Photodegradation Of Dye Molecules Research Articles

Photocatalytic degradation of acid blue 74 by Co: WO3 nanoparticles: Kinetics and response surface methodology studies

Energy-efficient sol-gel synthesis was achieved through the microwave assisted self-combustion route to produce hexagonal Tungsten oxide semiconductor (WO3). The photocatalytic activity was enhanced by doping Cobalt (Co) into the crystalline structure of the nanoparticle, which were subsequently sintered at 400 °C for an hour. The structural and morphological properties of the Co-doped WO3 were revealed using X-ray diffraction (XRD) characterization. The nanoparticles exhibited an amorphous structure before annealing, due to the short heating time during combustion synthesis. Sintering the nanoparticle transformed the nanoparticle from a monoclinic phase to orthorhombic phase structure. Additional analysis techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectrum analysis (EDS).To assess the photocatalytic performance of these particles, Acid Blue 74 (AB 74) was employed in photodegradation experiments under UV light irradiation within a semi-continuous reactor.The photodegradation of dye molecules was evaluated utilizing a UV–Vis spectrophotometer, and the mineralization efficiency of the dye was determined through total organic carbon analysis (TOC). The results indicated that the dimension of the synthesized nano catalyst fell within the range of 70–120 nm, and it exhibited the ability to completely degrade a solution with an initial dye concentration of 20 ppm within 60 min. Various parameters affecting the photocatalytic reaction, including the photocatalyst dosage, initial dye concentration, pH and temperature of the dye solution were also investigated. The experiments were designed using Response surface methodology (RSM), through which a mathematical model for the dye removal process was developed.

Highly efficient multifunctional graphene/chitosan/magnetite nanocomposites for photocatalytic degradation of important dye molecules

Multifunctional chitosan/magnetite (CS/Fe3O4) and graphene/chitosan/magnetite (Gr/CS/Fe3O4) nanocomposites (NCs) were synthesized using a simple hydrothermal method. The NCs were subsequently evaluated as magnetic photocatalysts towards the photodegradation of dye molecules that are detrimental to the environment. In the present study, sphere shaped Fe3O4 nanoparticles (NPs) were found to uniformly decorate CS and Gr surfaces. The synthesized Fe3O4 NPs, CS/Fe3O4 and Gr/CS/Fe3O4 NCs were characterized by powder X-ray diffraction, Fourier-transform infrared and Raman spectroscopy, thermogravimetric analysis, UV–visible diffuse reflectance and photoluminescence spectroscopy, and field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The Gr/CS/Fe3O4 NCs showed 100% photocatalytic efficiency against rhodamine B (40 min), bromothymol blue (60 min), methylene blue (80 min) and methyl orange (100 min) compared to Fe3O4 NPs (100 min for Rh-B, 120 min for BTB, 160 min for MB and 180 min for MO) and CS/Fe3O4 NCs (90 min for Rh-B, 100 min for BTB, 140 min for MB and 150 min for MO). The photocatalytic irradiation efficiency of Fe3O4 NPs, CS/Fe3O4 and Gr/CS/Fe3O4 NCs, evaluated against visible light, was found to be significantly higher for Rh-B (100% within 40 min) compared to the other tested dyes.

Mechanistic Insights into Photodegradation of Organic Dyes Using Heterostructure Photocatalysts

Due to its low cost, environmentally friendly process, and lack of secondary contamination, the photodegradation of dyes is regarded as a promising technology for industrial wastewater treatment. This technology demonstrates the light-enhanced generation of charge carriers and reactive radicals that non-selectively degrade various organic dyes into water, CO2, and other organic compounds via direct photodegradation or a sensitization-mediated degradation process. The overall efficiency of the photocatalysis system is closely dependent upon operational parameters that govern the adsorption and photodegradation of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity. Additionally, the charge-carrier properties of the photocatalyst strongly affect the generation of reactive species in the heterogeneous photodegradation and thereby dictate the photodegradation efficiency. Herein, this comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions. The operational factors affecting the photodegradation of either cationic or anionic dye molecules, as well as the charge-carrier properties of the photocatalyst, are also fully explored. By further analyzing past works to clarify key active species for photodegradation reactions and optimal conditions, this review provides helpful guidelines that can be applied to foster the development of efficient photodegradation systems.

Coloration and Decoloration of Textiles Using a TiO2 Composite Pigment

A colorable pigment was prepared by dye adsorption onto titanium dioxide and subsequent silane coating. The effects of pH value, dye concentration, and adsorption times on dye adsorption were discussed. Large adsorption capacity of an anionic dye was obtained at pH value of 2 and the adsorption process was well described by the Langmuir isotherm model. Good dyeability and color fastness of pigment dyed fabric were achieved in the normal life cycle under sunlight. The decoloration of pigment was realized through photocatalytic degradation of dye molecules by titanium dioxide under ultraviolet irradiation when reusing the pigment dyed textiles after disposal. The new absorption peaks in the FTIR spectrum at 2924.95 cm-1, 1714.91 cm-1, 1461.17 cm-1, and 1289 cm-1 verified silane modification. Silane modification improved fixation of dyes onto the pigment and immobilization of pigments onto substrates. The close attachment of silane coating layer to titanium dioxide was conducive to photodegradation of dye molecules in the pigment.

