Asphalt-derived hierarchical porous carbon as an efficient adsorbent for benzene

In this study, a series of asphalt-derived hierarchical porous carbons (A-HPCs) were synthesized using a chemical activation method with potassium hydroxide. The adsorption behavior of A-HPCs for benzene were investigated. The results of the dynamic adsorption experiment revealed a strong linear relationship (R2 = 0.955) between the adsorption capacity and the pore volume of A-HPCs ranging from 0.56 to 1.74 nm (1–3 times the kinetic diameter of benzene). Among the A-HPCs, A-HPC-4 (4:1 of KOH/asphalt) exhibited the highest adsorption performance (qe = 460 mg/g) for benzene. The kinetic analysis reveals that the adsorption of benzene on A-HPCs can be accurately described using the pseudo-first-order kinetic model. The adsorption process exhibits three distinct stages and the intraparticle diffusion process being the main controlling step of the adsorption rate. The adsorption isotherm and thermodynamic calculations demonstrated that the adsorption isotherm followed the Langmuir model, as well as the adsorption process is spontaneous, exothermic, and dominated by physical adsorption. Grand canonical Monte Carlo (GCMC) simulations reveal that the pore sizes of porous carbon significantly affects the adsorption potential between the carbon matrix and benzene molecules, thereby influencing the adsorption capacity. Furthermore, the reusability test reveals that A-HPC-4 remains 88 % of its initial adsorption capacity after five consecutive adsorption–desorption cycles, exhibiting a desorption efficiency exceeding 95 %. This research demonstrates the significant potential of A-HPCs for the removal of benzene.