Formation of dissolved high molecular organic substances in the bleaching of softwood kraft pulp

This study evaluated methods to reduce the formation of:dissolved high molecular sub stances during D(EP) and D(EP)DD bleaching of softwood kraft pulp. We focused on the possibility of influencing the formation of high molecular COD as a way to reduce the most problematic part of the COD from the bleach plaint omissions. We separated molecules of different sizes through ultrafiltration of the generated filtrates. The results showed that it was indeed possible to influence the formation of high molecular organic material in the bleaching, stages by adjusting the charge, the pH, and the temperature. The study showed that modifications of the conventional conditions in both the chlorine dioxide and the extraction stages were needed to obtain the best mix between a low formation of high molecular COD and high bleaching efficiency.