Decomposition Rate Of Methyl Orange Research Articles

Enhanced photocatalytic activity of liquid phase exfoliated WS2 nanosheets

Due to their large surface area and novel electronic properties, tungsten disulfide (WS2) nanosheets are promising materials for potential photocatalysis applications. The fabrication of large-scale WS2 nanosheets is a fundamentally important step to realize their applications. The liquid phase exfoliation method, which involves the mechanical exfoliation of layered materials in a solvent, has proven to be a feasible technique for fabricating nanosheets with high yields. Here, we systematically examine the optimization of the fabrication of WS2 nanosheets by exfoliating the WS2 powder in isopropyl alcohol, a low boiling point solvent, using a low-power probe sonicator and ball milling method. We show that prolonged sonication produces a concentration as high as 0.64 mg/ml, and the same concentration can be fabricated in less than half the time if the bulk powder is ball milled prior to the sonication. An atomic force microscopy study reveals that the proportions of monolayers and bilayers can be significantly increased if the nanosheet dispersions are centrifuged at a higher speed or sonicated for a long time. The photodegradation measurements reveal that the decomposition rate of methyl orange with nanosheets is at least 10% higher than that with WS2 powder, suggesting that the photocatalytic activity of WS2 can be enhanced if it is reduced to nanosheets.

Magnetic photocatalysts based on graphene oxide: synthesis, characterization, application in advanced oxidation processes and response surface analysis

The decomposition rate of methyl orange (MO) is studied in aqueous solution of magnetic photocatalysts based on graphene oxide (GO). ZnO photocatalytic nanoparticles are synthesized with controlled amounts on magnetized graphene oxide and two photocatalytic samples including GFZ1 and GFZ2 are prepared for use in advanced oxidation process. The characterization of the synthesized photocatalysts is done by XRD, FTIR and VSM. The crystal structure of magnetic Fe3O4 nanoparticles as well as photocatalytic ZnO nanoparticles on the graphene oxide network has been confirmed by XRD analysis in both synthesized samples. FTIR analysis of both GFZ1 and GFZ2 also shows the stretching vibration of Fe–O and Zn–O bonds in Fe3O4 and ZnO, respectively. The superparamagnetic properties of both samples can be confirmed using VSM analysis. It is also observed that with the increase of ZnO nanoparticles in GFZ2, the magnetic properties decrease compared to GFZ1. The effect of irradiation time time (between 5 and 40 min), weight fraction of the synthesized photocatalysts (0.1%wt, 0.2%wt, and 0.3%wt) and pH of the suspension (3, 7, and 11) on the changes in MO decomposition rate was investigated and the response surface method (RSM) was used to study the effect of the simultaneous change of two parameters of the mentioned factors on the MO removal efficiency. The results show that with the increase of irradiation time and also the weight fraction of both photocatalysts, the decomposition rate of MO also increases significantly. So that in all time intervals and weight fractions, the photocatalytic activity of GFZ2 is much higher than that of GFZ1. The effect of pH also shows that the maximum and minimum decomposition rates occur in acidic and neutral conditions, respectively.

Evaluation of the dependence of methyl orange organic pollutant removal rate on the amount of titanium dioxide nanoparticles in MWCNTs-TiO2 photocatalyst using statistical methods and Duncan’s multiple range test

ABSTRACT Here, we prepared two kinds of nanocomposites (MCT#1 and MCT#2) involving MWCNTs and TiO2 nanoparticles. The characterisation of the samples is carried out based on FTIR spectroscopy and TEM. The Ti-O groups that is attributed to the TiO2 nanoparticles can be confirmed according to the FTIR analysis. TEM images show that the average particle size of TiO2 nanoparticles in prepare MCT#1 and MCT#2 is equal to 13 nm and 15 nm, respectively. The influences of nanocomposites weight fraction and illumination time are investigated on the decomposition rate of methyl orange (MO) as pollutant. The photocatalytic results exhibit that the decomposition rate of MO is increased with respect to the weight fraction and illumination time. Meanwhile, higher decomposition rate can be observed using MCT#2 compared to MCT#1. Statistical analysis of the results based on Duncan’s multiple range test at α = 0.05 reveals that all of the applied levels of the factors have a significant effect on the decomposition rate. The response surface results confirm that the effect of illumination time is high that that of weight fraction of MCT#1 and MCT#2.

