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

Abstract

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.