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

Abstract

TiO 2 powders can be employed as both photocatalytic and structural materials, leading to applications in external coatings or in interior furnishing devices, including cement mortar, tiles, floorings, and glass supports. The technology of photocatalytic building materials is connected with the widespread production of photocatalytic active tiles. All the techniques proposed in the study involve the employment of nanosized TiO 2 : this represents a new problem to be dealt with, as inhaling nanoparticles exposes workers during industrial production and people in everyday locations to their dangerousness. Only very recently the employment of microsized TiO 2 has been proposed, and the authors in this manuscript report the use of micrometric titania materials, but employing a new deposition technique, which is digital inkjet printing. It represents an improvement of the classical spray coating methods, as it requires piezoelectric heads to precisely direct the deposition of the suspension with an electrostatic field. The mixture contains aqueous/ organic components containing micrometric TiO 2 : to form a suspension, which is printed onto the surface of porcelain grès, large slabs using a digital printer. Many advantages are immediately evident, namely rapid and precise deposition, (almost) no waste of raw materials, thereby highlighting the economy, environmental friendliness, and sustainability of the process. All the materials we obtained have been thoroughly characterized by means of several experimental physico-chemical techniques, such as Raman microspectroscopy and scanning electron microscopy coupled with elemental analysis. Two different model VOCs, ethanol and toluene, and NOx have been selected to test the © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. photocatalytic performances of the abovementioned tiles. Moreover, the antibacterial properties of the tiles have been determined, using Escherichia coli as example. Life cycle assessments (LCAs) for the two processes were modeled for 1 m 2 of tiles produced in Modena, Italy. The impact assessments revealed that jet spraying exhibited uniformly greater impacts than digital inkjet printing and that the principal impacts were in human toxicity, cancer effects, freshwater ecotoxicity, and climate change. Most of the impacts were associated with the energy required for the production processes. Further considerations revealed that jet spraying is projected to generate twice as much CO 2 and 30% more NOx than digital inkjet printing.

Digitally Printed AgNPs Doped TiO2 on Commercial Porcelain-Grès Tiles: Synergistic Effects and Continuous Photocatalytic Antibacterial Activity

“…After the ink deposition, tiles were calcined at 680 • C for 80 min in a kiln, with high-controlled temperature ramp avoiding thermal shock, and washed with water with a brushing system to remove the particle of non-adherent TiO 2 . The water used for degreasing was recovered and purified prior to recycling and any damaged tiles were recycled [5]. The main advantages of this procedure are reported as follows: green production with no waste of photocatalytic powder (TiO 2 ), no use of water, smaller consumption of energy, CO 2 emissions lower than 89%, possibility to work on large slabs (300 cm × 150 cm).…”

“…The micrometric TiO 2 decoration with Ag species allowed active ceramic slabs to be active under LED lights, bypassing the problem of the UVA radiation. The ceramic is digitally printed [5] with a tailored ink containing the AgNPs-TiO 2 , obtaining a final surface with an homogeneous distribution of the photocatalytic micro-sized particles.…”

Micro-TiO2 coated glass surfaces safely abate drugs in surface water

“…It contains a weight percentage of TiO2 of 12 % and silica-based compounds that vitrifies at the calcination temperatures and stabilizes the photocatalyst particles. The ink is employed for the production of [30] that were tested for aspirin and paracetamol abatement in water [31].…”