Decolorization Of Methyl Orange Solution Research Articles

Chemical waste treatment based on hydrogen energy (II): Aqueous methyl orange solution under the oxyhydrogen flame

The oxyhydrogen flame (OHF) can generate temperatures as high as 2800 K and a jet flow of highly reactive free radicals including H, OH, HO2 and O. Therefore, it could serve as an effective means for treating various chemical wastes, particularly organic wastes. Building upon our previous research on metal chlorides, we present here a study on the degradation mechanism of aqueous methyl orange (MO) solution under OHF. Although the decolorization of MO solution is rapid, complete degradation is a slow and intricate process. Initially, MO solution undergoes decolorization by breaking the azo bond followed by oxidation processes that convert aminobenzene compounds to benzoquinone and break down the benzene ring until ultimately being fully converted into CO2 and H2O.

Synthesis of lignin nanoparticle‑manganese dioxide complex and its adsorption of methyl orange

Lignin nanoparticles (LNPs) were synthesized using an anti-solvent method and subsequently loaded with manganese dioxide (MnO2) via potassium permanganate treatment, resulting in the formation of MnO2@LNPs. An extensive investigation was conducted to elucidate the influence of MnO2@LNPs on the decolorization of methyl orange solution. The LNPs were successfully obtained by adjusting the preparation parameters, yielding particles exhibited average sizes ranging from 300 to 600 nm, and the synthesis process exhibited a high yield of up to 87.3% and excellent dispersion characteristics. Notably, LNPs size was reduced by decreasing initial concentration, increasing stirring rate, and adding water. In the acetone-water two-phase system, LNPs self-assembled into spherical particles driven by π-π interactions and hydrogen bond forces. Oxidation modification using potassium permanganate led to the formation of nanoscale MnO2, which effectively combined with LNPs. Remarkably, the resulting MnO2@LNPs demonstrated a two-fold increase in methyl orange adsorption capacity (227 mg/g) compared to unmodified LNPs. The process followed the Langmuir isotherm model and was exothermic.

Preparation of a novel modified nanoscale zero valent iron particles and its decolorization of methyl orange solution

Preparation of a novel modified nanoscale zero valent iron particles and its decolorization of methyl orange solution

Photocatalytic plate‐like La2Ti2O7 nanoparticles synthesized via liquid‐feed flame spray pyrolysis (LF‐FSP) of metallo‐organic precursors

AbstractNanoparticles (NPs) of a perovskite‐slab‐type oxide, La2Ti2O7, were synthesized using LF‐FSP coupled with subsequent heat treatments, and their photocatalytic activity was evaluated using decolorization of methyl orange solution under Uv irradiation. The LF‐FSP process used metallo‐organic precursors to produce NPs with very low agglomeration with average particle sizes (APSs) of 26 nm (LF‐FSP NP). Optimized heat treatment of these NPs at 1000°C/3 h/air gave small, plate‐like NPs with high crystallinity, and BET specific surface areas (SSAs) of 14 m2/g, that exhibited the best observed photocatalytic activity. High‐angle annular dark‐field scanning TEM showed that heat‐treating eliminates microstructural defects in these NPs, improving photocatalytic activity by ≈30%. The current approach to perovskite‐slab‐type NPs using LF‐FSP provides a simple route to materials with superior photocatalytic activity and offers the advantage of good productivity, 30 g/h.

Individual effect of charge balance defects on the photocatalytic activity of Cr3+-modified TiO2

Loss in the photocatalytic activity of Cr3+: TiO2 powders upon hydrogen annealing shows that charge-compensating oxygen vacancies VO and Cr6+ ions can have opposite effects on the kinetics of photocatalytic decolorization of methyl orange solution. The former ones inhibit this reaction acting as electron–hole recombination centers, and the latter ones promote it playing the role of active sites. This conclusion is verified by an XPS technique for a Cr3+-doped TiO2 sample and by 121Sb Mossbauer spectroscopy for a co-doped (Cr3+,Sb5+): TiO2 sample.

