Biphase TiO₂ Microspheres with Enhanced Photocatalytic Activity

Abstract

TiO 2 microspheres (TMS) with perfect spherical morphology were synthesized by spray drying of a hydrothermally cured aqueous suspension of TiO 2 nanoparticles. TiO 2 powders (TP) obtained by drying the nanoparticle suspension were studied simultaneously to determine which was the most efficient photocatalyst. SEM images and laser granulometry on TMS show spherical morphology with the diameter ranging from 2 to 10 μm. TMS had high specific surface area after annealing as seen from BET analyses. XRD analyses show that TMS consist of anatase and rutile crystalline phases where the rutile fraction increases with annealing temperature and above 500 °C rutile dominates anatase. Raman spectroscopy shows several Raman bands from anatase and rutile phases and supports the XRD results of phase transformation with increasing annealing temperature. Photodegradation of organic pollutants in aqueous solution under UV light irradiation establishes the higher photocatalytic activity of TMS with respect to TP. The highest efficiency was found on the 400 °C annealed TMS.

Self-Cleaning Mineral Paint for Application in Architectural Heritage

“…To investigate the nature of the inorganic and organic binders of the paints, ATR-FTIR spectroscopy was employed and showed in Figure 3. A weak and broad band around 3400 cm −1 is observed due to the hydroxyl stretching vibration [14,19]. In the case of silicate paint a strong and relatively broad peak centered at 1078 cm −1 is observed which has a different appearance than the absorption band of the resin paint at a similar frequency region.…”

“…In both the paints some common features are observed that can be identified as the calcium carbonate (CaCO3) extender, which shows strong absorption around 1400-1427 cm −1 (asymmetric stretching of CO 3 ) and a relatively weak peak at 712 cm −1 due to CO 2− 3 in-plane bending [22][23][24]. Another common feature is the presence of a broad absorption band at 500-700 cm −1 , which is arising from the Ti-O-Ti stretching vibration of TiO2 pigments [19,20,24]. To investigate the nature of the inorganic and organic binders of the paints, ATR-FTIR spectroscopy was employed and showed in Figure 3.…”

“…Figures 6 and 7 show the pictures of rhodamine B and methylene blue dye droplets on three kinds of paint surfaces as a function of the solar light exposure along with the photocatalytic degradation kinetics. The reaction rate constants were calculated from the plot of C/C0 with the solar light irradiation time (t) assuming the first-order rate law [-ln(C/C0) = Kt], where K is the rate constant] [19] and are summarized in Table 3. The silicate paint showed 7 times higher efficiency than the resin and commercial paints in the case of rhodamine B dye and 4-6 times higher efficiency for methylene blue.…”

Photocatalytic and Photoelectrochemical Characteristics of Mesoporous Titanium Dioxide Microspheres

“…with annealing at 450-500°C [9][10][11][12][13][14]. The phase composition, crystallinity, size, and shape of the products of these processes are very sensitive to the structure of the Ti(IV) precursor, the nature of the solvent, and the conditions of the sol-gel transformation.…”

“…The phase composition, crystallinity, size, and shape of the products of these processes are very sensitive to the structure of the Ti(IV) precursor, the nature of the solvent, and the conditions of the sol-gel transformation. By using templates and introducing various additives that affect the interaction between the TiO 2 particles during the formation of the porous framework it is possible to achieve a wide variety of TiO 2 microspheres with hierarchical organization [5,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”