Synergistic Effect of Hierarchical Pores and Amine Functionalization on CO2 Adsorption Performance by Distillers' Grains-Derived Biochar Spheres
To address the high CO2 emission proportion in the industrial sector, distillers' grain waste was converted into biochar for CO2 adsorption from flue gas. Raw biochar suffers from weak pore adsorption and poor selectivity at elevated temperatures. This study employed ash self-templating and particle self-assembly to create hierarchical pores and simultaneously load amine groups onto distillers' grains-derived biochar, yielding amine-functionalized hierarchical porous carbon spheres. The amine loading significantly increased, providing more CO2 adsorption sites, while retaining macroporosity (total pore volume 0.0030–0.0066 cm3/g after amine loading), which enhanced morphological stability and CO2 mass transfer. The optimal sample, 0.2PW-K-CNF-PEI, exhibited a CO2 adsorption capacity of 1.03 mmol/g at 100 °C, a CO2 diffusion coefficient of 0.0495 min−1, and a selective adsorption capacity of 44 mg/g at 80 °C. This work offers a solution for valorizing distillers' grain by-products and capturing CO2 from low-temperature flue gas.