João L. F. Furtado, Maria do Carmo R. Peralba, Cláudia A. Zini, Elina B. Caramão
Chlorinated Phenolic Compounds in Bleaching Filtrates from a Mixed Eucalyptus and Acacia Pulp Using Different Sequences
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.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 02/2000
Pages: 159 - 164
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