Redox stabilization of iron and manganese in the +II oxidation state by magnesium precipitates and some anionic polymers. Implications for the use of oxygen-based bleaching chemicals

In this work, it is shown that iron(II) and manganese(II) can be protected against oxidation in highly alkaline and oxidative environments by being incorporated in magnesium precipitates. A prerequisite for this phenomenon is the presence of wood pulp or an anionic polymer such as polygalacturonic acid. In addition, magnesium must be present in a certain excess over iron and/or manganese. The function of the polymer is to change the physical characteristics of the precipitates formed into a negatively charged colloidal phase. The results presented facilitate the perception of the role of magnesium during alkaline oxygen delignification and peroxide bleaching. If iron and manganese are redox stabilized by being incorporated in a solid phase, their catalytic action through acyclic alteration of oxidation state in a Fenton-type reaction is disrupted.