Effects of the Brookite Phase on the Properties of Different Nanostructured TiO₂ Phases Photocatalytically Active Towards the Degradation of N‐Phenylurea

Abstract

Different sol-gel synthesis methods were used to obtain four nanostructured mesoporous TiO 2 samples for an efficient photocatalytic degradation of the emerging contaminant Nphenylurea under either simulated solar light (1 Sun) or UV light. Particularly, two TiO 2 samples were obtained by means of as many template-assisted syntheses, whereas other two TiO 2 samples were obtained by a greener template-free procedure, implying acidic conditions and, then, calcination at either 200°C or 600°C. In one case, anatase was obtained, whereas in the other three cases mixed crystalline phases were obtained. The four TiO 2 samples were characterized by X-ray powder diffraction (followed by Rietveld analysis); Transmission Electron Microscopy; N 2 adsorption/desorption at À 196°C; Diffuse Reflectance UV/Vis spectroscopy and ζ-potential measurements. A commercial TiO 2 powder (i. e., Degussa P25) was used for comparison. Differences among the synthesized samples were observed not only in their quantitative phase composition, but also in their nanoparticles morphology (shape and size), specific surface area, pore size distribution and pH IEP (pH at isoelectric point), whereas the samples band-gap did not vary sizably. The samples showed different photocatalytic behavior in terms of N-phenylurea degradation, which are ascribed to their different physico-chemical properties and, especially, to their phase composition, stemming from the different synthesis conditions.

Visible Light-Driven Photocatalytic Activity and Kinetics of Fe-Doped TiO2 Prepared by a Three-Block Copolymer Templating Approach

“…In contrast, other authors [ 54 ] measured different pH IEP with brookite, anatase, and rutile samples obtained by hydrothermal treatment (in the order pH IEP brookite < pH IEP anatase < pH IEP rutile), with brookite showing stronger Brønsted sites; the same authors also measured slightly lower pH IEP with more crystallized solids. With a set of undoped TiO 2 samples of different phase composition, we measured low pH IEP values with brookite-containing samples [ 44 ]. Other authors pointed out that the type of synthesis plays a prominent role on the TiO 2 surface properties [ 55 , 56 ].…”

“…In previous studies, Fe-doped TiO 2 samples (Fe content in the 0.8–2.5 wt.% range) were obtained by TASG method in the presence of a triblock copolymer and using Ti t -butoxide as precursor [ 44 , 45 ]. The samples were tested as catalysts in the degradation of AO7 in the presence of H 2 O 2 under different conditions of illumination, i.e., in dark conditions, under UV light, and under simulated solar light.…”

Suitability of Nanoparticles to Face Benzo(a)pyrene-Induced Genetic and Chromosomal Damage in M. galloprovincialis. An In Vitro Approach

“…Karnovsky fixative components, osmium tetroxide, uranyl acetate, and propylene oxide were purchased from Fisher Scientific Italia (Milan, Italy). Mesoporous n-TiO 2 (25 nm), namely MT, was synthetized at Politecnico di Torino (Turin, Italy), by following a published procedure [ 46 ] and by using ACS (American Chemical Society)-grade chemicals from Sigma-Aldrich (Milan, Italy). n-TiO 2 (25 nm), namely Aeroxide ® TiO 2 P25 (P25) was kindly supplied by Eigenmann & Veronelli, Milan (Italy).…”

“…The resulting MT powder was characterized in the media used for in vitro study in filtered (0.22 µm) ASW (10 mg mL −1 ) prepared according to the protocol ASTM D1141–98 [ 46 , 51 ] (32‰ salinity, pH 8 ± 0.1). MT stock suspension in ASW (10 mg mL −1 ) was probe-sonicated for 45 min (100 W, 50% on/off cycle), diluted to working suspension in ASW, and again sonicated for 15 min prior to use.…”

“…HNP presents an H/C ratio of 0.15 and an oxygen content of around 30 wt.%, in the form of carboxylic acid, lactone, lactol, and phenol groups [48]. MT (mesoporous titania) was synthetized by following a published procedure [46]. MT was characterized as previously described [49,50], using XRD (X-ray diffraction) powder diffraction at 40 kV and 40 mA equipped with Cu Kα radiation (step scan = 0.02 2θ, time per step = 2 s) and N 2 adsorption/desorption isotherms at −196 • C. Before N 2 adsorption, the powder was outgassed at 150 • C for 4 h to remove water and other atmospheric contaminants).…”