Light Photocatalytic Dye Degradation Research Articles

Enhanced visible light photocatalytic degradation of dyes by the oxygen-rich vacancy-assisted S-scheme heterojunction Al2O3/BiOBr: Catalytic mechanism and performance evaluation

A heterojunction Al2O3/BiOBr composite photocatalyst, characterized by an S-scheme structure and enriched with oxygen vacancies, was synthesized through a solvothermal reaction coupled with an in situ growth approach. Oxygen vacancies on the catalyst surface, enhanced by the robust coupling between Al2O3 and BiOBr, were corroborated by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Techniques such as UV–vis diffuse reflectance spectroscopy (DRS), UV photoelectron spectroscopy (UPS), Mott–Schottky characterization, and experimental radical trapping experiments collectively validated the pathways for migrating photogenerated carriers. The interplay between the surface oxygen vacancies and the S-scheme Al2O3/BiOBr heterojunction, which possesses potent redox capabilities, significantly improved the photocatalytic degradation. This enhancement was particularly evident in the outstanding visible photocatalytic degradation performance against rhodamine B (RhB), methyl orange (MO), and basic fuchsin (BF). The synthesized composite photocatalysts demonstrated 92% retention of degradation efficiency after five recycling cycles, indicating their considerable stability.

Silver doped barium titanate nanoparticles for enhanced visible light photocatalytic degradation of dyes

Due to the rapid growth of global population, new, fast and reliable methods must be developed to purify contaminated water. Various photocatalysts have been developed to remove organic dyes from water. Herein, Ag doped BaTiO3 has been synthesized using a facile solvothermal method and its excellent photocatalytic activities were demonstrated in degradation of both anionic and cationic dyes under visible light illumination. Ag doped BaTiO3 nanoparticles showed greater efficacy in the degradation of methylene blue (MB) and eosin yellow (EY) than undoped BaTiO3 nanoparticles, which makes them a better candidate for photocatalysis. 1.0 AgBT sample showed the highest photocatalytic activity for MB (99.1 % in 100 min) and EY (99.3 % in 60 min) dye degradation compared with those of other samples. Further, the trapping experiments revealed that hydroxyl radicals and holes are the active species in the photocatalytic process of MB and EY dye degradation and recycle test showed excellent stability of the synthesized material.

Visible light photocatalytic degradation of dyes by Ag3PO4/g-C3N4/CQDs composite

To facilitate the realize high-value utilization of coal tar pitch, carbon quantum dots (CQDs) were synthesized using ball-milling-assisted H₂O₂ oxidation method with tar pitch as carbon source. Subsequently, Ag₃PO₄/g-C₃N₄/CQDs composites were prepared through the electrostatic self-attraction of CQDs, Ag₃PO₄ and g-C₃N₄. These composites were then employed for the photocatalytic degradation of dyes, including methyl orange (MO), methylene blue (MB) and rhodamine B (RhB). A case study of MO, the degradation rate constant of Ag₃PO₄/g-C₃N₄/CQDs reached 0.02469 min−1, which was 11 times and 1.6 times higher than that of g-C₃N₄ and Ag₃PO₄. It found that Ag₃PO₄:g-C₃N₄ mass ratio of 1:1 and 5 mg/L CQDs solution loading were optimal. Characterization analysis revealed the specific surface area of the catalyst was increased and optimized band gap structure after the combination of CQDs as the co-catalyst. The possible reaction mechanism was also expounded, Ag₃PO₄/g-C₃N₄/CQDs constructed Z-scheme heterostructure, with CQDs as electron bridge. In addition, the impact of catalyst mass, initial concentration, and pH on the degradation process was studied, as well as the cyclic stability of the catalyst. Based on capture and ESR tests, the main active substances involved in the reaction were in the following order: h+ > ·OH > ·O2−. These experiments provided a new idea on the application of coal-based CQDs in the field of visible light catalytic degradation.

Dye degradation study of Malachite green and Congo red by using ZnIn2S4

In this manuscript, we demonstrate photocatalytic study of ZnIn2S4 powder sample under visible light irradiation on Malachite green and Congo red dye. The powder sample was synthesized usingIndium (III) sulphate, thioacetamide andZinc sulphate in aqueous solution. X-ray diffraction and FESEM were used to identify the hexagonal crystal structure and microspheres shape, while UV-Vis spectroscopy was used to acquire absorption and reflectance spectra under visible-light (λ = 420 nm) irradiation, the effects of process factors such as contact duration and adsorbent dose were studied on Malachite green and Congo red. Degradation efficiency of Malachite green and Congo red are 96.33%, 99.79% respectively.The results revealed that visible light photocatalytic degradation of dyes was highly efficient.

