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Modelling the distribution of "free", complexed and precipitated metal ions in a pulp suspension using Donnan equilibria
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2001 (English)In: Journal of Pulp and Paper Science, ISSN 0826-6220, Vol. 27, no 9, 296-301 p.Article in journal (Refereed) Published
Abstract [en]

Mill kraft pulps from oxygen delignification (O) and alkaline hydrogen peroxide (P) stages were ana analyzed for ion exchange capacity and metal content, and the O-stage pulp was manipulated to simulate a chelating treatment stage (Q). The anionic charge of the O-stage pulp fibres was balanced by Na+ ions, while the divalent metal ions were present as solid carbonates. On acidification, these carbonates gradually dissolve and the divalent cations predominantly replace Na+ in the fibre wall. Since the amount of cations exceed the fibre ion-exchange capacity, a significant portion of the metal ions end up in the suspension liquor. Addition of strong chelants forms anionic complexes with Mn2+, e.g. Mn(DTPA)(3) and these anions are expelled from the fibre wall. On pulp re-alkalization, as in a P stage, Mg2+ and a small portion of the Ca2+ are re-precipitated. The metal ion distribution can, in all of these cases, be quantitatively modelled by the Donnan theory if also precipitated and complexed forms of the metal ions are considered.

Place, publisher, year, edition, pages
2001. Vol. 27, no 9, 296-301 p.
Keyword [en]
kraft pulps, metals, ions, distribution, Donnan equilibrium, precipitation, complex compounds
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-9003OAI: diva2:148674
Available from: 2008-02-26 Created: 2008-02-26 Last updated: 2012-02-10Bibliographically approved

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Öhman, Lars-Olof
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Department of Chemistry
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