Efficient photocatalytic degradation of methyl orange dye using facilely synthesized α-Fe2O3 nanoparticles

In this paper, α-Fe₂O₃ nanoparticles were fabricated via the combustion process using glucose and sucrose as organic fuels for the first time. The fabricated products were characterized using XRD, FT-IR, HR-TEM, and UV–vis spectrophotometer. The average crystallite size of the α-Fe₂O₃ samples, which were synthesized using glucose and sucrose fuels, is 27.25 and 6.13 nm, respectively. The HR-TEM images confirmed the presence of spherical and irregular shapes with an average diameter of 31.92 and 8.83 nm for the α-Fe₂O₃ samples, which were synthesized using glucose and sucrose fuels, respectively. The optical energy gap of the α-Fe₂O₃ samples, which were synthesized using glucose and sucrose fuels, is 2.00 and 2.48 eV, respectively. Additionally, the synthesized α-Fe₂O₃ samples were employed as a photocatalyst for the degradation of methyl orange dye under UV irradiations in the absence and presence of hydrogen peroxide. The optimum pH, irradiation time, and dose of α-Fe₂O₃ that achieved the highest degradation efficiency in the presence of hydrogen peroxide (82.17 % in the case of using an α-Fe₂O₃ sample which was synthesized using glucose or 95.31 % in the case of using an α-Fe₂O₃ sample which was synthesized using sucrose) are 3, 100 min, and 0.05 g, respectively.     

α-Fe2O3 supported Bi2WO6 for photocatalytic degradation of gaseous benzene

The Bi₂WO₆/α-Fe₂O₃ composite photocatalyst was synthesized by using goethite as a precursor through hydrothermal-calcination method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis reflection spectrometer (DRS), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption-desorption measurement (BET). These results indicated that the self-made composite photocatalysts had excellent catalytic performance of degradation of gaseous benzene. When benzene initial concentration at 50 mg/m³, over the α-FeOOH/Bi₂WO₆ with molar mass of 0.8:1, calcined at 350 °C for 2 h and the pH of precursor solution was 3, the benzene degradation rate reached 71.9% and the mineralization efficiency reached 67.7% after 220 min UV irradiation, respectively. The h⁺ and O₂⁻ generated in the photocatalytic system should be played a pivotal role for the enhanced photodegradation performance of gaseous benzene.     

ZnO–Al2O3–CeO2–Ce2O3 mixed metal oxides as a promising photocatalyst for methyl orange photocatalytic degradation

In this research article, ZnO–Al₂O₃–CeO₂–Ce₂O₃ mixed metal oxides phases were prepared by calcination of Zn–Al/Ce–CO₃ layered double hydroxides (LDH) precursors, and evaluated for the photocatalytic degradation of methyl orange (MO) as a model textile dye from aqueous solution under UV irradiation. First, Zn–Al–CO₃ and a series of Zn–Al/Ce–CO₃ with different Ce content (5, 10, 15, 20%) were synthesized through co-precipitation method at Zn/(Al+Ce) molar ratio (r) of 3, then subjected to calcination at 500 °C for 6 h. Samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray analysis and pH point of zero charge. The experimental results of the photodegradation reveal that the photocatalyst developed from Zn–Al–Ce10%-CO₃ LDH exhibits the highest photocatalytic activity, with a degradation efficiency of 99.8% after 300 min of irradiation. This performance was mainly ascribed to the presence of difference state of Ce, leading a highest separation efficiency of electrons and holes. The recycling tests suggests a much high photostability and reusability of the photocatalyst.     

Microwave synthesis of sulfur-doped α-Fe2O3 and testing in photodegradation of methyl orange

α-Fe₂O₃, as a promising photocatalyst in environmental aspects, was doped by a nonmetal to enhance the optical and electronic properties. Sulfur-doped hematite was synthesized by microwave irradiation. The samples were investigated by X-ray diffraction and energy dispersive X- ray-scanning electron microscopy. Nanostructure particles have a hexagonal structure that did not change after sulfur incorporation. The optical studies via UV–Visible spectroscopy proved the high absorbance of S/α-Fe₂O₃under the visible region. Moreover, the band gap of S/α-Fe₂O₃ was shifted to higher wavelengths. However, nonmetals may exhibit a negative effect and act as recombination centers as the photoactivity of undoped hematite was still higher in the photodegradation of methyl orange as a pollutant. H₂O₂ as an oxidant was fourfold better than O₂, leading to the formation of the active oxygen species. The preparation method plays a crucial role in the shaping of nanostructure particles and its photoactivity.     

