Changes in the structure of sisal and flax lignins during soda-AQ pulping and TCF/ECF bleaching.
The structural modifications of lignins from sisal and flax during their soda-anthraquinone (AQ) pulping and subsequent totally chlorine-free (TCF) and elementary chlorine-free (ECF) bleaching have been studied. For this purpose, residual lignins were isolated from pulps, analyzed by Py-GC/MS and 2D-NMR, and their characteristics compared to the “milled-wood” lignin of the raw materials. Soda-AQ pulping caused a preferential removal of S-lignin and cleavage of β–O–4′ linkages but the structure of the residual lignin remained relatively similar to native lignin. TCF bleaching barely affected the lignin structure, and noticeable amounts of β–O–4′ linkages still occurs in these pulps. In contrast, ECF bleaching caused strong modifications in the lignin structure with the complete removal of lignin markers in ECF-bleached sisal pulp. However, residual lignin was still present in ECF-bleached flax pulp, with a predominance of G and H-lignin units and the presence of β–O–4′ linkages.
| Main Authors: | , , , , , |
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| Format: | comunicación de congreso biblioteca |
| Language: | English |
| Published: |
2013-06-12
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| Subjects: | Flax, Sisal, Residual lignin, Pulping, Bleaching, |
| Online Access: | http://hdl.handle.net/10261/86429 |
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