Improving peroxide bleaching of chemical pulps by stabilizing manganese

Based on the earlier results' that unlike Mn(III), Mn(II) is not catalytically active towards manganese induced peroxide decomposition under alkaline conditions, we studied to improve peroxide bleaching of an oxygen delignified pulp by reducing the manganese in the pulp fibers from its high oxidation state and then stabilizing the reduced manganese with additives such as DTPA. It was shown that pulp fibers under an acidic condition are effective reducing agents and so is sodium hydrosulfite. With such a strategy it was found that the peroxide decomposition catalyzed by the residual manganese present in pulp fibers can be minimized and, consequently, the peroxide bleaching performance can be improved.