Enhancement of CO2 Capture on Biomass-Based Carbon from Black Locust by KOH Activation and Ammonia Modification

A novel biomass-based carbon material was successfully prepared from black locust by KOH chemical activation in combination with surface modification by heat treatment with ammonia solution for enhancing CO2 adsorption. The textural and surface characteristics of the prepared activated carbons were analyzed with N-2 adsorption isotherms, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and X-ray photoelectron spectroscopy (XPS). The results show that the modified activated carbon possesses a high surface area of 2511 m(2)/g, a large micropore volume of 1.16 cm(3)/g, and a high nitrogen content of 7.21 wt %. The adsorption behavior of CO2 onto all activated carbon samples was experimentally evaluated by a volumetric method at three different adsorption temperatures of 0, 25, and 50 degrees C under atmospheric pressure (1 bar). High CO2 uptakes of 7.19 and 5.05 mmol/g at 0 and 25 degrees C were achieved for the sample AC-KOH-N due to its well-developed micropore structure and abundant basic nitrogen-containing functionalities. The thermodynamic parameters indicate that both physical adsorption and chemical adsorption mechanisms for CO2 adsorption coexist in the sample AC-KOH-N. The sample AC-KOH-N also shows a good selectivity for CO2/N-2 and fast adsorption kinetics that be easily regenerated with superior cyclic stability after multiple cycles. These results suggest that the obtained biomass-based activated carbon is promising for CO2 capture.