3.3. Antibacterial testing

powder decomposed only ~43% of toluene after 6 h, the digital inkjet-printed coating decomposes ~84% and the jet-sprayed coating decomposes ~75%. It is probable that the difference in results for ethanol and toluene is that while both involved decomposition by photocatalysis, the latter also included a contribution from direct photolysis, which was enhanced by the greater surface area of the coating exposed to UV in comparison to that of a powder bed. This component may be significant because the difference between the two coating techniques is

Figure 5. Photodegradation over time by digital inkjet-printed and jet-sprayed coatings of (A) ethanol, (B) toluene, (C)

These data confirm that the photocatalytic performance of the digital inkjet-printed coating is superior to that of the jet-sprayed coating for VOC decomposition. This is a result of the greater extent of coverage, more even areal distribution, a reduced agglomeration, a greater extent of exposed particle surface area, and a greater crystallinity of the TiO2 in the digital

Figure 5 also shows the UV photodegradation of NOx in both batch and continuous-flow reactors. Again, the digital inkjet-printed coating outperforms the jet-sprayed coating. After 6 h under static conditions, the digital inkjet-printed coating decomposes ~90% of the NOx

less than that for ethanol photodegradation.

270 Titanium Dioxide - Material for a Sustainable Environment

inkjet-printed coating.

static NOx, and (D) flowing NOx.

3.2.2. NOx photodegradation

Table 1 summarizes the results of the antibacterial testing, which reveals that both types of coatings were highly effective in destroying E. coli (gram-negative), which is part of the bacterial flora of human and animal intestines and hence a suitable indicator of potential contamination of drinking water and food. These data show that UV irradiation alone is capable of destroying ~45–72% of the bacteria while both photocatalytic coatings destroy essentially all of the bacteria. After photocatalysis (RL), the digital inkjet-printed and jetsprayed coatings are essentially equivalent. However, with photocatalysis (ΔR), the digital inkjet-printed coating clearly outperforms the jet-sprayed coating. Hence, these data are in basic agreement with those for the photodegradation of ethanol and toluene. However, they must be interpreted in light of the different surface topographies, where Figures 2 and 3 show that the jet-sprayed coating provides less homogeneous coverage and hence presents a more


Table 1. Summary of the antibacterial testing results on sprayed and digital printed tiles.

uneven surface that is likely to be more amenable to cell attachment and proliferation [41]. A second factor is the sizes of the species that were examined, where Table 2 [42, 43] contextualizes the view that the photocatalytic performance is correlated through size similarities between the photocatalyst and the species [42].

$$\mathbf{R}\_{\rm L} = \log\_{10} \left( \mathbf{B}\_{\rm L} / \mathbf{C}\_{\rm L} \right) \tag{1}$$

Figure 6. Graphical data for impact (μPt) assessments of digital inkjet-printed and jet-sprayed coatings.

Human toxicity, cancer effects 83.83 42.49 49.31 Freshwater ecotoxicity 48.74 27.41 43.76 Climate change 24.68 11.82 52.11 Human toxicity, non-cancer effects 19.35 10.62 45.10 Mineral, fossil and resource depletion 14.44 3.69 74.41 Freshwater eutrophication 12.99 8.36 35.62 Acidification 12.14 6.13 49.50 Particulate matter 10.70 5.40 49.56 Photochemical ozone formation 9.17 5.04 45.03 Ionizing radiation, human health 7.44 5.85 21.42 Water resource depletion 4.38 2.76 36.90 Marine eutrophication 3.52 2.77 21.36 Terrestrial eutrophication 3.48 2.75 20.95 Land use 2.04 1.18 42.40 Ozone depletion 1.16 0.70 39.99 Ionizing radiation, ecosystems (interim) 0.00 0.00 0.00

Table 3. Numerical data for impact (μPt) assessments of digital inkjet-printed and jet-sprayed coatings.

