American Chemical Society
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C,N-Codoped TiO2 Nanoparticles Immobilized on Floating Alginate Beads for Diazinon Removal under Solar Light Irradiation

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journal contribution
posted on 2023-11-13, 08:29 authored by Nurul 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.