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Multi-salt coagulation of soft pitch colloids


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Lee, R, Stack, KR, Richardson, DE, Lewis, T and Garnier, G 2012 , 'Multi-salt coagulation of soft pitch colloids' , Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 409 , pp. 74-80 .

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The dynamic coagulation of colloidal pitch was quantified under orthokinetic conditions. The effects of
single salt, multiple salt and cation valency on the stability of the colloidal pitch were investigated as a
function of salt concentration. Critical coagulation concentrations (CCCs) were determined for a range of
individual cations. The CCC in the presence of a number of divalent or trivalent cations was investigated
to gain an understanding of the effect of multiple salts normally found in industrial systems.
Electrostatic destabilisation of wood resin colloids by a single salt is strongly influenced by salt valency
(z) and mostly independent of the individual cation (at constant z). Addition of a second cation to solution
resulted in a decrease in the CCC for both calcium and aluminium ions in the presence of sodium ions.
The decrease in the CCC for the wood resin colloids was non-linear and showed restabilisation of the
colloids above the CCC, unlike the effects observed for a single salt. Comparison of the experimental CCC
results with the DVLO theory indicates that a higher Hamaker constant than reported for the interaction
of abietic acid with talc in water (used here as a model interaction) is needed. This suggests that
the aggregation process of the wood resin colloids involves a stronger interaction than abietic acid with
talc. Experimental CCC values for divalent and trivalent ions were also lower than those predicted theoretically.
To obtain agreement between theory and experimental results, reduced Stern potentials and
higher Hamaker constants were required, suggesting specific ion adsorption of the multivalent cations
is occurring to reduce surface charge of the colloid.

Item Type: Article
Authors/Creators:Lee, R and Stack, KR and Richardson, DE and Lewis, T and Garnier, G
Keywords: Soft colloid Pitch Multi-salt coagulation DLVO theory Critical coagulation concentration (CCC) Adsorption
Journal or Publication Title: Colloids and Surfaces A: Physicochemical and Engineering Aspects
ISSN: 0927-7757
Additional Information:

Copyright 2012 Elsevier

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