Browsing by Author "Akika, F. Z."

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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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    Structural and optical properties of Cu-substitution of NiAl2O4 and their photocatalytic activity towards Congo red under solar light irradiation
    (Elsevier, 2018) Akika, F. Z.; Benamira, M.; Lahmar, H.; Tibera, A.; Chabi, R.; Avramova, I.; Süzer, Şefik; Trari, M.
    The present work focuses on the effect of Cu substitution on the crystal structure and photocatalytic activity of nano-spinel oxides Ni(1−x)CuxAl2O4 (x = 0.0-1.0). The synthesized compounds by co-precipitation route are characterized by X-ray diffraction, FT-IR, X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and UV-vis diffuse reflectance. The photocatalytic activity is followed by UV-vis spectroscopy and Electrochemical Impedance Spectroscopy in order to confirm the good performance of the catalyst and the charge separation of photogenerated (e−/h+) pairs. The photocatalytic efficiency of the synthesized catalysts is investigated through the decomposition of Congo Red dye under solar light irradiation. The efficient catalyst is Ni0.2Cu0.8Al2O4 with a removal conversion of 90.55% of the dye after 180 min. The parameters influencing the dye degradation like initial concentration are studied for the optimum degradation and the results have been discussed. This study shows that the adsorption kinetic of the Congo red has well followed the Langmuir isotherm model. The high photocatalytic activity of Ni0.2Cu0.8Al2O4 can be attributed to the valence band of the catalyst which enhances the mobility of the photoexcited charge carriers.
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    Synthesis and characterization of Zn(1-x)NixAl 2O4 spinels as a new heterogeneous catalyst of biginelli's reaction
    (Korean Chemical Society, 2013) Akika, F. Z.; Kihal, N.; Habila, T.; Avramova I.; Süzer, Şefik; Pirotte, B.; Khelili, S.
    Zn(1-x)NixAl2O4 (x = 0.0-1.0) spinels were prepared at 800 °C by co-precipitation method and characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The specific surface area was determined by BET. SEM image showed nano sized spherical particles. XPS confirmed the valence states of the metals, showing moderate Lewis character for the surface of materials. The powders were successfully used as new heterogeneous catalysts of Biginelli’s reaction, a one-pot threecomponent reaction, leading to some dihydropyrimidinones (DHPMs). These new catalysts that produced good yields of DHPMs, were easily recovered by simple filtration and subsequently reused with persistent activity, and they are non-toxic and environmentally friendly. The optimum amount of catalyst is 20% by weight of benzaldehyde derivatives, while the doping amount has been found optimal for x = 0.1.