Simultaneous photocatalytic oxidation and adsorption for efficient As(III) removal by magnetic BiOI/γ-Fe2O3 core–shell nanoparticles

Addressing arsenite pollution in groundwater has drawn great attention. It is attractive to pre-oxidize highly mobile As(III) to relatively low-toxic As(V) with a subsequent adsorption separation process. Herein, BiOI anchoring on γ-Fe₂O₃ is performed to synthesize BiOI/γ-Fe₂O₃ core–shell nanoparticles for efficient removal of As(III) via a simultaneous photocatalytic oxidization–adsorption process. The physical and chemical structures of BiOI/γ-Fe₂O₃ are investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction measurements. The photoluminescence and electron spin resonance (ESR) characterization were employed to ascertain the possible reaction mechanism of visible-light-driven photocatalytic oxidation of As(III). Such BiOI/γ-Fe₂O₃ delivers a superior As(III) removal capability under visible light irradiation with an arsenic removal efficiency of 99.8% within 180 min, higher than those of BiOCl/γ-Fe₂O₃ (81.7%) and BiOBr/γ-Fe₂O₃ (98.9%). The optimal BiOI/γ-Fe₂O₃ (molar ratio of 2:1) is obtained by rationally adjusting the molar ratio of BiOI to γ-Fe₂O₃. The as-synthesized BiOI/γ-Fe₂O₃ performs well in a wide pH range of 2–8. Only coexisting PO₄^3? anions have a significant effect on the As(III) removal. The free radical trapping experiment and ESR results demonstrate that the ?O₂^? and h⁺ are the main active substances for the photocatalytic oxidation of As(III) on BiOI/γ-Fe₂O₃. This work not only gives a novel magnetic core–shell nanoparticle photocatalyst for efficient photocatalytic oxidation and adsorption of As(III) but also offers a new strategy to rationally design BiOX for its related practical applications.     

Thermal properties of the γ-Fe2O3/poly(methyl methacrylate) core/shell nanoparticles

Thermal properties of γ-Fe₂O₃/poly(methyl methacrylate) (PMMA) core/shell particles with an average core size of 4 nm were studied through measurements of thermogravimetry, powder X-ray diffraction and magnetization. The thermal degradation of the PMMA shell in the air was found to occur at temperatures lower by about 60 °C than that of free PMMA. Random scission of the PMMA chains seemed to be catalyzed by the core oxide. The γ-Fe₂O₃ to α-Fe₂O₃ structural transformation took place at different temperatures depending upon the shell material. Namely, α-Fe₂O₃ was the only product for the caprylate-capped γ-Fe₂O₃ nanoparticles treated at 400 °C, whereas γ-Fe₂O₃ still remained for the γ-Fe₂O₃/PMMA composite treated at 500 °C. It is possible that some species containing silicon of the polymerization initiator origin were formed on the surface and prevented interparticle atomic diffusions needed for the γ–α transformation.     

Synthesis and photocatalytic properties of α-Fe2O3 nanoellipsoids

A simple and a novel chemical approach was used for the growth of α-Fe₂O₃ nanostructures. Field emission scanning electron microscopy analysis revealed the monodisperse nanoellipsoid morphology of α-Fe₂O₃ nanostructures. The sizes of the short axis and the long axis of these ellipsoids were in the ranges of 50–60 nm and 40–50 nm, respectively. XRD analysis revealed that the product exhibited α-Fe₂O₃ phase. Comprehensive TEM and HRTEM analysis revealed that α-Fe₂O₃ nanoellipsoids are single crystal in nature. The methylene blue decomposition kinetics was studied for different irradiation time. The methylene blue was totally decomposed by increasing the irradiation time up to 220 min.     

Photocatalytic degradation kinetics of methyl orange in TiO2–SiO2–NiFe2O4 aqueous suspensions

Photocatalytic degradation of methyl orange by TiO₂–SiO₂–NiFe₂O₄ suspensions was investigated. Adsorption studies revealed photocatalytic degradation occurred mainly on the surface of the TiO₂–SiO₂–NiFe₂O₄. The disappearance of the compound followed the zero-order kinetics according to the Langmuir–Hinshelwood model and the rate constant was 0.0035 mg L^?1 min^?1. The rate constant depended on the amount of photocatalyst, initial pH, and the presence of additional scavengers. ^?OH radicals and h⁺ had important roles in the photocatalytic degradation of methyl orange by TiO₂–SiO₂–NiFe₂O₄.     

