The investigation of activated carbon by K₂CO₃ activation: Micropores- and macropores-dominated structure

In this study, the K₂CO₃ activation of bamboo was investigated in detail, and the structure and properties of the prepared activated carbons were tested for the feasibility of CO₂ capture application and the potential for both ion and bacteria adsorption for use in the field of hazardous wastewater treatment. Activated carbons were produced with different activator ratios, from 0.5 to 6 according to the sample mass ratio. The ratio of H or O to C (H/C or O/C) increased with the increasing amount of K₂CO₃ added for the activation. The samples had a highly-porous microporous structure, in which the micropore volume was calculated to be 0.6 cm³ g^-1 by the DR method of the CO₂ adsorption isotherm at 298 K. The BET surface area and total pore volume estimated from the N₂ adsorption isotherms at 77 K of the activated materials increased according to the increase of the K₂CO₃ impregnation ratio to a maximum value of 1802 m² g^-1 and 0.91 cm³ g^-1, respectively. Moreover, the K₂CO₃-activated samples had a specific morphology, that is, macropores which are presumed to be derived from bubbles. The X-ray-CT images showed that the bubble-like structure is not only on the surface but also inside the samples. The results of gas adsorption methods, mercury porosimetry, and SEM showed the co-existence of micropores (<2 nm) and macropores (100-10,000 nm). The results highlighted the unique pore structure, that is, the coexistence of micropores and macropores that would contribute to forming solutions for carbon sequestration in the atmosphere and wastewater treatment.