The leaching of lignin macromolecules from pulp fibres during washing /
A method was developed for measuring the rate of leaching of lignin macromolecules from the fibre walls of unbleached kraft pulp fibres suspended in water. From a comparison of a theoretical analysis with experimental results, it was concluded that the leaching process was governed by a diffusion me...
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| Format: | Others |
| Language: | en |
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McGill University
1981
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| Online Access: | http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68609 |
| Summary: | A method was developed for measuring the rate of leaching of lignin macromolecules from the fibre walls of unbleached kraft pulp fibres suspended in water. From a comparison of a theoretical analysis with experimental results, it was concluded that the leaching process was governed by a diffusion mechanism. Very low and widely polydisperse diffusion coefficients were observed for this system. The molecular weights of the leached lignins were found to increase with wash time. A comparison of the molecular dimensions with pore size indicated that a flat disk-like conformation, rather than a spherical conformation was appropriate for the lignin macromolecule. From 20(DEGREES) C to 70(DEGREES)C the change in the intrafibre diffusion coefficient with temperature varied directly as the ratio of the absolute temperature to the viscosity of water. Above 70(DEGREES)C there was a much larger dependence of the diffusion coefficient on temperature. The rate of leaching was also affected by the presence of electrolytes in the wash liquid; leaching was found to decrease with an increase in the ionic strength of the electrolyte. A conceptual model for this leaching effect is presented. The model offers a qualitative explanation for the experimental results noted above. |
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