Synthesis and photocatalytic properties of core–shell TiO~2@ZnIn_2S_4 photocatalyst

A novel core–shell TiO2@ZnIn2S4composite has been synthesized successfully by a simple and flexible hydrothermal route using TiO2as precursors.The as-synthesized samples were characterized by X-ray diffraction,UV–vis diffuse reflectance spectra and transmission electron microscopy.The photocatalytic properties of samples were tested by degradation of aqueous methylene blue（MB）under visible light irradiation.It was found that the as-synthesized TiO2@ZnIn2S4photocatalyst was more effcient than TiO2and ZnIn2S4in the photocatalytic degradation of MB.Moreover,TEM images confrmed the TiO2@ZnIn2S4nanoparticles possessed a well-proportioned core–shell morphology.     

Investigation of photocatalytic degradation of BTEX in produced water using γ-Fe2O3 nanoparticle

Journal of Thermal Analysis and Calorimetry - Among different methods for produced water treatment, photocatalytic process is an alternative and innovative technology that is more used in water...     

Stability of Ag@SiO_2 core–shell particles in conditions of photocatalytic overall water-splitting

Core–shell nanoparticles containing plasmonic metals(Ag or Au) have been frequently reported to enhance performance of photo-electrochemical(PEC) devices. However, the stability of these particles in water-splitting conditions is usually not addressed. In this study we demonstrate that Ag@SiO_2 core–shell particles are instable in the acidic conditions in which WO_3-based PEC cells typically operate, Ag in the core being prone to oxidation, even if the SiO_2 shell has a thickness in the order of 10 nm. This is evident from in situ voltammetry studies of several anode composites. Similar to the results of the PEC experiments, the Ag@SiO_2 core–shell particles are instable in slurry-based, Pt/ZnO induced photocatalytic water-splitting. This was evidenced by in situ photodeposition of Ag nanoparticles on the Pt-loaded ZnO catalyst, observed in TEM micrographs obtained after reaction. We explain the instability of Ag@SiO_2 by OH-radical induced oxidation of Ag, yielding dissolved Ag+. Our results imply that a decrease in shell permeability for OH-radicals is necessary to obtain stable, Ag-based plasmonic entities in photo-electrochemical and photocatalytic water splitting.     

Z-scheme structure SnS2–Au–CdS with excellent photocatalytic performance for simultaneous removal of Cr(VI) and methyl orange

Research on Chemical Intermediates - A highly efficient Z-scheme photocatalyst SnS2–Au–CdS was fabricated by photoreduction and thiourea medium deposition methods. It was found that Au...     

Efficient photocatalytic degradation of methyl violet with two metall–organic frameworks

Two metal–organic frameworks, [Co₂(L)(H₂O)₂(4,4′-bipy)]·3CH₃CN (1) and [Mn₂(L)(1,10-phen)(H₂O)]·H₂O (2) (H₄L = 5-[bis(4-carboxybenzyl)-amino]isophthalic acid; 4,4′-bipy = 4,4′-bipyridine, 1,10-phen = 1,10-phenanthroline), with two different N-donor ligands have been synthesized. The structures of both MOFs were determined using single-crystal X-ray diffraction technique. MOF 1 shows 3D uncommon (4,6,6)-c net with (4.5³.6²)₂(5⁷.6⁶.8²)(4².5⁴.6⁶.7².8) topology while in the case of 2, only L^4? ligands link Mn(II) ions into a 2D layer structure with chelating 1,10-phen ligand. The results demonstrate that variation in the N-donor ligands plays a pivotal role in deciding the framework of the two MOFs. Both MOFs have been exploited as photocatalyst materials for the degradation of MV. The photocatalysis results indicate that the two MOFs are stable and are prospective candidates for degradation of methyl violet under UV light irradiation. Additionally, 2 displayed superior photocatalytic activity in comparison to 1. The probable photocatalytic activity mechanism for both 1 and 2 against MV has been proposed using density of states (DOS) calculations.     

