Arundo donax L. reed: New perspectives for pulping and bleaching. 5. Ozone-based TCF bleaching of organosolv pulps

摘要

Three selected alkali-based organosolv pulps (alkali-sulWte-anthraquinone-methanol (ASAM), alkali-anthraquinone-methanol(organocell) and ethanol-soda) from agroWbre crop giant reed (Arundo donax L.) were bleached by an ozone-based TCF (totally chlorinefree)bleaching sequence AZERQP (where A is an acidic pulp pre-treatment, Z is an ozone stage, (ER) is an alkaline extraction in thepresence of reducing agent, Q is a pulp chelating, P is a hydrogen peroxide stage) without oxygen pre-bleaching, and compared with aconventional kraft pulp used as a reference. The diVerent response on bleaching conditions within each bleaching stage was noted for alltested pulps. The pulp bleachability, in terms of brightness improvement or lignin removal per unit of applied chemicals, was foundhigher for the organocell pulp. The ASAM and ethanol-soda pulps showed the highest bleaching selectivity, expressed by viscosity lossper unit of lignin removed or brightness improved. The overall bleaching results of organosolv pulps were superior to kraft.