2014 Volume 68 Issue 11 Pages 1317-1323
Peroxymonosulfuric acid has been examined as bleaching agent which has ability of delignification, not as degradation agent of hexenuronic acid.
We revealed, in this study first the reaction mechanism of peroxymonosulfuric acid which has some characteristics during pulp bleaching. It was found that lignin degradation proceeded at almost the same rate in the range of pH 1.5 to 5.0. The most effective pH for degradation of hexenuronic acid (HexA) was 3.0. The peroxymonosulfuric acid treatment at low pH resulted in the decrease of fiber qualities. A treatment for more than 60 minutes was required for the sufficient degradation of lignin and HexA. It became apparent that the condition of peroxymonosulfuric acid (Px) stage was similar to another bleaching stage.
We confirmed that the effect of converting a common bleaching stage into Px stage in a laboratory test ln a trial an acid-washing stage was converted into Px stage in Z-ECF, and in the second trial acidic peroxide stage, which was introduced as the first stage in D-ECF, was converted into Px stage. It was confirmed that the beneficial effects of conversion were mainly decrements of hexenuronic acid and of chlorine dioxide consumption in both cases. These effects also confirmed in mill scale, and therefore we installed peroxymonosulfuric acid bleaching stage in June 2007 at Tomioka mill and January 2012 at Kasugai mill.
