The Role of Transition Metal Species in Delignification with Distilled Peracetic Acid

Abstract

Abstract 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 Mn2+, Fe3+, Cu2+, V5+, or Co2+ caused wasteful decomposition of Pa while Ni2+ had no effect. None of the cations caused a significant decrease in kappa number while Co2+ at all pHs and Fe3+ at pH 2.5 resulted in lower viscosities. In pulp-free solutions, Co2+ and V5+ catalyzed Pa decomposition much more aggressively than the other cations. The kinetic data supported a previous free-radical mechanism for Co2+ and a similar type mechanism appears to be partially responsible for Pa decomposition by vanadium (V).