Adsorptive denitrogenation of model fuels using copper and nickel adsorbents supported on reduced graphene oxide nanosheets†

This study utilizes the impregnation method to produce reduced graphene oxide (rGO) nanosheets by a 15-weight percent loading of copper and nickel. The prepared samples were used as denitrogenation adsorbents for model fuels. Different instrumental techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, N₂ adsorption–desorption analysis, and field emission scanning electron microscopy (SEM), were used to characterize the synthesized samples. When copper and nickel oxides are impregnated, GO is partially reduced, according to the X-ray diffraction (XRD) patterns of the NiO/rGO and CuO/rGO adsorbents. The results show that the surface area and mean pore diameter of the CuO/rGO adsorbent are higher than those of the NiO/rGO adsorbent. The findings of the adsorption study indicate that the adsorption capacity of the CuO/rGO adsorbent (0.335 mmol g⁻¹) for the carbazole (CBZ) is higher than that of the NiO/rGO adsorbent (0.315 mmol g⁻¹) at 278 K. Still, the heat of adsorption on the NiO/rGO adsorbent (−18.60 kJ mol⁻¹) is higher than that on CuO/rGO (−13.73 kJ mol⁻¹). The activation energy of the intraparticle diffusion of the NiO/rGO adsorbent is higher than that of the CuO/rGO adsorbent due to the lower mean pore diameter of the NiO/rGO adsorbent. The activation energies of the pseudo-first-order kinetics of NiO/rGO and CuO/rGO adsorbents are 11.13 and 4.89 kJ mol⁻¹, respectively, which show the higher performance of the CuO/rGO adsorbent in the primary stages of CBZ adsorption.