Degradation Efficiency Of Methyl Orange Research Articles

Hydroxide MgSn(OH)6: A promising new photocatalyst for methyl orange degradation

Highly crystalline hydroxide MgSn(OH)6 (MHS) polyhedral particles were synthesized by changing reaction time (10, 15 and 20 h) in a hydrothermal process. The structural and morphological poperties of obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the MHS was further evaluated by the degradation of methyl orange (MO) under ultraviolet (UV) light illumination. Compared with commercial TiO2 (Degussa P25), the MHS prepared for 15 h showed similar degradation efficiency of methyl orange (MO), mainly due to its higher specific surface area (55 m2g−1) and better optical properties. Open image in new window

Fabrication of Ag/AgBr/Ga2O3 heterojunction composite with efficient photocatalytic activity

A novel Ag/AgBr/Ga2O3 composite with heterojunction microstructure was synthesized by using chemical deposition followed by UV reduction method. High resolution transmission electron microscopy showed that Ga2O3 microparticles were tightly attached with Ag/AgBr to form a heterojunction. UV–vis diffuse reflectance spectra revealed that light response capability of Ga2O3 was enhanced significantly when combined with Ag/AgBr. The degradation efficiency of methyl orange within 30min under UV light irradiation with Ag/AgBr/Ga2O3, Ag/AgBr and Ga2O3 were 89%, 74% and 48%, respectively. Ag/AgBr/Ga2O3 not only showed excellent photocatalytic activity under UV light, but also exhibited efficient photocatalysis capacity under visible light. Furthermore, the mechanism of charge separation in the heterojunction under UV light irradiation was proposed.

Electrospun H4SiW12O40/cellulose acetate composite nanofibrous membrane for photocatalytic degradation of tetracycline and methyl orange with different mechanism

H4SiW12O40 (SiW12)/cellulose acetate (CA) composite nanofibrous membrane was prepared by electrospinning in which CA was employed as the support of SiW12. Characterization with Fourier transformation infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) indicated that SiW12 has been successfully loaded into the CA membrane and its Keggin structure remained intact. The as-prepared composite membrane exhibited enhanced photocatalytic activity in the decomposition of tetracycline (TC) and methyl orange (MO) compared with pure SiW12 under ultraviolet irradiation. The optimal mass ratio of SiW12 to CA was 1:4, and the corresponding degradation efficiency for TC and MO was 63.8% and 94.6%, respectively. It is noteworthy that the degradation rate of MO increased more evidently than that of TC under the same conditions, which may be attributed to the different role that CA nanofibrous membrane played in the TC and MO photodegradation process. Besides providing more contact area between SiW12 and the pollutant in TC photodegradation, CA membrane played an additional role that donated electron to SiW12 in the MO degradation process, leading to a different photocatalytic mechanism with greatly enhanced degradation rate. Moreover, the composite membrane presented an excellent reusability, which was mainly ascribed to the water-insolubility of CA and the hydrogen bonds between CA and SiW12. This work will be useful for the design of biopolymer-based membrane photocatalysts applied to antibiotics and dyes wastewater treatment.

Phase- and size-controllable synthesis with efficient photocatalytic activity of ZnS nanoparticles

We report a simple solution-based method to synthesize phase- and size-controllable ZnS nanoparticles at low temperature. Cubic ZnS (c-ZnS) and hexagonal ZnS nanoparticles (h-ZnS) were obtained by heating an aqueous solution of Zn(NO3)2·6H2O and Na2S2O3·5H2O at different temperatures. When the system was heated at 65 °C for 24 h, hexagonal crystal structure of ZnS nanoparticles, with size of 50–350 nm, was obtained, as confirmed by X-ray diffraction and selected-area electron diffraction. When the reaction temperature was 100 °C under hydrothermal condition, c-ZnS nanoparticles were obtained and exhibited monodisperse nanoparticles with average size of 4 nm. Proper rate of S releasing tuned by the variation of pH value is believed to be critical to stabilize the hexagonal ZnS nanoparticles. Compared with large size of h-ZnS nanoparticles, c-ZnS nanoparticles show higher photocatalytic activity in degrading methyl orange (MO). The degradation efficiency of c-ZnS nanoparticles reaches 97% under UV irradiation for 120 min. The good ultraviolet absorbing ability, charge separation property, and large surface area of c-ZnS nanoparticles are believed to have a positive impact on improving the degradation rate and degradation efficiency of MO.

