Scalable and Sustainable Zinc (II) Ions‐Glue‐Assisted Conversion of Biomass Waste Bits into Carbon Aerogels for Efficient Uranium Extraction

Carbon aerogels (CAs) have garnered significant attention due to their multifunctional applications. Biomass waste, abundantly generated by agriculture and industry, serves as a primary carbon source. However, developing a facile, sustainable, and efficient method to produce CAs from biomass waste remains challenging. In this study, a one-step Zn²⁺ ion-glue-assisted carbonization technique was developed to produce large-scale, high-performance CAs. Various biomass materials (wood bits, peanut shells, bamboo bits, and straw waste) were treated in a molten salt system (ZnCl₂/KCl) at 300 °C for 2 h to obtain large-block CAs derived from biomass bits. Zn²⁺ ions cleave cellulose hydrogen bonds in natural biomass, facilitating the dehydration crosslinking reaction among cellulose, hemicellulose, and lignin, thus reconstructing the entire block structure. The resulting CAs exhibited high porosity (95 %) and low density (0.078 g/cm³). Numerous hydroxyl and carbonyl groups were preserved during the low-temperature treatment, facilitating chemical modification for diverse applications. For instance, amidoxime functionalized CAs were utilized as filters for selective and highly efficient extraction of U(VI) from wastewater. The adsorption capacity and extraction efficiency reached 801.2 mg/g and 95 % with a flux rate of 6.1×10³ L/m² ⋅ h.