Oxidation of disturbing metal ions in bleaching processes

摘要

A method for pulp delignification/bleaching with peroxide comprising a treatment step with chelating agents in order to free the pulp from disturbing metal ions. Disturbing metal ions are deactivated by separating a liquid phase from the pulp after the treatment with chelating agents and the separated liquid phase containing chelating agents is treated with oxidizing agents such as ozone or peroxide. The liquid phase treated accordingly, preferably with peroxide, is returned to the pulp which in a subsequent step is subjected to a bleaching step with peroxide.