To clarify the inconsistent behavior of the literatures' results, the impact of various Activated carbon (AC) oxygen functional groups (OFGs) were assessed systematically on the adsorption of thiophenic compounds (TCs). AC samples were oxidized with HNO3 and, afterwards, heat treated to load different OFGs. The adsorption capacity of TCs increases in the range of 30-100% by oxidation at 25 degrees C. At severe oxidation condition the adsorption capacity decreases 17.2-100% due to pore blocking. As methyl group or aromatic ring of adsorbate molecules increases, the most likely adsorption mechanism will be interaction to active site, whereas dispersion interaction is the governing adsorption mechanism of adsorbate molecules with lower number of aromatic ring.