Continuous decolorization of dye solution by homogeneous Fenton process in a rotating packed bed reactor

Continuous decolorization of Methyl Orange solution by homogeneous Fenton reaction was studied in a rotating packed bed reactor to intensify micromixing. In this equipment, the reactants flowed radially outward under centrifugal acceleration between a pair of rotating cylindrical disk packed with glass beads. The magnitude of the pseudo-first-order kinetic constant estimated from the experimental data was noted to increase with rotational speed and bed depth but did not significantly change with solution flow rate. It varied between 1.7 and 72 s−1 for the experimental conditions studied. The constant was over two orders of magnitude higher in rotating packed bed in comparison with conventional continuous stirred tank and packed bed reactors. Steady state was achieved in a much shorter time period in the former. The study also indicated that decolorization of a given volume of dye solution can be done at a faster rate by continuously recirculating the same volume of solution through rotating packed bed than in a mechanically agitated batch reactor.

Photocatalytic activity of hydrothermally-synthesized single-crystalline Bi3.15Nd0.85Ti3O12 nanoplates

Single-crystalline Bi3.15Nd0.85Ti3O12 (BNdT) nanoplates were synthesized through a hydrothermal process and BNdT microplates were obtained by post-annealing of the as-prepared nanoplates. Structural and morphological characterizations revealed that all the as-prepared products were orthorhombic layered-perovskite and plate-like in shape. The photocatalytic activity of the BNdT nanoplates was evaluated using the degradation of methyl orange (MO) solution. When the nanoplates were used as the catalyst, up to 70 % MO was decolorized after UV irradiation for 195 min, whereas lower than 8 % MO was decolorized when the microplates were used under the same conditions. The photocatalytic decolorization of MO solution by the catalyst was a pseudo-first-order kinetics reaction.

Photocatalytic decolorization of methyl orange solution with KIO3

The use of azo dyes must be controlled and the sewage must be properly treated before being released into the environment. Thus, it is crucial to develop processes that can destroy these azo dyes completely. It has been reported that a methyl orange (MO) aqueous solution can be effectively decolorized in KIO3 homogeneous system under UV light irradiation. In this study, the kinetics and effects of KIO4, H2O2, K2S2O8, and KBrO3 on the decolorization of MO with KIO3 under UV light irradiation were investigated in detail. The results show the decolorization reaction is a zero-order reaction when the concentration of MO is above 25 mg/L. IO4-, S2O82-, BrO3-, and H2O2 can greatly inhibit the photocatalytic decolorization reaction of MO. Several observations indicate the photocatalytic decolorization of MO with KIO3 under UV irradiation occurs by ⋅O2- attack only. A more detailed mechanism of KIO3 photocatalysis will be further investigated in the near future.

Facile synthesis and enhanced visible-light photocatalytic activity of Ag2S nanocrystal-sensitized Ag8W4O16 nanorods

Narrow band-gap (NBG) Ag2S nanocrystals (NCs) attaching on the surface of wide band-gap (WBG) Ag8W4O16 nanorods were prepared by employing a facile in situ anion exchange method with the reaction between S2− and WO42-, and the photocatalytic activity was evaluated by the photocatalytic decolorization of methyl orange solution under visible-light irradiation. It was found that in situ anion exchange could uniformly deposit Ag2S NCs on the surface of Ag8W4O16 nanorods, controllably adjust the size, distribution and amount of Ag2S NCs, and solidly connect Ag2S NCs to the Ag8W4O16 nanorods via the replacement of S2− in the solution with lattice WO42- on the Ag8W4O16 surface. The photocatalytic results indicated that the as-prepared Ag2S/Ag8W4O16 composite photocatalysts exhibited obviously higher activity compared with the pure Ag8W4O16 and N-TiO2 photocatalysts. On the basis of band structures of Ag2S and Ag8W4O16 semiconductors and the quantum size effect of Ag2S NCs, a possible photocatalytic mechanism about the Ag2S nanocrystal-sensitized Ag8W4O16 nanorods was proposed to account for the effective visible-light photocatalytic activities. This present work may provide some insight into the design of novel and high-efficiency NBG semiconductor NCs coupled with WBG semiconductor composite photocatalysts.

