Process for removing transition metal ions from ligno cellulose-contg. material prior to bleaching with peroxide-contg. cpd. - whilst retaining sufficient amt. of magnesium and calcium ions.

摘要

The process, using a peroxide-contg cpd, comprises: (i) treating the material at a pH up to 5 with a complexing agent in an opt. appts; (ii) adding a Mg cpd. and a Ca cpd. at a pH of 3.5 to 8 in order to reinsert Mg and Ca ions in the material; (iii) washing or rinsing the material with a fluid with a pH greater than 4 to remove unwanted metal ions; and (iv) bleaching the material at pH increments from 7 to 13.