Effect of initial temperature on the Efficiency of asphaltene adsorption onto lime nanoparticles: a molecular dynamics study

Molecular dynamics simulations were employed to investigate the adsorption behavior of asphaltene molecules onto lime nanoparticles (NPs) in an aqueous medium. Initially, atomic models comprising asphaltene molecules and 20 wt% lime NPs were equilibrated for 10 ns. Following equilibration, the adsorption process was simulated over an additional 10 ns. The results demonstrated substantial adsorption of asphaltene molecules, with the maximum atomic density reaching 180.72 atoms/ų at the center of the simulation box, where the NPs were initially positioned. The interaction energy between lime NPs and asphaltene molecules increased progressively to approximately 0.047 kcal/mol, indicating enhanced interfacial interactions and the establishment of a thermodynamically stable configuration. Adsorption analysis revealed that approximately 69% of asphaltene molecules adhered to the NP surfaces within the first 7 nanoseconds, after which the adsorption process approached saturation. As the initial temperature increased, the maximum atomic density decreased. This reduction is attributed to the higher kinetic energy of the molecules, which allows them to move more freely and spread out within the system, resulting in a lower local density. Additionally, the interaction energy between NPs and asphaltene dropped from 0.047 to 0.031 kcal/mol, indicating a weakening of the attractive forces between these components at elevated temperatures. This decrease in interaction energy leads to reduced adhesion and weaker binding of asphaltene molecules to the NP surfaces. Finally, the asphaltene adsorption ratio declined from 69% to 56%, reflecting a lower degree of asphaltene adsorption onto the NPs as the temperature rises.