Discoloration Of Methyl Orange Research Articles

Statistical Optimization and Modeling Approach for Fenton‐like Discoloration of Methyl Orange using Green Zero‐valent Iron Nanoparticle Catalysts

AbstractWastewater treatment is extremely beneficial to the environment by minimizing pollution. Water pollution caused by textile industries deteriorates ecosystems and threatens the environment. In this study, we fabricated nanoscale zerovalent iron nanoparticle (NZVI‐NPs) catalysts that act as Fenton‐like adsorbents, which remove methyl orange (MO) dye from wastewater much faster than microscale nanoparticles. The analysis of variance (ANOVA) led us to derive a quadratic model with R2=0.973. According to the central composite design in response surface methodology (CCD‐RSM) statistical optimization, 99.65 % of predicted decolorization was achieved with 1.0 g/L catalyst loading, pH initialization of 3.0, reaction temperature of 25 °C, and 22 mmol/L H2O2 concentration. By fitting a pseudo‐second‐order kinetic model, we calculated the rate constant of dye adsorption. The Langmuir isotherm demonstrated an excellent correlation between dye adsorption and catalyst with a maximum adsorption capacity (50.45 mg/g). The activation energy of the catalyst (62.26 kJ/mol) predicts a physical adsorption process. Newly developed catalysts are green efficient adsorbents suitable for significant dye removal from wastewater for the safety of aquatic life and human life. Moreover, these newly developed materials could be more suitable for the remediation of other harmful pollutants and the production of hydrogen, energy and water splitting applications.

Fe(III)-Complex-Imprinted Polymers for the Green Oxidative Degradation of the Methyl Orange Dye Pollutant.

One of the biggest problems worldwide is the pollution of natural water bodies by dyes coming from effluents used in the textile industry. In the quest for novel effluent treatment alternatives, the aim of this work was to immobilize Fe(III) complexes in molecularly imprinted polymers (MIPs) to produce efficient Fenton-like heterogeneous catalysts for the green oxidative degradation of the methyl orange (MO) dye pollutant. Different metal complexes bearing commercial and low-cost ligands were assayed and their catalytic activity levels towards the discoloration of MO by H2O2 were assessed. The best candidates were Fe(III)-BMPA (BMPA = di-(2-picolyl)amine) and Fe(III)-NTP (NTP = 3,3′,3″-nitrilotripropionic acid), displaying above 70% MO degradation in 3 h. Fe(III)-BMPA caused the oxidative degradation through two first-order stages, related to the formation of BMPA-Fe-OOH and the generation of reactive oxygen species. Only the first of these stages was detected for Fe(III)-NTP. Both complexes were then employed to imprint catalytic cavities into MIPs. The polymers showed catalytic profiles that were highly dependent on the crosslinking agent employed, with N,N-methylenebisacrylamide (MBAA) being the crosslinker that rendered polymers with optimal oxidative performance (>95% conversion). The obtained ion-imprinted polymers constitute cheap and robust solid matrices, with the potential to be coupled to dye-containing effluent treatment systems with synchronous H2O2 injection.

Photo-Fenton oxidation and mineralization of methyl orange using Fe-sand as effective heterogeneous catalyst

A novel heterogeneous photo-Fenton catalyst, iron coated sand (Fe-sand) was synthesized by impregnation-calcination method. The catalyst Fe-sand was characterized by XRD, BET, SEM, TEM, FTIR, XRF and DRS methods. X-ray diffraction (XRD) analysis showed that the Fe-sand catalyst mainly consists of Fe2O3 and SiO2 crystallites, and the Fe concentration of the prepared catalyst measured by AAS is 135.7 mg/g. BET results revealed that Fe-sand possess a mesoporous structure with a porosity of 23%. The catalytic performance of the Fe-sand was studied in the discoloration and mineralization of methyl orange (MO). The influence of reacting conditions on degradation efficiency of the oxidation process was analyzed. At optimal conditions (200 mg/L of H2O2, 100 mg/L of initial MO concentration, pH = 3 and without added alcohol) complete discoloration of MO can be obtained within 60 min. The reaction process of MO discoloration was followed by UV–vis and GC–MS spectroscopic techniques. Based on the oxidation products formed, a probable degradation mechanism has been distinguished. Leaching tests indicated a very low concentration of dissolved iron ion and satisfactory stability of prepared catalyst. Industrial application of this catalyst in textile effluent treatment has shown that the proposed catalytic process is suitable for producing reusable water quality.

