The adsorption of benzothiophene sulfone (BTO) and dibenzothiophene sulfone (DBTO) from model diesel fuel were evaluated using granular activated carbon (GAC) and modified activated carbon. Modified activated carbon was impregnated with metal ions, Cu2+, Fe3+, and Ni2+, and the effect on its adsorption characteristics was determined. Adsorption performance was investigated using batch process at room temperature and agitation speed of 120 rpm. Results indicated a significant increase in the adsorption capacity compared to that of the unmodified GAC. Increasing adsorption capacity followed the order Cu2+/AC < Ni2+/AC < Fe3+/AC for BTO, whereas for DBTO, increasing order is Ni2+/AC < Fe3+/AC < Cu2+/AC. Evaluation of equilibrium isotherms using Langmuir and Freundlich models yielded a good fit with values of R-2 > 0.90. Adsorption process seemed to proceed in a two-step process. First, a very fast rate for the first few minutes, then a markedly reduced rate until equilibrium is reached. All the adsorbents used have several functional groups present on its surface, and it is the nature of these surface groups that determine the character of these adsorbents.
