Browsing by Subject "Photocatalytic reduction"

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    Structural and optical properties of Cu-doped ZnAl2O4 and its application as photocatalyst for Cr(VI) reduction under sunlight
    (Elsevier, 2020) Akika, F. Z.; Benamira, M.; Lahmar, H.; Trari, M.; Avramova, I.; Süzer, Şefik
    Cu-doped ZnAl2O4 spinel oxides (Zn(1-x)CuxAl2O4, 0.0 ≤ x ≤ 1.0) were synthesized by co-precipitation method at 800 °C. The X-ray diffraction analysis of the as-prepared powders confirmed a spinel structure with a space group Fd-3 m. XPS was used to investigate the state of the material surface and the elemental composition. The SEM image confirmed the presence of nano spherical particles. The optical properties were characterized by UV–Vis diffuse reflectance and all band gap values, in the range of 1.71 to 3.54 eV, indicate a semiconductor character of our compounds. The energy bandgap (Eg) values of Zn(1-x)CuxAl2O4 decreased with increasing of the copper content. The photocatalytic activity was evaluated for Cr(VI) reduction under sunlight irradiation. The highest photoreduction efficiency was obtained for Zn0.2Cu0.8Al2O4 with a removal ratio of 75% after 150 min. The increase of surface area increases the photocatalytic activity as it implies larger contact surfaces exposed to Cr(VI). High surface area and pore volume are useful in the formation of photogenerated electron and hole pairs. The kinetics of photoreduction follow the modified Langmuir-Hinshelwood model. The obtained results indicate a good photocatalytic activity, in particular for compounds with a high content of Cu.
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    Visible light photocatalytic reduction of Cr(VI) by surface modified CNT/titanium dioxide composites nanofibers
    (Elsevier B.V., 2016) Mohamed, A.; Osman, T. A.; Toprak, M. S.; Muhammed, M.; Yilmaz, E.; Uheida, A.
    In this work we report a highly efficient photocatalytic reduction of Cr(VI) based on PAN-CNT/TiO2-NH2 composite nanofibers fabricated by using electrospinning technique followed by chemical crosslinking of surface modified TiO2 NPs functionalized with amino group. The structure and morphology of the fabricated composite nanofibers were characterized by FTIR, SEM, TEM, TGA, and XPS. The results indicate that the composite nanofibers possess excellent photoreduction performance for Cr(VI) under visible light (125 W) after 30 min, which is much faster than previous reports. The effects of various experimental parameters such as catalyst dose, irradiation time, initial concentration of Cr(VI), and pH on the photoreduction efficiency of Cr(VI) were investigated. The highest photoreduction efficiency of Cr (VI) was obtained at low acidity and low amount of TiO2/CNT photocatalyst. The kinetic experimental data was attained and fitted well with a pseudo-first-order model. The UV–vis spectrophotometer and XPS analyses proved that chromate Cr(VI) was reduced to Cr(III). In addition, it can be concluded that the addition of the phenol enhances the photocatalytic reduction of Cr(VI). Furthermore, the photoreduction mechanism has also been discussed. Finally, the fabricated composite nanofibers were found to be stable after at least five regeneration cycles. © 2016