Immobilized nanotubular TiO2 photocatalysts obtained by anodic oxidation for Cr(VI) transformation

ANABELA DWOJAK; VERA, MARÍA LAURA; H.D. TRAID; MARIO ROSENBERGER; CARLOS SCHVEZOV; M.I. LITTER

Photochemical and Photobiological Sciences

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2022

1474-905X

The photocatalytic and mechanical performance of TiO2nanotubular coatings obtained by anodic oxidation of commercialtitanium, using an NH4Fand 3.5% v/v water in ethylene glycol solution as electrolyte was investigated. After the anodization,the coatings were thermally treated at 450 °C for 2 h. The effects of the anodizing voltage (40–80 V) and NH4Fconcentration(0.06, 0.15, 0.27 M) on the formation of the nanotube arrays were evaluated. Nanotube diameters (57 to 114 nm), wallthicknesses (4 to 13 nm), and lengths (5 to 17 μm) increased with the anodizing voltage and the NH4Fconcentration. Thephotocatalysts were characterized by scanning electron microscopy, glancing incidence X-ray diffraction, and UV-Vis diffusereflectance spectroscopy. The mechanical properties of the photocatalysts were determined: adhesion using the tapetest (ASTM D3359) and erosion resistance through a 3 h accelerated test. The photocatalytic activity of the nanotubesunder UV irradiation was evaluated using hexavalent chromium (Cr(VI)) in the presence of ethylenediaminetetraacetic acid(EDTA), using a 1.25 EDTA/Cr(VI) molar ratio solution at pH 2. A complete Cr(VI) transformation after 3 h of irradiationwas obtained for all samples, with a better performance than that of an immobilized P25 sample. The photocatalyst obtainedwith 0.27 M NH4Fat 40 V presented a good behavior in adherence and erosion resistance, together with a very good photocatalyticactivity. This novel analysis, combining photocatalytic and mechanical tests, proved that the new TiO2nanotubularcoatings could be successfully used as immobilized photocatalysts in photoreactors for water treatment.