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Acid/base and metal adsorption properties of CMC-type softwood Kraft pulps of different charge
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2006 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 21, no 3, 372-381 p.Article in journal (Refereed) Published
Abstract [en]

Pulp materials ranging in charge from zero to 280 mmol/g were synthesised and characterised with respect to ion exchange properties. Both the Constant Capacitance and the Basic Stern Models were found applicable to simulate the acid/base properties. For all materials, the Donnan distribution model gave a good description for the metal binding properties.

Place, publisher, year, edition, pages
2006. Vol. 21, no 3, 372-381 p.
Keyword [en]
Basic Stern Model, Carboxymethyl cellulose (CMC), Carboxymethylation, Cellulose fibres, Constant capacitance model, Donnan Distribution Model, Ionic strength dependence, Kraft pulp, Metal ions, Potentiometric titration
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-12741DOI: 10.3183/NPPRJ-2006-21-03-p382-394OAI: diva2:152412
Available from: 2007-05-08 Created: 2007-05-08 Last updated: 2012-04-18Bibliographically approved
In thesis
1. Cation adsorption properties of substituted kraft fibres: an experimental and thermodynamic modelling study
Open this publication in new window or tab >>Cation adsorption properties of substituted kraft fibres: an experimental and thermodynamic modelling study
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Acid/base and metal ion adsorption properties have been investigated for a range of chemically modified bleached Kraft fibre materials (pulps). The studies were performed via potentiometric titrations, Flame Atomic Absorbtion (and Emission) Spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy and Extended X-ray Absorbtion Fine Structure measurements. As a result of a chemical modification procedure, the total concentration of acidic carboxylate groups in the fibre materials ranged between 43 and 590 μmol/g.

The preferable surface potential model for modelling the ionic strength dependent acid/base properties of fibre materials with low charge densities, i.e. unmodified fully bleached Kraft fibre materials, was found to be the Basic Stern Model. For fibre materials with high total charge, ≳100 μmol/g, this model resulted in poor fits to data, and for such materials a number of Constant Capacitance Models, one at each ionic strength, must be recommended.

With respect to metal ion adsorption, the results have indicated that the unspecific Donnan theory could correctly model the simultaneous adsorption of several metal ions, i.e. K+, Na+, Mg2+, Ca2+ and Cu2+, provided that the salt concentration in the fibre suspension is low. In suspensions of high salt concentration it was, however, found that this very same model strongly underestimated the adsorption of Ca2+ and Cu2+. Here, the Donnan model had to be complemented by specific ion exchange equilibria. These results were corroborated by spectroscopic evidence of specific interactions between Cu2+-ions and fibres. The spectroscopic indication of a complex formed between two fibre surface carboxylate groups and one Cu2+-ion, agree with the specific ion exchange model. It was therefore concluded that specific metal ionfibre interactions cannot be neglected, especially at high salt concentrations.

The interactions occurring between the polycation GaO4Al12(OH)24(H2O)127+ and fibre materials were studied by both adsorption and spectroscopic measurements. These indicate that GaO4Al12(OH)24(H2O)127+ is surprisingly stable in fibre suspensions and that intact GaO4Al12(OH)24(H2O)127+- ions are strongly adsorbed onto the fibres. Also for this ion, specific interactions has to be considered, since the strong adsorption registered was too strong to be explained by Donnan equilibria. In the thesis, the stochiometric composition and an equilibrium constant characterising these interactions is presented.

Place, publisher, year, edition, pages
Umeå: Kemi, 2008. 49 p.
Kraft fibres, Donnan equilibria, ion exchange, acid/base properties, potentiometric titrations, thermodynamic modelling, NPEs, GaAl12 7+, EXAFS
National Category
Other Basic Medicine
urn:nbn:se:umu:diva-1891 (URN)987-91-7264-672-8 (ISBN)
Public defence
2008-11-14, KB3A9, KBC-Huset, Umeå Universitet, Umeå, 10:00 (English)
Available from: 2008-10-24 Created: 2008-10-24 Last updated: 2009-07-03Bibliographically approved

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Sundman, OlaÖhman, Lars-Olof
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