High-Adsorption, Self-Extinguishing, Thermal, and Acoustic-Resistance Aerogels Based on Organic and Inorganic Waste Valorization from Cellulose Nanocrystals and Red Mud

Waste transformation as the source to valuable materials is an effective strategy for the high-valued valorization in view of socioeconomic and environmental issues. Inspired from the concept of organic–inorganic hybrid, we proposed the utilization of cellulose nanocrystals (CNCs, extracted from biomass waste) and red mud (RM, from industrial waste) to fabricate composite aerogels as potential construction materials with the multifunction of adsorption, thermal insulation, acoustic resistance, and flame retardancy. For equal loading level of modified CNC (Si-CNC) and RM (1:1, w/w) components, the obtained aerogel was chemically cross-linked with diisocyanate to enhance its structural stability and mechanical properties. It exhibited an improved compression modulus of 3.7 MPa together with high porosity (98.8%) and specific surface area (73.23 m2/g). As a result of the intrinsic features of organic Si-CNC (skeleton) and inorganic RM (particles aggregate), the Si-CNC/RM-1/c composite aerogel displayed significant functional performances such as magnetic conductivity, rapid oil adsorption of 30 times its mass, 20.8% reduction in thermal conductivity, 24.5% increase in sound-absorption coefficient, and highly efficient self-extinguishing behavior within 2 s.