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Surfactant molecules can change the hydrophobic nature of microplastic surfaces, thereby affecting the adsorption of heavy metals in the environment onto the microplastics. It is essential to explore the role of crack structure of microplastics in the adsorption of heavy metals, especially in the presence of surfactants. In this study, polyethylene (PE) and polypropylene (PP) were evaluated for Pb(II) adsorption and desorption mechanism in the presence of two surfactants: cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzenesulfonate (SDBS). The experimental results were analyzed using kinetics and the isothermal model fitting and spectrogram (FTIR, XPS). This study showed that the application of surfactants could greatly enhance the Pb(II) adsorption capacities of PE and PP by promoting Pb(II) into the fissures. The Pb(II), S, and N contents did not significantly decrease at different depths in the presence of surfactants, and the Pb(II) content without surfactants decreased with an increasing depth. The adsorption behavior was consistent with the Bangham channel diffusion model and the DR model, suggesting that the adsorption process was related to the pore structure of the microplastics. Furthermore, the release of Pb(II) from desorption using high concentration of surfactant solution was less than that of low concentration, it was difficult to release heavy metals primarily because of the crack structure of the microplastics, especially when more surfactant molecules entered the pores. This work contributes to a better understanding of the adsorption mechanism of heavy metals on microplastics in the presence of surfactants, which will better control the ecological risks of microplastics.

This experimental study focused on vapor cloud explosion and its chain reaction induced by an explosion venting flame. Two vapor clouds were installed in front of the explosion venting container along the horizontal direction. Explosion flame evolution process was recorded by a high-speed camera and a schlieren system. Pressure sensors at different locations were used to acquire the pressure data. The temperature data were collected by a high-speed infrared thermal imager and three thermocouples. The changes in flame propagation characteristics, flame temperature, and pressure distribution were determined, and the mechanisms of the vapor cloud explosion and its chain reaction induced by the venting flame were deeply analyzed. Results indicate that the venting flame could induce vapor cloud explosion and set off a chain reaction, leading to the high explosion intensity. As for the ignition condition, the venting flame directly came in contact with the vapor cloud and provided the required energy for the ignition. The pressure first increased and then decreased as the distance from the venting port increased, and the highest pressure appeared in the central region of the vapor cloud. The temperature distribution also presented a similar phenomenon.

The degradable properties of degradable plastics allow them to form microplastics (MPs) faster. Therefore, degradable MPs may easily be transported in the underground environment. Research on degradable MPs transport in porous media is necessary and urgent. In this study, polylactic acid (PLA) and polyvinyl chloride (PVC) were selected to compare the transport differences between degradable and nondegradable MPs under different factors (flow rates, ionic strengths (ISs), pH, and coexisting cations) through column experiments, and UV irradiation was used to further simulate the effect of aging on different types of MPs. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) were used to characterize functional groups and to determine the surface elements of MPs, respectively. The results showed that MPs were more mobile at higher flow rate, lower IS, higher pH, and monovalent cations. The order of transport capacity of MPs was PVCaged PVCPLAaged PLA. This result was mainly attributed to the more negative Zeta potential and higher dispersion stability of aged PLA and PLA, which were caused by abundant O-functional groups. Compared with PVC, the O/C ratio of PLA increased significantly after aging, indicating that PLA was more prone to aging. The advection-dispersion-equation (ADE) fitted the transport data of MPs well. The interaction energy of MPs and quartz sand was accurately predicted by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. This work contributes to a comprehensive understanding of the transport of degradable MPs in the environment.

The adhesion of surfactant molecules on the microplastics surface is affected by the surface structure of the microplastics. Little is known about the mobility of different microplastics in the medium under surfactants. In order to reveal the migration of different microplastics under the action of surfactants, the study selected five kinds of microplastics (polyethylene (PE), polypropylene (PP), polystyrene (PS), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA)) and two kinds of surfactants (cetyltrimethylammonium bromide, CTAB and sodium dodecyl benzene sulfonate, SDBS) as the research objects. The column experiment was used to explore the transport behavior of microplastics under different concentrations of surfactants and the convection dispersion model was used to simulate. The dynamic contact angle of the surfactant solution on the microplastics was measured and the adhesion work was calculated by the Young-Dupre equation to reveal the underlying mechanism of microplastics retention in the presence of surfactants. The results showed that the transport ability of microplastics followed the order of PTFEPMMAPSPEPP, and the mobility under high concentrations of surfactants was greater than that at low concentrations, which was mainly attributed to the difference in the adhesion of the surfactant on the surface of the microplastics, which lead to differences in the migration between the microplastics. When the microplastics were close to each other, if the reaction force of the electrostatic force was greater than the adhesion force of the surfactant molecules on the surface, the surfactant molecules would be separated from the microplastics and the stability of the microplastics would decrease. In addition, the migration ability of microplastics in anionic surfactants was weaker than that of cationic surfactants, because the osmotic and elastic repulsion produced by SDBS were weaker than CTAB. The research results were of great significance for understanding the environmental behavior of microplastics affected by surfactants, and objectively evaluating the transport and fate behavior of microplastics-surfactants in the environment.

