Civil Engineering Reference
In-Depth Information
Pollutant in
Pollutant out
Photocatalytic
paint
Environmental chamber
15.1
Schematic experimental set-up for the evaluation of
photocatalytic paints.
• the adsorption of the pollutant on the chamber surface
• the adsorption of the pollutant on the photocatalytic paint itself in the
absence of irradiation
• the photolytic degradation of the pollutant through decomposition
under UV radiation
•
the photocatalytic degradation of the pollutant.
Photocatalytic paints are generally activated by irradiating the paint in the
test chamber and fl ushing clean air (i.e., without pollutant) through it for
at least 12 hours (Aguia
et al.
, 2011). It is important to stress that, when
evaluating the photocatalytic effi ciency of paints, the activation conditions
are the critical parameters affecting the time required to reach the steady
state, after which the photoactivity of the paint either remains constant or
diminishes in the event of inactivation by the adsorption of intermediate
products on the active catalytic sites.
Aguia
et al.
(2010, 2011) evaluated the photocatalytic effi ciency and selec-
tivity towards the photodegradation of NO of 10 different anatase-based
photocatalytic paints using a typical outdoor base paint to which they added
different commercial TiO
2
photocatalysts in a concentration of 9% w/v.
They were quite surprised to observe that there was no direct correlation
between the photocatalytic activity of the pure photocatalyst and the cor-
responding derived photocatalytic paint, in the sense that the most effi cient
photocatalyst did not yield the optimum photocatalytic paint. Even if
further research is needed in order to understand the mechanism by which
paint components have such a critical infl uence on the activity of a photo-
catalytic paint, this result suggests that the paint components and the way
in which the photocatalyst is mixed in the paint matrix play a crucial role
in the photoactivity of the fi nal product.
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