Fengjun Zhang

Synthesis of Bi2WO6/Bi2O3 Composite with Enhanced Photocatalytic Activity by a Facile One‐step Hydrothermal Synthesis Route

In this study, the characterization and photocatalytic activity of Bi2WO6/Bi2O3 under visible‐light irradiation was investigated in detail. The results suggested that Bi2WO6/Bi2O3 can be synthesized by a facile one‐pot hydrothermal route using a super big 200 mL Teflon‐lined autoclave with optimal sodium oleate/Bi molar ratio of 1.25. Through the characterization of Bi2WO6/Bi2O3 by X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared, UV‐vis diffuse reflectance spectra and Photoluminescence spectra, it was found that the as‐prepared composite possessed smaller crystallite size and higher visible‐light responsive than the pure Bi2WO6. Moreover, it was expected that the as‐prepared composites exhibited enhanced photocatalytic activity for the degradation of Rhodamine B under visible‐light irradiation, which could be ascribed to their improved light absorption property and the reduced recombination of the photogenerated electrons and holes during the photocatalytic reaction. In general, this study could provide a principle method to synthesize Bi2WO6/Bi2O3 with enhanced photocatalytic activity by one‐step hydrothermal synthesis route for environmental purification.

One-step synthesis of Bi2WO6/Bi2O3 loaded reduced graphene oxide multicomponent composite with enhanced visible-light photocatalytic activity

In this study, the characterization and photocatalytic activity of Bi2WO6/Bi2O3 loaded reduced graphene oxide under visible-light irradiation was investigated in detail. The results suggested that the Bi2WO6/Bi2O3 loaded reduced graphene oxide can be synthesized by a facile one-step solvothermal process. Through the characterization of the composite photocatalyst by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, UV-vis diffuse reflectance spectra and photoluminescence spectra, it was found that Bi2WO6/Bi2O3@RGO composite was formed, meanwhile GO was completely reduced to graphene and bonded with Bi2WO6/Bi2O3 with by C–O to form composite. The as-prepared composite owned enhanced absorption in the UV to visible-light region and exhibited decreased radiative recombination of photogenerated charge carriers. Moreover, it was expected that the as-prepared composites exhibited enhanced photocatalytic activity for the degradation of Rhodamine B under visible-light irradiation. Among them, BWO@R3 (GO% = 5%) owned the best photocatalytic activity, which can photodegrade RhB (10−2 g L−1) reaching 99.6% in 20 min and high concentration RhB (30−2 g L−1) reaching 99.2% in 180 min. It can be ascribed to their improved light absorption property and the reduced recombination of the photogenerated electron–holes during the photocatalytic reaction.

Evaluation of CO2 solubility-trapping and mineral-trapping in microbial-mediated CO2–brine–sandstone interaction

Evaluation of CO₂ solubility-trapping and mineral-trapping by microbial-mediated process was investigated by lab experiments in this study. The results verified that microbes could adapt and keep relatively high activity under extreme subsurface environment (pH<5, temperature>50 °C, salinity>1.0 mol/L). When microbes mediated in the CO₂-brine-sandstone interaction, the CO₂ solubility-trapping was enhanced. The more biomass of microbe added, the more amount of CO₂ dissolved and trapped into the water. Consequently, the corrosion of feldspars and clay minerals such as chlorite was improved in relative short-term CO₂-brine-sandstone interaction, providing a favorable condition for CO₂ mineral-trapping. Through SEM images and EDS analyses, secondary minerals such as transition-state calcite and crystal siderite were observed, further indicating that the microbes played a positive role in CO₂ mineral trapping. As such, bioaugmentation of indigenous microbes would be a promising technology to enhance the CO₂ capture and storage in such deep saline aquifer like Erdos, China.

Simulation of CO2-water-rock interactions on geologic CO2 sequestration under geological conditions of China.

The main purpose of this study focused on the feasibility of geologic CO2 sequestration within the actual geological conditions of the first Carbon Capture and Storage (CCS) project in China. This study investigated CO2-water-rock interactions under simulated hydrothermal conditions via physicochemical analyses and scanning electron microscopy (SEM). Mass loss measurement and SEM showed that corrosion of feldspars, silica, and clay minerals increased with increasing temperature. Corrosion of sandstone samples in the CO2-containing fluid showed a positive correlation with temperature. During reaction at 70°C, 85°C, and 100°C, gibbsite (an intermediate mineral product) formed on the sample surface. This demonstrated mineral capture of CO2 and supported the feasibility of geologic CO2 sequestration. Chemical analyses suggested a dissolution-reprecipitation mechanism underlying the CO2-water-rock interactions. The results of this study suggested that mineral dissolution, new mineral precipitation, and carbonic acid formation-dissociation are closely interrelated in CO2-water-rock interactions.

CeO2/Bi2WO6 Heterostructured Microsphere with Excellent Visible-light-driven Photocatalytic Performance for Degradation of Tetracycline Hydrochloride

CeO2/Bi2WO6 heterostructured microsphere with excellent and stable photocatalytic activity for degradation tetracyclines was successfully synthesized via a facile solvothermal route. The photocatalytic experiments indicated that CeO2/Bi2WO6 heterostructured microspheres exhibited enhanced photocatalytic activity compared to pure Bi2WO6 in both the degradation of tetracycline hydrochloride (TCH) and rhodamine B (RhB) under visible‐light irradiation. The 1CeO2/2Bi2WO6 exhibited the best photocatalytic activity for degradation of TCH, reaching 91% after 60 min reaction. The results suggested that the particular morphological conformation of the microspheres resulted in smaller size and more uniform morphology so as to increase the specific surface area. Meanwhile, the heterojunction was formed by coupling CeO2 and Bi2WO6 in the as‐prepared microspheres, so that the separation efficiency of photogenerated electrons and holes was dramatically improved and the lifetimes of charge carriers were prolonged. Hence, introduction of CeO2 could significantly enhance the photocatalytic activity of CeO2/Bi2WO6 heterostructured microspheres and facilitate the degradation of TCH. This work provided not only a principle method to synthesize CeO2/Bi2WO6 with the excellent photocatalytic performance for actual produce, but also a excellent property of the photocatalyst for potential application in photocatalytic treatment of tetracyclines wastewater from pharmaceutical factory.

