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Complex formation and stability of colloidal wood resin pitch suspensions with hemicellulose polymers


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Stack, KR, Lee, R, Richardson, DE and Lewis, T , 'Complex formation and stability of colloidal wood resin pitch suspensions with hemicellulose polymers' , Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 441 , pp. 101-108 , doi: 10.1016/j.colsurfa.2013.08.057.

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tThis paper explores the impact of the wood polymers released by Pinus radiata on the stability of woodresin colloids under varying ionic strength conditions with the addition of calcium chloride. A photomet-ric dispersion analyser was used to study the kinetics of aggregation under shear conditions. Additionof the wood polymers to an aqueous dispersion of wood resins was found to cause destabilisation ofthe wood extractive colloids in two stages, separated by an apparent stabilisation region. The behaviourobserved is typical of aggregation due to polymer bridging at low polymer addition, followed by steric sta-bilisation of the colloids at medium polymer concentration and depletion flocculation at higher polymeradditions and then finally depletion stabilisation. At 10 mM calcium ion concentration, destabilisationof the colloids occurred at low wood polymer addition, while at wood polymer concentrations above50 mg/L restabilisation of the colloids occurred at this level of calcium. The wood polymers were foundto be unable to stabilise the colloids at high calcium levels of 50 mM. At high calcium levels the woodpolymers themselves were found to undergo aggregation. The stabilisation of the colloids was found tobe affected by the way in which the colloids and wood polymer complexes are formed and allowed toreorganise with time.Adsorption isotherms for the adsorption of the wood polymers onto wood resin coated surfaces weredetermined. A low affinity Langmuir isotherm was obtained in the absence of electrolyte indicating thatinteraction between the wood polymers and the wood resin arises due to hydrogen bonding between thecarboxylic acid groups despite the negative charge on both. The higher than expected loading capacityshowed that the wood polymers adsorb as aggregates which extend from the surface and act to screenthe negative charge of the wood resin colloids. In the presence of 10 mM CaCl2the isotherm was foundto be modelled by a Freundlich isotherm with a greater amount of wood polymer being adsorbed due tofolding of the wood polymer and reduction in its volume.

Item Type: Article
Authors/Creators:Stack, KR and Lee, R and Richardson, DE and Lewis, T
Keywords: Colloid stability Wood resin Pitch Hemicelluloses Adsorption isotherm
Journal or Publication Title: Colloids and Surfaces A: Physicochemical and Engineering Aspects
ISSN: 0927-7757
DOI / ID Number: 10.1016/j.colsurfa.2013.08.057
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Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved

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