Construction of an alginate-based aminated lignin composite foam with ultra-high service performance

Lignin, a complex natural 3D aromatic polymer compound known for its high thermal stability, stiffness, and ability to effectively withstand chemical and biological attacks. When combined with various other natural biomass components, lignin can offer the promise of fortifying the physical, chemical, and biological stability of matrix materials, which has garnered significant interest. Herein, through the incorporation of alginate with aminated lignin using chemical and ionic double cross-linking and freeze-drying techniques, alginate-lignin composite functional foams (SA-NAL) with improved water affinity, mechanical strength, and overall service performance have been successfully developed. Without further chemical modification, the as-fabricated SA-NAL composite foam demonstrates: i) outstanding mechanical robustness, enduring 2000 times its weight without significant deformation in dry condition, and withstanding tensile stress up to 0.67 MPa in wet condition, ii) superior water affinity and underwater superoleophobicity (θ_oil > 150° for various oils), coupled with effective oil/water separation performance (separation efficiency of 99.5 %, flux of 3.37 L·m^-2·s^-1, and ultimate operating oil pressure of 2.36 kPa), and iii) exceptional resistance to light, heat and oxidation, and excellent flame retardancy. In summary, the synergy between aminated lignin and alginate materials has resulted in complementary functions for high-value applications of polysaccharide-based alginate materials.