Study of asphaltene adsorption onto raw surfaces and iron nanoparticles by AFM force spectroscopy

The comprehension of dominant driving forces for Asphaltene self aggregation and adsorption onto surfaces are still under discussion. Experimental results point to combined effects of the local electrical fields, molecular polarization, and dispersion interactions play a relevant role in the adsorption. The nature and size of sorbent material has a determinant influence in the process, sorbent with size in the order of asphaltenes nanoaggregates could modificate the adsorption mechanism. This work focus to study the differences in asphaltenes adsorption driving forces of asphaltenes onto macro and nanosurfaces. AFM Force-displacement curves have been used to study the interaction forces between AFM tip and asphaltenes adsorbed onto macroscopy surfaces and Zero valent iron nanoparticles (FeNps). FeNps were prepared by laser ablation and used as sorbent material for Asphaltenes adsorption at very low Asphaltene in toluene concentration ranging from 1 to 10 mg/g. The FeNps were characterized by Uv-Vis Spectroscopy, Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). AFM Force vs Separation of asphaltenes adsorbed onto macroscopic surface compared with adsorption onto NPs curves shown the importance of the surface size and morphology and asphaltenes molecular arrangement in the adsorption process. Properties as Force interaction, adhesion and Hamaker constant for each system were obtained.