DECOLORACIÓN SONOQUÍMICA SINÉRGICA DEL ANARANJADO DE METILO UTILIZANDO TRICLOROMETANO EN DOS REACTORES ULTRASÓNICOS

The discoloration of methyl orange (AM), an azo dyer with mutagenic properties, is studied. The action of trichloromethane (HCCl 3 ) (TM) is analyzed as a synergistic agent, using batch and continuous ultrasonic reactors. It is demonstrated that the sonochemical discoloration of AM is widely favored by the addition of low concentrations of HCCl 3 . In the case of the batch reactor, discolorations of 17 and 98 % were obtained without and with TM, and the respective kinetic constants were statistically different. In the continuous reactor, discolorations of 7 % and greater than 80 % were reached without and with the addition of TM, respectively, once the reactor entered a steady state.

Comparative study of discoloration of mono-azo dye by catalytic oxidation based on wells-dawson heteropolyanion catalyst

The objective of this research was to study and compare the kinetic discoloration of mono azo dye Methyl Orange (MO) in aqueous solution by (H2O2) and (KMnO4) using a Wells-Dawson heteropolyanion (α2P2W17O61Cu)8−. The factors on the discoloration of methyl orange, such as initial pH of the aqueous solution, mass of the catalyst, concentration of the oxidants, initial dye concentration were investigated. The results reveal that the use of (α2P2W17Cu /H2O2) and (α2P2W17Cu /KMnO4) systems has a great activity in the discoloration of MO which can respectively reached 90,6 % and 9851%. However, the kinetic discoloration of MO by (α2P2W17Cu /KMnO4) system is more quickly than that of the system (α2P2W17Cu /H2O2); where the reaction time is respectively 60 min and 240 min. The kinetic parameters for both systems were also determined.

Photo-induced charge separation properties of NiO/Bi2O3 heterojuctions with efficient simulated solar-driven photocatalytic performance

The inherent drawbacks of Bi2O3 greatly limit the practical application of Bi2O3, thus it is crucial to boost the photocatalytic activity of Bi2O3, and therefore NiO was employed to couple with Bi2O3. In this paper, NiO/Bi2O3 heterostructures with improved sunlight driven -photocatalytic activity were constructed by a pore impregnating method. The samples were studied by Brunauer -Emmett- Teller (BET) method, X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), high-resolution transmission electron microscopy (HRTEM), surface photovoltage (SPV) spectroscopy and electron spin-resonance (ESR) spectroscopy. The photocatalytic activities of NiO/Bi2O3 heterostructures toward discoloration of methyl orange (MO) aqueous solutions were evaluated. The results display that the presence of NiO in the heterojuctions increases the specific surface area, the absorbance in the visible light region, the separation rate of the photo-induced charge pairs and the formation of ·O2− in the photocatalytic system.

Z-scheme TiO2/g-C3N4 composites with improved solar-driven photocatalytic performance deriving from remarkably efficient separation of photo-generated charge pairs

High recombination rate of electron-hole pairs and weak oxidation ability of holes from g-C3N4 greatly limit the catalytic degradation efficiency of g-C3N4-based photocatalysts, thus it is crucial to further improve the photocatalytic efficiency of g-C3N4. In this paper, TiO2 was successfully loaded onto the g-C3N4 surface to induce the electron−hole separation and enhance the photocatalytic efficiency. The results revealed the maximum photocatalytic performance toward discoloration of methyl orange (MO) aqueous solution under the simulated sunlight illumination at molar ratio of 3% TiO2 to g-C3N4 composite. The junction between TiO2 and g-C3N4 significantly accelerate the separation of the photo-generated charge pairs caused by the strong interactions between TiO2 and g-C3N4. Such highly efficient photo-generated charge separation can be explained by a Z-scheme charge separation and migration mechanism based on the results of the scavenger experiments and the energy band structures.

Effects of the molar ratio on the photo-generated charge separation behaviors and photocatalytic activities of (BiO)2CO3-BiOBr composites

The molar ratio of two semiconductors will remarkably influence the photo-induced charge separation behaviors of the composites constructed, thus affecting the corresponding photocatalytic activity. Therefore, it is critical to reveal the relationship between the molar ratio of two semiconductors and the photo-induced charge separation; the information can shed light on the study of nature of surface catalysis. In this work, (BiO)2CO3-BiOBr composites were facilely fabricated in-situ through a pore impregnating approach using HBr aqueous solution. The samples were studied by BET, XRD, SEM, UV–Vis DRS and surface photovoltage spectroscopy (SPS). The photocatalytic activities of the samples were evaluated by the discoloration of methyl orange (MO) aqueous solution upon the simulated sunlight illumination. The results reveal that the (BiO)2CO3-BiOBr composite with 3/4 M ratio of (BiO)2CO3/BiOBr displays the highest photo-induced charge separation rate and photocatalytic activity, the results further manifest that no different electronic transfer property occurs after coupling (BiO)2CO3 with BiOBr.

