Civil Engineering Reference
In-Depth Information
15
Nanotechnology in manufacturing paints for
eco-effi cient buildings
C. DEL CACHO, O. GEISS, P. LEVA, S. TIRENDI and
J. BARRERO-MORENO, European Commission,
Joint Research Centre, Institute for Health and
Consumer Protection, Italy
DOI
: 10.1533/9780857098832.3.343
Abstract
: The addition of a photocatalyst provides decontamination
properties to a paint. It is capable of continuously oxidizing both organic
and inorganic pollutants and microorganisms under the infl uence of light
during its lifetime. Photocatalytic paints are useful for degrading air
pollutants, reducing the costs of maintenance of the exterior aspect
and sterilizing the environment. TiO
2
is by far the most widely used
photocatalyst, but is only active under UV (e.g., solar) irradiation, thus
limiting its applicability. In this sense, in order to use photocatalytic
paints also in indoor environments, new photocatalysts with a higher
activity under visible irradiation is needed. Aspects such as the
formation of potentially harmful by-products should also be considered
in order to keep the purifying benefi ts of photocatalytic paints.
Key words
: Photocatalytic paints, indoor, outdoor, indoor air quality,
by-products.
15.1 Introduction
Photocatalytic paints are characterized by the addition of a photocatalyst
which, when irradiated, favours the oxidation of both inorganic and organic
air pollutants, and provides self-cleaning properties to the paint and presents
bactericidal and antimicrobial properties.
With a production of more than 3,500 million tonnes worldwide in 2011,
the paint industry is one of the largest chemical industries, being the biggest
markets located in Asia, Europe and North America. The 4,500 paint com-
panies in Europe employ around 175,000 people (WPCIA, 2011).
Basically, photocatalysis is based on the creation of holes on the elec-
tronic structure of the photocatalyst surface by the absorption of light of
the appropriate wavelength (generally, UV-A):
ν
⎯→⎯+
h
Photocatalyst
h
+
e
−
vb
cb
where h
+
vb
and e
−
cb
represent the hole and the electron created on the cata-
lyst surface as a consequence of the excitation of an electron present in the
343
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