Influence of silicon-modified TiO 2 nanocomposites on the photocatalytic degradation of methyl orange and imidacloprid

Photo-catalytic degradation of methyl orange and formaldehyde by Ag/InVO 4–TiO 2 thin films under visible-light irradiation

Rational construction of Z-scheme Ag2CrO4/g-C3N4 composites with enhanced visible-light photocatalytic activity

Well-crystallized iron(III)-doped TiO2 nanopowders with controlled Fe3+ doping concentration and uniform dopant distribution, have been synthesized with plasma oxidative pyrolysis. The photocatalytic reactivity of the synthesized TiO2 nanopowders with a mean particle size of 50-70 nm was quantified in terms of the degradation rates of methyl orange (MO) in aqueous TiO2 suspension under UV (mainly 365 and 316 nm) and visible light irradiation (mainly 405 and 436 nm). The photodecomposition of MO over TiO2 nanopowders followed a distinct two-stage pseudo first order kinetics. Interestingly, the photocatalytic reactivity depends not only on the iron doping concentration but also on the wavelength of the irradiating light. Under UV irradiation, nominally undoped TiO2 had much higher reactivity than Fe3+ -doped TiO2, suggesting that Fe3+ doping (> 0.05 at. %) in TiO2 with a mean particle size of approximately 60 nm was detrimental to the photocatalytic decomposition of methyl orange. Whereas, under visible light irradiation, the Fe3+ -doped TiO2 with an intermediate iron doping concentration of approximately 1 at. % had the highest photocatalytic reactivity due to the narrowing of band gap so that it could effectively absorb the light with longer wavelength. A strategy for improving the photocatalytic reactivity of Fe3+ -doped TiO2 used in the visible light region is also proposed.

This work aimed to enhance the photocatalytic degradation of methyl orange (MO) by crystallinity transformation of titanium dioxide (TiO2 ). In addition, the kinetic degradation of MO was determined. To transform its crystallinity, TiO2 was synthesized using a sol-gel method and calcined at between 200°C to 600°C. Calcination at a temperature of 250°C resulted in TiO2 that showed the best performance, corresponding to MO removal of 87%±7%. MO removal by TiO2 calcined between 250°C to 400°C was higher than for commercial TiO2 powder (Sigma-aldrich) (62%±4%). TiO2 with a small crystallite size and high anatase fraction enhanced the photocatalytic degradation of MO, while the specific surface area and surface roughness seemed to play a minor role. The photocatalytic degradation of MO was NaCl-independent, while the photocatalytic activity increased with decreased pH. Reused TiO2 showed similar photocatalytic degradation of MO compared with pristine TiO2 , at 84±2%. The oxidation kinetics of TiO2 calcined at 250°C were fitted to the Langmuir-Hinshelwood model (R2 =0.9134). The kr and Ks values were 0.027mgL-1 min-1 and 0.621L/mg, respectively. Crystallinity transformation was a major factor in the enhancement of photocatalytic degradation of MO. PRACTITIONER POINTS: Photocatalytic activity of TiO2 depends on calcination temperature, pH, and a number of UVC lamps. TiO2 with a small crystallite size and high anatase fraction enhanced the photocatalytic degradation of MO.

The advancement of industrialization has led to severe environmental challenges stemming from inadequate pollutant management. Photocatalytic technology has emerged as a research focus due to its eco-friendly nature and high degradation efficiency. However, the widespread application of photocatalysts is hindered by limitations in recoverability and reusability. Therefore, designing high-performance photocatalysts with facile recoverability has become a critical research direction. Thermo-responsive materials, which precipitate upon heating and disperse upon cooling, offer a promising solution for enhancing recovery efficiency. In this study, a composite photocatalyst with thermo-responsive properties was successfully synthesized by combining graphite carbon nitride (g-C3N4) with the thermo-responsive copolymer NIPAM-DADMAC (poly(N-isopropylacrylamide)-co-diallyl dimethylammonium chloride). Key parameters including the optimal mass ratio of g-C3N4 to DADMAC-NIPAM, and the optimal recovery conditions were systematically determined by measuring the material's lower critical solution temperature (LCST). Experimental results demonstrated that under visible light irradiation, the composite photocatalyst achieved a remarkable 98.15% degradation rate of methyl orange (MO) within 120 min. Moreover, the composite exhibited exceptional stability and reusability, retaining over 77.92% of its degradation efficiency even after eight consecutive cycles. Additionally, its inherent thermo-responsive nature enabled highly efficient recovery of the catalyst. This research provides valuable insights and a novel strategy for the development of high-performance photocatalysts with enhanced recyclability, holding significant potential for practical applications in environmental remediation.

