Photocatalytic Degradation Of Orange Research Articles

Photocatalytic Degradation of Orange G Dye by Using Bismuth Molybdate: Photocatalysis Optimization and Modeling via Definitive Screening Designs.

In the current study, Bismuth molybdate was synthesized using simple co-precipitation procedure, and their characterization was carried out by various methods such as FT-IR, SEM, and P-XRD. Furthermore, the photocatalytic degradation of Orange G (ORG) dye using synthesized catalyst under visible light irradiation was studied. Response surface Method was used for the optimization of process variables and degradation kinetics evaluated by modeling of experimental data. Based on the experimental design outcomes, the first-order model was proven as a practical correlation between selected factors and response. Further ANOVA analysis has revealed that only two out of six factors have a significant effect on ORG degradation, however ORG concentration and irradiation time indicated the significant effects sequentially. Maximum ORG degradation of approximately 96% was achieved by keeping process parameters in range, such as 1 g L−1 loading of catalyst, 50 mg L−1 concentration of ORG, 1.4 mol L−1 concentration of H2O2 at pH 7 and a temperature of 30 °C. Kinetics of ORG degradation followed the pseudo first order, and almost complete degradation was achieved within 8 h. The effectiveness of the Bi2MoO6/H2O2 photo-Fenton system in degradation reactions is due to the higher number of photo-generated e- available on the catalyst surface as a result of their ability to inhibit recombination of e- and h+ pair.

Effects of MnII and EuIII Cation Exchange in Sepiolite‐Titanium Dioxide Nanocomposites in the Photocatalytic Degradation of Orange G

AbstractTwo primary mechanisms of titanium dioxide (TiO2) efficiency inhibition in ultraviolet (UV)‐driven photocatalytic reactions are the high recombination rate and sintering. To address these challenges, TiO2 nanocrystals were grown in‐situ onto sepiolite modified with MnII and EuIII ions. The resulting nanocomposites were characterized and evaluated for photocatalytic activity for Orange G (OG) degradation under UV irradiation. Resultant reduction in activity over Mn‐sepiolite‐TiO2 is attributed to charge‐carrier scavenging by unstable Mn and adsorption‐mediated chromophore protection by Mn‐oxyhydroxide. Dye removal over Eu‐sepiolite‐TiO2 was only slightly more efficient than over the control despite relevant Eu concentrations; potentially related to inhibited TiO2‐Eu interfacial synergy and superoxide radical scavenging. The results of this investigation corroborate prior observations that substrate cation‐exchange results in unpredictable behavior of the cations introduced during subsequent fabrication steps which may be of benefit or detriment to the final material.

Facile Hydrothermal Synthesis of Tungsten Tri-oxide/Titanium Di-oxide Nanohybrid Structures as Photocatalyst for Wastewater Treatment Application

In this study, tungsten trioxide/titanium dioxide (WO3–TiO2) nanohybrid structures were prepared using a facile hydrothermal method. The nanosheets-like morphology was achieved for the prepared WO3–TiO2 nanohybrid that were confirmed by scanning electron microscopy. Provided X-ray photoelectron spectroscopy results also confirm the element existence and surface composition of the nanohybrid structure. The optical properties of the WO3–TiO2 nanohybrid were verified using UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence spectroscopy. The UV–Vis DRS results indicated that the absorption edge for the WO3–TiO2 nanohybrid found a red shift towards the visible region due to the reduced bandgap (2.83 eV). The photocatalytic activity of the as-prepared WO3–TiO2 nanohybrid was evaluated by the photocatalytic degradation of Orange G dye in wastewaters under visible light. 94% Orange G dye was degraded in 210 min at neutral pH in the presence of WO3–TiO2 nanohybrid, which indicates the enhanced photocatalytic activity. The photo-luminescence technique has also confirmed the formation of –OH radicals during photodegradation by utilizing terephthalic acid as a probe molecule. These results indicate that the prepared nanohybrid material is a simple, low-cost, and efficient photocatalyst for the degradation of pollutants in wastewater treatment applications.

