Adsorption performance of multiwall carbon nanotubes and graphene oxide for removal of thiophene and dibenzothiophene from model diesel fuel

Multiwall carbon nanotubes (MWCNT) and graphene oxide (GO) are promising compressible nano adsorbents that can be used in the deep desulfurization process for mobile applications. In this study, the adsorption isotherm and the adsorption kinetics of thiophene and dibenzothiophene (DBT) introduced in hexane as a model diesel fuel have been investigated. The adsorption performance of thiophene and DBT on MWCNT and GO were compared with the adsorption performance on activated carbon (AC) as a reference material. In addition, the effect of agitation speed and adsorbent dosage amount were studied. The DBT adsorption results on the three adsorbents were represented by Langmuir and Freundlich isotherm models. The Freundlich isotherm was found to be more favorable with squared correlation coefficient (R₂>0.97. The thiophene adsorption isotherm was fitted only by the Freundlich isotherm model with R₂>0.989. The adsorption rate for these sulfur compounds follows the pseudo-second-order adsorption kinetic. The removal efficiency of DBT using the MWCNT was 68.8 % almost twice the GO removal efficiency but lower than the AC removal efficiency by about 25 %. In addition, the ability of these adsorbents to remove the DBT from the model fuel was much higher than their capability to remove the thiophene.