Enhanced Photocatalytic Activity of W‐Doped and W‐La‐Codoped TiO2 Nanomaterials under Simulated Sunlight

W‐doped TiO2 and W‐La‐codoped TiO2 nanomaterials were successfully synthesized via the sol‐gel method. The products were characterized by X‐ray diffraction, UV‐vis diffuse reflectance spectrophotometer, transmission electron microscopy, and X‐ray photoelectron spectroscopy. The presence of W and La results in significant red shift of absorption edge for TiO2‐based nanomaterials. The weight ratios of La and W in the composites play important roles in the absorption edge for TiO2‐based nanomaterials. The photocatalytic activities of both W‐doped TiO2 and W‐La‐codoped TiO2 photocatalysts for decolorization of methyl orange solution were evaluated under simulated sunlight irradiation. The results showed that both W‐doped and W‐La‐codoped can effectively improve the photocatalytic behaviors of TiO2 nanomaterials ascribed to the improved photoinduced charge carriers separation, enhanced light absorption, and large surface area. Furthermore, W‐La‐codoped TiO2 exhibited higher photocatalytic activity than W‐doped TiO2. Considering their high photocatalytic activity, the doped TiO2 nanomaterials could be applied in wastewater treatment and environmental purification.

Enhanced decolorization of azo dye solution by cadmium sulfide/multi-walled carbon nanotubes/polymer composite in combination with hydrogen peroxide under simulated solar light irradiation

Cadmium sulfide/multi-walled carbon nanotubes/polymer nanocomposite (CdS/MWCNTs/polymer) was fabricated via a facile precipitation process by depositing nanocrystalline CdS on carbon nanotubes/crosslinked chitosan nanocomposite and characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). Under simulated solar light irradiation, a combination of CdS/MWCNTs/polymer and H2O2 was found to be highly efficient for photocatalytic decolorization of a soluble azo dye, methyl orange (MO), even at neutral pH values. 99.9% of MO solution was successfully decolorized after 90min under simulated solar light irradiation with 15mgL−1 of initial MO concentration, 1.0mM of H2O2 concentration and 0.70gL−1 of photocatalyst dosage. Experimental results also indicated that the photocatalytic decolorization of methyl orange solution was strongly influenced by operational parameters and followed a simplified Langmuir–Hinshelwood (L–H) kinetic model with high R2 values. When the CdS/MWCNTs/polymer–H2O2 system was reused for the 5th time, the decolorization efficiency was still about 88.0% after 90min under simulated solar light irradiation. As a result, the CdS/MWCNTs/polymer–H2O2 will potentially provide cheaper and cleaner means for the effective treatment of dyeing effluents since it increased substantially the efficiency of dye decolorization and could take full advantage of economical solar light.

Effect of several reagents on decolorization of methyl orange solution with KIO4

Increasing environmental pollution caused by toxic dyes due to their toxicity makes the removal of these dyes imperative. So, it is crucial to develop processes that can destroy these dyes effectively. It has been generally agreed that methyl orange (MO) solution can be effectively decolorized in KIO4 homogeneous system under UV light irradiation. The knowledge on the influence of several reagents possesses both practical and theoretical values. The effects of H2O2, K2S2O8, and KBrO3 were investigated in detail. The results of the effects of five ·OH scavengers are presented. The results show that S2O82- and BrO3- can promote the photocatalytic decolorization of MO solution and H2O2 can enhance the decolorization efficiency of MO in the dark. However, the results of the effects of five ·OH scavengers cannot substantially support the argument that the degradation mechanism of KIO4 involves hydroxyl radical attack. A more detailed mechanism needs to be further investigated in the near future.

