Degradation Of Orange Research Articles

Kinetic evaluation of ZnO/TiO2 thin film photocatalyst in photocatalytic degradation of Orange G

Abstract The ZnO/TiO2 solution of the thin-film photocatalyst was prepared by using the sol-gel method. The prepared solution was coated on a quartz plate by using the dip-coating method. For the characterization of synthesized ZnO/TiO2 photocatalyst, SEM-EDS, XRD and chronoamperometry measurements were used. To determine photocatalytic activity and kinetic model studies, the degradation of Orange G dye which is frequently used in the textile industry on ZnO/TiO2 photocatalyst was investigated. Using the results of kinetic experiments by examining the effects of different initial dye concentrations, temperature and light intensities, the degradation of Orange G dye on ZnO/TiO2 photocatalyst was found to be in accordance with the Network Kinetic Model, and the calculated equilibrium constant and activation energies of the ZnO/TiO2 thin film photocatalyst are 20.02 and 16.16 kJ/mol, respectively.

Heterojunctions for Photocatalytic Wastewater Treatment: Positive Holes, Hydroxyl Radicals and Activation Mechanism under UV and Visible Light

AbstractForming heterojunctions by coupling two or more semiconductors is an important strategy to develop stable and efficient photocatalysts able to operate both under near-UV and visible light. Five novel heterojunction systems were synthesized in the present study, using a modified sol-gel method: Bi2Mo3O12/TiO2, ZnFe2O4/TiO2, FeTiO3/TiO2, WO3(US)/TiO2 and WO3/TiO2. These heterojunction semiconductors were characterized by using XRD, SEM and EDX, UV–Vis diffuse reflectance spectroscopy and BET. Their photocatalytic activities were evaluated using methyl orange (MO) degradation under both near-UV and visible light. From the various heterojunctions developed, the WO3(US)/TiO2 photocatalyst was the one that showed the highest photocatalytic efficiency with this being assigned to the formation of a double heterojunction involving anatase, rutile and monoclinic WO3 phases. On this basis, a photocatalyst activation mechanism applicable to near-UV and visible light irradiation was proposed. This mechanism explains how the photogenerated electrons (e–) and positive holes (h+) can be transferred to the various phases. As a result, and given the reduced holes and electron recombination surface, hydroxyl radicals found were more abundant. To confirm this assumption, hole formation in the valence band was studied, using hole-scavenging reactions involving ion iodine (I–), while hydroxyl radical production used fluorescence spectroscopy.

Facile Preparation and Enhanced Visible-Light Photocatalysis of ZnO Arrays@BiOI Nanosheets Heterostructures

A simple two-step method of growing ZnO nanorod arrays on the surface of BiOI nanosheets was developed under mild environment. The hierarchical structure of ZnO arrays@BiOI nanosheets was characterized by various measurements like X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray detector. The optical absorption of the ZnO arrays@BiOI nanosheets composite was investigated by UV-Vis diffuse reflectance spectra. The photocatalytic degradation of methanol orange under visible light shows that the obtained ZnO arrays@BiOI nanosheets heterostructures exhibit enhanced photocatalytic activity, contrasting to the sum of BiOI nanosheets and ZnO nanorods. The mechanism of the photocatalytic process was discussed. This method of growing ZnO nanorod arrays on other nanosheets also provides a potential method to fabricating other complex structures.

Fabrication and characterization of novel graphene/iodine doped CdS nanoplates and their photocatalytic performances

A photocatalyst consisting of graphene/iodine doped CdS nanoplates (G/I-CdS NP) was fabricated using a microwave method. The phase structure, surface morphology, and optical bandgap were analyzed using X-ray diffractometry, photoluminescence spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, emission scanning electron microscopy, and transmission electron microscopy. Excellent photocatalytic performance was demonstrated based on the degradation of methylene orange (MO) under visible light irradiation. Therefore, doping of iodine in CdS nanoplates resulted in a bandgap reduction. The coupling of CdS with graphene could effectively suppress the recombination of light-induced electron–hole pairs. As a result, an excellent synergetic effect could be achieved for improved photocatalytic performance. These findings will have a positive impact on the use of metal sulfides for future environment-related applications.

