| In this paper, bamboo pulps were bleached with the sequence of oxygen deligninfication (O), laccase and natural mediator system bleaching (LMS), chelating treatment (Q) and hydrogen peroxide bleaching (P). Then, the residual lignins in the TCF bleached pulp were characterized by using GPC, TGA, FT-IR, 1H-NMR, and 13C-NMR, in order to study the bleaching mechanism, especially the mechanism of LMS bleaching. The GPC studies showed that the molecular weight of lignin decreased with the bleaching process, while Mw/Mn changed remarkably. The TGA studies showed that the thermal stability of lignin decreased in the bleaching process; The FT-IR, 1H-NMR, 13C-NMR studies showed that the lignin type of the bamboo pulp was GSH, the percentage of G unit was higher than that of (S+H), β-O-4′, β-1′ and β-5′were the linkages of C9, and the main linkage was β-O-4′; There are alphatic OH and aromatic OH in the bamboo lignin; The —OCH3 was removed, benzene was broken, and the percentage of alphatic OH inceased in bleaching; After LMS stage, the percentage of S increased, the percentage of H decreased and the percentage of β-1′ linkage increased. |
