinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

We recently found that subsequent treatments of hardwood kraft pulps with a tertiary amine (DABCO; 1,4-diazabicyclo[2.2.2]octane) catalyzed hypochlorous acid (Hcat), ozone (Z) and hydrogen peroxide (P) may provide full brightness with low chemical dosages in a short overall reaction time. Here we report chemical characteristics and stability of Hcat–Z–P bleached eucalyptus kraft pulps. In comparison with a normal ECF (elementary chlorine free) bleached pulp the Hcat–Z–P bleached pulps had low carbonyl group content while the degree of polymerization of cellulose remained at high level. However, the brightness of the Hcat–Z–P bleached pulps was reversed more easily under humid ageing conditions in comparison with the ECF bleached pulp. The discoloration was accompanied by an increase in Raman emission at 1560 cm−1 which is indicative of formation of highly conjugated chromophores. The brightness reversion did not correlate with the carbonyl content that is often considered to be the main origin of the brightness loss under humid conditions. In contrast, the brightness instability of the catalytically bleached pulps possibly resulted from the relatively high organochlorine content.

Original languageEnglish
Pages (from-to)2047-2054
JournalCellulose
Volume26
Issue number3
DOIs
Publication statusPublished - 15 Feb 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • Brightness reversion
  • Carbonyl content
  • Catalytic bleaching
  • Degree of polymerization
  • Organochlorine content

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