Novel ternary photocatalyst TiO 2 -ZnO/g-C 3 N 4 was synthesized via a ball milling-assisted sol-gel method and its photocatalytic performance was tested in the photocatalytic degradation of methyl orange (MO) and metoprolol (MTP) under UV-LED and visible light. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption (BET), UV-visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS) and positive hole production. Optical measurements confirmed that the combination of TiO 2 , ZnO, and g-C 3 N 4 extended the visible light absorption to 2.63 eV. SEM, TEM, FTIR and XPS revelated correct coupling between the three semiconductors, and hole density analysis suggested a synergistic effect, reducing the charge recombination. Additionally, reusability tests demonstrated the chemical stability of the material. In terms of pollutant degradation, the TiO 2 -ZnO/g-C 3 N 4 composite efficiently removed 97.75 % of MO under UV-LED light and 98.57 % under visible light in 180 min. Similarly, MTP degradation test reached 86.42 % and 86.08 % under UV-LED and visible light, respectively, after 180 min. These results highlight the mate-rial’s potential for environmental applications, particularly in contaminant removal through photocatalysis.

In this work, anionic RR4 dye was used to sensitize TiO2/PVA and TiO2/PEG immobilized system in enhancing photocatalytic degradation of anionic methyl orange (MO) dye. 0.3g of TiO2 and polymer binder was coated onto a clean glass plate by using brush technique to develop optimum immobilize TiO2 system. A comparison study between immobilized TiO2/PVA (Im/TiO2/PVA) and immobilized TiO2/PEG (Im/TiO2/PEG) system with and without RR4 sensitizer were carried out under 55-W fluorescent lamp and visible light irradiation. The photocatalytic degradation of MO was significantly enhanced for both RR4 dye sensitized Im/TiO2/PVA and Im/TiO2/PEG with first order rate constant was ca. 0.080 min-1 and 0.071 min-1 respectively under 55-W fluorescent lamp. Same observation as well under visible light irradiation whereby enhanced of those RR4 sensitized immobilized photocatalysts were recorded as compared with immobilized photocatalysts without RR4 as sensitizer. The photocatalytic enhancement under Im/TiO2/PVA/RR4 and Im/TiO2/PEG/RR4 are due to the ability of RR4 dye to become electron (e-) donor for conduction band (CB) of TiO2, thus making TiO2 CB riches with electron, eventually this e is used to remove MO dye by producing hydroxyl radical.

This research studied the synthesis and application of black titanium dioxide in the photocatalytic degradation of methyl orange (MO). First, titanium dioxide was prepared via a sol-gel method. Then sodium borohydride was used as the reducing agent in order to synthesize black titanium dioxide. Thus, a 2x2x3 factorial experimental design was employed to assess the significance of the following three factors: (A) calcination temperature (400 and 500 ?C); (B) calcination time (5 and 10 h); and (C) the molar ratio of NaBH4 to TiO2 used (0:1, 0.5:1, and 1:1). The removal of MO under UV and visible light were the responses for the analysis of variance. Prior to the photocatalytic experiment, the catalyst was stirred in the dark for one hour before irradiation by either UV or visible light bulbs for three hours. The concentration of MO was measured by UV-Vis spectrophotometer. The highest conversion of MO (82.17% under UV irradiation and 71.92% under visible irradiation) was obtained by black titanium dioxide that was calcined at 500 ?C, 10 h, molar ratio of NaBH4 to TiO2 of 1:1. The catalyst contained the largest amount of surface defect, which trapped photoexcited electrons on the surface and prevent the recombination of electrons and holes. Moreover, the band gap of black TiO2 was narrower and the light absorption in the visible region was enhanced, leading to more photogeneration of charge carriers. From statistical analysis, three main effects and their interactions between factors A and C and factors B and C in the synthesis of white and black TiO2 catalysts were significant for both photocatalytic degradation of MO under UV and visible light.

