Improving pulp whiteness in alkali de-inking process

摘要

A biological process for improving whiteness or stabilisation in a flotation method deinking process, in which a slurry of old paper and alkali is bleached with peroxide in the presence of a chelating agent and then the contaminant particles are removed using fatty acids as scavengers and foaming agents. A bacteria suspension is added to the deinking medium in a concentration of 10<7>-10<10> cells/g old paper and before flotation the pulp is incubated for 30-120 minutes at 30-60 deg C. Preferably Bacillaceae or pseudomonadaceae genus bacteria are used.