Background: The textile industrial effluents cause profound imbalances
in ecosystems, when released into nature; dyes are oxidized by micro-organisms,
resulting in a decrease in the dissolved oxygen, which is necessary for
the aquatic life. For this reason, it is important to implement economic, efficient,
and green methods ensuring both the discoloration and detoxification of water.
Objective: TiO2 and ZnO nanoparticles were synthesized by sol-gel and precipitation
methods, respectively. These two nanoparticles were used to compare photocatalytic
degradation under UV and solar irradiation for three reactive azoic dyes
(trichromatic): Reactive Bezactive Yellow (RBY), Reactive Bezactive Red (RBR),
and Reactive Bezactive Blue (RBB).
Methods: The structural, i.e., morphological surface properties of the synthesized
photocatalysts were characterized by Fourier Transform Infrared, X-ray diffraction,
UV-Visible diffuse reflectance spectroscopy, and Scanning Electron Microscopy.
X-ray diffraction shows that TiO2 has a tetragonal structure with an anatase form.
The effects of some operational parameters, such as the amount of TiO2 and
ZnO, initial dye concentration, dye mixtures, and pH, were examined.
The progress of photodegradation reaction was monitored by UV-Visible spectroscopy
for decolorization and by High-Performance Liquid Chromatography
for degradation, and the efficiency of degradation was confirmed by Chemical
Oxygen Demand measurement.
Results: The dye degradation was found to be better in the presence of solar irradiation
than under UV irradiation. The photocatalytic activity of ZnO was higher
than TiO2 when used in its optimal conditions.
Conclusion: The percentage of degradation of each dye is different, and the order
of degradation of the three reactive dyes is as follows: RBY> RBR> RBB.