Photocatalytic degradation
by the titanium dioxide (TiO2) photocatalyst attracts tremendous
interest due to its promising
strategy to eliminate pollutants from wastewater. The floating photocatalysts
are explored as potential candidates for practical wastewater treatment
applications that could overcome the drawbacks posed by the suspended
TiO2 photocatalysis system. The problem occurs when the
powdered TiO2 applied directly into the treated solution
will form a slurry, making its reuse become a difficult step after
treatment. In this study, the immobilization of titanium dioxide nanoparticles
(TiO2 NPs) on the floating substrate (cork) employing polyvinyl
alcohol (PVA) as a binder to anchor TiO2 NPs on the surface
of the cork was carried out. Characterizations such as Fourier transformer
infrared, X-ray diffraction (XRD), ultraviolet–visible spectroscopy
(UV–vis), zeta potential, photoluminescence spectroscopy, femtosecond
to millisecond time-resolved visible to mid-IR absorption spectroscopy,
ion chromatography, and scanning electron microscopy–energy-dispersive
X-ray spectroscopy (SEM–EDX) analyses were employed. XRD analysis
revealed the formation of anatase-phase TiO2 NPs. The results
demonstrated that the crystallite size was 9.36 nm. The band gap energy
of TiO2 NPs was determined as 3.0 eV. PL analysis verified
that TiO2 NPs possessed a slower recombination rate of
electron–hole pairs as compared to anatase TiO2.
The result was attributed by the behavior of photogenerated charge
carriers on TiO2 NPs, which existed as shallowly trapped
electrons that could survive longer than a few milliseconds in this
study. Furthermore, SEM–EDX analysis indicated that TiO2 NPs were well distributed on the surface of the cork. At
the optimal mole ratio of TiO2/PVA (1:8), the TiO2/PVA/cork floating photocatalyst degraded at 98.43% of methylene
blue (MB) under a visible light source which performed better than
under sunlight irradiation (77.09% of MB removal) for 120 min. Besides,
the mineralization result has measured the presence of sulfate anions
after photocatalytic activities, which achieved 86.13% (under a visible
light source) and 65.34% (under sunlight). The superior photodegradation
performance for MB was mainly controlled by the reactive oxygen species
of the superoxide radical (•O2
–). The degradation kinetics of MB followed the first-order kinetics.
Meanwhile, the Langmuir isotherm model was fitted for the adsorption
isotherm. The floating photocatalyst presented good reusability, resulting
in 78.13% of MB removal efficiency even after five cycles. Our TiO2/PVA/cork floating photocatalyst fabrication and high photocatalytic
performance are potentially used in wastewater treatment, especially
under visible light irradiation.