Impact category Jet sprayed Digital inkjet printed Difference (%)

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$$
\Delta \mathbf{R} = \log\_{10} \left( \mathbf{B}\_{\mathrm{L}} / \mathbf{C}\_{\mathrm{L}} \right) - \log\_{10} \left( \mathbf{B}\_{\mathrm{D}} / \mathbf{C}\_{\mathrm{D}} \right) \tag{2}
$$

#### 3.4. Life cycle assessment

In 1993, the Society of Environmental Toxicology and Chemistry (SETAC) standardized the process for life cycle assessment (LCA) to include four components: (1) goal and scope, (2) inventory, (3) impact assessment, and (4) data interpretation [44]. LCA normally is applied to early-stage plants in order to investigate environmental hot spots arising from new technologies [45] or to establish industrial-scale processes for the comparison of divergent designs and optimization of environmental profiles [46]. In this work, the LCA has been modeled for the production of photocatalytic ceramic tiles by digital inkjet printing and jet spraying.

The approach applies gate-to-gate boundaries using a functional unit of 1 m2 of tiles produced in Modena, Italy. SimaPro (Version 8.3.0.0) extracted the secondary data from the Ecoinvent 3 database. ILCD 2011 Midpoint + (Version 1.08) and IPCC 2013 GWP 100a methods were used to calculate the impacts, which are given in terms of micro-eco-points (μPt). An eco-point is defined as one thousandth of the total environmental impact caused by a statistical European citizen per year [47]. The LCA was done in accordance with the ISO/TC 207/SC 5 Life Cycle Assessment methodologies for the principles and framework as well as the requirements and guidelines. For the inventory phase, these two processes were divided into substeps.

In order to highlight the differences between the two production processes, LCA comparison calculations were performed using the ILCD 2011 Midpoint + method, weighting the results for the 16 impact categories that were considered. Figure 6 shows the results graphically and Table 3 lists them numerically.


Table 2. Sizes of tested and other relevant species.

Photocatalytic TiO2: From Airless Jet Spray Technology to Digital Inkjet Printing http://dx.doi.org/10.5772/intechopen.72790 273

Figure 6. Graphical data for impact (μPt) assessments of digital inkjet-printed and jet-sprayed coatings.

uneven surface that is likely to be more amenable to cell attachment and proliferation [41]. A second factor is the sizes of the species that were examined, where Table 2 [42, 43] contextualizes the view that the photocatalytic performance is correlated through size similarities

In 1993, the Society of Environmental Toxicology and Chemistry (SETAC) standardized the process for life cycle assessment (LCA) to include four components: (1) goal and scope, (2) inventory, (3) impact assessment, and (4) data interpretation [44]. LCA normally is applied to early-stage plants in order to investigate environmental hot spots arising from new technologies [45] or to establish industrial-scale processes for the comparison of divergent designs and optimization of environmental profiles [46]. In this work, the LCA has been modeled for the

The approach applies gate-to-gate boundaries using a functional unit of 1 m2 of tiles produced in Modena, Italy. SimaPro (Version 8.3.0.0) extracted the secondary data from the Ecoinvent 3 database. ILCD 2011 Midpoint + (Version 1.08) and IPCC 2013 GWP 100a methods were used to calculate the impacts, which are given in terms of micro-eco-points (μPt). An eco-point is defined as one thousandth of the total environmental impact caused by a statistical European citizen per year [47]. The LCA was done in accordance with the ISO/TC 207/SC 5 Life Cycle Assessment methodologies for the principles and framework as well as the requirements and

In order to highlight the differences between the two production processes, LCA comparison calculations were performed using the ILCD 2011 Midpoint + method, weighting the results for the 16 impact categories that were considered. Figure 6 shows the results graphically and

Species Size (nm) Reference Ethanol 0.437 [43] Toluene 0.564 [43] E. coli <sup>1000</sup> � <sup>3000</sup>\* [42] Viruses 10–300 [42] Bacteria 500–5000 [42] Fungi 5000–15,000 [42]

production of photocatalytic ceramic tiles by digital inkjet printing and jet spraying.

guidelines. For the inventory phase, these two processes were divided into substeps.

RL ¼ log <sup>10</sup> ð Þ BL=CL (1)

ΔR ¼ log <sup>10</sup> ð Þ BL=CL – log <sup>10</sup> ð Þ BD=CD (2)

between the photocatalyst and the species [42].

272 Titanium Dioxide - Material for a Sustainable Environment

3.4. Life cycle assessment

Table 3 lists them numerically.

Table 2. Sizes of tested and other relevant species.

\*

Rod-like shape.


Table 3. Numerical data for impact (μPt) assessments of digital inkjet-printed and jet-sprayed coatings.

