Structural evolution and reaction kinetics of lignin-carbohydrate complex oxidized by chlorine dioxide.

[Display omitted] • The reaction mechanism of ClO 2 oxidizing LCC was elucidated. • The degree of LCC degradation depends on the type of lignin structural units. • A reaction kinetic model of ClO 2 oxidation of LCC was established. • Provides a clear structure for the LCC present in pulp after ClO 2 oxidation. Lignin-carbohydrate complexes (LCC) present a significant barrier to pulp purification, and their oxidation mechanisms remain unclear. In this study, chlorine dioxide (ClO 2), a common oxidant in the paper industry, was used to treat LCCs from various plant sources. The chemical composition, structural changes, and reaction kinetics of LCC were analyzed. After ClO 2 oxidation, the LC bonds connected to syringyl (S)-type lignin structural unit and FA/ p CA structures in LCC were effectively degraded, whereas those connected to guaiacyl (G) and p -hydroxyphenyl propane (H)-type units remained stable. Kinetic studies revealed that under conventional oxidation conditions, the degradation rates of LCCs from bagasse, bamboo, and eucalyptus were 0.40, 1.12, and 1.75, respectively, with consumption amounts of 6.23 mg, 10.92 mg, and 15.48 mg. The differences in the degree of LCC oxidative degradation were determined by the composition of lignin structural units. The findings provide theoretical support for the action mechanism of ClO 2 on LCCs during the pulp purification process, and offer important guidance for optimizing the pulp purification process. [ABSTRACT FROM AUTHOR]