Environmental implications of the delignification of eucalyptus kraft pulps using peracids

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Petit Breuilh, Ximena
Zaror, C.
Roa, P.
Mardones, C.
Romero, J.
Barrientes, F.
Encina Montoya, Francisco
Datos de publicación:
Celulosa y Papel, Vol.23, N°5, 18-25, 2007
Pulpas kraft de Eucalipto - Celulosa - Peróxidos - Ácidos
Because of great environmental pressures, the cellulose industry has studied the potential of use of new bleaching agents among which peroxymonosulfuric acid and peracetic acid stand out. This survey summarizes the results of various laboratory investigations using peracids to delignify eucalyptus kraft pulps. The effect of a step using peroxymonosulfuric acid followed by a D-Eo-D sequence [free of elemental chlorine] was studied and compared with the use of peracetic acid and mixtures of these two acids. It was shown that a mixture of peroxymonosulfuric acid and peracetic acid reduced more lignin (measured as kappa index) than the individual peracids, and reduced more hexenuronic acid than peracetic acid with less degradation of the cellulose than with peroxymonosulfuric acid. This was explained on the basis of the electrophilic and nucleophilic properties of these acids that improved the delignification of eucalyptus kraft pulp. The effluents generated in these steps involving the peracids had greater color, chemical oxygen demand (COD), and total phenols correlating with the amount of lignin removed and the analyses of bioassays did not show acute toxicity from effluents coming from a peroxymonosulfuric acid step. The delignification with peracids may possibly reduce the use of chlorine dioxide in a sequence involving bleaching with elemental free chlorine (ECF), in this way reducing the concentration of organic chlorides (AOX) in the bleaching effluent.