A Mild in-Situ Method to Construct Fe-Doped Cauliflower-Like Rutile TiO2 Photocatalysts for Degradation of Organic Dye in Wastewater

A mild in situ method was developed to construct an iron doped rutile TiO2 photocatalyst like cauliflower for degradation synthetic textile dye-methyl orange. The synthesized photocatalysts presented distinguished photocatalytic activity. At the optimal Fe concentration (0.5%), the decomposition rate of methyl orange (MO) was about 90% under 40 min of ultraviolet (UV) light irradiation. Whereas, to our knowledge, only 70% of the decomposition rate of MO was achieved by commercial photocatalyst P25 under the similar reaction condition. Additionally, the rutile preparation temperature did not exceed 100 °C, which was much lower than the traditional preparation calcination temperature (e.g., 600 °C). The specific surface area of Fe doped catalysts was bigger than that of the control sample and the catalyst characterization indicated that the doped iron was incorporated into the rutile TiO2 lattice and resulted in the lattice disorder. The lattice disorder would have generated surface defects in the crystal structure, which was in favor of the photocatalytic reaction. The UV-Vis diffuse refection characterization and Density Functional Theory (DFT) calculation suggested that doping a small amount of Fe into the lattice of rutile would lead to a narrower band gap and the formation of a doping energy level between conduction and valence bands of TiO2. This further increased the degradation efficiency of synthetic textile dyes in wastewaters. Our study has provided a relatively easy operation for synthesis Fe doped rutile TiO2, which is a benefit to decrease the cost in wastewater treatment process.

Magnetically recoverable Ag/Bi2Fe4O9 nanoparticles as a visible-light-driven photocatalyst

This paper reports magnetically recoverable Ag/Bi2Fe4O9 nanoparticles (BFO NPs) using as a photoexcited catalyst. The Ag NPs are uniformly distributed on the surface of BFO NPs. Compared to BFO NPs, the decomposition rate of methyl orange for Ag/BFO NPs under the visible-light is greatly enhanced due to the high surface plasmon resonance and electron conductivities of Ag NPs. Moreover, Ag/BFO NPs have a higher saturation magnetization than BFO NPs, which makes them can be collected easily under magnetic fields. Therefore, Ag/BFO NPs are potential recoverable visible-light-driven photocatalyst for environmental pollutants degradation.

Synthesis of Emulsion-Templated Magnetic Porous Hydrogel Beads and Their Application for Catalyst of Fenton Reaction.

The pristine Fe3O4 nanoparticle (FeNP) is supposed to be a good catalyst of Fenton processes which have shown significant potential for water purification. Herein the magnetic macroporous hydrogel beads, having an open-cell structure, were synthesized by sedimentation polymerization of pristine FeNP stabilized oil-in-water high internal phase emulsions. The effects of the FeNP amount, internal phase fraction, and the costabilizer Tween85 concentration on the structure, such as interconnecting degree, void size, and its distribution of both the surface and inner of the beads, were investigated. With a methyl orange (MO) aqueous solution passing through a chromatography column that was filled with the FeNPs loaded hydrogel beads, the efficiency of these hydrogel beads as catalyst for Fenton reaction to decompose MO in water was tested. The MO was decomposed quickly at the first hour, followed by decomposed gradually in a further 5 h, and the decomposition rate of MO could be up to 99.6% at the end of the test. Moreover, MO decomposition rate remained over 98.2% in six batches which were run in the same beads filled column. The results showed that these FeNPs loaded porous hydrogel beads were reusable and highly efficient supporter for catalysis of Fenton reaction for decomposing organic pollutants in water.

Ultrathin g-C3N4 films supported on Attapulgite nanofibers with enhanced photocatalytic performance

A novel visible-light-responsive photocatalyst is fabricated by introducing g-C3N4 ultrathin films onto the surface of attapulgite (ATP) via a simple in-situ depositing technique, in which ATP was pre-grafted using (3-Glycidyloxypropyl) trimethoxysilane (KH560) as the surfactant. A combination of XRD, FT-IR, BET, XPS, UV–vis, TEM and SEM techniques are utilized to characterize the composition, morphology and optical properties of the products. The results show that with the help of KH560, g-C3N4 presented as ultrathin layer is uniformly loaded onto the surface of ATP by forming a new chemical bond (SiOC). Comparing with g-C3N4 and ATP, ATP/g-C3N4 exhibits remarkably enhanced visible-light photocatalytic activity in degradation of methyl orange (MO) because of its high surface area, appropriate band gap and the synergistic effect between g-C3N4 and ATP. To achieve the best photocatalyst, the ratio of g-C3N4 was adjusted by controlling the mass portion between ATP-KH560 and melamine (r = m (ATP-KH560)/m (melamine)). The highest decomposition rate of methyl orange (MO) was 96.06% when r = 0.5 and this degradation efficiency remained unchanged after 4 cycles, which is 10 times as that of pure g-C3N4 particles. Possible photocatalytic mechanism is presented.