VISIBLE LIGHT IRRADIATED PHOTCATALYTIC DEGRADATION OF ORANGE II DYE IN PRESENCE OF ZnO NANOPARTICLES

Zinc oxide nanoparticles were obtained by chemical precipitation method using zinc nitrate and aqueous solution of sodium hydroxide as precursors. The ZnO nanoparticles exhibited excellent photocatalytic activity for Orange-II dye degradation under visible light irradiation. ZnO nanoparticles are easy to recover and can be used upto three times without loss of degradation activity. We observed that Fenton reagent showed good activity for Orange II dye decolourization and degradation. Photocatalytic degradation of Orange II dye using H2O2/Fe3+ has also been studied and optimum conditions for the decolourization and degradation of dye has been established.

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.

Photocatalytic degradation of Orange G using sepiolite-TiO2 nanocomposites: Optimization of physicochemical parameters and kinetics studies

Highly photoactive nanocomposites Sep-TiO2 with various ratios of Ti/Sep were prepared by a novel microwave-hydrothermal method and were compared for their photocatalytic activity. The catalyst with the Ti/Sep ratio of 40 mmol/g showed the highest photodegradation activity on account of its relatively intact sepiolite structure and more anatase active sites. The effects of operational conditions, including photocatalyst amount, initial dye concentration and pH on photocatalytic degradation performance were analyzed and optimized, which demonstrated low and negligible photodegradation efficiency in the presence of sepiolite only and in the absence of photocatalyst, respectively. The photocatalytic degradation kinetics under different reaction conditions was elucidated by modeling. The results showed that the photocatalytic degradation of Orange G could be described by the modified Langmuir-Hinshelwood model. The photocatalytic degradation process fits into first-order kinetics for most of the operational parameters, while follows zero-order kinetics for the condition of high dye concentration. The apparent rate constants kapp for each degradation reaction were calculated by fitting the model to experimental data and the highest value was obtained at catalyst dosage 0.8 g/L, initial dye concentration 10 mg/L and pH = 3. Moreover, the recycling experiments confirmed the stability of the catalyst.

Sonochemical synthesis of Ga-doped ZnS nanoballs with enhanced photocatalytic activity for Orange II dye degradation in wastewater

In this study, different molar amounts (0-3.0 mol%) of gallium ions doped onto the lattice of ZnS nanoballs were synthesised by sonochemical irradiation approach without using any template. From the results, we could find that the gallium-doped ZnS particles are held together and assembled into irregular spherical shapes, which were arranged in the form of clusters, with 50-200 nm sizes. The peak positions of Zn2p and S2p of the 3.0 Ga/ZnS nanoballs shifted slightly towards lower binding energy compared to the pristine ZnS. The emission intensity of photoluminescence was enhanced with the increasing doping gallium concentration due to the crystal quality with higher defects. Gallium-doped ZnS nanoballs had a sufficient over-potential of CB and VB to improve the degradation efficiency of Orange II dye. Upon performing photocatalytic degradation of Orange II dye under UV light irradiation, the highest first-order rate constant (0.0143 min-1) was obtained for 1.0 Ga/ZnS nanoballs. In addition, the degradation mechanism is discussed in detail.

Effect of Al3+ substituted zinc ferrite on photocatalytic degradation of Orange I azo dye

Aluminum substituted zinc ferrite catalysts were prepared by the sol–gel auto-combustion method and characterized by using Mössbauer spectroscopy and nitrogen adsorption–desorption isotherm measurements. The photocatalytic activity of ZnFe2−xAlxO4 (0 ≤ x ≤ 2) spinel ferrites was evaluated for the first time on Orange I azo dye degradation under UV light illumination. The results showed that the photocatalytic process was promoted when aluminum cations substituted iron cations located in octahedral sites of zinc ferrite lattice. Therefore, the Orange I azo dye best removal efficiency was observed when the Al3+ and Fe3+ are presents in equimolar amounts. The dye degradation performance of the ZnFe2−xAlxO4 (0 ≤ x ≤ 2) catalysts was related to the crystallite size than to the BET surface area values and to the presence of secondary phases, such as α-Fe2O3 and ZnO.

Nanocrystalline ZnO Doped on Lanthanide Oxide Dy2O3: A Novel and UV Light Active Photocatalyst for Environmental Remediation

Doping of ZnO on Dy2O3 was studied for its enhanced photocatalytic activity under UV light irradiation. Various doping concentrations were prepared employing precursor nitrates, and 20 mol % ZnO-doped Dy2O3 was found to be highly active under UV irradiation for the degradation of a model pollutant, Orange G dye. The photocatalyst was highly crystalline with a particle size of 40–50 nm and possessed a highly porous and rough surface (26.12 nm) as evidenced by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and atomic force microscopy analysis. The band alignment and surface area were determined by X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller analyses. The band gap energy of the prepared photocatalyst was found to be 3.15 eV from UV–diffuse reflectance spectroscopy measurements, and the metal oxide stretching frequencies were analyzed by Fourier transform infrared analysis. Free radical formation by the photocatalyst during the in situ process was confirmed by electron paramagnetic resonance studies. The photocatalytic degradation of Orange G dye was monitored with a UV–visible spectrophotometer, COD, and positive mode electrospray ionization mass spectrometry analyses.

