Preparation and CO2 adsorption of N-doped biochar and effect of acetone on its adsorption performance.

CO2 adsorption is a promising carbon capture technology. Boiler flue gas is a major source of CO2 emissions, with a complex composition. The influence of coexisting components (especially VOCs) on CO2 adsorption performance is an urgent problem to be explored. In this study, wheat stalk and wood were selected as the raw materials, and urea and melamine as nitrogen sources, a series of N-doped biochars were prepared. They were characterized by SEM, BET, FTIR, and XPS, and their adsorption properties and mechanism for single-component CO2 and binary-component CO2 and acetone were systematically studied. The results show that CO2 adsorption increase by melamine modification (26.96%-48.58%) was better than urea modification (2.98%-43.60%). The N-doped biochar had a high specific surface area (1753.445 m2 g-1) and ultramicropores structure, and the CO2 adsorption capacity was up to 3.17 mmol g-1 under normal pressure and 40 °C. The adsorption process was well fitted to the R-P model (R2 = 0.9999) and the PSO model (R2 = 0.998), respectively, indicating that the CO2 adsorption on biochar was the multi-layer adsorption, which could be determined by both physical and chemical adsorption. CO2 and acetone in the binary-component had a certain competitive synergistic effect on the N-doped biochar, and acetone had a synergistic effect on the CO2 adsorption, while CO2 was not conducive to the acetone adsorption. The schematic diagram of possible adsorption mechanism for binary-component CO2 and acetone on the N-doped biochar was given. The findings further improved the theoretical system of CO2 adsorption by biochar.