Fabrication of Sc2O3-magneli phase titanium composite electrode and its application in efficient electrocatalytic degradation of methyl orange

Sc2O3-magneli phase titanium (Sc2O3-MPT) composite electrode was successfully fabricated via a simple pressing-sintering method and used for electrocatalytic degradation of methyl orange (MO). It was shown that Sc2O3 was successfully composited with MPT. Compared with MPT electrode, Sc2O3-MPT composite electrode had less spherical particles and more pores. Linear scanning voltammetry indicated that Sc2O3-MPT composite electrode presented higher oxygen evolution overpotential than MPT electrode, suggesting that Sc2O3-MPT electrode was much more suitable for the degradation of MO. The electrocatalytic degradation of MO was evaluated under different parameters including current density, temperature, initial pH and electrolysis time. Under the optimal parameters (current density 10mAcm−2, temperature 25°C, initial pH 3 and electrolysis time 120min), the degradation efficiency of MO on Sc2O3-MPT composite electrode reached up to 90.16%. All these results demonstrated that Sc2O3-MPT composite electrode was effective for electrocatalytic degradation of MO and had a great potential application in the treatment of dyes wastewater.

In situ fabricated Ag/AgCl—polymer nanocomposite thin film: An appraisal of the efficient and reusable photocatalyst

Ag/AgCl nanocomposite is a versatile plasmonic photocatalyst studied extensively in recent times; however, its stability and evolution through catalytic runs have not been explored. A simple protocol for the in situ fabrication of nanocomposite thin films of Ag/AgCl in poly(vinyl alcohol) (PVA) is developed. AgCl-PVA film formed first is photo-irradiated in water to form Ag/AgCl-PVA; the fabrication is monitored through spectroscopy, microscopy and chemical analysis. Photocatalytic application of Ag/AgCl-PVA is demonstrated by its efficient degradation of methyl orange under low power visible light; the ‘dip catalyst’ nature of the film facilitated several efficient reuses. Significantly, the thin film form facilitated rigorous monitoring of the composite through the reuse cycles; a small but steady evolution of the AgCl to Ag is revealed. In addition to the facile in situ fabrication of an efficient nanocomposite thin film plasmonic photocatalyst, the study presents a convenient approach to evaluate its fate through multiple reuses.

Preparation of transition metal composite graphite felt cathode for efficient heterogeneous electro-Fenton process.

A composite graphite felt (GF) modified with transition metal was fabricated and used as cathode in heterogeneous electro-Fenton (EF) for methyl orange (MO) degradation. Characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), the morphology and surface physicochemical properties of the cathodes after modification were observed considerably changed. After loading metals, the current response became higher, the accumulation of H2O2 and the degradation efficiency of MO were improved. Under the same conditions, GF-Co had the highest catalytic activity for electro-reduction of O2 to H2O2 and MO degradation. At pH 3, 99% of MO degradation efficiency was obtained using GF-Co after 120min treatment and even at initial pH 9, 82% of that was obtained. TOC removal efficiency reached 93.8% using GF-Co at pH 3 after 120min treatment while that was 12.3% using GF. After ten-time runs, the mineralization ratio of the GF-Co was still 89.5%, suggesting that GF-Co was very promising for wastewater treatment. The addition of isopropanol proved that ·OH played an important role in degradation of MO.

Studies on facile synthesis and properties of mesoporous CdS/TiO2 composite for photocatalysis applications

CdS/TiO2 composites in different ratios were prepared by a simple two-step sol gel route. The morphology, structure and composition of the composite were characterized with various techniques, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy, UV visible diffuse reflectance spectroscopy (UV–Vis), Raman spectra and nitrogen adsorption-desorption tests. The results show that the product is in a mesoporous structure with uniformly dispersed particles. In particular, 2% CdS/TiO2 possesses the largest specific surface area of 18.980 m2/g, with a total pore volume of 0.3176 cm3/g and an average pore diameter of 15.51 nm. This sample also delivers the highest photocatalytic degradation efficiency of Methyl Orange (MO). Photocurrent measurements reveal the excellent photoelectrochemical properties of the 2%CdS/TiO2 composite.

