Effect of microwave modification on activated carbon and its adsorption of methanol

Activated carbon (AC) was modified with microwave irradiation at 600, 700 and 800°Crespectively. Specific surface area and pore size analyzer, Boehm titration and Fourier transformed infrared spectroscopy were used to measure the physicochemical properties of the activated carbons. Fixed-bed adsorption experiments were conducted at 10°C with methanol as the adsorbate. The research shows that, after microwave modification, the specific surface area and total pore volume of activated carbons decrease slightly, but the micropore specific surface area increases remarkably. With the rise of temperature, large numbers of surface acidic functional groups of activated carbons resolve and surface basic functional groups are formed gradually. Both the Langmuir equation and Freundlich equation can well describe the adsorption of methanol on the activated carbons. Pseudo-second-order kinetic equation describes the dynamic adsorption process of methanol most suitably, which illustrates that methanol adsorption is a physical and chemical composite adsorption process, and adsorption is affected by the surface functional groups of the activated carbons. The fitting result of intra-particle diffusion model is divided into three linear stages: surface adsorption stage, asymptotic adsorption stage and adsorption equilibrium stage. After microwave modification, the adsorption energy of activated carbons for methanol increases, and the adsorption energy is proportional to the contents of surface nitrogen groups of the activated carbon.