Contribution of lignin to the microstructure and physical performance of three-dimensional lignocellulose hydrogels

Abstract

Lignocellulose hydrogels (LCGs) with varying lignin content were prepared by the dissolution–regeneration process using N-methylmorpholine-N-oxide solvent system. The varying lignin content in LCGs can lead to different aggregation states due to the hydrophobic association of lignin, with an important impact on the micromorphology and pore structure of hydrogel. The presence of lignin is beneficial for the mechanical improvement of LCGs when lignin content is lower than 6.5%. LCGs with 6.5% lignin exhibits better viscoelasticity (580.0 kPa), compressive modulus (55.0 kPa), and a more homogeneous structure than others. The LCGs with a lignin content of 11.6% exhibit the best adsorption property (86.1 mg g−1 for Pb2+ and 69.3 mg g−1 for Cu2+), which is dominated by chemisorption and multiple diffusion mechanisms. The work provides a feasible route for lignin-containing hydrogel production and develops a method for tailoring micromorphology and the physical properties of the hydrogel by controlling lignin content.