Enhanced visible-light photocatalytic properties of g-C3N4 by coupling with ZnAl2O4

A series of g-C3N4/ZnAl2O4 composites were prepared using a conventional calcination method and the heterostructures were systematically characterized. It was found that the combination of g-C3N4 with ZnAl2O4 significantly improve their photocatalytic activities. The optimum photocatalyst of composite is at 5% (wt%) of ZnAl2O4, whose degradation efficiency for methyl orange (MO) was 96% within 120min under visible-light irradiation. The formation of heterojunction between g-C3N4 and ZnAl2O4 can facilitate efficient charge separation of photogenerated electron-hole pairs, which were confirmed by electrochemical impedance spectroscopy (EIS). As a result, the photocatalytic properties of composites were enhanced.

Modification of TiO2 to enhance photocatalytic degradation of organics in aqueous solutions

Heterogeneous photocatalysis, an advanced oxidation process (AOP), has shown to be efficient for the degradation of refractory organics in aqueous solutions into simple compounds. Two issues that arise with the use of unmodified TiO2 are the fast recombination of electron/hole pairs and the lower effectiveness in the presence of visible irradiation. This study aims to develop a photocatalyst by doping transition metals, especially noble metals such as Ag, onto the original TiO2. The combination of photocatalysts is a method to improve the photocatalytic activity for the degradation of organic compounds in wastewater. In this study, first Ag-doped TiO2 is prepared and then, a composite of Fe2O3/TiO2 is synthesized in different mass ratios. A series of experiments is conducted for the treatment of two azo dyes, Congo Red (CR) and Methyl Orange (MO), by photocatalysis under the UV–vis irradiation. The degradation of organic materials is measured in terms of total organic carbon (TOC). Scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) along with the Brunauer, Emmet, and Teller (BET) method have been utilized to illustrate the characteristics of the prepared powder photocatalysts. X-ray diffraction (XRD) was used to identify crystallinity and phase conversion of the photocatalyst. Results show that silver doped TiO2 increases the degradation of MO (12.2%) and CR (14.5%) compared to that of the bare TiO2. The degradation efficiency of MO and CR increases by applying composite photocatalyst of Fe2O3/TiO2 in the range of 28.9 and 25.1%, respectively, compared to that of the bare TiO2.

Improved degradation of methyl orange dye using bio-co-catalyst Se nanoparticles impregnated ZnS photocatalyst under UV irradiation

The present work outlines the importance of biosynthesized selenium nanoparticles (SeNPs) as co-catalyst for the enhanced photocatalytic activity of as-prepared ZnS photocatalyst for degradation of methyl orange (MO) dye under UV light irradiation. SeNPs of different wt% were impregnated onto ZnS by calcination at 200°C to make Se-ZnS nanocomposites (Se-ZnSNCs) and characterized by UV–Vis spectroscopy, DLS, XRD, SEM-EDX, TEM and BET surface area analysis. The specific surface area notably increased from 54m2g−1 (ZnS) to 75m2g−1 with different wt% of Se loading. The band edge absorption at 330nm (3.77eV) of bare ZnS significantly red-shifted to 357nm (3.30eV), after 1wt% Se loading (3.30eV). 1wt% Se-ZnSNCs exhibited the highest degradation efficiency (95%) of MO as compared to bare ZnS (55%) under 160min UV light irradiation. The reaction followed pseudo first-order kinetics with an apparent rate constant k=8.42×10−3min−1 where CO2 evolution gradually increased depending on the extent of MO degradation by Se-ZnSNCs under different time period of UV light irradiation.

Heterogeneous electro-Fenton oxidation of azo dye methyl orange catalyzed by magnetic Fe3O4 nanoparticles.

Azo dye methyl orange (MO) degradation by heterogeneous electro-Fenton (EF) with a magnetic nano-Fe3O4 catalyst was investigated. In this study, Fe3O4 was synthesized by a coprecipitation method and characterized by X-ray diffraction and scanning electron microscopy. The influences of the main operating parameters such as current density, pH, catalyst dosage and aeration rate were studied. The results revealed that higher current density, catalyst dosage and aeration rate facilitated the degradation of MO, whereas the degradation efficiency of MO was decreased with an increase in the initial pH. After 90 min EF process, the volume of 500 mL, the initial concentration of 50 mg L(-1) MO solution could be degraded by 86.6% with the addition of 1 g L(-1) Fe3O4 under the current density of 10 mA cm(-2) and pH 3, compared with 69.5% for the electrolytic process alone. Meanwhile, a total organic carbon removal of 32% was obtained, up to 35.5 mg L(-1) accumulated H2O2 and less than 3.5 mg L(-1) Fe leaching were detected. Moreover, based on the results of natural bond orbital (at B3LYP/6-311G (d, p)) and liquid chromatograph-triple quadrupole mass spectrometer analysis, nine intermediates were identified and the proposed degradation pathways were investigated.