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

Effect of calcium oxalate on the photocatalytic degradation of Orange II on ZnO surface

The photocatalytic degradation of aqueous solution of Orange II, has been investigated in the presence of ZnO catalyst with calcium oxalate as sacrificial agent. This study demonstrated that the performance of ZnO photocatalyst can be improved by addition of calcium oxalate. Results show that adsorption is an important parameter controlling the degradation phenomena. Indeed, the added oxalate causes a drop in the pH medium, what causes a better adsorption of Orange II on the ZnO surface. The effect of calcium oxalate is to increase the concentration of superoxides (O 2 ·− ) and hydroperoxides (HO2·) radicals, which are key intermediaries in the mechanism of photodegradation because of their powerful force of oxidation.

Photocatalytic degradation of Orange G dye under solar light using nanocrystalline semiconductor metal oxide

The photocatalytic degradation of Orange G (OG) dye has been investigated using synthesised nanocrystalline ZnO as a photocatalyst and sunlight as the irradiation source. The formation of ZnO prepared from its precursor was confirmed through FT-IR and powder X-ray diffraction analyses. Surface morphology was characterised by scanning electron microscope and transmission electron microscope analysis. Band gap energy of synthesised nanocrystalline ZnO was calculated using diffuse reflectance spectroscopy (DRS). Different experimental parameters such as effects of pH, dye concentrations and mass of catalyst were standardised in order to achieve complete degradation of the dye molecules under solar light irradiation. The kinetics of oxidation of OG was also studied. The complete degradation of OG was evident after 90min of irradiation at an initial pH of 6.86. The degradation of OG was confirmed by UV-Visible spectrophotometer, high-pressure liquid chromatography, ESI-Mass and chemical oxygen demand analyses. The adsorption of dye onto catalytic surface was analysed employing model equations such as Langmuir and Freundlich isotherms, and it was found that the Langmuir isotherm model best fitted the adsorption data. The solar photodegradation of OG followed pseudo-first-order kinetics. HPLC and ESI-Mass analyses of the degraded samples suggested that the dye molecules were readily degraded under solar irradiation with nanocrystalline ZnO.

New Shape-Controlled Nanocrystalline SrSiO<sub>3</sub> Photocatalyst: Template-Free Syntheses and Photocatalytic Activity

Nanocrystalline SrSiO3 with different morphologies was first selectively prepared by a facile template-free solvothermal method at different water/ethanol volume ratios. The as-prepared samples were characterized by X-ray diffraction, N2-sorption, field emission scanning electron microscopy. The results showed that the as-prepared samples SrSiO3 displayed nanoflakes in pure water while obtained nanofibres in mixed solvent of water and ethanol (the volume ratio of water to ethanol is 1:1.). The BET specific surface area of SrSiO3 nanofibre is 161.7 m2 g-1, which is much higher than that of nanoflake one. The mechanisms about the formations of shape-controlled SrSiO3 are proposed and discussed based on a reaction-crystallization process. As a novel photocatalyst, the photocatalytic activity of as-prepared samples SrSiO3 were evaluated by the photocatalytic degradation of orange II (20 mg L-1) and the total organic carbon (TOC) value indicated that orange II solution can be mineralized in 120 min.

Mechanistic studies of photoinduced degradation of Orange G using LC/MS

Photocatalytic degradation of Orange G dye was carried out with UV light in the presence of TiO2 mixed with 20% chromium oxide as a catalyst. The conditions for maximum dye degradation were optimized in terms of catalyst amount, dye concentration, pH and time. The dye degradation followed pseudo first-order kinetics. LC-MS/MS was used to track the numerous intermediate products formed during the course of dye degradation. Major intermediate products confirmed were substituted phenols, aromatic hydroxyl amine, nitroso hydroxyl aromatic amines and dicarboxyl aromatic compounds. These intermediates along with some minor products were correlated to suggest a possible degradation pathway of Orange G. The dye degradation occurred mainly by three pathways, namely the hydroxylation of the aromatic ring, desulfonation and oxidative cleavage of the azo bond.

