In the present work, cobalt adsorbents supported on graphitic carbon nitride (g-C3N4) were prepared using the impregnation method. The g-C3N4 support was prepared with melamine (GNM) and urea (GNU) as precursors by the direct heat method. The different instrumental techniques, including the BET, FTIR, FESEM, and XRD, were used to characterize the prepared samples. The adsorption outcomes indicate that the adsorption capability of dibenzothiophene (DBT) by Co/GNU adsorbent is higher than Co/GNM adsorbent. The cobalt particle size of Co/GNU is smaller than Co/GNM, and Co/GNU has a larger surface area than Co/GNM, which would improve the adsorption capacity. The experimental data were examined by the Langmuir, Temkin, and Freundlich models of adsorption, and the Langmuir isotherm was very well-fitted. The experimental data showed better fitting with the pseudo-second-order kinetic model. Finally, the thermodynamic outcomes showed that adsorption onto adsorbents is exothermic, and a negative Gibbs free energy displayed that DBT was adsorbed spontaneously onto adsorbents.

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