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.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.68609 |
| Date | January 1981 |
| Creators | Favis, Basil D. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000139373, proquestno: AAINK54790, Theses scanned by UMI/ProQuest. |
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