PRODUCTION AND USE OF DIFFERENT PERACIDS IN CHEMICAL PULP BLEACHING

In the present study various peracids were compared to determine their beneficial and detrimental effects on pulp bleaching. The peracids co mpared were equilibrium solutions of performic acid, Care's acid and p eracetic acid. The effects of distilling ;the equilibrium peracetic ac id on bleaching and effluents were also studied. Comparisons were also made of the preparations of different peracids, and the contents of p eracids and unreacted compounds in the product. The content of unreact ed acid in the product varied from one peracid to another. Selectivity was shown to be influenced by the reaction pH. Peracetic acid was the most selective among the peracids compared, mainly due to the optimum pKa (4.8) of the liberated acetic acid, which buffers the pH to a val ue with in the selective range. Distilling peracetic acid (PAA) reduce d the content of free acetic acid in the product, which in turn minimi zed the need for neutralization during bleaching. Effluents from PAA d elignification were found to be move easily circulated due to the abse nce of free peroxide. The oxalate content of PAA stage filtrate teas l ower than that of the other acidic bleaching filtrates studied.