Charge separation and photocatalytic properties of BiOI prepared by ionic liquid-assisted hydrothermal method

As a prospective sunlight-driven photocatalyst, photocatalytic property of BiOI under sun light irradiation should be further boosted. In this work, IL-BiOI with enhanced charge separation rate and sunlight photocatalytic activity was prepared through a hydrothermal method with the aid of ionic liquid (IL) 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIm]PF6). The samples were studied by Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), UV/Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and surface photovoltage spectroscopy (SPS). The photocatalytic performance of the samples toward discoloration of methyl orange (MO) aqueous solution under the simulated solar irradiation was evaluated. The results reveal that IL-BiOI exhibits better photocatalytic activity than BiOI.

In situ anchor of magnetic Fe3O4 nanoparticles onto natural maifanite as efficient heterogeneous Fenton-like catalyst

In situ anchor of magnetic Fe3O4 nanoparticles (NPs) onto the surface of natural maifanite was realized by chemical oxidation coprecipitation in hot alkaline solution. The Fe3O4/maifanite composites were characterized by XRD, FTIR, SEM, and TEM. These results indicated that polycrystalline Fe3O4 NPs with inverse spinel structure were formed and tightly dispersed on maifanite surface. Based on the measurement of surface Zeta potential of maifanite at different medium pHs, the possible combination mechanism between natural maifanite and Fe3O4 NPs was proposed. Then, the asobtained composites were developed as highly efficient heterogeneous Fenton-like catalyst for the discoloration of an azo dye, Methyl Orange (MO). The comparative tests on MO discoloration in different systems revealed that Fe3O4/maifanite composite exhibited much higher Fenton-like catalytic activity than Fe3O4 NPs and the heterogeneous Fentonlike reaction governed the discoloration of MO. Kinetic results clearly showed that MO discoloration process followed the second-order kinetic model. Fe3O4/maifanite composites exhibited the typical ferromagnetic property detected by VSM and could be easily separated from solution by an external magnetic field.

Glass capillaries with TiO2 supported on inner wall as microchannel reactors

In this work, we have successfully immobilized TiO2 nanoparticles with small particle size and narrow size distribution on the inner surface of glass capillaries. By integrating the beneficial properties of nano-sized TiO2 particles with microreactors, the highly efficient catalytic system showed good performance in oxidation of dibenzothiophene (DBT) and photocatalytic discoloration of methyl orange (MO). The mean particle size and loading amount (Ti content: 0.21–2.81wt.%) are both controllable via the simple manufacturing procedure. The diameter varied from 6.8 to 20.8nm with the pH increased from 1.59 to 6.48 using ethanol as the solvent. Particles prepared by methanol showed the largest size (18.2nm) and broadest size distribution compared with those synthesized with ethanol and isopropanol. DBT was converted completely within 2.8min with an initial concentration of 20ppm, and 100% discoloration of MO was obtained after 40s. The highly efficient microreactor is easy to be integrated on a large scale, thus providing a highly promising alternative for a broad range of catalytic applications.

Discoloration of Methyl Orange in the Presence of Schorl and H2O2: Kinetics and Mechanism

Kinetics and mechanism on discoloration of an azo dye, methyl orange (MO), by heterogeneous Fenton-like reaction using natural schorl as catalyst were investigated in this study. Among the three kinetic models (the first-order, the second-order, and the Behnajady–Modirshahla–Ghanbery (BMG)), the BMG kinetic model was the best one to describe MO discoloration at different reaction conditions, due to its highest determination coefficients. The BMG model parameter, 1/m, increased with initial hydrogen peroxide (H2O2) concentration, and schorl dosage and reaction temperature increased while the pH solution decreased. The phenomenon indicated that the initial MO discoloration rate increased with the ascending of the initial H2O2 concentration, schorl dosage, and reaction temperature and the descending of the pH solution. Meanwhile, another BMG parameter, 1/b, except for the one at pH = 5, were all around 1, implying that the schorl-catalyzed Fenton-like reaction had high capacity for MO discoloration. The possible reason for these phenomena was interpreted from the point of view of OH generation and Fe dissolution. Generally speaking, the amount of hydroxyl radicals increased with initial H2O2 concentration, increased schorl dosage and reaction temperature, and decreased pH solution, playing an important role in the change of 1/m values. The concentration of soluble iron ions at all adopted experimental conditions ranged from 0.23 to 1.14 mg/L, much lower than the European Union directive (2 mg/L), which demonstrated that natural schorl would be a promising heterogeneous catalyst for the Fenton-like reaction. Finally, a possible mechanism for this process was put forward.