Optical and magnetic properties of small-size core–shell Fe3O4@C nanoparticles

Core–shell Fe₃O₄@C magnetic nanoparticles which are of great interest for research have a widely applied prospect. However, people know little about the optical and magnetic properties of the small-size Fe₃O₄@C nanoparticles due to the difficulty of uniformly coating small size Fe₃O₄ nanoparticles. In this paper, the influence of carbon shell coating on the optical and magnetic properties of small size Fe₃O₄ nanoparticles was presented. Carbon coating can strengthen the absorption intensity in the UV–visible light region through the introduction of oxygen defects on the surface of the nanoparticles by nitric acid treatment. Fe₃O₄ and Fe₃O₄@C nanoparticles both display typical superparamagnetic behavior in the high-temperature regime and a blocked state at low temperature from hysteresis loop, zero-field cooled and field cooled curves. Carbon coating reduce the surface uniaxial anisotropy, thus the average blocking temperature <T_B> decreases from 59 K of Fe₃O₄ nanoparticles to 50 K of Fe₃O₄@C nanoparticles.     

Magnetic core–shell Fe3O4@C-SO3H nanoparticle catalyst for hydrolysis of cellulose

Catalytic hydrolysis of cellulose over solid acid catalysts is one of efficient pathways for the conversion of biomass into fuels and chemicals. High catalytic activity and easy separation from reaction media are two important factors for evaluating the performance of the solid acid catalysts for the cellulose hydrolysis. In this study, we report a core–shell Fe₃O₄@C-SO₃H nanoparticle with a magnetic Fe₃O₄ core encapsulated in a sulfonated carbon shell, as recyclable catalyst for the hydrolysis of cellulose. The sulfonated carbon shell shows a good activity, presenting 48.6 % cellulose conversion with 52.1 % glucose selectivity under the moderate conditions of 140 °C after 12 h reaction. Importantly, the magnetic Fe₃O₄ core makes the catalysts easily separated from reaction mixtures by using the externally applied magnetic field. In addition, the Fe₃O₄@C-SO₃H nanoparticle catalyst shows a high stability in the activity and magnetization during recycling tests, suggesting it a promising solid acid catalyst for the hydrolysis of cellulose.     

α-Fe2O3 nanoflowers: synthesis,characterization, electrochemical sensing and photocatalytic property

Nanoflower structured α-Fe₂O₃ was synthesized by adding hexamine to an aqueous solution of ferrous sulphate followed by drying and annealing at 600 °C for 6 h. X-ray diffraction analysis, Fourier-transformed infrared spectroscopy, Raman and DRS UV–visible absorption spectroscopy showed the formation of α-Fe₂O₃ with good crystalline nature. Field emission-scanning electron microscopy investigation revealed that the α-Fe₂O₃ has flower-like morphology, which is composed of nanorods. Cyclic voltammetry and chronoamperometry were used to investigate their electrochemical sensing property towards uric acid (UA). α-Fe₂O₃ exhibited enhanced sensing behavior with respect to that of bare GCE. Additionally, the α-Fe₂O₃ nanoflowers exhibit better photocatalytic activity of up to 71.7 % against rhodamine B (RhB) in short time of 60 min under visible light irradiation. It is found that the smaller crystallite size and flower-like morphology play a vital role in allowing an interaction between α-Fe₂O₃ and UA or RhB dye which enhances both the electrochemical sensing and photocatalytic activity.     

Synthesis and magnetic properties of the γ-Fe2O3/poly-(methyl methacrylate)-core/shell nanoparticles

The synthesis of γ-Fe₂O₃/poly-(methyl methacrylate)-core/shell nanoparticles and their magnetic properties are reported. Specific γ-Fe₂O₃ nanoparticles capable of initiating atom transfer radical polymerization (ATRP) were prepared by a ligand exchange reaction of ((chloromethyl)phenylethyl)-dimethylchlorosilane and caprylate-capped γ-Fe₂O₃ nanoparticles of 4 nm in diameter, and the ATRP of methyl methacrylate was carried out subsequently. These nanoparticles were characterized with Fourier transform infrared spectroscopy, transmission electron microscopy and Mössbauer spectroscopy. Low temperature magnetic properties investigated with SQUID magnetometry revealed that the coercivity and the blocking temperature changed slightly owing to surface effects.     

β-MnO2 microrods for the degradation of methyl orange under acid condition from aqueous solutions

Research on Chemical Intermediates - Beta-manganese dioxide (β-MnO2) microrods were hydrothermally synthesized from ammonium persulfate [(NH)4S2O8] solution using manganese sulfate (MnSO4) as...     

Size and shape controlled of α-Fe2O3 nanoparticles prepared via sol–gel technique and their photocatalytic activity

Journal of Sol-Gel Science and Technology - Haematite (α-Fe2O3) nanoparticles (NPs) of different sizes and morphologies were prepared from two different iron precursors (iron acetate (A) and...