Facile synthesis of Bi2WO6/Bi2O3-loaded polyurethane sponge with enhanced visible light photocatalytic activity

In this study, Bi2WO6/Bi2O3-loaded polyurethane sponge composite photocatalyst was successfully synthesized via a facile two-step approach. The composite was characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance, and scanning electron microscopy. The Bi2WO6/Bi2O3 photocatalyst was successfully loaded on polyurethane sponge and the composite displayed enhanced absorption in the ultraviolet-to-visible light region. Furthermore, the composite exhibited enhanced photocatalytic activity and reusability towards the degradation of rhodamine B (RhB) under visible light. This work demonstrates a facile method for synthesizing Bi2WO6/Bi2O3-loaded polyurethane sponge with enhanced photocatalytic activity and easy immobilization of the photocatalyst for application in environmental purification.

Heat-Activated Persulfate Oxidation of Chlorinated Solvents in Sandy Soil

Heat-activated persulfate oxidative treatment of chlorinated organic solvents containing chlorinated ethenes and ethanes in soil was investigated with different persulfate dosages (20 g/L, 40 g/L, and 60 g/L) and different temperatures (30°C, 40°C, and 50°C). Chlorinated organic solvents removal was increased as persulfate concentration increase. The persulfate dosage of 20 g/L with the highest OE (oxidant efficiency) value was economically suitable for chlorinated organic solvents removal. The increasing temperature contributed to the increasing depletion of chlorinated organic solvents. Chlorinated ethenes were more easily removed than chlorinated ethanes. Moreover, the persulfate depletion followed the pseudo-first-order reaction kinetics (, ). Heat-activated persulfate appeared to be an effective oxidant for treatment of chlorinated hydrocarbons.

Abatement efficiency and controlling strategy of a cylindrical and a conical fluidized bed flocculator

The aggregation efficiency of colloidal kaolin particles by the turbulence caused by random movement of silica gel beads in a cylindrical (CFB) and an 8 degrees conical fluidized bed (TFB) was studied in this paper, focusing on the control strategies of these novel processes. The abatement efficiencies as a function of the Camp number, velocity gradient (G) and flocculation time (T) were exploited. In general, the abatement efficiency tended to be improved with the increase of Camp number (in the study range of this work: Camp number lower than 8058 and 5639 in CFB and TFB, respectively). However, the efficiency was relatively low and sensitive to the Camp number as G was more than 186 s⁻¹ in CFB and 178 s⁻¹ in TFB, respectively. Whereas, increasing flocculation time clearly contributed to the improvement of the abatement efficiency, which is considered to be an effective strategy to enhance the treatment ability. Velocity gradient and flocculation time could be controlled by means of superficial liquid velocity and properties of packing particles. It should be noted that the backmixing in the TFB caused formed flocs to break and thus lower abatement efficiencies were found in the TFB than those in the CFB.

Effects of H2S injection on the CO2-brine-sandstone interaction under 21MPa and 70°C.

In this study, laboratory experiments were conducted to investigate the influences of H2S injection on the capacity of CO2s solubility trapping and mineral trapping. Results demonstrated that the preferential dissolution of H2S gas into brine (compared with pure CO2) resulted in the decrease of pH, consequently inhibiting the CO2s solubility trappings to some extent. Then, the lower pH droved more severe corrosion of primary minerals, favored more secondary mineral to be formed. In addition, the discovery of pyrite demonstrated that H2S could precipitate by the formation of sulfide mineral trapping. As the secondary carbon sink minerals, ankerite and dawsonite were observed in the pure CO2-brine-sandstone interaction. However, there were no secondary carbonates found through the SEM images and EDS analyses, implied that the injection of H2S probably may partially inhibit the precipitation of Fe-bearing carbonate minerals such as ankerite in the CO2-H2S-brine-sandstone interaction in this short term experiments.

The Synthesis and Photocatalytic Properties of TiO2 Nanotube Array by Starch-Modified Anodic Oxidation.

In this study, the characterization and photocatalytic activity of TiO2 nanotube arrays prepared by anodization process with starch addition were investigated in detail. The results suggested that the optimum mass fraction of starch added in anodization process was 0.1%, with which TiO2 nanotube arrays owning good tubular structure were synthesized. The tube length and average inner diameter of nanotubes were approximately 4 μm and 30 nm, respectively. Through the characterization of TiO2 nanotube arrays by energy dispersive spectrometer, scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy, it was found that the as‐prepared nanotubes possessed well uniformed and higher photodegradation responsive than the pure TiO2. Moreover, it was expected that the as‐prepared nanotubes exhibited good photocatalytic activity for the degradation of RhB under UV‐light irradiation, which could be ascribed to their good morphology, enhanced UV‐light absorption property and electron transmission ability during the photocatalytic reaction. In addition, the nanotubes were not significantly regenerated during the cycling runs experiment. Overall, this study could provide a principle method to synthesize TiO2 nanotube arrays with enhanced photocatalytic activity by anodization process with starch addition for environmental purification.