Enhanced photocatalytic properties of graphene oxide/ZnO nanohybrid by Mg dopants

In this study, the enhancement of photocatalytic activity of a graphene oxide/ZnO (GO/ZnO) nanohybrid was achieved via introducing Mg as a co-dopant element by the co-precipitation method. The Mg-doped ZnO nanoparticles were adsorbed on GO sheets. Compared with the catalyses with GO/ZnO nanohybrids, GO/Zn1−xMgxO nanohybrids exhibited better photocatalytic activity, in which the decomposition rate of methyl orange (MO) reached 100% within 60 min. The enhancement is attributed to Mg-doping and efficient charge transfer of the photogenerated electrons in the conduction band of ZnO to graphene.

Enhanced Photocatalytic Activity of Titanium Oxide Nanotubes After Heating Treatment

Titanium oxide nanotubes were obtained by an electrochemical anodization method. Scanning electron microscope results demonstrate that the diameter of the tubes is about 120 nm and the length of the tubes is around 13 microm. Transmission electron microscope results indicate that the nanotubes are assembled by numerous nanoparticles and tube-like structure remains well after heat treatment at 400-600 degrees C. The photocatalysis performance of the nanotubes was evaluated in terms of the decomposition rate of methyl orange under UV irradiation. The results show that the photocatalytic activity was enhanced through the heating treatment of the nanotubes, and the nanotubes heated at 600 degrees C exhibits the best photocatalytic activity. X-ray diffraction patterns indicate that there is no phase transformation during the heat treatment. Therefore, the enhanced activity can be attributed to the improvement of nanotubes crystallinity, which may provide more insights about the effect of the crystallinity on the photocatalytic performance.

Comparative study of photocatalytic performance of titanium oxide spheres assembled by nanorods, nanoplates and nanosheets

TiO2 spheres assembled by nanorods, nanoplates and nanosheets were fabricated by facile hydrothermal/solvothermal methods. The three samples were thoroughly characterised by scanning electron microscopy, X-ray diffraction, the Brunauer–Emmett–Teller method and UV spectroscopy. The surface area of spheres assembled by nanosheets was 83.9 m2g–1, which is larger than that obtained for nanorods (10.8 m2g–1) and nanoplates (6.31 m2g–1). Their photocatalytic performance was evaluated in terms of the decomposition rate of methyl orange in these three samples under UV irradiation. The best photoactivity was observed in the samples constructed from nanosheets.

Plasmonic enhancement of photocatalytic decomposition of methyl orange under visible light

By integrating strongly plasmonic Au nanoparticles with strongly catalytic TiO 2, we observe enhanced photocatalytic decomposition of methyl orange under visible illumination. Irradiating Au nanoparticles at their plasmon resonance frequency creates intense electric fields, which can be used to increase electron–hole pair generation rate in semiconductors. As a result, the photocatalytic activity of large bandgap semiconductors, like TiO 2, can be extended into the visible region of the electromagnetic spectrum. Here, we report a 9-fold improvement in the photocatalytic decomposition rate of methyl orange driven by a photocatalyst consisting of strongly plasmonic Au nanoparticles deposited on top of strongly catalytic TiO 2. Finite-difference time-domain (FDTD) simulations indicate that the improvement in photocatalytic activity in the visible range can be attributed to the electric field enhancement near the metal nanoparticles. The intense local fields produced by the surface plasmons couple light efficiently to the surface of the TiO 2. This enhancement mechanism is particularly effective because of TiO 2’s short exciton diffusion length, which would otherwise limit its photocatalytic efficiency. Our electromagnetic simulations of this process suggest that enhancement factors many times larger than this are possible if this mechanism can be optimized.

TiO2 Supported on Crude Sepiolite by Liquid Phase Method

TiO2 was supported on crude sepiolite by boiling reflux method. According to the X-ray diffraction, TiO2 is rutile-anatase mixing type while the composite prepared by the same method is rutile crystal. Scanning electron microscope study shows that TiO2 balls grow onto fibrous sepiolite like strings of grapes. The binding energy of Ti2p becomes 0.2eV lower in the composite. The photocatalytic performances are evaluated through studying the ability of generating hydroxyl radical（•OH）by electron spin resonance(ESR), and the decomposition rate of methyl orange in aqueous solution. It is found that the quantity of hydroxyl radical increases and the photocatalytic activity is enhanced for TiO2/sepiolite composite under natural light.

