Application of Novel Fe3O4–Polyaniline Nanocomposites in Asphaltene Adsorptive Removal: Equilibrium, Kinetic Study and DFT Calculations

Abstract

Recent investigations have shown that surface modification can improve the colloidal stability and chemical properties of the metallic nanoparticles. In this study, poly aniline (PANI) coated Fe3O4 nanoparticles were synthesized and used for asphaltene adsorption. The prepared nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier-transform infrared spectroscopy and vibrating-sample magnetometer techniques. The effects of adsorbent amount, initial asphaltene concentration and heptane to toluene volume ratio on the sorbents adsorptive capability were studied. The experimental sorption isotherm data was fitted to the Langmuir isotherm model for coated and uncoated adsorbents. The kinetic data was consistent with Pseudo second order kinetic model. Asphaltene adsorption on Fe3O4/PANI composite was much higher than pure Fe3O4 due to the significant π–π interactions between asphaltene and adsorbent and stability effect of PANI. The results indicated that PANI coated Fe3O4 is an appropriate candidate for crude oil upgrading. Moreover, density functional theory calculations confirm that the adsorption energy of asphaltene over the Fe3O4/PANI composite is larger than that over the bare Fe3O4. This can be mainly attributed to the more favorable orbital interactions as well as charge-transfer effects between asphaltene and PANI in the former system.