Abstract
Titanium dioxide (TiO2) films with dominant {001} facets coated on a titanium sheet (Ti) were synthesized with the simple hydrothermal method by using Ti as the precursor and substrate. The effect of addition of isopropanol into the hydrothermal solution on the structure, photocatalytic activity, and stability of as-synthesized TiO2films was investigated. The presence of isopropanol obviously influenced the microstructure of as-synthesized TiO2films, which was converted from microspheres into irregular close stack of truncated tetrahedrons. And the percentage of exposed {001} facets calculated from the Raman spectra increased from 48.2% to 57%. Accordingly, the TiO2films prepared with addition of isopropanol showed high and stable photocatalytic activity, which is nearly 2.6 times as that of the conventional P25 TiO2coated on Ti-substrate. In addition, the photocatalytic activity of as-synthesized TiO2films was greatly enhanced after calcination treatment at 600°C, which can be attributed to removal of fluoride ions and organic residuals adsorbed on the surface of the catalyst. Photoluminescence (PL) technique was used for the detection of produced hydroxyl radicals (•OH) on the surface of UV-illuminated TiO2using terephthalic acid as probe molecule. The photocatalytic degradation intermediates of bezafibrate were analyzed by an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and accordingly the degradation pathways were proposed.
Highlights
Semiconductor-based photocatalysis has found increasing interest to solve global environmental problems and has been proven to effectively degrade a great number of organic pollutants
The removal of bezafibrate has been investigated using different advanced oxidation processes (AOPs) such as photo-Fenton [24], photodegradation using solar-simulated irradiation [25], ozonation, and UV/H2O2 [26]; no studies have been reported for the photocatalytic removal of bezafibrate by using TiO2films with dominant {001} facets
Truncated tetrahedrons with exposure of {001} facets can be clearly observed on the as-synthesized TiO2 films
Summary
Semiconductor-based photocatalysis has found increasing interest to solve global environmental problems and has been proven to effectively degrade a great number of organic pollutants. Yang et al [7] for the first time synthesized single-crystalline anatase with 47% exposed {001} facets through hydrothermally heating a mixed aqueous solution of TiF4and HF, where the selective adsorption of fluoride ions stabilized the high-energy {001} facets. Wang et al [17] for the first time fabricated the TiO2-film with exposed {001} facets by International Journal of Photoenergy hydrothermal treatment of Ti-foil at 140∘C in 40 mL of 0.01 M. To the best of our knowledge, there is little research on the role of isopropanol or other alcohols on the fabrication and photocatalytic stability of {001} facets exposed TiO2 films immobilized on Ti-substrate. We found the presence of isopropanol in the hydrothermal solution makes {001} facets exposed TiO2 films have sheet-like morphology, which possess higher activity and stability towards removal of organic contaminants as compared to TiO2 microspheres with exposure of {001} facets. The removal of bezafibrate has been investigated using different advanced oxidation processes (AOPs) such as photo-Fenton [24], photodegradation using solar-simulated irradiation [25], ozonation, and UV/H2O2 [26]; no studies have been reported for the photocatalytic removal of bezafibrate by using TiO2films with dominant {001} facets
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