Polysaccharide degradation during ozone-based TCF bleaching of non-wood organosolv pulps

Carbohydrate behaviour of ASAM (alkali-sulfite-anthraquinone-methanol), Organocell (alkali-anthraquinone-methanol) and ethanol-alkali giant reed organosolv pulps during TCF (totally chlorine free) ZEP bleaching (Z-ozone stage; E-alkaline extraction; P-hydrogen peroxide stage) has been examined and compared with conventional kraft pulp. The moderate carbohydrate losses of 4.1–5.5% were noted, as a result of transition metals removal before ozonation and reduction of ozonated pulp before alkaline treatment. Xylan and cellulose (as the principal polysaccharides) were degraded respectively by 12% and 2.5%, without significant variation between different pulps. The drop in intrinsic viscosity of kraft pulp was more intensive in comparison with organosolv (21% versus 12–18%, respectively). The substantial loss of hexenuronic acids (by 58–76% for organosolv and 67% for kraft pulp) was observed during bleaching.