Abstract
Mesoporous TiO2 photocatalysts intended for the advanced removal of clofibric acid (CA) from water were synthesized by the sol-gel method in a medium containing cetyl-trimethyl-ammonium bromide (CTAB) and urea, using either ethanol or isopropanol to dilute the TiO2 precursor. The activation of the samples was undertaken at 550, 650 and 750 °C. The XRD revealed that the nature of the solvent resulted in significant differences in the anatase-to-rutile ratios obtained at different temperatures. The specific surface area values were situated between 9 and 43 m2·g−1 and the band gap values were similar for all the samples. The photocatalytic activity of the prepared samples was examined for the degradation of CA, an emergent water contaminant. The photocatalytic tests performed under UV-A irradiation revealed that the photo-reactivity of these materials depends on the calcination temperature. The best results were obtained for the samples calcined at 750 °C, which showed high yields of CA elimination, as well as almost complete mineralization (over 95%) after 180 min of reaction. Good results in terms of catalyst reusability in the reaction were found for the catalyst showing the highest photo-reactivity. Therefore, the samples can be considered good candidates for future water remediation applications.
Highlights
Titanium dioxide is currently considered the most popular photocatalyst due to its convenient band gap value, easy availability, reasonable price and low toxicity
In order to provide a complete investigation of the catalytic performance of the prepared samples, we firstly focused our attention on the evaluation of the photocatalytic activity of the E series
The nature of the alcohol used for the dilution of the precursor before mixing it with aqueous solutions played a significant role in relation to the structure, phase purity and thermal stability of the product: when isopropanol was used in the preparations, the formation of rutile phase was completely hindered if the calcination was made at temperatures below 650 ◦C
Summary
Titanium dioxide is currently considered the most popular photocatalyst due to its convenient band gap value, easy availability, reasonable price and low toxicity. The great interest in this material is mainly due to the limitations and drawbacks of the existing TiO2-based materials, especially the widely available commercial product P-25. Since the adsorption of the target compound on the surface of the photocatalyst is a mandatory step for the success of its oxidative degradation [9], the synthesis of mesoporous TiO2 has gained great attention in recent years. Mesoporous materials are valuable alternatives for the formulation of active heterogeneous catalysts, offering high specific area values and wide pores, which do not impose diffusion restrictions on the species to be adsorbed [10,11,12]. An excellent review by Gu and Schüth [21] brings together information about many of the systems, synthesis strategies and solutions used in obtaining non-silica mesoporous materials. Various template types, including amines, quaternary ammonium salts (CTAB), non-ionic surfactants (polyether block copolymers: P123, F127), esthers (Tween 80), alcohols, dodecylsulfate and numerous combinations thereof have been involved in obtaining mesoporous TiO2 with various degrees of crystallinity and specific structure types, in consonance with the detailed mode of structuration of the template and the detailed preparation procedure
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