The role of pH and Fe (III) in delignification with distilled peracetic ACID

摘要

An acid-washed,oxygen-delignified,softwood kraft pulp was further delignified with peracetic acid (Pa) at initial pH 2.5,4.8 and 7.0.The inclusion of 5 ppm on pulp of Mn (II),Fe (III),Cu(II),V(V) or Co(II) caused wasteful decomposition f pa while Hi (II) had no effect.Pa utilization was lowest at pH 2.5 but the peracid was significantly decomposed by Fe(III),V(V),and Co(II).Free radical mechanisms that are partially repsonsible for V-and Co-induced decomporsition are already in the literature.Those mechanisms involve the acetoxy and peracetoxy radicals.The dilute Pa solutions hydrolyzed to H_2O_2 and CH_3COOH when delignification was performed at pH2.5.the Haber-Weiss mechanism was oeprable for Fe~3+/H_2O_2,a sizable amount of OH was generated,and the pulp viscosity was lower than for V(V) or Co(II).