A novel 2D graphene oxide modified α-AgVO3 nanorods: Design, fabrication, and enhanced visible-light photocatalytic performance

Silver vanadates are promising visible-light-responded photocatalysts with suitable bandgap for solar absorption. However, the easy recombination of photogenerated carriers limits their performance. To overcome this obstacle, a novel 2D graphene oxide (GO) modified α-AgVO3 nanorods (GO/α-AgVO3) photocatalyst was designed herein to improve the separation of photocarriers. The GO/α-AgVO3 was fabricated through a facile in-situ coprecipitation method at room temperature. It was found that the as-prepared 0.5 wt% GO/α-AgVO3 exhibited the most excellent performance for rhodamine B (RhB) decomposition, with an apparent reaction rate constant 18 times higher than that of pure α-AgVO3 under visible-light irradiation. In light of the first-principles calculations and the hetero junction analysis, the mechanism underpinned the enhanced photocatalytic performance was proposed. The enhanced photocatalytic performance was ascribed to the appropriate bandgap of α-AgVO3 nanorods for visible-light response and efficient separation of photocarriers through GO nanosheets. This work demonstrates the feasibility of overcoming the easy recombination of photogenerated carriers and provides a valuable GO/α-AgVO3 photocatalyst for pollutant degradation.

Optimization of opeation parameters for methylene blue degradation by UV/TiO2/H2O2 process in an annular reactor

In this study, the degradation of methylene blue (MB) by UV/TiO2/ H2O2 process was ivestigated in an annular reactor. The effects of the factors: TiO2 concentration, H2O2 dosage, UV density, and hydrodynamic conditions on the reaction rate constant were evaluated by the response surface methodology. The results showed that TiO2concentration, H2O2dosage and UV density had a great influence on the kapp, hydrodynamics had a lower influence. Design Expert V.11 software is used to optimize the reaction conditions, the optimal apparent reaction rate constant is 0.168 min-1 under the following conditions: TiO2 concentration of 0.2 g/l, H2O2 dosage is 0.063 mol/l, UV density of 287 W/m2 and Re number is 10000.

Turbulent Flow Simulation of Supercritical Hydrothermal Synthesis in T-Shaped Channel

Turbulent mixing flows of supercritical water and a metal-salt solution were investigated using Reynolds-averaged Navier–Stokes (RANS) simulations. The mass conservation equations for metal-salt and metal-oxide in an aqueous solution, which were coupled with Navier–Stokes equations and the Shear Stress Transport (SST) turbulence model, were solved by considering production by the hydrothermal reaction. The reaction rate in the numerical simulation was interpolated linearly using the experimental data. The mixing flows in a T-shaped channel for various Reynolds numbers were simulated numerically. Fluid mixing causes a hydrothermal reaction in a high temperature region. In a situation with a low temperature and low Reynolds number, the mixing became a steady state, and the metal oxide was generated along the channel wall. For a high Reynolds number, the periodic vortexes were observed at the mixing point and the fluid temperature increased rapidly. A numerical simulation reproduced the apparent reaction rate of the experimental measurements, except for the low Reynolds number case. The time-averaged temperature distributions indicated that the increasing temperature rate in the mixing reactor depends on the inlet supercritical water temperature, which affects the distribution of the concentration of metal oxide. If the turbulence effects were ignored in low-temperature instances, the apparent reaction rate was estimated to be quite low. The turbulent diffusivity and thermal conductivity crucially affected the conversion rate, especially for conditions with a low Reynolds number.

A Novel 2D Graphene Oxide Modified α-AgVO3 Nanorods: Design, Fabrication and Enhanced Visible-Light Photocatalytic Performance

Silver vanadates are promising visible-light-responded photocatalysts with suitable bandgap for solar absorption. However, the easy recombination of photogenerated carriers limits their performance. To overcome this obstacle, a novel 2D graphene oxide (GO) modified α-AgVO3 nanorods (GO/α-AgVO3) photocatalyst was designed herein to improve the separation of photocarriers. The GO/α-AgVO3 was fabricated through a facile in-suit coprecipitation method at room temperature. It was found that the as-prepared 0.5 wt.% GO/α-AgVO3 exhibited the most excellent performance for Rhodamine B (RhB) decomposition, with an apparent reaction rate constant 18 times higher than that of pure α-AgVO3 under visible-light irradiation. In light of the first-principles calculations and the heterojunction analysis, the mechanism underpinned the enhanced photocatalytic performance was proposed. The enhanced photocatalytic performance was ascribed to the appropriate bandgap of α-AgVO3 nanorods for visible light response and efficient separation of photocarriers through GO nanosheets. This work demonstrates the feasibility of overcoming the easy recombination of photogenerated carriers and provides a valuable GO/α-AgVO3 photocatalyst for pollutant degradation.

