Carbon aerogels derived from waste paper for CO2 and SO2 adsorption: Pyrolysis temperature-driven evolution of surface nitrogen groups, pore structure, and adsorption performance

Developing low-cost and high-performance adsorbents is crucial for reducing CO 2 and pollutants in coal-fired flue gas. Herein, a new waste paper-based carbon aerogel is synthesized for the combined adsorption of CO 2 and SO 2 in coal-fired flue gas. The evolution of physicochemical properties of waste paper-based carbon aerogels at different pyrolysis temperatures, and their adsorption performances in fixed beds were investigated. The results show that with the increase of pyrolysis temperature, the surface N-containing groups and narrow micropores of carbon aerogels first increase and then decrease. Although the paper-based carbon aerogel pyrolyzed at 600 °C (PCA-600) does not have the highest BET surface area (530 m 2 /g), it exhibits the highest microporosity (86.75%) and a rich abundance of narrow micropores, as well as the highest surface nitrogen content (4.2%) and pyrrolic nitrogen fraction (37%). These characteristics enable it to achieve the highest CO 2 and SO 2 adsorption capacities in the fixed bed, reaching 66.0 mg/g and 116.4 mg/g, respectively under 298 K and 1 bar. During combined adsorption, CO 2 and SO 2 show obvious competitive adsorption on carbon aerogels, leading to 13–23% decreases in adsorption capacities. Among them, surface N-containing groups have a stronger impact on the competitive adsorption of SO 2 , which is confirmed by DFT calculation results. This work provides new insights for solid waste resource utilization and the design of CO 2 adsorbents.