posted on 2023-11-13, 08:29authored byNurul
Hidayah Mohamad Idris, Kuan Yew Cheong, Siwaporn Meejoo Smith, Hooi Ling Lee
Filtration
is a critical step during wastewater treatment,
in which
the catalyst must be separated from the aqueous system for the next
treatment. For effective separation of the catalyst, a proper strategy
is demanded to overcome the filtration issue in the suspended catalyst
system. Therefore, an innovative photocatalytic system with C,N-TiO2 NPs immobilized on floating alginate beads was designed via
the ionotropic gelation method to treat diazinon as a model pollutant
under solar light irradiation. The synthesized C,N-TiO2 NPs showed unique features including an anatase phase with a crystallite
size of 11 ± 2.1 nm, active under the visible light region with
a lower bandgap energy of 2.94 eV than 3.2 eV of bulk anatase TiO2, and has slower recombination of electron–hole pairs
than the bulk anatase TiO2. The XPS analysis also confirmed
that C and N were codoped into TiO2 from the shift of binding
energy for Ti 2p. SEM analysis provided evidence that many accumulated
powders of the synthesized C,N-TiO2 NPs were dispersed
onto the alginate bead surface. The designed C,N-TiO2 NP/alginate
bead floating photocatalyst achieved the excellent removal of diazinon
of 80.61% and a mineralization degree of 60.08% with the presence
of dominant ROS (·O2– radicals)
under solar light for 8 h. The degradation kinetics followed first-order
kinetics, whereas the Langmuir isotherm model was fitted for the adsorption
isotherm. It could be reused for five cycles with 76.84% diazinon
removal, reflecting the great reusability of the floating photocatalyst
during photodegradation. Thus, this work creates a novel designation
of C,N-TiO2 NP/alginate bead floating photocatalysts that
have great potential for application in photocatalytic wastewater
treatment.