The role of soil clay minerals is often ignored in studying the polycyclic aromatic hydrocarbons (PAHs) adsorption in soil. In this work, Monte Carlo and molecular dynamics simulations are used to study the adsorption of PAHs on several typical soil clay mineral surfaces, such as (0 0 1) and (0 0 − 1) of kaolinite, pyrophyllite, mica, and montmorillonite. Results show that van der Waals and cation-π interactions dominate the interactions between PAHs and mineral surfaces. Bridging oxygen atom on the mineral surface structure is the main site of hydrophobic interaction with PAHs. The cation-π effect can significantly enhance the PAHs adsorption energy. In addition, the adsorption on clay minerals is enhanced with the increase in the number of PAHs aromatic rings. In the presence of water, different minerals exhibit different adsorption properties. A layer of water molecules is formed close to the kaolinite (0 0 1) surface, reducing PAHs adsorption. The self-diffusion coefficient (D) of PAHs in Ca²⁺-montmorillonite is more significant than that in K⁺-mica, due to the different hydration properties of mineral cations. These findings reveal the adsorption mechanism of PAHs on the surfaces of typical clay minerals at a molecular scale and provide a new perspective for soil adsorption of PAHs.

The reactive adsorption desulfurization (RADS) of a model gasoline n-hexane containing thiophene was carried out with a NiO/ZnO-Al₂O₃-SiO₂ adsorbent in N₂ and H₂, respectively. A declining RADS trend has been observed in N₂, without the presence of H₂, indicating that NiO is sulfurized and exhibits activity for RADS. TPR and XPS results presented NiO in the adsorbent is hard to be reduced because of the powerful interaction between NiO and the support. The sulfurization of NiO into NiSx is a primary condition for the RADS process, the same as the presulfurization of hydrotreating catalyst, while metallic Ni is an intermediate reduction product of NiSx. Results of a low RADS temperature at 300 °C, much lower than the reduction temperature of NiO, suggest that NiO plays an important role. Based on assumption of NiO as the main active component, the RADS could reduce the reaction temperature and energy consumption significantly. The participation of hydrogen and n-hexane in pretreatment conducted at 420 °C contributes to the activation of adsorbent. Also, these methods of pretreatment improved the desulfurization performance under the reaction temperature of 300 °C.