Research Output
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PublicationAnodic oxidation of Zr-5Fe alloy in ethylene glycol/fluoride electrolyte for Cr(VI) removal under sunlight( 2024-01-01)In this work, Fe-doped ZrO2nanotubes (Fe-ZNTs) were synthesized by anodization of Zr-5 wt% Fe alloy in fluoride-containing ethylene glycol (EG)/8 vol% H2O electrolyte at varying ammonium fluoride (NH4F) concentrations (0.1, 0.3 and 0.5 wt%) at 40 V for 3 h. The morphology and crystal structure of as-anodized Fe-ZNTs were analyzed by Field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively. The as-anodized Fe-ZNTs were annealed at 500 °C for 3 h in a tube furnace for crystallization of the oxide film. The crystal structure, surface functional groups, and surface chemistry of annealed Fe-ZNTs were analyzed by XRD, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. From the FESEM results, large inner diameter (79 nm) with short nanotubes (1.9 μm) were grown in 0.5 wt% NH4F due to enhanced chemical dissolution of Fe-ZNTs in high fluoride content. XRD result of as-anodized Fe-ZNTs indicate the enhanced intensity of tetragonal-ZrO2peaks with increasing fluoride content from 0.1 to 0.3 wt% NH4F. The cubic-ZrO2started to emerge at 0.5 wt% NH4F. For annealed Fe-ZNTs, pure monoclinic-ZrO2was observed in 0.1 wt% NH4F, while tetragonal-ZrO2+ monoclinic-ZrO2, and cubic-ZrO2+ monoclinic-ZrO2were co-existed in 0.3 wt% NH4F and 0.5 wt% NH4F, respectively. Cr(VI) photoreduction under sunlight indicates 93 % Cr(VI) removal efficiency over annealed Fe-ZNTs synthesized in 0.3 wt% NH4F which ascribed to high Cr(VI) adsorption and high photocatalytic activity of tetragonal-ZrO2
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PublicationFormation of self-organized ZrO2-TiO2and ZrTiO4-TiO2nanotube arrays by anodization of Ti-40Zr foil for Cr(VI) removal( 2022-07-01)In this work, anodic oxidation of Ti-40 wt.% Zr alloy in EG/NH4F/H2O electrolyte was done to produce anodic self-aligned oxide nanotube arrays. The nanotubes were amorphous but upon annealing at 400° C they were crystallized into ZrO2-TiO2 nanotubes and ZrTiO4-TiO2 nanotubes at 600 °C. The nanotubes were used to reduce 60 ppm Cr(VI) ions under sunlight or UV irradiation. 100% removal of Cr(VI) was achieved on ZrTiO4-TiO2 nanotubes after 5 h of exposure to UV light but only 53% removal was obtained on ZrO2-TiO2 nanotubes. The higher photocatalytic activity of the ZrTiO4-TiO2 nanotubes can be related to the presence of the ZrTiO4 phase which has good acid-base properties as well as the junction formation between ZrTiO4 and TiO2 that can further enhance the reduction process.
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PublicationFormation of Fe-doped ZrO₂ nanotube arrays in glycerol/formamide at varying fluoride content for Cr(VI) photoreduction( 2024-01-01)Fe-doped ZrO2nanotubes (Fe-ZNTs) were produced by anodizing a Zr-5 wt% Fe (Zr-5Fe) alloy in a mixture of fluoride-containing glycerol/formamide (FA) (1:1 ratio)/1 vol% H2O at 50 V for 3 h in different concentrations of ammonium fluoride (NH4F) (0.3, 0.5, and 1.0 wt%). These materials were synthesized to serve as photocatalysts for the removal of hexavalent chromium, Cr(VI) ions by photoreduction. To crystallize the oxide film, the as-anodized Fe-ZNTs were subjected to annealing at 500 °C for 3 h in a tube furnace. The morphology and crystal structure of the annealed Fe-ZNTs were analyzed using Field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively. The surface functional groups and surface chemical of the samples were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The formation of hollow structure of the Fe-ZNT was validated by High-resolution transmission electron microscopy (HRTEM). The dimensions of the Fe-ZNTs were measured using Image J. UV-Visible spectroscopy was used to determine the Cr(VI) concentration remaining in the sample after photoreduction. From the FESEM micrographs, the diameter of the Fe-ZNTs was enlarged with higher fluoride content, while the length abruptly decreased due to excessive etching of the oxide film at oxide|electrolyte interface. The XRD results indicate the high intensity of tetragonal-ZrO2in high fluoride content after annealing. From the photocatalytic results of 30 ppm Cr(VI) under sunlight, the Fe-ZNTs synthesized in 1.0 wt% NH4F exhibited the highest Cr(VI) removal efficiency with 100 % after 5 h due to enhanced Cr(VI) adsorption and high photoactivity of tetragonal-ZrO2
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