g-C3N4 decorated Bi2WO6 microspheres with scales of 2.0∼3.0 μm were prepared via a hydrothermal method. The matching of energy band between g-C3N4 and Bi2WO6 facilitate the absorption visible light and the separation of electron-carrier. The morphology, constitute and optical properties of the as-prepared samples is confirmed by different characterization techniques, such as, XRD, XPS, EDS, SEM, UV–vis, and N2 adsorption-desorption. The photocatalytic activities were assessed by the photodegradation of Methyl orange (MO) and phenol under visible light irradiation. The results indicated that the decoration of g-C3N4 evidently improves the photocatalytic activity of Bi2WO6, and the content of g-C3N4 has significantly effect on the catalytic activity of Bi2WO6. By comparison of other samples, 3 wt% g-C3N4/Bi2WO6 composites present an extraordinary enhanced photocatalytic activity for the photodegradation of MO and phenol under visible light. On the basis of the result and discussion, the possible mechanism of enhanced photocatalytic activity of g-C3N4/Bi2WO6 composites is proposed. It implies that the combination of g-C3N4 and Bi2WO6 provided synergistic photocatalytic activity via an efficient electron transfer process. Furthermore, the photocatalytic degradation of MO over g-C3N4/Bi2WO6 is promoted mainly by h+, and the same time •OH also plays a positive role in this degradation process.

By combining the photochemical reaction and liquid–liquid extraction (PODS), we studied desulfurization of model fuel and FCC gasoline. The effects of air flow, illumination time, extractants, volume ratios of extractant/fuel, and catalyst amounts on the desulfurization process of PODS were analyzed in detail. Under the conditions with the air as oxidant (150 ml·min − 1 ), the mixture of DMF–water as extractant (the volume ratio of extractant/oil of 0.5) and photo-irradiation time of 2 h, the sulfur removal rate reached only 42.63% and 39.54% for the model and FCC gasoline, respectively. Under the same conditions, the sulfur removal rate increased significantly up to 79% for gasoline in the presence of Cu 2 O catalyst (2 g·L − 1 ). The results suggest that the PODS combined with a Cu 2 O catalyst seems to be a promising alternative for sulfur removal of gasoline.

To develop highly efficient photocatalyst for treatment of phenol-contained wastewater, Cu-doped Bi2WO6 (Cu-Bi2WO6) photocatalyst is synthesized via an optimized hydrothermal method. The influences of the synthesis parameters such as Cu loading, initial pH, reaction time and temperature on the crystal structure of Cu-Bi2WO6 are systematically examined from XRD, XPS, DRS and SEM analyses. The results show Cu doping leads to a significant red-shift of the absorption band of Cu-Bi2WO6 in visible light region. When Cu loading is 0.5 wt%, Cu-Bi2WO6 shows sharp diffractions due to higher crystallinity, and further for pH = 0.6, the prepared Cu-Bi2WO6 shows a narrow diffraction with greater intensity. Further analyses show that Cu-Bi2WO6 is characterized by a 3D flower spherical morphology expressing a relatively large micro-porosity size, with specific surface area as high as 85 m2/g. The photocatalytic activity of Cu-Bi2WO6 for degradation of phenol in wastewater under visible light irradiation is systematically examined. The related kinetic study shows that Cu doping can greatly improve the photocatalytic activity of the resulting Cu-Bi2WO6, and moreover Cu loading has a great impact on the photocatalytic activity. Optimally, Cu-Bi2WO6 doped with 0.5 wt% Cu exhibits the highest photocatalytic activity with the efficiency for phenol removal as high as 92%, 23% higher than that of pristine Bi2WO6 under the same condition. Our work provides a facile, cost-effective and environmentally friendly way to enhance the efficiency of Bi2WO6 for photo-catalytically degradative removal of phenol pollutants in wastewater.