Removal of 4,6-dimethyldibenzothiophene from model diesel fuel using activated carbon with sulfo group

Adsorption of 4,6-dimethyldibenzothiophene (DMDBT) from model diesel fuel was performed using commercial petroleum pitch based activated carbon treated by (NH4)2S2O8 in 1 M H2SO4 and/or SO3. The treatment of (NH4)2S2O8 in 1 M H2SO4 mainly increased the number of carboxyl groups, whereas the introduction of sulfo group was observed for SO3 treatment. The adsorption of DMDBT on each prepared activated carbon followed the tri-Langmuir isotherm. Carboxyl and sulfo groups on the activated carbon surface increased the amount of DMDBT adsorption, in which the amount adsorbed for each sulfo group was six times greater than that for a carboxyl group. Increasing amounts of 1-methylnaphthalene as an inhibitor caused a decrease in the amount of DMDBT adsorption. However, 1-methylnaphthalene did not affect the adsorption on the sites of carboxyl and sulfo groups. When methanol was used as a polar solvent, adsorption on carboxyl group sites showed a decrease in the amount of DMDBT adsorption, while sulfo groups showed the opposite results. These results were attributed to the oxidation of DMDBT to sulfoxide and/or sulfone by sulfo group on the carbon surface.