A New Frontier of Photocatalysis Employing Micro-Sized TiO2: Air/Water Pollution Abatement and Self-Cleaning/ Antibacterial Applications

Abstract

This chapter presents the use of a commercial micro-sized TiO 2 powder as an alternative to the traditional nano-powders as semiconductors in photocatalytic processes. Results of the photocatalytic efficiency towards the photodegradation of the traditional pollutant molecules both in gas phase (nitrogen oxides (NO x) and volatile organic compounds (VOCs)) and in water phase (phenol) are presented and compared to the results obtained with two nano-sized reference powders. Micro-sized TiO 2 is also industrially coated at the surfaces of porcelain grés tiles (Active Clean Air and Antibacterial Ceramic™). The possibility to have a photocatalytic material, strongly stuck at the surface of a vitrified tile, increases the use of photocatalysis in real conditions: no problem of filtration of the semiconductor from the liquid medium after use and no risks of leakage of nanoparticles in the atmosphere. Tests were performed using reactors equipped with UV-A lamps and with suitable analytical systems, depending on the final purpose. Characterization data from both powders and coated tiles are put in correlation with the photocatalytic results to understand the semiconductor action during the photocatalytic process. Polluting molecules were chosen in order to cover all the common aspects of environmental pollution: NO x and some VOCs represent the model molecules to test the efficiency of the micro-sized TiO 2 (degradation from the pristine molecule to CO 2 or inorganic salts) in gas phase. As for the water pollution, phenol was chosen as common pollutant in worldwide rivers. Moreover, tests on self-cleaning and antibacterial properties are also reported. The positive results of micro-sized TiO 2 both in powder and coated onto the surface of porcelain grés tiles open the way to new photocatalytic products that do

Photocatalytic TiO2: From Airless Jet Spray Technology to Digital Inkjet Printing

“…Both sets of data demonstrate the superior photocatalytic performance of the digital inkjet-printed coating. While similar testing of Kronos 1077 bulk powder has been shown to decompose ethanol completely in 1 h [37], this work for the deposition of this TiO 2 powder as a digital inkjet-printed coating shows that nearly complete decomposition (~97%) requires 6 h. By contrast, the jet-sprayed coating decomposes only~47% of the ethanol after 6 h. Interestingly, both coatings outperform the powder when decomposing the more stable aromatic toluene ring. While Kronos 1077 bulk powder decomposed only~43% of toluene after 6 h, the digital inkjet-printed coating decom-poses~84% and the jet-sprayed coating decomposes~75%.…”

“…Conventional, industrial-scale, airless, jet spray deposition was used for the deposition of coatings, as described in brief previously by the authors [37]. However, with the new, innovative, automated decoration of ceramic surfaces by digital instruments, it has become possible to manufacture products of considerably superior quality.…”

“…A fluorescent UV lamp (18 W, Royal Philips, Amsterdam, Netherlands) was used for the testing at an intensity of 0.25 mW/cm 2 for 8 h. A viability count was performed by dilution and plating on nutrient agar incubated at 37 C for 48 h. More details are reported elsewhere [37].…”

Smart, Photocatalytic and Self-Cleaning Asphalt Mixtures: A Literature Review

“…Anatase phase can be converted to the rutile phase by heating higher than 700 • C. Anatase and rutile crystallize in the tetragonal system while brookite presents an orthorhombic form. The structure of the anatase phase shows bipyramid tetragonal symmetry with four units per elementary cell, and, for rutile, it is tetragonal, with two formula units per elementary cell [19]. Concerning the photocatalytic ability, the literature reports that TiO 2 anatase structure is more efficient than rutile due to its more exposed structure.…”

Design of Multifunctional Titania-Based Photocatalysts by Controlled Redox Reactions

“…Microscale platforms may also provide significant advantages in terms of photocatalyst recovery. The fact that the nanosized TiO 2 usually offers an improved performance over microscale particles [6], however, does not exclude advantages of microstructured TiO 2 -based photocatalyst in specific scenarios, namely where the larger size may facilitate the photocatalyst separation, increase a dispersibility for potential long-range transport [7], and avoid erosion by a high medium flux. One should also account for the costs and environmental impacts associated with the production of nanomaterials, as compared to micropowders.…”