Lignin-containing cellulose nanofibers with gradient lignin content obtained from cotton gin motes and cotton gin trash

The use of agricultural waste and residues in composite materials is a potential high-value commercial application for underutilized renewable resources and provides alternative commercial markets to the agricultural industry. Cotton gin trash (CGT) and cotton gin motes (CGM) are underutilized low-value commodities that are attractive targets due to their high cellulose content; however, each contains various amounts of lignin, hemicellulose and other components that impede their utilization as commercial products. In this work, lignin-containing cellulose nanofibers (LCNFs) with gradient degrees of lignin content were prepared from CGT and CGM. Analyses showed the lignin content and other components affected the physical properties of LCNFs, modestly altering their thermal stability and crystallinity. The degree of polymerization (DP) was smaller after successive rounds of processing and was also dependent upon the source (CGT or CGM) with CGT providing nanofibers with a smaller DP than CGM. This translated into slightly different suspension viscoelastic behavior as determined by rheological measurements.