Multistage Alkali Peroxide Bleaching in Low Kappa Kenaf Bast Pulp

摘要

Soda-anthraquinone kenaf bast pulps of 12.5 kappa number and about 32% ISO brightness has been bleached with different totally chlorine free (TCF) sequences (multistage peroxide) without and with activator (tetraacetylethylenediamine, TAED) to about 80% ISO brightness. Full bleached pulp production with high brightness and viscosity and also, of course, low chemical oxygen demand (COD) load and no adsorbable organic halogens (AOX) in bleaching effluent are the aims of this study. The effects of temperature, retention time, chemical charges, TAED/peroxide ratio and alkalinity have been studied in order to maximize the brightness gain at lowest viscosity loss. Hydrogen peroxide was activated as bleaching agent under milder conditions, such as low alkalinity or low temperature, by TAED activator. Therefore, TAED charge caused to an improvement in viscosity, pulp yield, bleaching duration and effluent COD load. Pre-treatment with EDTA in acidic condition for 30 min gave 2-4% gain in ISO brightness.