F.S. Chakar, A.J. Ragauskas
The Kismet of Residual During LMS Delignification of High-Kappa Kraft
Pulps
Summary
A series of laccase-mediator treatments (LMS) with 1-hydroxybenzotriazole (HBT) and N-acetyl-Nphenylhydroxylamine
(NHAA) (Fig. 1) as the mediators were performed on a laboratory prepared southern
softwood conventional kraft pulp (kappa # 75.4). Subsequent to the LMS treatments, the treated
pulps were subjected to various oxidatively reinforced alkaline extraction stages (E*). The kappa results
suggested that both LMSHBT and LMSNHAA treatments delignified this high-kappa pulp. The E* stages
were beneficial in countering the darkening effect observed after the LMS treatments. Structural changes
in residual lignins isolated before and after laccase-mediator (LMSNHAA (E*) and LMSHBT (E*)) treatments
were explored. The spectral analysis of phosphitylated residual lignins revealed an increase in carboxylic
acid content and a depletion of phenolic hydroxyl groups in non-condensed at C-5 lignin moieties.
Aliphatic hydroxyl groups were substantially decreased when NHAA was used. Overall, it appears
that LMSHBT and LMsNHAA treatments on high-kappa kraft pulps primarily attack phenolic hydroxyl
groups in non-condensed at C-5 lignin structures.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 10/2000
Pages: 647 - 653
Show full article (external site)
Show all available items of this journal
Search