Enhanced photoinduced stability and photocatalytic activity of AgBr photocatalyst by surface modification of Fe(III) cocatalyst

Recently, AgBr material was demonstrated to be a new and efficient visible-light photocatalyst for the decomposition of various organic compounds. Owing to its excellent photosensitive properties, however, AgBr phase is unavoidably decomposed into metallic Ag under visible-light irradiation, resulting in an obvious destroy of its surface structure. In this study, Fe(III) cocatalyst was grafted on the surface of AgBr particles to form Fe(III)/AgBr photocatalysts by an impregnation method and their photocatalytic performance was evaluated by the photocatalytic decolorization of methyl orange solution under visible-light irradiation. It was found that the Fe(III) cluster could act as a new and effective cocatalyst not only to improve the photocatalytic activity of AgBr photocatalyst, but also remarkably enhance the photoinduced stability of photosensitive AgBr. After surface coating by Fe(III) cocatalyst (8.2at.%), the photocatalytic activity of AgBr photocatalyst can be greatly improved by a factor of 73% even after five cycles of photocatalytic reactions. Simultaneously, the decomposed amount of AgBr can be significantly deduced from 8.8at.% to 2.9at.% by the surface loading of Fe(III) cocatalyst. On the basis of the experimental results, an possible mechanism for the enhanced photocatalytic activity and photoinduced stability of AgBr by Fe(III) cocatalyst was proposed. Compared with the well-known noble metal cocatalysts (e.g., Pt, Au, Ag), the present abundant and cheap Fe(III) cocatalyst can be regarded as one of the ideal cocatalyst for the smart design and development of high-performance photocatalytic materials in various potential applications.

CTAB-assisted fabrication of TiO2 with improved photocatalytic performance

TiO2 photocatalyst with high photocatalytic performance was prepared by the sol–gel method with the assistance of cetyltrimethylammonium bromide (CTAB). The specific surface area, structure, morphology and the photoinduced charge separation rate of the photocatalyst prepared (CTAB–TiO2) were characterized by the Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface photovoltage spectroscopy (SPS), respectively. The results show that CTAB alters the surface parameters and the morphology, enhances the photoinduced charge separation rate of TiO2. The photocatalytic activity of photocatalysts for decolorization of methyl orange solution was investigated. The results demonstrate that the photocatalytic activity of CTAB–TiO2 is more than three times of that of the reference TiO2 and the underlying reason was discussed.

CdS nanocrystals/TiO2/crosslinked chitosan composite: Facile preparation, characterization and adsorption-photocatalytic properties

CdS nanocrystals deposited on TiO2/crosslinked chitosan composite (CdS/TiO2/CSC) were prepared in an attempt to photocatalyze decolorization of water soluble azo dye in aqueous solution under simulated solar light irradiation. CdS/TiO2/CSC was characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The characterization results proved that CdS nanocrystals has successfully been deposited on/in TiO2/crosslinked chitosan composite. The adsorption ability of CdS/TiO2/CSC was approximately 2.66mg methyl orange (a typical water soluble azo dye) per gram. The photocatalytic decolorization of methyl orange solution reached 99.1% by CdS/TiO2/CSC after simulated solar light irradiation for 210min. Kinetics analysis indicated that photocatalytic decolorization of methyl orange solution by CdS/TiO2/CSC obeyed first-order kinetic Langmuir-Hinshelwood mechanism (R2>0.997). CdS/TiO2/CSC exhibited enhanced photocatalytic activity under simulated solar light irradiation compared with photocatalysts reported before and the photocatalytic activity of CdS/TiO2/CSC maintained at 89.0% of initial decolorization rate after five batch reactions. The presence of NO3− accelerated the decolorization of methyl orange solution by CdS/TiO2/CSC, while SO42− and Cl− had an inhibitory effect on the decolorization of methyl orange. Therefore, present experimental results indicated to assess the applicability of CdS/TiO2/CSC as a suitable and promising photocatalyst for effective decolorization treatment of dye-containing effluents.