Photocatalytic discoloration of Methyl Orange by anatase/schorl composite: optimization using response surface method

The anatase/schorl composites were prepared and employed for the photocatalytic discoloration of an azo dye, Methyl Orange (MO). X-ray diffraction results indicated that TiO2 existed in the form of anatase phase and no diffraction peaks of schorl could be observed for all the composite samples. Scanning electron micrographs showed that the particles of anatase were well deposited and dispersed on the surface of schorl. Photocatalytic experiments revealed that the anatase/schorl composites exhibited higher photocatalytic activity for MO discoloration than pure TiO2 and more than 90% discoloration ratio could be obtained within 60 min UV irradiation when the sample containing 3 wt.% of schorl as TiO2 support was used. Then, the central composite design (CCD) under the response surface methodology (RSM) was employed for the experiment design and process optimization. The significance of a second-order polynomial model for predicting the optimal values of MO discoloration was evaluated by the analysis of variance (ANOVA) and 3D response surface plots for the interactions between two variables were constructed. Based on the model prediction, the optimum conditions for the photocatalytic discoloration of MO by TiO2/schorl composite were determined to be 15 × 10(-3) mM MO initial concentration, 2.7 g/l photocatalyst dosage, solution pH 6.6 and 43 min reaction time, with a maximum MO discoloration ratio of 98.6%. Finally, a discoloration ratio of 94.3% was achieved for the real sample under the optimum conditions, which was very close to the predicted value, implying that RSM is a powerful and satisfactory strategy for the process optimization.

Treatment of methyl orange dye wastewater by cooperative electrochemical oxidation in anodic–cathodic compartment

Electrochemical oxidation of methyl orange wastewater was studied using Ti/IrO(2)/RuO(2) anode and a self-made Pd/C O(2)-fed cathode in the divided cell with a terylene diaphragm. The result indicated that the appropriate rate of feeding air improved the methyl orange removal efficiency. The discoloration efficiency of methyl orange in the divided cell increased with increasing current density. The initial pH value had some effect on the discoloration of methyl orange, which became not obvious when the pH ranged from 2 to 10. However, the average removal efficiency of methyl orange wastewater in terms of total organic carbon (TOC) can reach 89.3%. The methyl orange structure had changed in the electrolytic process, and the characteristic absorption peak of methyl orange was about 470 nm. With the extension of electrolysis time, the concentration of methyl orange gradually reduced; wastewater discoloration rate increased gradually. The degradation of methyl orange was assumed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H(2)O(2), ·OH, O(2)(-)· produced by oxygen reduction at the cathode in the divided cell. Therefore, the cooperative electrochemical oxidation of methyl orange wastewater in the anodic-cathodic compartment had better degradation effects.

Preparation and Application of TiO2Nanowires-loaded Porous Ti-Ni Alloy

Porous Ti-Ni alloy was prepared by dipping method and vacuum sintering. Glue and Ti-Ni powders (95 wt% Ti+ 5 wt% Ni) were mixed together to get a slurry. Then a piece of open cell polymer foam (20 mm×20 mm×2 mm) was dipped into the slurry. After being stirred in the slurry for 1 h, the polymer foam was pulled out and squeezed to remove extra slurry. The polymer foam loaded with Ti-Ni slurry was sintered at 1473 K in vacuum for 2 h. With the decomposition of polymer foam at high temperature, an open cell porous Ti-Ni alloy with pore diameter about 0.2 mm was obtained. Because of the addition of Ni powders, porous Ti-Ni alloy has obvious metal luster. A hydrothermal process was applied for TiO2 nanowires preparation. 5 g of porous Ti-Ni alloy was placed in 20 mL H2O2 (30%) aqueous solution at 373 K for 16 h. Then the porous Ti-Ni alloy was filtered out and washed with deionized water. After being dried at 373 K for 6 h, TiO2 nanowires-loaded porous Ti-Ni alloy (TWP-alloy) was obtained. Then the TWP-alloy was characterized by X-ray diffraction and scanning electron microscope. The length of TiO2 nanowires on the surface of Ti-Ni porous alloy was about 2 μm and the diameter of the nanowires was about 20 nm. In the XRD pattern of TWP-alloy, the major phase was Ti and minor phase was TiNi. After being heat-treated at 723 K for 4 h, the phase of the TiO2 nanowires coated on porous Ti-Ni alloy was changed into rutile. During the heat-treatment from 298 K to 723 K, no anatase phase was observed. This means the formation of anatase phase was blocked by the dimension effect of TiO2 nanowires. Then a kind of streaming wastewater treatment instrument was as- sembled by using TWP-alloy as anode and porous Ni as cathode. Methyl orange solution was taken as a sample to investigate the wastewater processing efficiency of TWP-alloy. Under the anode voltage of 30 V, the discoloration of methyl orange can get 93% under the flow velocity of 200 mL/min. Keywords porous Ti-Ni alloy; TiO2; nanowires; methyl orange; electrolysis