Browsing by Author "Kleiman, Ariel"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Photocatalytic activity of TiO2 films prepared by cathodic arc deposition: dependence on thickness and reuse of the photocatalysts
    (2020-01-25) Meichtry, Jorge Martín; Vega, Daniel; Kleiman, Ariel; Litter, Marta Irene; Márquez, Adriana
    In this work, the photocatalytic activity of anatase films with thicknesses up to 1100 nm prepared by cathodic arc deposition (CAD) on glass substrates is reported. The photocatalytic activity under UV?Vis irradiation (λ > 330 nm) was evaluated through the efficiency in the reduction of 0.80 mM Cr(VI) in the presence of 1 mM ethylenediaminetetraacetic acid (EDTA) at pH 2, and compared with the performance of samples obtained by dip-coating using commercial P25. The CAD films were optically transparent, with visible light transmittance ≥ 50% even for the thickest samples. The photocatalytic efficiency of the films increased as the thickness increased. The possibility of obtaining thicker films allowed cathodic arc films reaching better performance than P25 samples. For the most active films obtained by CAD, complete Cr(VI) reduction could be obtained in <300 min under a 28 W m−2 UV-A irradiance. The photocatalytic reaction for all the studied TiO2 films obeyed pseudo-first order kinetics. A decrease of the reaction rate constant was observed for both types of films after reusing the photocatalysts. The fate of the reduced Cr(VI) was also analyzed.
  • No Thumbnail Available
    Item
    Preliminary results of photocatalytic Cr(VI) reduction using TiO2 films grown by cathodic arc deposition: effect of the film thickness and the N-doping
    (2023-06-08) Kleiman, Ariel; Meichtry, Jorge Martín; Xaubet, M.; Grondona, D.; Litter, Marta Irene; Márquez, Adriana
    TiO2 is the most studied photocatalyst for the treatment of pollutants; however, its rather large band gap and the need for a removal step when used as a suspension hinder the wide application of this technology. Immobilized TiO2 films grown by cathodic arc deposition (CAD) have shown superior adhesion to the substrate and activities similar to that of P-25 TiO2 films, the reference photocatalyst, but they still require UV light to be excited [1]. N-doping is a strategy frequently used to extend the TiO2 band gap to the visible range [2], but it has a scarce application on CAD-grown films. In this work, TiO2 CAD films, with and without N-doping, were prepared and tested on the photocatalytic removal of Cr(VI), a priority water pollutant, in the presence of ethylenediaminetetraacetic acid (EDTA) as an organic donor. TiO2 films of different thicknesses: (290 ± 40 nm), (440 ± 40) nm, and (850 ± 70) nm, were deposited by CAD according to a reported method [1]. The doping of the films was performed by plasma immersion ion implantation in a N2 environment. For comparison, P-25 TiO2 films of (280 ± 20) nm and (480 ± 30) nm thicknesses were prepared by dip-coating; thicker P-25 films were not stable. All films were grown over a borosilicate glass substrate. Photocatalytic experiments were performed in thermostatted cylindrical glass cells (T = 25 °C) magnetically stirred and irradiated from the top with a HPA 400S lamp (λ > 320 nm, mean UV irradiance 28 W m-2), equipped with an IR filter. 10 mL of a 0.8 mM Cr(VI) and 1 mM EDTA solution at pH 2 (HClO4) were poured into each cell, and 0.25 mL samples were periodically taken for Cr(VI) quantification by the diphenylcarbazide method; at the end of the experiments, a Cr(III)-EDTA complex in solution was determined by direct spectrophotometry [1]. After 5 h of irradiation, Cr(VI) removals of 58% and 85% were obtained with pure and N-doped 290 nm CAD films, respectively, while for pure and N-doped 440 nm CAD films the corresponding removals were 70% and 85%; with the 280 nm and 480 nm P-25 films, Cr(VI) removals were 81% and 88%, respectively. Although thicker CAD films were more efficient (99% of Cr(VI) removal with 850 nm films), no difference could be appreciated between N-doped and undoped films. Cr(VI) evolution could be adjusted to a pseudo-first-order kinetics. In all cases, Cr(III)-EDTA represented 75% of the reduced Cr(VI), the remaining Cr(III) being retained on the TiO2 surface, [1]. The photocatalytic efficiency increased with the thickness of the films. Although P-25 films showed a higher photoactivity than the CAD films of similar thickness, thicker and more active CAD films can be surely obtained in future works. N-doping increased slightly the photocatalytic activity of the thinnest films.