Photocatalytic Decolourisation of Orange II Aqueous Solutions by TiO<sub>2</sub> and ZnO Active Layers Screen Printed on Ceramic Tiles

In this work TiO2 and ZnO layers have been deposited by screen-printing in common glazed ceramic tiles. These layers were evaluated for the photocatalytic degradation of Orange II in aqueous solutions, in a batch photoreactor under visible light. The photocatalytic behaviour was assessed by taking into account experimental variables which include: (i) firing temperature of the TiO2 printed layer; (ii) layer thickness; (iii) operation time; (iv) pH; and (v) dye concentration. Optimal processed layers showed an interesting decolourisation performance (over 90% efficiency after 7-8 h). It is anticipated that these new ceramic materials might be developed as an interesting alternative to TiO2 or ZnO suspensions, for example in photocatalytic applications excusing the particles removal at the end of the process.

Photocatalytic Degradation of Orange II in Aqueous Iron-Rich Montmorillonite Solutions

In this work the photodegradation of orange II was carried out in the presence of iron-rich montmorillonite (MMt) (2.24% Fe2O3) using a 15-W low-pressure ultraviolet lamp (λ=254 nm, I=48.4 μW/cm2). The effects of pH, MMt dose, and dye concentration were studied. A low pH value is favorable for the decolorization of orange II. The hydroxyl radical (O•H) concentration increased with increasing concentration of MMt in aqueous solutions in the range of 0–1.5 g/L. Concentrations higher than 5.0 g/L MMt inhibited the O•H production. There was no significant decrease in photocatalytic activity when the catalyst was reused. Hydroxyl radicals were detected by tert-butyl alcohol in aqueous MMt suspensions under ultraviolet irradiation and were responsible for the degradation of orange II. Free iron ions dissolved in MMt suspensions, structural iron in the MMt structural and the charged surface of nanoclay are responsible for the hydroxyl radical (O•H) production. Free iron ions dissolved in solution plays a predominant role in the degradation of orange II. This study shows that iron-rich MMt is a potential photocatalyst for dye wastewater treatment.

Photocatalytic degradation of Orange II by titania addition to sol–gel glasses

Glasses on SiO2–CaO–ZnO–B2O3–K2O–Al2O3 oxide system modified by addition of titania (0, 3, 5, 12, and 20% w) have been prepared by sol–gel method. The obtained gels were aged, dried and fired at 600 °C/1 h in order to stabilise the glass. The resulting fired powders were characterised by UV–Vis–NIR spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Their photocatalytic capacity on the degradation of Orange II dye has been studied. The XRD and TEM studies indicate that system becomes amorphous with a nanostructured microstructure. From UV–Vis–NIR results the band gap calculated is around 3.5 eV for all modified glasses. Photoactivity of powders depends on amount of titania in glass composition and the specific surface area of prepared samples. The sample with highest surface area and lowest addition of titania (3% w sample) shows similar activity than commercial anatase used as reference.

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

The homogeneous hydrolysis mixture of titanium oxo-sulphate and zirconium oxo-sulphate with urea at tem- perature 100°C has been used to prepare Zr 4+ doped anatase with high specific surface area. The structure of the prepared samples was determined by X-ray powder diffraction (XRD) and selected area electron diffraction (SAED). The mor- phology and microstructure characteristics were also obtained by scanning electron microscopy (SEM) and high resolu- tion electron microscopy (HRTEM). The nitrogen adsorption-desorption was used for surface area (BET) and porosity de- termination. These oxides were taken for experimental evaluation of their reactivity with yperite (2,2´-dichloroethyl sul- fide or HD or sulphur mustard), soman (3,3-dimethyl-2-butyl methylphosphonofluoridate or GD) and matter VX (O-ethyl S-2-(diisopropylamino)ethyl methylphosphonothionate). The photoactivity of the prepared samples was assessed by the photocatalytic decomposition of Orange 2 dye in an aqueous slurry under irradiation of 254 nm and 365 nm wavelength.

Photocatalytic degradation of Orange G on nitrogen-doped TiO 2 catalysts under visible light and sunlight irradiation

In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO 2 photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO 2 nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO 2, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H 2O 2 was 5.0 and 15.0 mmol/l, respectively.