Study on the adsorption mechanism of polar and non-polar VOCs by the activated carbon with surface oxygen

In this study, CO2 was converted to activated carbon by the molten salt CO2 capture and electrochemical conversion (MSCC-EC) method, and the surface oxygen content of the activated carbon was further modified for the adsorption of polar molecules (chlorobenzene) and nonpolar molecules (toluene), the role of the pore structure and surface O-containing functional groups of the adsorbents in contributing to the adsorption process was systematically investigated. The results showed that MS-AC500-10, MS-AC500-15, and MS-AC550-15 have rich pore structures with specific surface areas of 811.56 m2/g, 835.35 m2/g, 1249.104 m2/g, and surface oxygen contents of about 10 %, 15 %, 15 %, respectively. The toluene adsorption capacity of MS-AC500-10, MS-AC500-15, and MS-AC550-15 was 203.82 mg/g, 229.72 mg/g, and 358.97 mg/g, respectively, and was dominated by pore adsorption, which was positively proportional to the specific surface areas and pore volumes, the adsorption process belonged to the pseudo-first-order kinetic model. The adsorption amounts of chlorobenzene by MS-AC500-10, MS-AC500-15, and MS-AC550-15 were 287.98 mg/g, 363.11 mg/g, and 495.41 mg/g, respectively. In addition to the pore adsorption, the oxygen content on the surface of the adsorbents had a non-negligible promotion effect on the adsorption of chlorobenzene, mainly because chlorobenzene is a polar molecule, and the asymmetric electrons on its surface have strong interactions with the O-containing functional groups on the surface of the adsorbents. Moreover, the prepared adsorbents were thermally stable, and the decay rate of adsorption performance was less than 5 % after five adsorption–desorption cycles.