Absorbable Organic Halide Reduction Research in Elemental Chlorine-Free Bleaching of Eucalyptus Kraft Pulp

The parameters of elemental chlorine-free (ECF) bleaching (D0EpD1) of eucalyptus kraft pulp were optimized to reduce AOX formation. The optimal conditions were pulp concentration 10%, ClO2 dosage 2.8%, pH 3.5, temperature 60°C, time 60 min at D0; H2O2 dosage 1.25%, alkali dosage 2.0%, temperature 65°C, time 105 min at Ep; ClO2 dosage 0.2%, pH 4.5, temperature 60°C, time 55 min at D1. AOX formation was 0.553 kg.tp–1, each stage was 0.470 kg.tp–1, 0.060 kg.tp–1 and 0.023 kg.tp–1, respectively. Compared with un-optimized AOX formation decreased by 23.7%.The brightness and viscosity was 84.36% ISO, 834.6 mL.g–1. In fact, good quality of the pulp was obtained when AOX formation has fallen dramatically. These provide a theoretical basis for reducing the produce of AOX and realizing the clean bleaching.