Effect of lignin on the performance of biodegradable cellulose aerogels made from wheat straw pulp-LiCl/DMSO solution

To expound the effects of existing endogenous or exogenous lignin on the performance of cellulose-based aerogels, both the cellulose aerogels and composite aerogels were fabricated by the dissolution-regeneration process by using LiCl/DMSO solvent system. The varying content of endogenous and exogenous lignin could lead to different aggregation states of cellulose, hemicellulose and lignin, thus causing different micromorphology and mechanical properties of cellulose aerogels and composite aerogels. The increased endogenous lignin in lignocellulose restricted the dissociation of cellulose and hemicellulose in dissolving process, which led to the appearance of enlarged pores, and then resulted in the decreased mechanical strength. However, for composite aerogels, externally added exogenous lignin deposited on the cellulose chains and then restricted the movement of polymer chains. It could not only bring about the increased pore size of aerogels, but also help to improve the mechanical strength, which was different from that of cellulose aerogels. Furthermore, two types of aerogels with higher lignin content both exhibited better adsorption capacity for methylene blue, especially for composite aerogel. This study provides a feasible way to tailor the morphology and physical properties of the aerogels by controlling the existential state or content of lignin.