Chlorinated Phenolic Compounds in Bleaching Filtrates from a Mixed Eucalyptus and Acacia Pulp Using Different Sequences

Abstract

Summary Bench filtrates from three-stage conventional bleaching sequences (CEoD) with substitution degrees of chlorine by chlorine dioxide in the first stage equals to zero, 25%, 75% and 100% have been analysed for their content of chlorinated phenolic compounds (CPCs). Alternatively, CPCs filtrates content of an AZEoPD sequence were also determined. A cellulose pulp obtained from a mixture of 85% Eucalyptus saligna (young trees) and 15% Acacia mearnsii delignified with oxygen (kappa number 10.0) was employed in all bleaching tests. Levels of CPCs were determined by using an in situ acetylation method followed by GC/ECD technique. GC/MS of bleaching filtrates was employed in qualitative analyses. CPCs content in filtrates and the Kovacs' equivalent toxicity for the total filtrates of the studied bleaching sequences are presented. The lowest content of CPCs was found in AZEoPD filtrates, as expected due to the utilised bleaching agents. CPCs were not detected in the filtrates of stage D from the AZEoPD sequence probably due to the low lignin content of the pulp. Mixed filtrates of the sequence DEoD, showed the lowest CPCs content among conventional bleachings. Results are in accordance with those found in the literature for hardwood and softwood pulp. The equivalent toxicity in the sequences Dc(75/25), DEoD and AZEoPD was found to be lower than the limit given by Kovacs to characterise chronical toxicity.

Influence of the Chemical Structure on Odor Qualities and Odor Thresholds of Halogenated Guaiacol-Derived Odorants

“…Chlorinated guaiacol derivatives are potentially formed during bleaching of pulp and wood pulp, as a result of degradation and chlorination of lignin and its derivative guaiacol. In agreement with this, different chlorinated guaiacols, like 4-chloro-, 5-chloro-, 6-chloro-, or 4,5-dichloroguaiacol, could be identified in bleaching liquors, bleaching filtrates, and pulp mill wastewater or river sediments, surrounding pulp and paper mills, processing pine wood, eucalyptus, rice straw, wheat straw, or bamboo (Sequeira and Taylor, 1991 ; Owens et al, 1994 ; Judd et al, 1996 ; Sharma et al, 1997 ; Sinkkonen et al, 1997 ; Sharma and Kumar, 1999 ; Furtado João et al, 2000 ). Further, 4-chloro- and 4,5-dichloroguaiacol were detected in fish tissue of animals living downstream of bleached-kraft pulp mills (Owens et al, 1994 ; Araki et al, 2001 ).…”