Role of exposed facets and surface OH groups in the Fenton-like reactivity of lepidocrocite catalyst

Heterogeneous Fe-based Fenton-like reaction is an efficient technology in wastewater treatment. However, few studies reveal the effects of exposed facets and surface OH groups of iron oxides on its reactivity. In this study, two lepidocrocite samples with lath- and rod-like morphologies were synthesized and applied to the adsorption and degradation of Orange G (OG). The OG molecule could be adsorbed vertically on the lath-like sample by the interaction with the μ−OH groups of the (010) facet. The molecule could also be adsorbed laterally on the rod-like sample by the interactions with the μ−OH and μ3−OH groups of the (010) and (001) facets. When the data were normalized to the unit surface area, the adsorption capacity of OG, the production efficiency of OH, the degradation rate in dark, and the total degradation rates under visible light irradiation in the lath-like system were 9.625-, 3.34-, 2.75-, and 1.98-fold higher than those in the rod-like system, respectively.

Synthesis and characterisation of TiO 2 nanoparticles/Fe 2 O 3 waste chips composite

Water contamination along with the environmental issues resulted by industrial wastewaters have caused a trend in applying semiconducting photocatalysts, among which TiO2 composites have been particularly focused on to overcome the drawbacks of titanium(IV) oxide also known as titania. In the current investigation, waste chips of a structural steel bar with the chemical composition of Fe2O3 were utilised to obtain the TiO2–Fe2O3 composite. X-ray diffraction (XRD), field-emission scanning electron microscopy, energy dispersive spectroscopy, diffusive reflectance spectra, and Brunauer–Emmett–Teller analyses were made to evaluate the composition and structure of the samples. Furthermore, the photocatalytic performance of the samples was studied by methyl orange (MeO) degradation. XRD spectra proved the presence of anatase and Fe2O3 phases in the sample of 10%wt. Fe2O3. The results indicate that as the Fe2O3 content rises, the bandgap narrows. However, the specific surface area enlarges as this amount goes up to a certain limit (10%wt.), from which any further increase leads to a reduction in the specific surface area. The obtained results of MeO decolourisation presented the Fe2O3 of 10%wt. and bandgap of 2.72 eV, and the specific surface area of 63 m2/g to be of the highest efficiency (96%).

Enhancing visible light photocatalytic performance with N-doped TiO2 nanotube arrays assisted by H2O2

N-doped TiO2 nanotube arrays were prepared by an electrochemical anodization method and subsequent ammonia annealing. Microstructures, morphology, optical properties and photocatalytic properties of the N-doped TiO2 nanotube arrays were measured and analyzed. In the degradation of Acid Orange II(AO-II), the photocatalytic degradation efficiency of the N-doped TiO2 nanotube arrays assisted by H2O2 are 12 times, 2 times and 5 times higher than TiO2 nanotube arrays, TiO2 nanotube arrays assisted by H2O2 and H2O2, respectively. Experimental results show that the N-doped TiO2 nanotube arrays is a promising photocatalytic material for organic pollutant degradation under visible light, especially under the assistance of H2O2.

Photocatalytic degradation of Orange G using TiO2/Fe3O4 nanocomposites

Titanium dioxide (TiO2) is one among the best photocatalysts used in commercial applications. However, its large intrinsic bandgap (~ 3.23 eV) limits its photocatalytic application only to the ultraviolet (UV) region that is only 4% of the solar spectrum. The recombination of photogenerated electron–hole pairs reduces the quantum efficiency and photocatalytic activity. The visible region allows us to use 43% of the solar spectrum. Therefore, to extend the photocatalytic activity of TiO2 to visible light spectrum, its bandgap must be decreased that suppresses the recombination reactions. This can be achieved by coupling of semiconductor metal oxides having different bandgap values with TiO2 for the efficient use in the visible light region. In this work, magnetite (Fe3O4) nanoparticles were synthesized by a modified co-precipitation method, and it was used to prepare a TiO2/Fe3O4 nanocomposite with three different ratios (0.2/0.8, 0.5/0.5, and 0.8/0.2). The obtained nanocomposite was characterized using X-ray diffraction, Raman and ultraviolet–visible spectroscopies, and scanning electron microscopy fitted with scanning transmission electron microscopy to understand the various properties such as crystallinity, optical properties, and morphology of the nanocomposites. We noticed that the crystallite size of TiO2 in the nanocomposite, as well as the bandgap energy of the nanocomposite, decreases with the increasing Fe3O4 content. The degradation of Orange G with Fe3O4, TiO2, and nanocomposites with three different ratios was studied in a solar simulator under different exposure times. Our studies show that (TiO2)0.2(Fe3O4)0.8 nanocomposite having small crystallite size and bandgap gives the best photocatalytic activity under visible light among other ratios.