Enhancing sonocatalytic properties of TiO2 nanocatalysts by controlling the surface conditions: effect of particle size and PVA modification

The influence of particle size and surface modification on sonocatalytic activity of TiO2 nanoparticles was investigated by measuring the degradation efficiency of methyl orange (MO) as a model pollutant. Crystalline TiO2 nanoparticles with different particles and aggregate size were prepared through solution-phase method with varying synthesis temperatures. Coating with polyvinyl alcohol was performed to enhance colloidal stability of the particles over a wide range of pH values (1.5–7.5). Characterization was carried out using X-ray diffraction, high-resolution transmission electron microscopy, dynamic light scattering, and Fourier-transformed infrared techniques. It was found that sonodegradation of MO decreased as the synthesis temperature increased. Moreover, sonoactivity of the modified nanoparticles improved because polymeric coating inhibited particles collision and also their growth due to sonication-induced Ostwald ripening mechanism.

Preparation of Visible-light-induced g-C3N4/Bi2S3 Photocatalysts for the Efficient Degradation of Methyl Orange

Visible light responsive heterojunctions of graphitic carbon nitride (g-C3N4) and Bi2S3 were successfully designed and constructed by a simple solvothermal process. The as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectroscopy (DRS). Under visible light irradiation, the as-prepared g-C3N4/Bi2S3 photocatalysts exhibited highly enhanced photochemical efficiency in the degradation of methyl orange (MO) compared with pure g-C3N4 and Bi2S3. On the basis of the calculated energy bands, the excellent enhancement was attributed to the efficient separation of photoinduced electron-hole pairs. In addition, a detailed degradation pathway of MO degradation by g-C3N4/Bi2S3 composites was proposed to further elucidate the inner photodegradation mechanism. This research may provide a cost-effective and easy-scaling up approach to develop visible-light-driven photocatalysts, which could be applied in wastewater treatment.

Nanostructured CuAl2O4: Co-precipitation synthesis, optical and photocatalytic properties

In this work, nanostructured CuAl2O4 particles were synthesized by a co-precipitation process with the aid of diethylamine as a precipitating agent. The photocatalytic activities of the synthesized powders were investigated for degradation of methyl orange used as a model wastewater contaminant. The characteristics of synthesized powders were studied using a variety of techniques including X-ray diffraction, thermogravimetric and differential thermal analysis, transmission electron microscope, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy. The TEM results showed that CuAl2O4 nanopowders are mainly composed of irregular particles with a mean diameter of about 20nm. The band gap energies of samples decreased from 3.5eV to 1.8eV as the calcination temperature increased from 100°C to 700°C. It was found that the sample calcined at 700°C provided maximum methyl orange degradation efficiency (~98%).

AgI-modified TiO2 supported by PAN nanofibers: A heterostructured composite with enhanced visible-light catalytic activity in degrading MO

A highly visible-light responsive AgITiO2/PAN had been successfully synthesized by the electrospinning technique, hydrogenation reduction, solvothermal synthesis, and gas/solid oxidation. The component and morphology of the as-prepared catalysts were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy (FTIR). In the degradation experiments, the as-prepared AgITiO2/PAN showed a highly photocatalytic activity in degrading methyl orange (MO) under visible light irradiation and the AgI content had a strong effect in their photocatalytic activity. Moreover, the degradation efficiency of MO over AgITiO2/PAN was much higher as compared to that of pure PAN, AgI/PAN and TiO2/PAN, which was attributed to the synergistic effect between AgI and TiO2. Besides, AgITiO2/PAN had an excellent stability in the cycling tests due to the intimate connect and stable heterostructure of AgITiO2. It’s astonished to find that the application of PAN nanofibers, which presented in membranous form, made it easy separate the catalysts from an aqueous solution without any loss.

