Improving peroxide bleaching of chemical pulps by stabilizing manganese

Based on the earlier results' that unlike Mn(III), Mn(II) is not catalytica lly active towards manganese induced peroxide decomposition under alkaline conditions, we studied to improve peroxide bleaching of an oxygen delignifi ed pulp by reducing the manganese in the pulp fibers from its high oxidatio n state and then stabilizing the reduced manganese with additives such as D TPA. 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 p resent in pulp fibers can be minimized and, consequently, the peroxide blea ching performance can be improved.