Patent ID: 6524437
Filing Date: 2003-02-25
Classification: D21C

Abstract:
A process for peroxide bleaching of pulp comprising,treating pulp using a peroxide bleaching solution comprising at least one of magnesium oxide and magnesium hydroxide; maintaining the concentration of Mn to less than 10 ppm and the concentration of Fe to less than 20 ppm by selecting a chelating agent and adding the selected chelating agent to the peroxide bleaching solution in accordance with the following criteria: monitoring a concentration of Mn in the peroxide bleaching solution and when the Mn concentration is greater than 10 ppm adding a chelating agent selected from the group consisting of DTPMPA, DTPA, EDTA and HEDTA, and; monitoring the concentration of Fe in the peroxide bleaching solution and when the Fe concentration is greater than 20 ppm adding a chelating agent comprising an alkali metal silicate.