INFLUENCE OF LIGNINS ON THE DEGRADATION OF CELLULOSE DURING OZONE TREATMENT

Three lignin-carbohydrate model systems were studied to determine the mechanism of the effect of lignin on cellulose degradation during ozon e bleaching. The three model systems are: methyl a-D-glucopyranoside d extran and fully-bleached kraft pulps in the presence of various ligni n model compounds. It was found that the lignin models can both promot e and suppress the degradation of the carbohydrate during ozone treatm ent. The presence of the lignin models can exhibit a protective effect by competing with the carbohydrates for the ozone available in the sy stem. On the other hand, the ozone-lignin reactions give rise to the f ormation of hydroxyl radicals which promote the carbohydrate degradati on. It is suggested that much more hydroxyl radicals are formed via th e ozone-lignin reaction route than via ozone self-decomposition. Among the lignin model compounds studied, the phenolic lignin structures ha ve a more pronounced effect on carbohydrate degradation. This is expla ined by the easier formation of hydroxyl radicals from phenolic lignin models than from non-phenolic models.