Iso-concentration hydrogen peroxide bleaching of poplar chemi-thermomechanical pulp

Maintaining a constant chemical concentration (Iso-concentration, IC) has been found to be an effective method to improve peroxide bleaching efficiency for chemi-thermomechanical pulp (CTMP). In this study, the mechanism of IC bleaching was investigated. The concentrations of H₂O₂ and total alkali in IC bleaching were monitored and compared with those in conventional bleaching processes. Control experiments without pulp were carried out to explore the effects of bleaching additives on H₂O₂ decomposition. The results showed that the concentrations of H₂O₂ and the total alkali at the early and later stages of IC bleaching were relatively low and high, respectively; thus, undesired decomposition of H₂O₂ was inhibited, and brightness was improved. Moreover, the stabilizer played an important role in inhibiting the undesired H₂O₂ decomposition. This may explain why high bleaching efficiency was achieved in IC bleaching. These findings would provide valuable insight for the production of high-brightness bleached chemi-thermomechanical pulp (BCTMP).