Photocatalytic Activity of TiO<sub>2</sub>-C Composites under the Visible Light

TiO2-C composites of high photocatalytic activity were in-situ fabricated with nano-TiO2 powders and resins. The composites were characterized by differential scanning calorimetry and thermal gravimetric analysis (DSC-TG), X-ray diffraction (XRD), UV-Vis diffuse reflection spectrum (DRS), transmission electron microscope (TEM) and scan electronic microscopy (SEM). XRD results indicated that the composites consist of carbon and anatase phases. UV-Vis DRS showed that composites not only have a good performance in the ultraviolet region, but also have a very good performance in the visible light region. Photocatalysis degradations of methyl orange with purity nano-TiO2 and TiO2-C composite were tested by lighting of visible light. After methyl orange liquid was lighted by visible light for 1 hour, the decolorization ratio of methyl orange can be up to 96.3%( reactive brilliant red X-3B:98.7%) with TiO2-C powders, while it was only 34.7% (reactive brilliant red X-3B:66.9%) with purity nano-TiO2 powders. In-situ fabricated carbon can change the width of energy band of TiO2 and adsorb methyl orange and reactive brilliant red X-3B molecules. The former accelerate the absorption of visible light, and the later raise the decomposition rate of methyl orange and reactive brilliant red X-3B. All of these can improve photocatalytic activity of TiO2-C composites under the visible light.

Fabrication of Dy2Ti2O7 nanocrystalline at 700°C and its photocatalytic activity

Abstract Dy2Ti2O7 nanocrystalline was fabricated by a soft-chemistry route named as citric acid sol–gel method (CAM). The fabricating process was monitored by XRD, FT-IR and TG-DTA methods. It was found that compared with traditional solid state reaction (SSR), Dy2Ti2O7 was synthesized at a relatively low temperature (700 °C) and with shortened reaction time (2 h). The morphology and surface composition of obtained products were determined by TEM and SEM-EDX experiments. Results showed that the obtained Dy2Ti2O7 with good dispersibility were all square-like; the average size was about 50 nm and there was ample oxygen-deficient (40%) on the product interfaces. Also, the obtained products had higher BET surface area (25.10 m2/g). These properties are very helpful for a catalyst to achieve excellent photocatalytic activity. Photodecomposition of methyl orange was used as the model system to evaluate its photocatalytic property. It was found that Dy2Ti2O7 showed good photocatalytic activity and the decomposition rate of methyl orange was about 99% within 60 min.

Synthesis, structure and photocatalytic reactivity of layered CdS/H2La2Ti3O10 nanocomposites

A fabrication process has been optimized to produce photocatalytic H2La2Ti3O10/CdS nanocomposites by a stepwise exchanging reaction of H2La2Ti3O10 with n-C3H7NH2 (or n-C8H17NH2), Cd(CH3COO)2 and H2S gas, which was obtained by H+-exchanging reaction of K2La2Ti3O10 with HCl other than the normally used HNO3. XRD, TEM, FT-IR, TG, ICP and BET methods were used to investigate the pillaring-process. Results showed that the particle size of pillared cadnium sulphide was less than 1nm and the amount of intercalated CdS increased from 12.2 wt% to 16.5 wt% when n-C8H17NH2 took the place of n-C3H7NH2 to “pre-expand” the interlayer of H2La2Ti3O10. The possible reason of this success was mentioned. The photocatalytic properties of the resulting powders were evaluated by using photodecomposition of methyl orange as the model system. Compared with the unpillared K2La2Ti3O10, the pillaring of CdS gave rise to a remarkable enhancement of its photoactivity and the decomposition rate of methyl orange was improved from 50% to 95%.

UV/TiO2에 의한 수용성 염료의 분해에 관한 연구

The characteristics of photocatalytic decomposition of dye waste water by titanium dioxide was studied in a batch reactor under constant strength of ultra-violet ray. The decomposition rate of methyl orange by TiO<TEX>$_2$</TEX> was pseudo-first order, anatase type TiO<TEX>$_2$</TEX> was more effective than rutile type below the dosage of 5g. The decomposition rate was increased with decreasing initial pH, increasing reaction temperature and oxidant concentration. The decomposition rate of water soluble dyes was decreased in order of rhodamine B>eosin Y>methyl orange.