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Although widely used in the textile industry, methyl orange is considered one of the most toxic dyes, which have negative impacts on the aquatic environment and needs to be removed from water bodies. Hence, the present paper reports the synthesis of new floating photo-Fenton catalysts based on the immobilization of Fe2O3 nanoparticles on the surface of Luffa sponges for the oxalate-induced-degradation of methyl orange. The floating catalytic sponges were prepared through a simple precipitation method followed by a reflux heating process and then characterized by field emission scanning electron microscopy, X-ray diffraction, atomic absorption spectrometry, and nitrogen adsorption-desorption experiments. According to the experimental results, methyl orange was effectively degraded over our floating catalytic sponges under light illumination at near neutral pH. The catalytic activity was also found to be enhanced with the increase in crystallinity of Fe2O3 nanoparticles, which can be achieved by the reflux heating. Besides, owing to the floating feature, these sponges are easily separated from the solution, thereby not forming a secondary source of pollution for water

Al-doped TiO2 nanoparticles with different Al contents were prepared by a simple sol–gel method and were applied as UV filters for sunscreen products. These materials were characterized by XRD, Raman, FESEM, N2 adsorption-desorption, WDXRF, FTIR, and UV–visible diffuse reflectance spectroscopy. Their color and photocatalytic activity were evaluated through CIE L*a*b* colorimetric method and the degradation of methylene blue under UV light, respectively. According to the results, the insertion of Al3+ ions into TiO2 successfully reduced the photocatalytic performance via the decrease in the mass fraction of rutile phase, the decrease in surface hydroxyl groups, and the increase in dislocation density. These Al-doped powders display better UV absorption than the undoped TiO2, which can be attributed to the increase in anatase content and the decrease in particle size due to Al-doping. Consequently, the sunscreen using 4 mol% Al-doped TiO2 reveals the enhanced SPF value and improved color stability, which are suitable for UV protection cosmetics. Highlights: Preparation of Al-doped TiO2 nanoparticles by sol-gel method. Al-doping successfully reduces the photocatalytic activity of TiO2. Al-doped TiO2 nanoparticles show high UV absorption and bright ivory-white color. Sunscreen using Al-doped TiO2 display high SPF values and high color stability. Al-doped TiO2 nanoparticles can be safety used as UV filters in sunscreens. [ABSTRACT FROM AUTHOR]

The present paper reports the synthesis of magnetic photo-Fenton catalysts based on CuFe2O4 via an environmentally friendly sol-gel method at different annealing temperatures (700, 800, and 900°C) using tamarind fruit extract as a chelating agent. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, Fourier-transform infrared spectroscopy, and vibrating sample magnetometry. Their photo-Fenton catalytic performance was tested with oxalic acid for the degradation of Methylene Blue under UVA light and under visible light. According to the results, the annealing temperature was found to be the important factor, significantly affecting the oxalic acid-induced-photo-Fenton activity. When the annealing temperature increased from 700 to 800°C, the catalytic performance was strongly improved, which can be explained by the enhanced Fe3+ content on the catalyst surface. At higher annealing temperature, due to the growth and agglomeration of particles, the specific surface area was decreased, consequently reducing the catalytic activity. The sample prepared at 800°C also displayed good ferromagnetic properties, making it the most promising recyclable material for wastewater treatment in this study. [ABSTRACT FROM AUTHOR]

The aim of this study was to synthesise magnetic CuFe2O4-Fe2O3 composite materials with enhanced photo-Fenton catalytic activity for the degradation of organic dyes in the presence of oxalic acid as radical-producing source. The composite catalysts were prepared by a simple hydroxide precipitation process followed by an annealing at 300°C with different annealing times. Their phase composition, morphology, surface atomic composition, surface functional groups and magnetic properties were characterised by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The catalytic tests were carried out using methylene blue as a cationic dye and methyl orange as an anionic dye. According to the results, all CuFe2O4-Fe2O3 composite catalysts exhibited significantly higher photo-Fenton activities than CuFe2O4 sample under UVA light and visible light, which can be attributed to the enhanced content of Fe species and the high roughness observed on composite surface. These composite catalysts were found effective in degrading both cationic and anionic dyes although the decomposition of methyl orange was more difficult than that of methylene blue. Moreover, oxalic acid was also experimentally proved to be an excellent radical-producing source, which is superior to H2O2, in our photo-Fenton catalytic system. When the annealing time used in the synthetic procedure was extended, the catalytic performance of composite samples tended to increase but their magnetic properties were reduced, revealing that the annealing time is an important factor to be considered for the preparation of magnetic photo-Fenton composite catalysts. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks have been extensively studied in catalysis owing to their unique physicochemical properties. However, this class of materials has not yet been directly applied to the catalytic ozonation of organic pollutants. In this study, MIL-100(Fe) was synthesized by a solvothermal method and characterized by powder X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, N2 adsorption–desorption and scanning electron microscopy. A range of reaction conditions such as pH, solute concentration and catalyst content were applied to investigate the catalytic activity of our MIL-100(Fe) sample for the ozonation of p-nitrophenol in water. According to the experimental results, at a neutral initial pH, the catalytic ozonation of p-nitrophenol proceeded mainly through radical reactions, whereas in the absence of the MIL-100(Fe) catalyst, ozone could react with p-nitrophenol via the direct reaction pathway. The catalyst achieved a conversion of up to 98% and chemical oxygen demand removal of up to 75%. Moreover, our MIL-100(Fe) catalyst retained this performance for seven cycles of operation, which offers potential applications for metal–organic frameworks as catalysts in wastewater treatment. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.3103/S1063455X24030123 [ABSTRACT FROM AUTHOR]

