Activated carbon fiber derived from wasted coal liquefaction residual for CO₂ capture

Wasted coal liquefaction residual was used to synthesize activated carbon fibers (ACFs) for CO₂ capture, and the properties of the developed ACFs were optimized by adjusting the activation conditions, including the reaction temperature and soaking time. The yield, element distribution, pore structure, composition, functional group, morphology, and adsorption capacity of the as-synthesized ACFs were characterized by various apparatuses. In addition, static and dynamic adsorption experiments were conducted to investigate the adsorption capacity of CO₂ in flue gas. The results revealed that the synthesized ACFs are mainly composed of carbon, accounting for more than 90% of the total elements. The specific surface area, pore volume, and pore width distribution of the prepared ACFs were optimized by changing the activation conditions, and ACFs with a specific surface area higher than 1400 m²/g were successfully developed by activation at 950 for 3 h. The amount of micropores occupied more than 90% of the total pore volume. The pore width distribution dominated by micropores is beneficial for CO2 adsorption since the diameter of CO₂ is 0.33 nm. From FTIR and XPS analysis, it is found that the main structure of ACFs is a carbon skeleton composed of polycyclic aromatic hydrocarbons with a small number of oxygen-containing functional groups. The adsorption isotherm of ACFs for CO₂ conforms to the Langmuir model, indicating that the adsorption process of CO₂ by ACFs can be attributed to monolayer adsorption. Both the specific surface area and oxygen-containing functional groups have crucial effects on the adsorption capacity of CO₂. The dynamic adsorption experiment determined that ACFs-920-3 had the highest adsorption capacity for CO₂ in flue gas, and adsorption equilibrium was achieved after 7 min of adsorption. The adsorption process of CO₂ in flue gas by the as-synthesized ACFs fits well with the pseudosecond kinetic model. The CO₂ adsorption capacity of the obtained ACFs remained unchanged after 10 cycles of adsorption. A high-value-added route for synthesizing ACFs for CO₂ capture using CLR as a raw material was developed.