Nanotechnology in manufacturing paints for eco-efficient buildings - Nanotechnology in Eco-efficient Construction - page 352

g m −3 NO 2 . Similarly, the formation of 30 and formation of up to 12 μ

7.5 g m −3 , respectively, of formaldehyde and acetaldehyde was observed,

as a result of the decomposition of the paint components.
In order to minimize the formation of intermediate products during the
photocatalytic degradation of indoor air pollutants by photocatalytic active
paints, the parameters affecting the photocatalytic process need to be opti-
mized, in order to achieve the maximum possible rate of photocatalytic
oxidation. Thus, particular attention should be paid to the development of
more active photocatalysts in order to optimize the nature and concentra-
tion of the sensitizers/dopants used to enable activation by visible light.
Two possible alternative approaches that attempt to minimize the sec-
ondary emission of potentially harmful compounds from the degradation
of paint constituents during the photocatalytic process have been
proposed.

μ

Development of more stable supporting materials

An increase in the stability of the supporting material towards the photo-
catalytic oxidation should considerably diminish the amount of carbonyl
compounds released. In order to increase this stability, a careful selection
of the ingredients used in the preparation of the supporting materials
should be made. As an example, Fig. 15.4 presents the reduction obtained
for the formation of carbonyl compounds during the irradiation of
photocatalytic paints, following the appropriate selection of the paint
components.

25

Formaldehyde
Acetaldehyde
Acetone
Propanal
Butanal
Benzaldehyde
Hexanal

20

￿ ￿ ￿ ￿ ￿ ￿

15

10

5

0

After optimization of
paint components
Photocatalytic paint

Before optimization of
paint components

15.4 Reduction in the secondary emissions of photocatalytic paints
with an appropriate selection of paint constituents.