Hydrothermal pretreatment of lignin-derived activated carbon for enhanced competitive adsorption of benzene and NO: Mechanistic insights from DFT simulations

In this study, mesoporous activated carbon with high specific surface area was synthesized using lignin as the carbon source through hydrothermal pretreatment and alkali activation. The prepared activated carbon HL-4–200–800 exhibited a specific surface area as high as 3057 m²/g and a pore volume of 2.80 cm³/g. The excellent physicochemical properties were confirmed by comprehensive characterization methods including nitrogen adsorption/desorption isotherms, elemental analysis (EA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). Moreover, the prepared samples demonstrated outstanding adsorption performance, with a saturated adsorption capacity of 2030.13 mg/g for gaseous benzene and 140.41 mg/g for NO at 298 K. Further analysis through isotherm fitting, adsorption kinetics modeling, and ideal adsorbed solution theory (IAST) indicated that the material showed significantly better adsorption selectivity for benzene than for NO. Density functional theory (DFT) simulations revealed the competitive adsorption mechanism between benzene and NO, highlighting the crucial role of surface functional groups in enhancing adsorption efficiency.