Decreasing the peroxide decomposition in the magnesia slurry

Abstract

AbstractThe peroxide bleaching process for mechanical pulps using weak alkali sources such as magnesium hydroxide (Mg(OH)2), received much attention recently. The magnesia slurry (containing 61.2% Mg(OH)2) can be used for this purpose. In this paper, we studied the manganese‐induced peroxide decomposition in commercial magnesium hydroxide slurry (magnesia). The results showed that peroxide decomposition occurs under the conditions of magnesia based bleaching process. This is due to impurities, particularly manganese in the magnesia slurry. Similar to the conventional sodium hydroxide based process, sodium silicate can effectively decrease the manganese‐induced peroxide decomposition. However, the amount of silicate required is significantly less. It was found that diethylenetriaminepentaacetic acid (DTPA) or its sodium salt, can also be an effective stabiliser in the system. The chemistry of the manganese‐induced peroxide decomposition was discussed.