Photo-Fenton catalysts with floating features based on the immobilization of Fe2O3 particles on the surface of perlite granules were synthesized by a simple precipitation-annealing method. The effects of annealing temperature on the crystal structure, phase composition, morphology, surface area, surface functional groups, and surface atomic composition of the prepared catalysts were investigated by powder X-ray diffraction, field emission scanning electron microscope, nitrogen adsorption-desorption, Fourier transform infrared spectroscopy, and low voltage energy-dispersive X-ray spectroscopy. The catalytic activity was evaluated via the degradation of methylene blue in the presence of oxalic acid under UVA light and visible light. Immobilization of Fe2O3 on the perlite surface resulted in photo-Fenton catalytic activity for all samples, attributable to the formation of the hematite phase and the presence of surface Fe species. Owing to the low density of perlite, all catalysts float on the surface of the solution, which allows them to be easily separated. [ABSTRACT FROM AUTHOR]

In this work, we proposed to synthesize CuFe2O4/Fe2O3 core-shell materials with different Fe2O3 contents in order to create new and efficient photo-Fenton-like catalysts for the degradation of methylene blue with oxalic acid as a radical-producing source. The catalysts were prepared through two stages: first, CuFe2O4 was prepared by a hydroxide coprecipitation – annealing method and then, Fe2O3 was immobilized on CuFe2O4 surface by a simple impregnation – annealing procedure. According to the experimental results, our CuFe2O4/Fe2O3 core-shell materials exhibit high photo-Fenton-like catalytic activity for the degradation of methylene blue under both UVA light and visible light, as well as good ferromagnetic properties, which allows them to be easily separated from the solution by a magnet. Among them, the catalyst prepared with the molar CuFe2O4/Fe2O3 ratio of 1:2 showed the best catalytic performance with the rate constant of 2.103 h–1 under UVA light and 0.542 h–1 under visible light, which were 2 times higher than CuFe2O4 sample. The enhanced catalytic activities of our core-shell materials can be attributed to the high content of surface Fe3+ species, high specific surface area and the presence of rod-like Fe2O3 particles on their surface. [ABSTRACT FROM AUTHOR]

N-doped ZnO photocatalysts with enhanced UVA-light and visible-light-driven activities were prepared by hydrothermal treatment of various zinc-containing precursors, including zinc oxide, zinc hydroxide and zinc nitrate, with urea as a doping agent. The influences of zinc-containing precursors used in hydrothermal process on the crystal structure, morphology, surface functional groups and optical properties of N-doped ZnO catalysts were investigated by XRD, SEM, FTIR, Raman and UV-visible diffuse reflectance spectra, respectively. Their photocatalytic activity was evaluated via the degradation of methylene blue. According to the results, zinc hydroxide was found to be the most appropriate precursor for the synthesis of N-doped ZnO. The best photocatalytic performance of this catalyst under both UVA and visible light illumination can be attributed to the increase of surface hydroxyl groups, the formation of surface oxygen defects and surface Zn-N bonds as well as the reduction of particle size and the production of rod-like particles. [ABSTRACT FROM AUTHOR]

In this work, Al-doped ZnO nanoparticles were prepared with different Al contents by a simple co-precipitation method in order to suppress the photocatalytic activity without modifying their UV light absorption. The effects of Al-doping on the crystal structure, phase composition, surface morphology, surface structure, optical properties and photocatalytic activity of ZnO powder were investigated by XRD, TEM, Raman spectroscopy, UV-Visible diffuse reflectance and photocatalytic experiments for the degradation of methylene blue, respectively. According to the results, the photocatalytic activity of all Al-doped ZnO was notably lower than undoped ZnO sample. Among them, the 3 at% Al-doped ZnO sample nearly showed no photocatalytic performance under UV light irradiation, which can be attributed to the low crystallinity and the intrinsic defects created by Al-doping. Moreover, when Al3+ ions were inserted into ZnO lattice, the particle size tent to decrease but the UV light absorption remained unchanged in comparison with undoped ZnO sample. These results prove that the Al-doped ZnO nanoparticles can be a good candidate for the application in sunscreen products. [ABSTRACT FROM AUTHOR]