Treatment of filtrates from peroxide bleaching of pulp using an aluminium compound to precipitate interfering substance

摘要

A method for bleaching pulp, in which the pulp is subjected to a peroxide bleaching step, whereupon the pulp in washed and the washing liquid from the washing is separated from the pulp in the from of a filtrate, characterised in that: i) The filtrate is treated with an aluminium compound for precipitating interfering substances ii) The precipitated material is removed from the filtrate iii) The aluminium content of the filtrate after precipitation of interfering substances is adjusted to at most 20ppm, and iv) The filtrate is then recirculated to the peroxide bleaching step.