Bacterial community dynamics involved in Reactive Orange M2R dye degradation using a real time quantitative PCR and scale up studies using sequence batch reactor

ABSTRACTBacterial consortium volatile suspended soil (VSS) (Vatva soil sample) with a capability of azo dye Reactive Orange M2R (ROM2R) decolorization and degradation (shown in our earlier studies using Fourier transform infrared spectroscopy (FTIR) and phytotoxicity studies) was isolated from industrial wastewaters by enrichment culture technique. The present study was carried out to study bacterial population dynamics in consortium Vatva soil sample (VSS) during azo dye ROM2R degradation and to identify the consortium members that were actively involved in the degradation process. To achieve this goal, a real-time Polymerase chain reaction (PCR) assay targeting species-specific region of 16S rDNA of each consortial bacteria was developed to provide quantitative information about the bacterial abundance during azo dye degradation. The real-time PCR assay indicated that Pseudomonas aeruginosa (VSS-6) dominated consortium bacterial community during the active continuous bioremediation process. Attempt has been made to scale up from 100 ml volume to 10 L operation volume with intermittent additions (batch fed loadings) in a Sequence batch reactor (SBR). The development of VSS consortium biomass (MLVSS), changes in COD and biochemical oxygen demand, and the dye degradation were studied under conditions simulating the operations of biological effluent treatment in an attempt to develop a commercially applicable dye effluent treatment process unit.

Surface photochemical modification of TiO2 nanotube/Ti plates for photocatalytic elimination of methylene orange dye

A facile strategy has been employed to fabricate efficient TiO2 nanotubes/Ti plate for photocatalyst application via photochemical modification with benzene. Microstructure studies show that benzene with formation of carbonaceous polymeric deposits has been uniformly grown on the walls of TiO2 nanotubes/Ti plates. The results of photocatalytic experiments demonstrate that the plates modified by benzene are more efficient than bare TiO2 nanotubes/Ti for the photocatalytic degradation of methylene orange (MO) dye. The new obtained plates can be recycled 4 times, while remaining at 89.25% MO degradation ratio. The enhanced photocatalytic performance was attributed to the increased separation rate of photogenerated charge carriers and adsorption efficiency of MO by modified electrode.

Degradation of Acid Orange 7 in a persulphate-bisulfite system under visible light

Degradation of Acid Orange 7 in a persulphate-bisulfite system under visible light

Facile synthesis of ternary TiO2 NP/Rh & Sb-codoped TiO2 NR/titanate NT composites photocatalyst: Simultaneous removals of Cd2+ ions and Orange (II) dye under visible light irradiation (λ ≥ 420 nm)

In this study, rhodium and antimony doped nanorod (RS-TONR) was prepared by a molten salt solid state chemical reaction, and TiO2 nanorod and titanate nanotube (RS-TONR/TiNT) composite photocatalyst was synthesized by a hydrothermal method for different reaction times. The structural and chemical analyses of nanomaterials were performed by FE-SEM, XRD, UV-DRS and surface BET characterizations. The XRD and HR-TEM data confirmed that the as-synthesized material had mixed phase of TiO2 nanorod and Titanate nanotube (RS-TONR/TiNT). The photocatalytic activity of the composite photocatalyst was observed over the degradation of Orange (II) dye under visible light irradiation. Acid treatment and copper loading was conducted to enhance the surface property of RS-TONR/TiNT sample. The formation of TiO2 nanoparticle with anatase phase was observed by TEM and XRD analysis. The TEM mapping data also confirmed that copper oxide nanoparticles were well dispersed on the surface of titanate nanotubes. These dispersed nanoparticles were observed by XPS and STEM characterizations. The higher removal efficiency of Cd2+ ions was observed over the acid treated and untreated Cu3-TNP/TiNT/RS-TONR in the presence of Orange (II) dye. A higher photocatalytic activity of acid treated and Cu3-TNP/TiNT/RS-TONR was simultaneously obtained in the presence of cadmium ions during the degradation of Orange (II) dye.