Photocatalytic Decolorization of Methyl Orange Solution with Phosphotungstic Acid

Photocatalytic decolorization of Methyl Orange (MO) solution has been studied using phosphotungstic acid (HPA) as photocatalyst. The decolorization reaction of MO solution is photocatalysis. The paper reveals that the optimal loading of photocatalyst for decolorization of MO solution (10 mg/L) is 0.6 g/L. The results show that the photocatalytic decolorization reaction of MO with HPA in a homogenous solution can be described by Langmuir-Hinshelwood equation; the results manifest that the reaction is first order with lower concentration, the limiting rate constant and the adsorption constant in this case are 0.3378 mg/(Lmin) and 0.5988 L/mg, respectively. The effect of pH value on the decolorization efficiency was also demonstrated, where special attention was paid on the nature of photocatalyst itself. Several observations indicate that only hydroxyl radicals participate the photocatalytic decolorization of MO with HPA under UV irradiation.

Fabrication of Pr-Doped Bi<sub>2</sub>O<sub>3</sub> with Enhanced Photocatalytic Performance under Visible Light

This paper reveals that photocatalytic activity of Bi2O3 under visible light towards the decolorization of Methyl Orange solution can be greatly enhanced by doping Pr into the lattice of Bi2O3 using a sol-gel method. The photocatalysts were characterized by BET, UV-Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy (SPS), respectively. The result shows that 4%Pr doped Bi2O3 possesses the best photocatalytic activity under visible light.

Fabrication of tin-doped zinc oxide by parallel flow co-precipitation with enhanced photocatalytic performance

Sn-doped ZnO photocatalysts with different molar ratios of Sn/Zn (1%, 2% and 3%) were prepared by a parallel flow precipitation. The photocatalysts fabricated were characterized by BET surface area, X-ray diffraction, scanning electron microscope, UV/Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy, respectively. The results showed that doping ZnO with Sn increased BET surface area of ZnO. The XRD patterns of Sn-doped ZnO photocatalysts calcined at 573K showed only the characteristic peaks of wurtzite-type. Doping ZnO with Sn changed the morphology of ZnO, the morphology changed from irregular lump and particle to irregular honeycomb. The photoinduced charge separation rate of 1% Sn doped-ZnO was higher than that of ZnO, while 2% and 3% Sn doped-ZnO had lower photovoltage than that of ZnO. The photocatalytic activity of Sn-doped ZnO photocatalysts for decolorization of methyl orange solution was evaluated, of all photocatalysts prepared, Sn-doped ZnO with 1% Sn exhibited the best photocatalytic activity and the underlying reason was discussed.

Fabrication and Photocatalytic Activity of Ag/Bi<sub>2</sub>O<sub>3</sub>

It has been found that the photocatalytic activity of Bi2O3toward the decolorization of Methyl Orange solution can be greatly improved by loading Ag on the surface of Bi2O3using a photodeposition method. The photocatalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy (SPS), respectively. 0.5%Ag/Bi2O3possesses the best photocatalytic activity.

Effect of Surface Plasmon Resonance on the Photocatalytic Activity of Au/TiO<SUB>2</SUB> Under UV/Visible Illumination

In this study, gold-loaded titanium dioxide was prepared by an impregnation method to investigate the effect of surface plasmon resonance (SPR) on photoactivity. The deposited gold nanoparticles (NPs) absorb visible light because of SPR. The effects of both the gold content and the TiO2 size of Au/TiO2 on SPR and the photocatalytic efficiency were investigated. The morphology, crystal structure, light absorption, emission from the recombination of a photoexcited electron and hole, and the degree of aggregation were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-visible-diffuse reflectance spectra (UV-VIS-DRS), photoluminescence (PL) spectroscopy, and turbidimetry, respectively. Photocatalytic activity was evaluated by the decolorization of methyl orange solution over modified titania under UV and UV/GLED (green light emitting diode) illumination. Au/TiO2 NPs exhibited an absorption peak (530-570 nm) because of SPR. The results of our photocatalytic experiments indicated that the UV-inducedly photocatalytic reaction rate was improved by simultaneously using UV and green light illumination; this corresponds to the adsorption region of SPR. Au/TiO2 could use the enhanced electric field amplitude on the surface of the Au particle in the spectral vicinity of its plasmon resonance and thus improve the photoactivity. Experimental results show that the synergistic effect between UV and green light for the improvement of photoactivity increases with increasing the SPR absorption, which in turn is affected by the Au content and TiO2 size.