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Colour removal from kraft mill caustic extraction effluent using aluminum and iron
Author(s) -
Nasr M. S.,
Macdonald D. G.
Publication year - 1978
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450560112
Subject(s) - chemistry , extraction (chemistry) , effluent , bleach , kraft paper , caustic (mathematics) , metal ions in aqueous solution , kraft process , lignin , nuclear chemistry , metal , aluminium , inorganic chemistry , pulp and paper industry , chromatography , organic chemistry , waste management , engineering , mathematical physics , physics
The highly coloured compounds found in the caustic extraction effluents of kraft mill bleach plants can be removed by chemical reaction with trivalent metal ions (Me 3+ ). At pH 2.8, these ions react stoichiometrically with carboxylic acid groups (A − ) on the lignin compounds to form moderately soluble MeA 3 salts. Above pH 2.8, hydroxyl ions compete with the A − groups to form highly insoluble hydroxy metal salts. Maximum colour removals of 99.6 and 98.8% were obtained for an effluent containing 12000 APHA colour units treated with 7 mol/m 3 of Al 3+ at pH 5.0 and Fe 3+ at pH 3.3, respectively.
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