Abstract
The adsorption of three typical polycyclic aromatic hydrocarbons (PAHs), naphthalene, phenanthrene, and pyrene with different ring numbers, on a common mesoporous material (MCM-41) was simulated based on a well-validated model. The adsorption equilibriums (isotherms), states (angle distributions and density profiles), and interactions (radial distribution functions) of three PAHs within the mesopores were studied in detail. The results show that the simulated isotherms agreed with previous experimental results. Each of the PAHs with flat molecules showed an adsorption configuration that was parallel to the surface of the pore, in the following order according to the degree of arrangement: pyrene (Pyr) > phenanthrene (Phe) > naphthalene (Nap). In terms of the interaction forces, there were no hydrogen bonds or other strong polar forces between the PAHs and MCM-41, and the O–H bond on the adsorbent surface had a unique angle in relation to the PAH molecular plane. The polarities of different H atoms on the PAHs were roughly the same, while those of the C atoms on the PAHs decreased from the molecular centers to the edges. The increasing area of the π-electron plane on the PAHs with the increasing ring number could lead to stronger adsorption interactions, and thus a shorter distance between the adsorbate and the adsorbent.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) generally refer to hydrocarbons that have two or more benzene rings [1,2]
Figure 6(1) shows that the H atoms on the polycyclic aromatic hydrocarbons (PAHs) at different positions were the same distance from the O atoms on the surface of MCM-41
The adsorption model was validated by use of experimental adsorption isotherms
Summary
Polycyclic aromatic hydrocarbons (PAHs) generally refer to hydrocarbons that have two or more benzene rings [1,2]. Molecular simulation has obvious benefits in the adsorption isotherm calculation and adsorption state analysis of adsorption molecules. It can analyze the adsorption mechanism [17,18] and the nature of action in depth, and it has been widely used in adsorbent selection and design [19,20]. Studying the adsorption of typical PAHs such as Nap, Phe, and Pyr on mesoporous adsorbents is helpful to understand the adsorption mechanism and its application in the removal of PAHs. Analysis of the state of molecules inside the adsorbent is extremely important for research and the improvement of adsorption efficiency. The potential adsorption mechanism will be discussed based on the adsorption states of the three molecules in the pores
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