Civil Engineering Reference
In-Depth Information
large urban centres. This has driven great improvements in advanced oxida-
tion processes (AOPs), specifi cally considering heterogeneous photocataly-
sis as a substitute for older, less effi cient or more expensive techniques
(Palmisano
et al.
, 2007; Sievers, 2011).
In this fi eld, a great number of scientifi c studies and patents deal with
titanium dioxide nanopowder production and characterization (Paz, 2010;
Shapovalov, 2010). Integrating TiO
2
in construction materials has gained
much interest (Fujishima and Zhang, 2006; Hüsken
et al.
, 2007) in the
attempt to meet air quality requirements promoted by several national and
international committees, such as the quality standards introduced in early
1990s by the US Environmental Protection Agency (EPA), through the
1990 Clean Air Act Amendments which reported ozone, particulate matter,
carbon monoxide, NO
x
, SO
2
and lead as the most hazardous air pollutants
causing severe concern for human health (Fig. 13.6).
As previously cited, several types of devices implementing the use of
titanium dioxide have been designed and are currently commercialized.
Examples of functionalized materials are photoactive paints for interior or
exterior, tiles, self-cleaning fabrics for clothing; complete devices, like TiO
2
-
containing air purifi ers, are also available. These examples, which list just
some of the available photocatalytic materials, make clear the interest in
active principles capable of solving the cited air quality issues, or at least to
mitigate them.
Construction materials represent the most easily available medium to
distribute photoactive substances over the widest surface area possible,
gaining the maximum effi ciency thanks to a versatile support for the pho-
tocatalyst and to a limited increase in material costs. The introduction of
heterogeneous photocatalysis principles in building materials also allows
the exploitation of the self-cleaning attitude conferred by the simultaneous
Atmospheric pollution sources
VOC emission sources
Machinery (1)
Aircrafts/ships (1)
Consumer
goods (8)
25
Heating (1)
Road transport (23)
Agriculture (10)
Transportation
(27)
71
Other (2)
4
Coatings (33)
Mobile source
Combustion (boilers)
Evaporation
Printing (16)
Industry (52)
Refuelling (10)
Cleaning (9)
(a)
(b)
13.6
(a) Generic sources of emission of atmospheric pollutants
and related percentages (source: Environment Canada website);
(b) specifi c case: typical sources of VOC release (source: Tokyo
Metropolitan Government website).
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