Adsorption of Naphthalene on Clay Minerals: A Molecular Dynamics Simulation Study

Abstract

Naphthalene, as one of the representative polycyclic aromatic hydrocarbons, widely exists in contaminated sites and is a potential threat to human health due to its high mobility in soil. The interaction between naphthalene and clay minerals is of great significance to the environmental behavior of naphthalene and the design of remediation technology. In this study, montmorillonite and kaolinite were selected as representative clay minerals. Naphthalene adsorption behavior on mineral surfaces and water-wet kaolinite surfaces was investigated using molecular dynamics (MD) simulation. The interaction energy was calculated to represent the interaction between naphthalene and soil fractions, and the relative concentration and density distribution of naphthalene was analyzed to describe the distribution of naphthalene on the clay surfaces. The self-diffusion coefficient of naphthalene was obtained to represent its mobility under different water content. The electron density calculation was performed to reveal the different adsorption behavior of naphthalene on different surfaces of kaolinite. The simulation results show that montmorillonite had a stronger interaction with naphthalene due to larger electrostatic interaction energy compared to kaolinite, and naphthalene distributed more intensively on the montmorillonite surface. With regards to kaolinite, naphthalene tended to be absorbed on the alumina octahedral surface rather than the silicon tetrahedral surface due to the weak hydron bond interaction. The results indicate that water impeded the adsorption of naphthalene, and the optimal initial thickness of water film, which was 10 Å, was put forward for the application of thermal remediation technology. Furthermore, the average interaction energies between water and mineral surfaces largely depended on the water content, and the competitive adsorption between water and naphthalene only occurred under absorbed and bound water conditions. Overall, the knowledge of naphthalene–soil fractions interaction gained in this study is critical to the understanding of the environmental behavior of naphthalene and the reference for remediation technology.

Determining the Geometric Surface Area of Mesoporous Materials

“…Muscovite, mica, and montmorillonite were selected as representative 2:1 clay minerals. The basic structure and unit cell of these six minerals come from the Surface Model Database V1.5 of INTERFACE , (Figure ). A (5 × 3 × 1) supercell was created for each clay mineral surface to ensure that the box length was larger than 10 times the collision diameter of nitrogen.…”

Application of molecular dynamics simulations in interface interaction of clay: Current status and perspectives

“…In order to research the synergistic adsorption of multiple kinds of polymers on the surface of montmorillonite (Mt) substrates in an aqueous environment, MD method was used to reveal the different adsorption characteristics of cationic (chitosan), neutral (PAM), and anionic (MF) polymers on the surface of negatively charged montmorillonite substrates, providing a theoretical ground for the experimental implementation of synergistic flocculation of various polymers 64 . Chen et al 65 chose kaolinite and montmorillonite as representatives among the clay minerals and studied the adsorption behavior of naphthalene on the mineral surface and water‐wet kaolinite surface using MD simulation, revealing the interaction mechanism of naphthalene with clay minerals, which has important implications for the environmental behavior of naphthalene in soil and the design of remediation techniques. Ren et al 66 showed the true density distribution of surface water when NPAM was adsorbed with kaolinite and the horizontal mean mass density field for different amounts of NPAM on the kaolinite surface, as shown in Figure 4 66 …”

“…In order to research the synergistic adsorption of multiple kinds of polymers on the surface of montmorillonite (Mt) substrates in an aqueous environment, MD method was used to reveal the different adsorption characteristics of cationic (chitosan), neutral (PAM), and anionic (MF) polymers on the surface of negatively charged montmorillonite substrates, providing a theoretical ground for the experimental implementation of synergistic flocculation of various polymers. 64 Chen et al 65 chose kaolinite and montmorillonite as representatives…”

Determining the geometric surface area of mesoporous materials

“…Muscovite, mica, and montmorillonite are selected as representative 2:1 clay mineral s. The basic structure and unit cell of these six minerals come from the Surface Model Database V1.5 of INTERFACE [31,32] (Fig. 3a).…”