Effect of Temperature and Relative Humidity on CO₂ Adsorption Performance of Biomass-Derived Aerogels

The safe and efficient capture of CO₂ in confined environments such as coal mine goafs remains a significant challenge, posing both environmental and safety risks. To address this issue, this study developed a novel biomass-based aerogel adsorbent using CNF-C and CS through sol-gel synthesis and freeze-drying. A series of composite aerogels with varying mass ratios were systematically characterized by SEM, BET, FTIR, and TG-DSC to analyze their microstructure, specific surface area, pore characteristics, chemical properties, and thermal stability. A constant temperature and humidity experimental setup was specially designed to explore the effects of various temperatures, humidity, and material ratios on CO₂ adsorption performance. FTIR analysis confirmed that -NH₂ served as the primary adsorption site, with its density increasing with higher chitosan content. The 1:3 ratio exhibited the optimal specific surface area (7.05 m²/g) and thermal stability, withstanding temperatures up to 350.0 °C, while the 1:1 ratio demonstrated the highest porosity (80.74%). Adsorption experiments indicated that 35.0 °C and 50% humidity were the optimal conditions, under which the 1:2 ratio biomass aerogel achieved an 18% increase in CO₂ adsorption capacity compared to room temperature. The sample with a 1:1 high cellulose ratio is primarily dominated by physical adsorption, making its performance susceptible to environmental fluctuations. The sample with a 1:3 high chitosan ratio is predominantly governed by chemical adsorption, exhibiting more stable adsorption characteristics. The 1:2 ratio achieved the best balance under 35.0 °C and 50% humidity. The biomass aerogel synergistically combined physical barriers from its three-dimensional network structure and chemical adsorption via active functional groups, enabling efficient CO₂ capture and stable sequestration. This study demonstrates the feasibility of biomass-derived aerogels for CO₂ adsorption under complex conditions and provides new insights into the design of sustainable materials for environmental remediation and carbon reduction applications.