Enhanced Heterogeneous Photodegradation of Organic Pollutants by a Visible Light Harvesting CoO@meso–CN@MoS2 Nanocomposites

Developing simple and effective synthetic strategies regarding the formation of heterostructure photocatalytic semiconductors remains an intense challenge in research matters. Uniform heterostructure cobalt oxide@meso–CN@MoS2 (CoO@meso–CN@MoS2) photocatalyst exhibits excellent photocatalytic redox performance for pollutant degradation under visible light. By adjusting the weight ratio of CoO@meso–CN and MoS2, we fabricated a CoO@meso–CN@MoS2 heterostructure photocatalyst, and the established heterostructure between CoO@meso–CN and MoS2 was indicated by various physicochemical and morphological characterizations. The photocatalytic response to the fabricated hybrid was determined by rodamine B (RhB), methylene blue (MB), and congo red (CR) degradation in aqueous solution under visible light, and the nanocomposites with a slight content consisting of CoO@meso–CN achieved better catalysis than pure MoS2. This finding confirmed the propriety of this heterostructure as a valuable photocatalyst. The experimental results demonstrated that the apparent reaction rate constant of the 3 wt% CoO@meso–CN modified MoS2 was about two times higher than that of pure MoS2. The present work serves as a new approach for designing highly efficient visible light-induced heterostructure-based photocatalysts for environmental applications in the future.

Design of Multifunctional Titania-Based Photocatalysts by Controlled Redox Reactions

This work aims at the preparation of multifunctional titania-based photocatalysts with inherent capabilities for thermal co-activation and stabilisation of anatase polymorph, by designing the phase composition and microstructure of rutile-silicon carbide mixture. The processing involved a conventional solid state route, including partial pre-reduction of rutile by SiC in inert Ar atmosphere, followed by post-oxidation in air. The impacts of processing conditions on the phase composition and photocatalytic activity were evaluated using Taguchi planning. The XRD studies confirmed the presence of rutile/anatase mixtures in the post-oxidised samples. The results emphasise that pre-reduction and post-oxidation temperatures are critical in defining the phase composition, while post-oxidation time is relevant for the photocatalytic performance. Microstructural studies revealed the formation of core-shell particles, which can suppress the photocatalytic activity. The highest apparent reaction rate of the photodegradation of methylene blue was observed for the sample pre-reduced in Ar at 1300 °C for 5 h and then calcined in air at 400 °C for 25 h. Though its performance was ~1.6-times lower than that for the same amount of nanostructured industrial P25 photocatalyst, it was achieved in the material possessing 2–3 times lower surface area and containing ~50 mol% of SiO2 and SiC, thus demonstrating excellent prospects for further improvements.

Retardation of the reaction kinetics of polymers due to entanglement in the post-gel stage in multi-chain slip-spring simulations

The retardation in the apparent reaction rate in the network formation of polymers is a long-standing problem. We have tackled this issue by a coarse-grained model to clarify the effect of entanglement between polymers.

Efficiency Optimization of Organic Pollutant Removal in Pharmaceutical Wastewater by Microwave-Assisted Fenton-Like Technology

Ferric sulfate or cupric nitrate was utilized as catalyst, hydrogen peroxide was utilized as oxidant, with the assistant of microwave (MW), the efficiency of Fenton-like process was improved, which included increasing TOC removal and apparent reaction rate of TOC removal, reducing the catalyst dose and oxidant dose, shortening the reaction time. Under MW radiation, the technology not only utilized dissolving ferric iron, but also used ferric flocculation, which could be seen by eyes.

Investigation of the effect of ultrasonic waves on the enhancement of efficiency of direct photolysis and photooxidation processes on the removal of a model contaminant from textile industry

The effect of ultrasonic waves (US) was studied on the degradation of Malachite Green (MG) as a model contaminant from textile industry by direct photolysis with ultraviolet (UV) radiation and UV/H2O2 processes. The US (35 kHz) and UV (253.7 nm) radiations were carried out with an ultrasonic bath and a 15 W low-pressure mercury lamp, respectively. Degradation of MG follows pseudo-first order kinetics in all cases. The apparent reaction rate constant (kap) for UV/US process is greater than sum of the UV and US processes but it is relatively low for practical uses. However UV/H2O2 treatment more efficiently decomposes this organic contaminant and combining this process with US can improve its efficiency. kap is influenced by variation of operational parameters such as power density, temperature, initial concentration of MG and H2O2 for US/UV/H2O2 process and activation energy was 9 kJ mol-1 in the range of 294-307 K for this process. UV-vis spectral change of MG showed hypsochromic shift occurred with increasing sonication time, suggested N-demethylation process of MG.