Efficient degradation of orange II by ZnMn2O4 in a novel photo-chemical catalysis system

Improvement of the photocatalytic activity of ZnO thin films doped with manganese

In the herein report, we synthesized ZnO thin films doped with manganese (Mn). We studied the impact of Mn doping loads (1 %, 3 %, 5 % wt.) on physicochemical properties of the compounds. Furthermore, we presented the photocatalytic efficiency in removal of methylene blue dye. The structural assay indicated ZnO conserve the wurtzite crystalline structure after dopant insertion. Furthermore, the crystalline size of catalysts was reduced after dopant incorporation. The SEM analysis showed a change in surface morphology after modification of ZnO thin films. Furthermore, Raman spectroscopy verified the Mn insertion inside the ZnO lattice. After the doping process, band gap was reduced by 16 %, in comparison to bare ZnO. After the photocatalytic test, the doped catalysts showed better performance than bare ZnO in removing MB. The best test showed a kinetics constant value of 2.9 × 10-3 min-1 after 120 min of visible irradiation. Finally, the Mn(5 %):ZnO thin film was suitable after five degradation cycles, and the degradation process efficiency was reduced by 32%.

G-C3N4 Dots Decorated with Hetaerolite: Visible-Light Photocatalyst for Degradation of Organic Contaminants

In this paper, a facile hydrothermal approach was used to integrate graphitic carbon nitride dots (CNDs) with hetaerolite (ZnMn2O4) at different weight percentages. The morphology, microstructure, texture, electronic, phase composition, and electrochemical properties were identified by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), ultraviolet-visible diffuse reflectance (UV-vis DR), photoluminescence (PL), electrochemical impedance spectroscopy (EIS), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), and photocurrent density. The results of XRD, FT-IR, EDX, and XPS analyses confirmed the synthesis of CNDs/ZnMn2O4 (20%) nanocomposite. As per PL, EIS, and photocurrent outcomes, the binary CNDs/ZnMn2O4 nanocomposite revealed superior features for interfacial transferring of charge carriers. The developed p–n heterojunction at the interface of CNDs and ZnMn2O4 nanoparticles partaken a significant role in the impressive charge segregation and migration. The binary nanocomposites were employed for the photodegradation of several dye pollutants, including rhodamine B (RhB), fuchsin, malachite green (MG), and methylene blue (MB) at visible wavelengths. Amongst the fabricated photocatalysts, the CNDs/ZnMn2O4 (20%) nanocomposite gave rise to about 98% RhB degradation efficiency within 45 min with the rate constant of 747 × 10−4 min−1, which was 66.5-, 3.44-, and 2.72-fold superior to the activities of CN, CNDs, and ZnMn2O4 photocatalysts, respectively. The impressive photodegradation performance of this nanocomposite was not only associated with the capacity for impressive visible-light absorption and boosted separation and transport of charge carriers, but also with its large surface area.

Development of a Sustainable Tungsten and Iron Bimetal-Immobilized SBA-15 Composite for Enhanced Wet Catalytic Oxidation of Dye Capacity

In this study, wet catalytic decomposition of Orange (II) dye was carried out with tungsten and iron bimetal-incorporated mesoporous SBA-15 (W-Fe@SBA-15) under visible light. The synthesized hybrid composite material was characterized by physicochemical methods, powder X-ray diffraction (PXRD) spectroscopy, scanning electron microscopy combined with energy-dispersive X-ray (SEM-EDX) spectroscopy studies, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and surface property studies to understand the nature of the dye degradation process and for catalytic studies. The maximum degradation of Orange (II) dye measured by a UV-visible spectrophotometer was 99% at a contaminant volume of 2.7 × 10^-4 mol/L and a catalyst quantity of 2 g/L in 140 min reaction time. Using gas chromatography-mass spectrometry (GC-MS), the final products were chemically identified. The mechanistic steps of the process were carried out through a series of experiments. The recyclability of the catalyst added a novel feature for such a heterogeneous catalysis that can reduce secondary pollutants in water with no leaching effect observed.

Visible-light-driven activation of sodium persulfate for accelerating orange II degradation using ZnMn2O4 photocatalyst

A special catalytic system was obtained by using ZnMn₂O₄ (ZMO) materials to activate Na₂S₂O₈ and catalytically degrade organic dye orange II under visible light irradiation. The ZMO nanoparticles were prepared by a simple one-step method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). In this study, the ZMO/Na₂S₂O₈ system was used to degrade orange II, and the degradation rate reached 97.44% in 60 min. ZMO catalysts could be recycled for at least five times, and its degradation rate was only decreased by 1.84%. The free radicals produced during the degradation of orange II were studied by classical quenching experiments, and the different types of free radicals produced in the system were further confirmed by electron paramagnetic resonance (EPR) spectroscopy. The catalytic degradation of orange II in this system was mainly caused by the production of superoxide, sulfate and hydroxyl radicals, which achieved high degradation.