New Insights into Lignin Modification During Chlorine Dioxide Bleaching Sequences (II): Modifications in Extraction (E) and Chlorine Dioxide Bleaching (D1)

• Published in: Journal of wood chemistry and technology 2005-01, Vol.24 (3), p.221-237
• Main Authors: Brogdon, Brian N., Mancosky, Douglas G., Lucia, Lucian A.
• Format: Article
• Language: English
• Subjects: Alkali reactions; Applied sciences; Bleaching; Chlorine dioxide delignification; Exact sciences and technology; Extraction; Kappa number; Klason lignin; Kraft pulps; Lignin and derivatives; Lignin modification; Muconic acids; Natural polymers; Paper, paperboard, non wovens; Phenolics; Physicochemistry of polymers; Polymer industry, paints, wood; Pulp manufacturing; Quinones; Wood. Paper. Non wovens
• ISSN: 0277-3813; 1532-2319
• DOI: 10.1081/WCT-200038087

Previously, it was shown that chlorine dioxide delignification (D 0 ) modifies kraft residual lignin by oxidizing phenolic groups to both quinonoid and muconic structures in ∼2-to-1 ratio (1.7 mmol/g lignin vs. 0.8 mmol/g lignin), respectively. Alkali extraction (E), in addition to removing solubilized lignin and saponifing muconic acid methyl esters, re-activates the residual D 0 lignin towards ClO 2 oxidation by converting quinones to polyphenols. This action of alkali on D 0 oxidized lignin is analogous to that of hydrosulfite reduction (Y). Chlorine dioxide oxidation of D 0 E and D 0 Y treated pulps generally afforded ∼1.7 mmol quinones/g lignin onto the oxidized lignin, like that of the D 0 stage. This study clearly indicates that quinones formed during the D 0 stage can be easily re-activated toward ClO 2 oxidation in a D 1 by alkali treatment, such as an E stage. # Dedicated to Drs. Donald R. Dimmel and Thomas J. McDonough on their retirement from the Institute of Paper Science and Technology.