Degradation of Orange G by Fenton-like reaction with Fe-impregnated biochar catalyst

This study was conducted to evaluate the catalytic activity of Fe-impregnated sugarcane biochar (FSB) for removing azo dye Orange G (OG) from solution under various Fenton-like oxidation conditions. The optimum molar Fe concentration for impregnation to achieve maximum catalytic activity of FSB in Fenton-like reaction with acceptable effluent Fe release was 0.25 M (163.4 Fe mg/g in FSB). High removal efficiency of 99.7% was achieved within 2 h of reaction at optimum conditions of 0.075 g/L H2O2, 0.5 g/L FSB for 0.1 g/L OG at initial pH 5.5 under 25 °C. For every 10 °C increase, the time for maximum OG degradation efficiency decreased by 0.5 h. The OG removal by FSB exhibited a slow induction reaction followed by fast OG decomposition. FSB can be used successively for at least 4 runs with >89.3% OG removal. The FSB was more economical, efficient, and recyclable than other conventional Fenton oxidation catalysts.

Nanostructured TiO<sub>2</sub> Materials: Preparation, Properties and Potential Applications (3P’s)

Nanostructured materials are a new class of materials which provide one of the greatest potentials for improving performance and extended capabilities of products in a number of applications. In particular nanostructured TiO2 was used as photocatalysts, gas sensor, solar cells and nanocomposite biomaterials. For each of these applications, aspects such as surface morphology, crystallinity and chemistry of the titania-based materials are the key parameters to be settled for the process optimization. A series of nanostructured TiO2 materials (TiO2 nanotubes, TiO2 nanorods, TiO2 nanoparticles) was synthesized using simple hydrothermal methods. X-Ray Diffraction (XRD), Field Emission Scanning Electron microscope (FESEM) and Brunauer–Emmett–Teller (BET) surface area characterization was carried out to study the properties of synthesized nanostructured TiO2 materials. The performance of synthesized nanostructured TiO2 was evaluated for various applications such as photocatalyst for methyl orange (MO) degradation and anti-bacterial thin film for biomedical and food packaging. Among the nanostructured TiO2 materials, TiO2 nanotubes shows the highest activity regardless of their applications. This is probably due to their nanotubular morphology in which provided high surface area materials. The surface area of TiO2 nanotubes was found to be 226.52 m2/g. The outer and inner diameters of nanotubes are 4 nm and 10 nm, respectively with several hundred nanometers in length. Anatase TiO2 phase structure and crystallinity of TiO2 nanotubes supports the good performances of the nanostructured materials.

Photocatalytic Degradation of Naphthol Orange Under Cr0.9Zr0.1O2 Nanoparticles and Visible Light

Photocatalytic Degradation of Naphthol Orange Under Cr0.9Zr0.1O2 Nanoparticles and Visible Light

Solvothermal synthesis of magnetic Fe3O4 nanospheres and their efficiency in photo-Fenton degradation of xylenol orange

Magnetic Fe3O4 nanospheres with a average diameter of (201±0.5) nm were synthesized at 200 °C via a solvothermal method. The as-synthesized Fe3O4 nanospheres performed an efficiency in the Fenton degradation of xylenol orange with a degradation rate of 90%—95%. Additionally, the catalyst was easily recyclable and the recovery rate was greater than 90%. Moreover, the catalyst could be regenerated under an ultrasonic treatment, and the degradation performance remained essentially the same. More importantly, the degradation rate varied with respect to the amount of H2O2 and the pH of the best reaction process. And the reaction efficiency was achieved with 1.5 mL of H2O2 in an acidic environment.

Facile synthesis nanocrystalline YVO4 in the presence of amino acids as a capping agent and study of their photocatalytic properties

In this research, precipitation method was employed for the synthesis of nano-sized spherical yttrium vanadate (YVO4) particles, which is based on chemical reactions between raw materials in presence of different amino acids such as glycine, aniline and valine. YVO4 nanoparticles were synthesized by calcinations of the yttrium vanadate precursor precipitates at 550 °C for 5 h. The crystallite size and structure of the products have been confirmed by XRD. Also, the morphology and particle size of YVO4 nanoparticles was analyzed by SEM images. The optical properties were investigated by UV–Vis spectroscopy. Moreover the direct precipitation technique is a feasible method for production of YVO4 nanopowders. The methyl orange (MO) degradation model was used for assessment of photocatalytic properties of as-prepared nanoparticles under UV irradiation. The results have been shown that the YVO4 nanoparticles can be decomposed about 85% of MO after 70 min UV irradiation.

