Formation Characteristics of Chloroorganics from Hardwood Kraft Pulp during Chlorine Bleaching

Abstract

By chlorine treatment, residual lignin in hardwood kraft pulp became soluble in water more easily than that in softwood kraft pulp. Majority of adsorbable organic halide (AOX) and about half of total organic carbon (TOC) produced by chlorine treatment of hardwood kraft pulp was found to be present in a chlorination stage (C-stage) effluent rather than in an alkali extraction stage (E-stage) one, which makes a contrast to the significance of E-stage effluent of softwood kraft pulp. By oxygen treatment, a part of residual lignin in kraft pulp is converted to a part which is very reactive to chlorine, resulting in an increase of a delignification at C-stage.