Effects of Magnesium-Based Alkali on the Dissolved and Colloidal Substances in the Alkaline Peroxide Bleaching of Poplar CTMP

Abstract

Some of the dissolved and colloidal substances (DCS) such as extractives and pectic acids have great negative influence through the whole papermaking process, and their control and understanding would benefit the production, especially in the mills with closed water system. In this work, the DCS from the alkaline peroxide bleaching of poplar chemi-thermomechanical pulp (CTMP) with partial substituting MgO for NaOH were analyzed. The results showed that the amount, pH value, lignin content, conductivity, and cationic demand (CD) of the DCS decreased with increasing substitution percentage of MgO for NaOH. The methyl tert-butyl ether (MTBE) extractives were characterized by a gas chromatograph coupled to a mass spectrometry (GC-MS). The substitution of MgO for NaOH in the bleaching process improves the bulk, light-scattering coefficient, and opacity of the bleached poplar CTMP, reduces the pulp brightness, and decreases the tensile and burst indices.