Photocatalytic properties of mesoporous TiO2 nanocomposites modified with carbon nanotubes and copper

The photocatalytic activity of mesoporous TiO2 modified by the addition of carbon nanotubes (CNTs) and Cu is reported. Nanocomposites of carbon nanotubes (CNTs) containing varying amounts of Cu were formed by treatment with Cu2+ then reduced to Cu0 using NaBH4 as the reducing agent. The mesoporous TiO2, synthesized by a sol-gel method from titanium isopropoxide, was combined with the CNT/Cu nanocomposites to form the photocatalysts which were characterized by XRD, SEM, TEM, FTIR, XPS and BET surface area analysis. The photocatalytic properties of the mesoporous TiO2 composites were studied by measuring the degradation of methyl orange (MO) which was optimal in the sample containing 20wt% of the Cu-CNT nanocomposite. The degradation efficiency for MO was a synergistic effect of photo-degradation of TiO2 and may be due to improvement of the electrical conductivity of the system by the presence of the CNT/Cu networks, since the photodegradation of MO and the photocatalytic activity of the photoactive systems increased with increasing copper content.

Preparation, characterization and photocatalytic study of wood-flour/β-cyclodextrin/TiO2 hybrid composite

A new wood-flour-based photocatalytic composite of wood flour/β-cyclodextrin/titanium dioxide (WF/β-CD/TiO2) was synthesized via the photoinduced assembly method. For evaluation of the photocatalytic efficiency of methyl orange (MO) by WF/β-CD/TiO2, three materials of TiO2, β-CD/TiO2 and WF/TiO2 were prepared and assessed under the same photocatalytic conditions. The morphology of these composites was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The chemical composition was detected by X-ray photoelectron spectroscopy (XPS). By means of phenolphthalein probe technique and back titration method, the contents of active β-CD (3.5 %) and TiO2 (0.0581 g/0.1 g) in the prepared WF/β-CD/TiO2 composite were obtained. In the experiments of photocatalytic reaction, for completely degradation of 0.1 mmol L−1 MO, the degradation time of WF/β-CD/TiO2 was similar to that of β-CD/TiO2 but shorter than those degraded by pure TiO2 and WF/TiO2. The kinetics of photocatalytic degradation of MO by WF/β-CD/TiO2 was also investigated. The intraparticle diffusion kinetic model gave a better correlation for the photocatalytic reaction. In addition, after recycling for five times, the degradation efficiency of MO by WF/β-CD/TiO2 was still above 86 %, which was obviously higher than that by WF/TiO2, indicating a good regeneration property.

Combination Mechanism and Enhanced Visible-Light Photocatalytic Activity and Stability of CdS/g-C3N4 Heterojunctions

In this study, CdS/g-C3N4 (CSCN) heterojunctions were in situ fabricated with a large amount of CdS nanoparticles anchored on g-C3N4 nanosheets. A wet chemical method was developed for the first time to determine the actual content of CdS in CSCN composites. X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS) were employed to characterize the composition, structure and optical property of CSCN composites. Based on the isoelectric point (IEP) analysis of g-C3N4, a conclusion was obtained on the combination mechanism between CdS nanoparticles and g-C3N4 nanosheets. The photocatalytic activity of CSCN composites was much better than those of individual CdS and g-C3N4 for the degradation of azo dye Methyl Orange (MO) by 40 min adsorption in the dark followed by 15 min photocatalysis under visible light irradiation. After 5 cycles, CSCN composites still maintained high reactive activity with the MO degradation efficiency of 93.8%, exhibiting good photocatalytic stability. The Cd2+ concentration dissolved in the supernatant detected by atomic absorption spectroscopy (AAS) of CSCN composites was lower than that of pure CdS, implying that the photocorrosion of CdS could be suppressed via the combination with g-C3N4. Photoluminescence emission spectra (PL) results clearly revealed that the recombination of photogenerated electron-hole pairs in CSCN composites was effectively inhibited due to the formation of heterojunctions. Based on the band alignments of g-C3N4 and CdS, the possible photocatalytic mechnism was discussed.

A Facile Synthesis of Flower-shaped ZnO/Reduced Graphene Oxide Microsphere Composites for Photocatalytic Degradation of Methyl Orange

Flower-shaped ZnO/reduced graphene oxide (RGO) microsphere composites were successfully fabricated via a facile hydrothermal treatment of the aqueous solution containing graphene oxide and ZnO microspheres, and their photocatalytic performance in degradation of methyl orange (MO) was investigated. The results indicated that ZnO/RGO microsphere composites with 3 wt.% GO achieves a maximum MO degradation efficiency of 88% under ultraviolet light irradiation for 140 min, compared with pure ZnO microspheres (78%). The improved photocatalytic performance can be attributed to the suppression of charge carriers recombination resulting from the interaction between ZnO and RGO. Keywords: Mircosphere composites, photocatalytic degradation, reduced graphene oxide, ZnO.