These data show that jet spraying makes consistently greater impacts than digital inkjet printing does, with the most significant impacts being on human toxicity, cancer effects, freshwater ecotoxicity, and climate change. The first two of these categories have been examined in more detail using USEtox calculations and the third category also has been examined using IPCC 110a calculations. These analyses reveal that their impacts derive almost entirely from the energy required by the production processes. This explains why jet spraying projects very high impact values since this process also is relatively energy-intensive. It is notable that the impacts of climate change and mineral, fossil and resource depletion reveal differences of >50% between the two production methods. Again, these significant differences are attributed to energy requirements. Three other categories (human toxicity, cancer effects, acidification, and particulate matter) also show nearly the same differential of ~50%. The single-score analysis, which is the average of all values in the 16 categories, shows that digital inkjet printing is ~46% lower than jet spraying.

Acknowledgements

ney, Australia.

Author details

Claudia L. Bianchi<sup>1</sup>

Valentino Capucci<sup>5</sup>

Alessandro Di Michele<sup>3</sup>

5 GranitiFiandre Group, Italy

References

\*, Carlo Pirola<sup>1</sup>

\*Address all correspondence to: claudia.bianchi@unimi.it 1 Dipartimento di Chimica, Università di Milano, Italy 2 Dipartimento di Chimica, Università di Torino, Italy

, Serena Biella<sup>1</sup>

3 Dipartimento di Fisica e Geologia, Università di Perugia, Italy

4 School of Materials Science and Engineering, UNSW Sydney, Australia

Geneva, Switzerland: World Health Organization (WHO); 2016

research priorities. PLOS Medicine. 2013;10:paper 1001455 (8 pp)

Disease. Geneva, Switzerland: World Health Organization (WHO); 2016

In memory of Benedetta Sacchi, a worthy researcher and a collaborator for years of the UNIMI research group. The authors would like to thank Dr. A. Carletti (Artest, Italy) for the antibacterial testing and Mr. R. Pellini (GranitiFiandre, Italy) for the preparation of the photocatalytic tiles. This research was supported financially by the LIFE+ Environment Policy and Governance project Digitalife LIFE13 ENV/IT/000140. The UNSW authors acknowledge the characterization facilities provided by the Mark Wainwright Analytical Centre, UNSW Syd-

, Marta Stucchi<sup>1</sup>

, Wen-Fan Chen<sup>4</sup>

[1] Prüss-Ustün A, Wolf J, Corvalán C, Bos R, Neira M. Preventing Disease through Healthy Environments: A Global Assessment of the Burden of Disease from Environmental Risks.

[2] Anonymous. Ambient Air Pollution: A Global Assessment of Exposure and Burden of

[3] Martin WJ II, Glass RI, Araj H, Balbus J, Collins FS, Curtis S, Diette GB, Elwood WN, Falk H, Hibberd PL, Keown SEJ, Mehta S, Patrick E, Rosenbaum J, Sapkota A, Tolunay HE, Bruce NG. Household air pollution in low- and middle-income countries: Health risks and

[4] Tefera W, Asfaw A, Gilliland F, Worku A, Wondimagegn M, Kumie A, Samet J, Berhane K. Indoor and outdoor air pollution—Related health problem in Ethiopia: Review of related

literature. Ethiopian Journal of Health Development. 2016;30(special issue):5-16

, Giuseppina Cerrato<sup>2</sup>

, Pramod Koshy<sup>4</sup>

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

http://dx.doi.org/10.5772/intechopen.72790

, Federico Galli<sup>1</sup>

, Charles Sorrell<sup>4</sup> and

,

275

Further, the calculation of the CO2 equivalents, carried out by the IPCC 100a method, demonstrates that jet spraying has a greater impact than digital inkjet printing by a difference of 3.42 kg CO2 versus 1.63 kg CO2. A final point of difference is that the application of the ILCD method reveals that NOx production demonstrates the same trend, with 2.10 g NOx from jet spraying and 1.65 g NOx from digital inkjet printing.

The preceding LCA data suggest that the traditional method of jet spraying is considerably inferior to that of digital inkjet printing and that further detailed analysis of each step of the process is likely to improve the process and its outcomes commercially, environmentally, and performatively.