Photocatalytic degradation of textile dye derivative Methyl Orange (M.O) has been studied in aqueous medium using 2% copper doped zinc oxide (2% Cu-ZnO) nanoparticles under UV irradiation. Simple inexpensive chemical precipitation method was used for synthesis of pure and copper doped zinc oxide nanoparticles. The prepared nanoparticles pure and copper doped zinc oxide was characterized by X-ray Diffraction Technique (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis. The prepared nanoparticles were hexagonal wurzite structure. Photocatalytic efficiency of 2% Cu-ZnO were evaluated by studying mineralization of methyl orange (M.O.) as a model compound. The M.O. kinetics degradation was investigated under different parameters such as pH of the medium, catalyst dosage, M.O concentration, intensity of light etc. In addition reusability aspects of nanoparticles where also studied, which reveals that reused nanoparticles exhibited same results as that of virgin particles. Copyright © 2018 VBRI Press.

Background: In recent years, azo dyes have become the dominant choice in the textile industry, accounting for about 60-70% of all dyes used, which has led to growing environmental concerns. Aim: This research focused on the photocatalytic degradation of methyl orange (MO) and methyl green (MG) dyes using a novel g-C₃N₄ (GCN)/polyaniline (PANI)/Ag composite under visible light. Methods: This composite was synthesized through a straightforward preparation process and characterized by using various techniques, including UV-visible spectroscopy (UV-Vis), Fourier- transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and cyclic voltammetry (CV). Results: Characterization results confirmed the incorporation of PANI and Ag nanoparticles into the GCN matrix. This composite enhanced the visible light absorption and improved charge separation, leading to increased photocatalytic efficiency. Photocatalytic experiments were conducted under visible light irradiation with a catalyst dosage of 10 mg in a 10-ppm solution of the MO and MG dyes mixture. Conclusion: The GCN/PANI/Ag composite achieved significant degradation efficiencies of 70% for MO and 69% for MG within 120 minutes. The degradation process followed first-order kinetics, with rate constants of 0.0087 min⁻¹ for MO and 0.0086 min⁻¹ for MG, respectively. Reusability tests showed that the composite retained over 60% of its initial efficiency after five cycles. These findings highlight the potential of the GCN/PANI/Ag composite as a sustainable and effective photocatalyst for visible-light-driven dye degradation, offering an eco-friendly approach to wastewater treatment.

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

Influence of inorganic anions and organic additives on photocatalytic degradation of methyl orange with supported polyoxometalates as photocatalyst

Recent advances in g-C3N4/Metal organic frameworks heterojunctions for high-performance photocatalytic environmental remediation and energy production

In order to enhance the photodegradation of methyl orange (MO) by ZnO under visible light irradiation, ZnO nanoparticles co-doped with Ag and N and supported on activated carbon (AC) with different properties were synthesized through the sol-gel method. The prepared photocatalysts were characterized in terms of the structure and properties through X-ray diffraction, N2 adsorption-desorption, ultraviolet-visible (UV-vis), diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and electron spin resonance. The photocatalytic activities of these photocatalysts followed the order: Ag-N-ZnO/ACs > Ag-N-ZnO > N, or Ag single-doped ZnO > commercial ZnO. This result was attributed to the small particle size, large surface area, narrow band gap, and high charge separation of Ag-N-ZnO/ACs. The Ag-N-ZnO/coconut husk activated carbon (Ag-N-ZnO/CHAC) exhibited the highest degradation efficiency of 98.82% for MO under visible light irradiation. This outcome was due to the abundant pore structure of Ag-N-ZnO/CHAC, resulting in stronger adsorption than that of other Ag-N-ZnO/ACs. Moreover, the degradation of MO on photocatalysis followed first order kinetics. The reactive species ·OH and ·O2− played more important roles in the photocatalytic degradation of MO over composite photocatalyst. Ag-N-ZnO/CHAC photocatalyst exhibited higher photocatalytic activity than unsupported Ag-N-ZnO after five recycling runs.

Preparation and studies of photocatalytic silver-loaded TiO2 films by hybrid sol–gel method