Temperature-Induced Transition from Indirect to Direct Adsorption of Polycyclic Aromatic Hydrocarbons on Quartz: A Combined Theoretical and Experimental Study

Abstract

Adsorption of polycyclic aromatic hydrocarbons (PAHs) on mineral surfaces plays an important role in many engineering fields, such as oil recovery and oil sand production. In this work, the adsorption behaviors of a PAH compound, violanthrone-79 (VO-79), on quartz surface were investigated at different temperatures by molecular dynamics (MD) simulation and atomic force microscopy (AFM). Our simulations demonstrated that with increasing temperature, the rate of adsorption increased, whereas the total amount of stably adsorbed VO-79 molecules hardly changed. On the other hand, the adsorption mode had a strong dependence on the temperature. At 323 K, approximately half of the adsorbed VO-79 formed a monolayer with their polyaromatic cores directly contacting and parallel to the quartz surface. The other half were in an aggregated form and adsorbed indirectly, via interaction with directly adsorbed molecules. The polyaromatic cores of VO-79 in the aggregates tend to be oriented slant to the surface. A transition from indirect to direct adsorption was observed as temperature increased, and nearly 90% of VO-79 molecules were adsorbed in direct form at 523 K. AFM imaging confirmed the observations in the MD simulations, showing that smaller and more uniformly distributed VO-79 aggregates adsorbed on the surface with increasing temperature. This work provides valuable insights, at the molecular level, into the effect of temperature on the adsorption of PAHs on mineral surfaces.

Understanding the Aggregation of Model Island and Archipelago Asphaltene Molecules near Kaolinite Surfaces using Molecular Dynamics

“…Our simulations show that adding HEX has no distinct effect on the structure of adsorption of the poly aromatic hydrocarbon on the mineral surface. 35 Although the center of mass of the asphaltenes seems further from the kaolinite surface than toluene, we expect that the presence of oxygen atoms could lead to bonds with the hydroxyl groups on the surface. To confirm this, we calculated the atomic density distribution of 2 oxygen atoms present in the asphaltene structure.…”

Understanding the Properties of Bitumen Froth from Oil Sands Surface Mining and Treatment of Water-in-Oil Emulsions

“…Sparks et al proposed that the interface-active components were highly associated with the adsorbed toluene-insoluble organics, which together with the solids played a vital role in stabilizing the emulsions. An opinion is widely held that the properties of the interface-active components, such as particle size distribution and wettability, have a significant influence on the demulsification efficiency . Dongbao et al postulated that colloidal clays could adversely influence the bitumen recovery in the rag layer during the demulsification.…”

“…An opinion is widely held that the properties of the interface-active components, such as particle size distribution and wettability, have a significant influence on the demulsification efficiency. 58 Dongbao et al 59 postulated that colloidal clays could adversely influence the bitumen recovery in the rag layer during the demulsification. Hence, the fine solids remaining in the diluted bitumen (top layer in Figure 1) after centrifugation were separated and their characteristics were investigated.…”

Interfacial and Confinement-Mediated Organization of Gas Hydrates, Water, Organic Fluids, and Nanoparticles for the Utilization of Subsurface Energy and Geological Resources

“…329−331 The adsorption behavior of asphaltenes on silica surfaces is favored at higher temperatures. 332 Alumina surfaces, on the other hand, showed a lower affinity for asphaltene adsorption compared to silica surfaces, and the adsorption capacity increases with the acidity of alumina. 333,334 Further, alumina nanoparticles showed enhanced asphaltene adsorption capacity due to spontaneous adsorption and exothermic thermodynamics.…”

“…Asphaltene adsorption on silica and alumina surfaces and nanoparticles showed that the adsorption capacity is directly affected by the surface chemistry and morphology of the sorbent and the associated thermal and mechanical conditions. Hydrophilic silica surfaces favor asphaltene adsorption over hydrophobic surfaces. − The adsorption behavior of asphaltenes on silica surfaces is favored at higher temperatures . Alumina surfaces, on the other hand, showed a lower affinity for asphaltene adsorption compared to silica surfaces, and the adsorption capacity increases with the acidity of alumina. , Further, alumina nanoparticles showed enhanced asphaltene adsorption capacity due to spontaneous adsorption and exothermic thermodynamics …”