THE ROLE OF TRANSITION METAL SPECIES IN DELIGNIFICATION WITH DISTILLED PERACETIC ACID

摘要

An acid-washed, oxygen-delignified, softwood kraft pulp was delignified with peracetic acid (Pa) at initial pH 2.5, 4.8 and 7.0. The inclusion of 5 ppm on pulp of Mn~(2+), Fe~(3+), Cu~(2+), V~(5+), or Co~(2+) caused wasteful decomposition of Pa while Ni~(2+) had no effect. None of the cations caused a significant decrease in kappa number while Co~(2+) at all pHs and Fe~(3+) at pH 2.5 resulted in lower viscosities. In pulp-free solutions, Co~(2+) and V~(5+) catalyzed Pa decomposition much more aggressively than the other cations. The kinetic data supported a previous free-radical mechanism for Co~(2+) and a similar type mechanism appears to be partially responsible for Pa decomposition by vanadium (Ⅴ).