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.

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.

The Efficient Photocatalytic Degradation of Organic Pollutants on the MnFe2O4/BGA Composite under Visible Light

The MnFe2O4/BGA (boron-doped graphene aerogel) composite was prepared by hydrothermal treatment of MnFe2O4 particles, boric acid, and graphene oxide. When applied as a photo-Fenton catalyst for the degradation of rhodamine B, the MnFe2O4/BGA composite yielded a degradation efficiency much higher than the sum of those of individual MnFe2O4 and BGA under identical experimental conditions, indicating a strong synergetic effect established between MnFe2O4 and BGA. The catalytic degradation of rhodamine B was proved to follow pseudo first-order kinetics, and the apparent reaction rate constant on the MnFe2O4/BGA composite was calculated to be three- and seven-fold that on BGA and MnFe2O4, respectively. Moreover, the MnFe2O4/BGA composite also demonstrated good reusability and could be reused for four cycles without obvious loss of photocatalytic activity.

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.

Solar Based Photocatalytic Decolorization of Four Commercial Reactive Dyes Utilizing Bound TiO2-Fe3O4 Nanocomposite

Dye effluent is one of the most prominent source of water contamination. This study investigated the solar based photocatalytic decolorization of four commercial reactive dyes, which are Reactive Turquoise Blue G 133, Reactive Yellow M4g, Reactive Bordeaux B, and Reactive Red M8b using immobilized TiO2-Fe3O4 on three kind of binders as the support, specifically cyanoacrylate glue, oil-based paint, and white Portland cement on PVC plate. TiO2-Fe3O4 was synthesized using sol-gel method and placed in muffle furnace at 773 K. The composite of TiO2-Fe3O4 was characterized using SEM-EDX and XRD. White cement emerged as the best binder in term of the color removal efficiency of all four dyes compared to other binders, which were more than 90% color removal after 3 h of solar irradiation. Moreover, there was significant enhancement on color removal using immobilized photocatalyst on white cement compared to mobile photocatalyst. The kinetic of the decolorization performance followed the pseudo-first-order reaction. The apparent reaction rate constant was found to decrease along with the increase of the dye concentration. The photodecolorization kinetics fitted the Langmuir-Hinshelwood model. These protocols and results can be applied into textile industrial primary wastewater treatment using solar as a sustainable light and energy source.

Preparation of Coated CMC-nZVI Using Rheological Phase Reaction Method and Research on Degradation of Chloroform in Water

This study reported the synthesis of nanoscale zero-valent iron (nZVI) by rheological phase reaction method in the presence of sodium (CMC). The synthesized CMC coated nZVI (CMC-nZVI) was then characterized with x-ray diffraction (XRD) and transmission electron microscope (TEM) and was tested for the removal of chloroform from simulated groundwater. The investigated parameters in the uptake experiments included different adsorbents, initial concentrations of chloroform and different water flow. The results show that:(1) the prepared CMC-nZVI has good stability and dispersibility; (2) when the concentration of chloroform is 0.1 mg/L, the dosage of CMC-Fe0 is 0.01 g, the removal rate of chloroform is 91.2%;(3)The reaction follows the first-order kinetic reaction equation, and the apparent reaction rate constant increases with decreasing the concentration of chloroform.

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.

Influence of Reaction Temperature on Nitrate Removal from Water by SSI

Spherical sponge iron (SSI) with high activity and intension could be could be utilized to remove nitrate from wastewater. Influence of reaction temperature on nitrate removal by SSI from wastewater was investigated. Because of erosion battery reaction of SSI in solution, pH in solution increased quickly once SSI was added in and then maintain above 10 despite of nitrate original concentration. The reaction temperature has certain influence under higher nitrate original concentration, while little influence under lower nitrate concentration. It was concluded that nitrate removal by SSI appeared to be the first-order reaction because most of the reaction order was 1. The apparent reaction rate constant of nitrate removal was change slightly with the reaction temperature. It was suggested that the limited key of nitrate reduction by SSI was the diffusion of reactant because the activity energy, which was 11.37 and 7.24kJ/mol, was lower than 30kJ/mol.

Influence of Reduction Agent of SSI on its Cadmium Removal from Wastewater

Spherical sponge iron (SSI) with high activity and intension could be prepared through direct reduction by charcoal or hydrogen. The capability of cadmium removal by SSI was investigated in. It was suggested that the reaction of SSI reduced by hydrogen was higher than that reduced by charcoal, and the increasing rate of pH and cadmium removal in solution by SSI reduced by hydrogen was higher than that reduced by charcoal. Moreover, cadmium removal percentage by SSI reduced with hydrogen was much higher than that reduced by charcoal. When the original concentration of cadmium was 50mg/L, cadmium removal by SSI appeared to be the pseudo-first-order reaction because the reaction order was from 0.861 to 0.984. The apparent reaction rate constant of cadmium removal by SSI reduced with charcoal was 0.586 h-1. While hydrogen was utilized as reduction agent, the apparent reaction rate constant of cadmium removal was increased by 7.3 and 13.7 times.