Facile fabrication of heterostructured g-C₃N₄/Bi₂MoO₆ microspheres with highly efficient activity under visible light irradiation.

A facile and template-free solvothermal method was developed for the synthesis of microspheric g-C3N4/Bi2MoO6 photocatalysts. The obtained g-C3N4/Bi2MoO6 composites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photo-electron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible diffuse reflection spectroscopy (DRS). The XRD, FTIR, and HRTEM characterization results confirmed the formation of heterojunction structures at the interfaces of g-C3N4 and Bi2MoO6. The DRS results showed that the absorption edges of g-C3N4/Bi2MoO6 composites were red shifted in the visible light region with the increase of g-C3N4 content. The SEM and TEM images revealed that the composites exhibited a microsphere-like morphology and were composed of smaller nanoplates. The elemental mapping images revealed that g-C3N4 and Bi2MoO6 nanoflakes uniformly assembled together to form hierarchical flowers. Compared with pure g-C3N4 and Bi2MoO6, the as-prepared samples exhibited superior photocatalytic activity towards the degradation of dyes (Rhodamine B and Methyl blue) under visible light irradiation. The enhanced photocatalytic activity of g-C3N4/Bi2MoO6 composites could be attributed to their strong visible light absorption, the high migration efficiency of photo-induced carriers, and the interfacial electronic interaction. The electrochemical impedance spectroscopy (EIS) confirmed that the interface charge separation efficiency was greatly improved by coupling g-C3N4 with Bi2MoO6. It was also confirmed that the photo-degradation of dye molecules is mainly attributed to the oxidizing ability of the generated holes (h(+)) and partly to the oxidizing ability of ·O2(-) and ·OH radicals.

Transmission booster from SiO2 incorporated TiO2 crystallites: Enhanced conversion efficiency in dye-sensitized solar cells

Dye-sensitized solar cell (DSSC) is a promising solution to energy depletion, environmental pollution, and ecological destruction. However, the further elevation of power conversion efficiency is limited by low electron density on conduction band (CB) of TiO2 crystallite, resulting from the low dye-excitation efficiency, recombination of electrons with ions in liquid electrolyte as well as photodegradation of dye molecules. With an aim of enhancing the power conversion efficiency, here we designed SiO2 incorporated TiO2 crystallite photoanode to elevate dye excitation, to suppress the recombination of electron-electrolyte, and to enhance the dye photostability. We found that the highest conversion occurred at 1 wt% SiO2 incorporated TiO2 crystallite-based DSSC, giving an impressive power conversion efficiency of 9.98% (measured under standard AM1.5 test conditions) in comparison with 6.13% from pure TiO2 photoanode-based DSSC. This strategy provides new opportunities for the fabrication of highly efficient DSSCs.

Transmission enhanced photoanodes for efficient dye-sensitized solar cells

The power conversion efficiency elevation of dye-sensitized solar cell (DSSC) is limited by the incomplete dye excitation, recombination of photogenerated electrons with ions in liquid electrolyte, low electron density in conduction band (CB) of TiO2 nanoscrystalline as well as photodegradation of dye molecules. With an aim of enhancing the power conversion efficiency, here we describe an employment of SiO2 incorporated TiO2 to enhance transmission, to suppress the recombination of electron-electrolyte, to elevate the dye loading and to increase the dye photostability. We find that the highest conversion occurs at 7 wt% SiO2 in SiO2 incorporated TiO2 nanocrystallines is 9.13% (measured under standard AM1.5 test conditions) in comparison with 6.26% from pure TiO2 photoanode, giving an efficiency enhancement by 45.8%. This strategy provides new opportunities for the fabrication of highly efficient DSSCs, and the efficiency record is expected to be surpassed by scalable technique and components.

Effect of emission wavelength on photo-stability of laser dye: experimental and theoretical study

Photo-stability of laser dyes has been an important consideration for dye lasers. In this work, photo-stability of dye and its effect has been investigated as a function of dye laser wavelengths rather than commonly studied photo-chemical degradation pathways upon excitation with pump laser. Here, we report a significant improvement in photo-stability of the liquid dye laser at peak emission wavelength compared to edge wavelengths of the dye gain curve, which was related with an increase in rate of stimulated emission of dye at peak wavelength. Thus, high laser efficiency harmonizes to high photo-stability of the dye at peak wavelength which is useful for the applications of dye lasers. As a representative case, the photo-stability rates of pyrromethene 567 (PM567) dye at different laser emission wavelengths were studied using a 10-Hz Nd-YAG (532 nm) laser-pumped dye laser set-up under lasing and non-lasing conditions. Deterioration of dye laser efficiency on account of photo-degradation of dye molecules was theoretically simulated using a time-dependent rate equation model, which has been found to be in good agreement with the experimental observations.