Role of delignification in water state changes during water absorption and air drying of wood characterized with LF-NMR

ABSTRACT

Delignification, recently much used in wood modification and functional material preparation, is closely related to wood-water interactions. To attain more information on the role of delignification in wood, this study characterized the water state changes during water-absorption and air-drying process with LF-NMR. By adjusting delignification time, lignin was removed about 15%, 34%, and 61%, respectively. Water absorption increased after delignification, and free water was generated more and faster than bound water. This was because delignification changed wood-water interaction environments suggested by SEM and FTIR analysis. Specifically, delignification increased hygroscopic polysaccharide percentage and sorption site concentration. New pore generation and enlargement after delignification provided more water exchanging paths and accommodation. Besides, delignified wood had higher and faster moisture decrease, and wood air drying was facilitated because of enriched water exchanging paths and higher initial moisture gradient difference in water-saturated delignified wood. Therein, free water decreased more and faster than bound water. The T_2s of bound water and free water were both shortened after delignification, indicating water had tighter intermolecular interaction with delignified wood. The study provided new insight for understanding the role of lignin in water state changes during wood-water interactions and may facilitate better preparation of functional material and wood modification.

KEYWORDS:

• Delignification
• LF-NMR
• water state changes
• water absorption and air drying
• wood-water interaction

Acknowledgements

This work was supported by the National Natural Science Foundation of China (32201489) and the Research Start-up Funding of Nanjing Forestry University (163020242).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Natural Science Foundation of China [grant number 32201489], Research Start-up Funding of Nanjing Forestry University [grant number 163020242].