Adsorption and removal of asphaltene using synthesized maghemite and hematite nanoparticles

Abstract

In this study, the synthesized maghemite (γ-Fe2O3) and hematite (α-Fe2O3) nanoparticles were used for the adsorption and removal of asphaltene from prepared solution. The co-precipitation of ferric and ferrous ions method was applied to synthesis the maghemite nanoparticles (MNPs) and followed by the hematite nanoparticles (HNPs) synthesis via calcination of the MNPs. Both of the synthesized nanoparticles were characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The prepared nanoparticles were used for the removal of asphaltene in the adsorption process. The processes were carried out systematically by batch experiments to investigate the influence of different factors, such as the temperature, contact time, initial concentration of asphaltene, and type of the nanoparticles. The FTIR spectra of nanoparticles containing the adsorbed asphaltene (i.e., MNP/Asph and HNP/Asph) confirmed that asphaltenes adsorb well on the nanoparticles. The experimental data of asphaltene adsorption isotherms were adequately fitted by the solid-liquid equilibrium (SLE) thermodynamic model, indicating asphaltene self-association and multilayer adsorption onto the nanoparticles. The results also showed that maximum adsorption capacity of MNPs and HNPs is 108.1 and 45.8 mg/g, respectively. The kinetic data of adsorption of asphaltene on the synthesized nanoadsorbents were best described by the double-exponential model (DEM). The overall initial mass-transfer rate calculation indicated that the adsorption of asphaltene onto HNPs is faster than MNPs, and therefore, the process in the presence of HNPs quickly reaches equilibrium compared to MNPs. Furthermore, the calculated Gibbs free energies, entropies, and enthalpies demonstrated that the adsorption of asphaltene onto MNPs and HNPs is endothermic and exothermic, respectively, and the process is spontaneous. This work showed that synthesized MNPs and HNPs can be considered as asphaltene nanoadsorbents, although MNPs are more effective.