Narrow Results

The purification process of polycyclic aromatic hydrocarbons was carried out by extraction of diesel fraction from the primary oil refining using the effect of magnetic field. A mixture of N-methylpyrrolidone with sulfuric acid was used as an extractant. The content of aromatic hydrocarbons in the diesel fraction decreased by 39.8% under normal conditions and by 50.8% under the influence of magnetic field after extraction. The samples were investigated by infrared (IR) spectroscopy method before and after extraction. Vibartional modes corresponding to different atomic bonds have been observed. Deodorization of diesel was determined by interpreting obtained modes.

This study aimed to investigate the different performance of pile–soil interfaces when the concrete was subjected to sulfuric acid corrosion. A series of large-scale direct shear tests were carried out to study the influence of sulfuric acid corrosion on the interface between soil and concrete pile. Concrete specimens immersed in sulfuric acid solution for different durations (0, 31, 93 and 154 days) were used to simulate the concrete pile surface roughness under sulfuric acid environment, which would be more realistic than the artificially roughened surfaces. Sand was used to simulate the soil. Geometric models of concrete specimens attacked by sulfuric acid were captured using a 3D laser scanning technology, and fractal dimension was adopted to evaluate the surface characterization of concrete subjected to sulfuric acid. The shear stress–displacement curves of the interface between sand and corroded concrete were measured. The shear strength parameters and the Clough–Duncan hyperbolic model parameters were obtained. The relationship between friction angle and fractal dimension was established. The results of the tests showed that with the increase of the corrosion duration, the concrete surface became rougher, the fractal dimensions of concrete surface, the sand-corroded concrete interface friction angle, and the shear displacement at peak stress became larger. A nonlinear relationship was found between the fractal dimension and interface friction angle. The results could provide a reference to diagnose, evaluate, and analyze the interface behavior between sulfuric acid corroded concrete materials and soil.

Density functional theory calculations are performed to provide a molecular-level understanding of the mechanism of mercury adsorption on sulfuric acid-impregnated carbonaceous surface. The carbonaceous surface is modeled by a nine-fused benzene ring in which its edge carbon atoms on the upper side are unsaturated to simulate the active sites for reaction. SO₄ clusters with and without charge are examined to act as the representative species to model the sulfuric acid absorbed on the carbonaceous surface. All of the possible approaches of SO₄ clusters with and without charge on the carbonaceous surface are conduced to study their effects on mercury adsorption. The results suggest that sulfuric acid effect on the mercury adsorption capacity of the carbonaceous surface is very complicated, and it depends on a combination of concentration and charge of SO₄ cluster. SO₄ cluster presents a positive effect on mercury adsorption on the carbonaceous surface, but higher concentration of SO₄ cluster decreases the adsorption capacity of the carbonaceous surface for mercury removal because there is considerable competition for active sites between Hg and SO₄ cluster. Since all of the possible approaches of mercury on the carbonaceous surface with cluster, excluding one that mercury is adsorbed at bridge active site, can lead to the decrease in the adsorption energies of mercury on the carbonaceous surface, cluster presents a negative effect on the capacity of the carbonaceous surface for mercury adsorption regardless of the concentration of cluster. The results also indicate that SO₂ cluster and surface oxygen complex can be formed from SO₄ cluster with or without charge if mercury is adsorbed at bridge active site, which facilitates the mercury removal for the carbonaceous surface.

Using computational calculations, we have revisited the potential energy surface (PES) of the reaction between OH and SO₂, which is believed as the rate-limiting step in the atmospheric formation of H₂SO₄. In this work, we report for the first time the presence of a pre-reaction hydrogen-bonded complex between OH and SO₂ in the reaction PES. Based on this finding, it has been shown that the reaction can be considered as a two-step process in which the first step is the formation of the pre-reaction complex and the second step is the transformation of this complex to the product. It was observed that due to the presence of this pre-reaction complex as a potential well in the reaction PES, the barrier height got increased by around two-fold for the second step. Based on this observation, it has been proposed that the kinetics of the reaction is going to be affected. Also based on the analysis of the geometries of this pre-reaction complex and the transition state, it has been argued that the step involving the transformation of this pre-reaction complex to the product via the transition state is going to be the slowest step as this transformation involves large structural changes of the stationary points involved.