Water Hyacinth: A Sustainable Lignin-Poor Cellulose Source for the Production of Cellulose Nanofibers

The extraction of cellulose nanofibers (CNFs) from a lignocellulosic source containing less lignin would be an effective way to avoid repetitious and energy-consuming chemical treatments. In the present study, we used water hyacinth (Eichhornia crassipes)-a fast-growing, rapidly reproducing, sustainable, and inexpensive raw material with a low lignin content (4.1%)-to successfully prepare CNFs with diameters of 10-30 nm and lengths of several mu m. We used three different chemical approaches: chemical-free, alkaline, and combined sodium chlorite and alkaline treatments. The results indicate that the alkaline treatment alone was sufficient to eliminate most of the lignin and hemicellulose from water hyacinth, providing CNFs with morphological, crystallinity, and thermal characteristics similar to those of CNFs prepared using combined sodium chlorite and alkaline treatment. Also, mechanical properties and thermal expansion of the nanopapers prepared from these chemically treated CNFs were comparable. Water hyacinth has potential as a sustainable cellulose source for the large-scale production of CNFs for advanced applications in tropical and subtropical countries in comparison with wood or other lignocellulosic sources due to a lower requirement for chemical treatments. Moreover, water hyacinth has other positive aspects such as its rapid breeding rate, availability, and economical price.