Production and Characterization of Self-Cleaning Clay-Based Roofing Tiles as a Building Material for Environmental Remediation

Within the scope of this thesis, two different semiconductor metal oxide coated visible light-driven self-cleaning clay-roofing tiles have been developed for environmental remediation. A ready-made commercial clay mixture was used for the production of photoactive roofing tiles with iron oxide (α-Fe2O3 phase) and zinc oxide (ZnO) applied as coatings. The main objectives are both to ensure that the applied coatings provide self-cleaning properties by maintaining or even improving the desired physical properties of the tiles and to optimize the firing temperature and coating concentration parameters.In the initial stage, roofing tiles were produced by firing at various temperatures,
ranging from 1000°C to 1100°C in 25°C increments, for optimizing the firing
temperature. Subsequently, these tiles were characterized in both their pristine
(uncoated) forms and α-Fe2O3 coated forms at the selected concentration (50 mM).
The characterization included analyses of their physical, chemical, morphological,
optical, wettability, and photocatalytic properties. The findings indicated that the
roofing tiles coated with α-Fe2O3 exhibited superior photocatalytic activity, reduced
water absorption, and lower porosity compared to the pristine tiles. Additionally, a
notable transition in surface wettability towards lower contact angles was observed
under light illumination. The best photocatalytic performance was achieved with tiles
and α-Fe2O3 coated samples fired at 1025°C, which demonstrated an 86.1% total
removal efficiency and an apparent reaction rate of 29.21×10-2 h-1
. Although tiles fired at 1050 °C exhibited better stability and aesthetic appeal, they had slightly lower
photocatalytic performance with an 83.7% total removal percentage and an apparent
reaction rate of 26.81×10-2 h-1 . Therefore, even minor adjustments in the firing
temperature significantly affected both the photocatalytic and physical properties of
the clay roofing tiles. Ultimately, considering the desired physical properties and selfcleaning performance, 1050 °C was determined to be the optimal firing temperature.
In the second stage, the tiles produced by applying the optimized firing temperature of
1050°C were coated with different concentrations (1mM, 5mM, 25mM, 50mM, and
100mM) of ZnO coating solution. At this point, similar characterization procedures as
in the first stage were carried out, but in addition, the mechanical properties of the tiles
were also examined. The results demonstrated a significant enhancement in the
properties of clay roofing tiles due to the ZnO coating process. Tiles coated with higher
concentrations of ZnO showed proportional improvements in photocatalytic activity
and physical characteristics, such as reduced water adsorption and porosity, compared
to the original pristine tiles. Notably, the coating application did not adversely affect
the mechanical performance of the tiles. Light exposure caused a significant shift in
surface wettability, leading to photo-induced superhydrophilicity in all samples.
Among the various concentrations tested, the optimal solution concentration was
found to be 50 mM, with an apparent reaction rate of 40.63×10-2 h-1 and a total removal
efficiency of 93.72%. In contrast, the pristine tile exhibited a degradation rate of
26.59×10-2 h-1 and achieved a removal efficiency of only 79.98% under the same
conditions.