Development of Facile and Green Fabrication of Cellulose–Chitosan Composite Aerogel and Lignin/Silica Hybrid from Agro-wastes

Cellulose–chitosan (CECS) aerogels are novel, green, biodegradable materials with many applications in water treatment, food packing, and thermal insulation. Using cellulose (CE) from biomass wastes can be regarded as one of the best ways to prepare CECS aerogel due to its low cost, sustainability, and environmentally friendly properties. However, most current procedures have harsh conditions and use many chemicals; thus, releasing waste is inevitable. Here, we developed a green and facile approach for fabricating cellulose–chitosan (CECS) aerogel from rice straw and shrimp waste-based chitosan (CS). The rice straw treatment step without using organic solvents and oxidants was, respectively, conducted with sodium hydroxide 1 wt.% and sulfuric acid 2 wt.% for cellulose preparation. The CECS aerogel was created by the freeze–thaw process without using a cross-linker. The aerogels have high porosity (98%), low density (18.65 mg/cm 3 ), and low thermal conductivity (0.035 W/m.K), which could be used as an insulator. The characterization of aerogel was determined by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA) for elucidating the chemical structure. In addition, wastewater obtained from alkaline treatment and acid hydrolysis processes was used to produce lignin/silica hybrid material. The lignin/silica hybrid material has an amorphous structure with a lignin/silica ratio of 0.936.