Enhancement of the reaction between pulp components and hydroxyl radical produced by the decomposition of hydrogen peroxide under alkaline conditions

Experiments on alkaline hydrogen peroxide treatments with stepwise addition and oxygen pressurization were performed to determine whether they enhance the reaction between pulp components and hydroxyl radicals produced by the decomposition of hydrogen peroxide. In this study the degradation of methyl beta-D-glucopyranoside (MGP), a model compound of pulp components, was an indicator of the progression of the reaction between pulp components and hydroxyl radicals. When comparing the degradation of MGP in the stepwise and one-time addition systems, MGP was degraded more in the stepwise addition system than in the one-time addition system when Fe3+ was added. This result indicates that the hydroxyl radical produced by the decomposition of hydrogen peroxide efficiently attacks MGP in the stepwise addition system. MGP was degraded to the same degree in the stepwise addition system as in the one-time addition system when Fe2+ or Mn2+ was added. Aggregation and precipitation of metal ions might affect their catalysis. Oxygen-pressurized hydrogen peroxide treatment caused almost no enhancement of the degradation of MGP compared to the treatment under atmospheric pressure. Instead, high stability of hydrogen peroxide was produced by oxygen-pressurized hydrogen peroxide treatment. Such high stability can result in frequent attacks of the hydroperoxide anion, the conjugate base of hydrogen peroxide, against some chromophores and quinones.