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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]

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]