Enhanced visible light photocatalytic degradation of dyes in aqueous solution activated by HKUST-1: performance and mechanism

HKUST-1 is a copper-based metal–organic framework (MOF) and potential photocatalyst, but minimal research has addressed the performance and mechanism of HKUST-1 in the visible light photocatalytic degradation of dyes. In the present work, HKUST-1 was applied as a photocatalyst to activate peroxomonosulfate (PMS) under visible light (Vis) for dye removal in aqueous solution. The results showed that the removal efficiency of two cationic dyes [rhodamine B (RhB) and methylene blue (MB)] was greater than 95% within 120 min. Free radicals such as SO4−˙, ·OH were present in the degradation process, with SO4−˙ playing a dominant role. Zeta potential, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy data were used to investigate the degradation mechanism. In the degradation process, surface charge attraction between HKUST-1 and cationic dyes promotes removal efficiency, with the degradation efficiency of cationic dyes (MB and RhB) more than 50% higher than for anionic dyes [acid orange 7 (AO7) and methyl red (MR)]. On the other hand, HKUST-1 has been proved to activate PMS by conducting photoelectrons, which accelerated the degradation of dyes. Compared with the reaction conditions of PMS/Vis, when the HKUST-1 was present (HKUST-1/PMS/Vis), the degradation rates of MB and RhB increased by 62.7 and 63.2%, respectively.

Visible light photocatalytic degradation of dyes by a new polyaniline/β-Bi2O3 composite

ABSTRACTA new polyaniline-modified β-Bi2O3 photocatalyst (PANI/β-Bi2O3 composite) was prepared via the chemical oxidative polymerization. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-Vis absorption spectra were used to characterize the phase structure, morphology, and optical properties of the samples, respectively. The photocatalytic activity of the prepared samples was evaluated by degrading Acid orange 7(AO 7), and the highest photocatalytic activity was shown by PB-3 (5%). Compared with pure β-Bi2O3, 30% photocatalytic activity can be improved by the PB-3. PANI modification can effectively enhance the photocatalytic activity of the β-Bi2O3. The possible photocatalytic mechanism of the PANI/β-Bi2O3 composite was proposed.

Synthesis of ternary rGO–ZnO–Fe3O4 nanocomposites and their application for visible light photocatalytic degradation of dyes

The rGO–ZnO–Fe3O4 nanocomposites were synthesized by a simple, economical and environmentally benign solvothermal method. The morphology, structure and photocatalytic activity of rGO–ZnO–Fe3O4 nanocomposites were characterized, and the effects of the preparation conditions were analyzed. The 25 mg of rGO–ZnO–Fe3O4 nanocomposites performed efficient photocatalytic activity for the degradation of 25 mL of 4.79 mg/L Rhodamine B under both ultraviolet and visible light irradiation. The nanocomposites could be easily retrieved from the wastewater by extra magnetic field due to the presence of magnetic Fe3O4 nanoparticles. After the degradation experiment was carried out five times, the degradation ratio is still close to 90% after irradiation after 5 cyclic, indicating that the rGO–ZnO–Fe3O4 nanocomposites have high stability for reuse. Therefore, the prepared rGO–ZnO–Fe3O4 nanocomposites may be a promising potential material for wastewater treatment.

Visible light photocatalytic degradation of dyes by bismuth oxide-reduced graphene oxide composites prepared via microwave-assisted method

Bi2O3-reduced graphene oxide (RGO) composites were successfully synthesized via microwave-assisted reduction of graphite oxide in Bi2O3 precursor solution using a microwave system. Their morphologies, structures, and photocatalytic performance in the degradation of methylene blue (MB) and methyl orange (MO) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, UV–vis absorption spectroscopy, and electrochemical impedance spectroscopy, respectively. The results show that the RGO addition can enhance the photocatalytic performance of Bi2O3–RGO composites. Bi2O3–RGO composite with 2 wt.% RGO achieves maximum MO and MB degradation rates of 93% and 96% at 240min under visible light irradiation, respectively, much higher than those for the pure Bi2O3 (78% and 76%). The enhanced photocatalytic performance is ascribed to the increased light adsorption and the reduction in electron–hole pair recombination in Bi2O3 with the introduction of RGO.

Photocatalytic Degradation of Dyes by ZnIn2S4 Microspheres under Visible Light Irradiation

ZnIn2S4 microspheres were successfully synthesized by a hydrothermal method. A series of synthesis temperatures from 80 to 200 °C was investigated. The samples were characterized by X-ray diffraction, UV−vis spectroscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy (SEM). The results indicated that the crystalloid structure and optical property of temperature series products were almost the same. The specific surface area (SBET) of ZnIn2S4 products declined with increasing synthesis temperature. The 80 °C sample had the largest SBET (85.53 m2 g−1). SEM images demonstrated that the morphology of ZnIn2S4 was marigold-like microspheres, and the 80 °C sample had a well-proportioned morphology. Several dyes (methyl orange, congo red, and rhodamine B) were applied in the ZnIn2S4 photocatalytic reactivity investigation. It showed efficient visible light photocatalytic degradation of dyes. A liquid chromatogram−mass spectrometer ...