| Abstract:Some dissolved and colloidal substances (DCS) tend to release during the alkline hydrogen peroxide bleaching of mechanical pulp, and the anionic groups (AGs) in DCS are mainly uronic acids. In this paper, the aspen CTMP were bleached with alkaline hydrogen peroxide under different conditions, and the content of uronic acids in the resultant DCS was determined by spectrophotometric method. The results showed that the amount of uronic acids dissolved was mainly affected by the alkalinity of the system; Peroxide could obstruct the release of the uronic acids under high alkalinity. High reaction temperature (e.g. above 80℃) could result in a significant increase of the content of uronic acids. The results of orthogonal experiments indicated that factors affecting the uronic acids relasase were the dosage of NaOH, temperature, dosage of H2O2, consistency of pulp and reaction time in order. |