Synthesis of hierarchical RGO@Cu2O@Cu nanocomposites: optimization of photocatalytic degradation of Direct Orange 39 using a response surface methodology

The RGO@Cu2O@Cu nanocomposites were prepared by hydrothermal method using ethylene glycol, copper acetate and graphene oxide. The molar ratio of Cu2O to Cu in the nanocomposites was changed by adjusting the hydrothermal reaction time. The synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and UV–Vis spectroscopy. The field emission scanning electron microscopy (FE-SEM) image shows the reduced graphene oxide (RGO) sheets decorated by uniform hierarchical Cu2O@Cu spheres. The photocatalytic activity of synthesized nanocomposites on degradation of Direct Orange 39 (DO39) as a pollutant was determined by visible light irradiation. For this purpose, a model was developed by the central composite design to describe the degradation efficiency of DO39 as a function of the operational parameters. The interaction effects and optimal parameters were obtained by using statgraphics software. The percentage of degradation efficiency (%DE) of DO39 approached 90% under optimal conditions. Predicted values were found to be in good agreement with experimental values (R2 = 99.20 and Adj-R2 = 98.65) which confirm suitability of the model.

Magnetic EDTA functionalized CoFe2O4 nanoparticles (EDTA-CoFe2O4) as a novel catalyst for peroxymonosulfate activation and degradation of Orange G.

EDTA functionalized CoFe2O4 nanoparticles (EDTA-CoFe2O4) synthesized using a facile one-pot solvothermal method were employed as catalysts to activate peroxymonosulfate (PMS) with Orange G (OG) as the target pollutant. Effects of operating parameters including initial solution pH, catalyst dosage, PMS dosage, and water matrix components such as Cl-, NO3-, CO32-, and humic acid were evaluated. A degradation efficiency of 93% was achieved in 15min with 1mM PMS and 0.2g/L EDTA-CoFe2O4 catalyst, while only 57% of OG was degraded within 15min in CoFe2O4/PMS system. The degradation of OG followed pseudo-first-order kinetics, and the apparent first-order date constant (k obs) for OG in EDTA-CoFe2O4/PMS and CoFe2O4/PMS system was determined to be 0.152 and 0.077min-1, respectively. OG degradation by EDTA-CoFe2O4/PMS was enhanced with the increase of catalyst and PMS doses at respective range of 0.1-2.0g/L and 0.5-10.0mM. Higher efficiency of OG oxidation was observed within a wide pH range (3.0-9.0), implying the possibility of applying EDTA-CoFe2O4/PMS process under environmental realistic conditions. Humic acid (HA) at low concentration accelerated the removal of OG; however, a less apparent inhibitive effect was observed at HA addition of 10mg/L. The k obs value was found to decrease slightly from 0.1601 to 0.1274, 0.1248, and 0.1152min-1 with the addition of NO3-, CO32-, and Cl-, respectively, but near-complete removal of OG could still be obtained after 15min. Both of the sulfate radicals and hydroxyl radicals were produced in the reaction, and sulfate radicals were the dominant according to the scavenging tests and electron paramagnetic resonance (EPR) tests. Finally, a degradation mechanism was proposed, and the stability and reusability of the EDTA-CoFe2O4 were evaluated.

Facile approach to synthesize nanocrystalline NiMoO4 in the presence of amino acids as capping agent

In this work various morphologies of nickel molybdate (NiMoO4) nanostructures were synthesized via chemical reaction between nickel chloride hexahydrate, ammonium heptamolybdate tetrahydrate and different capping agents like alanine, asparagine, and phenylalanine. The products were also characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS) and diffuse reflectance spectroscopy (UV–Vis). Vibrating sample magnetometer (VSM) was used to study the magnetism properties of NiMoO4 sample. The photocatalytic behavior of nanoparticles was evaluated using the degradation of a methyl orange (MeO) aqueous solution (as an organic pollution) under ultraviolet (UV) light irradiation. The results confirm that nanoparticles are promising materials with excellent performance in photocatalytic applications.