Photocatalysis of S-metolachlor in aqueous suspension of magnetic cerium-doped mTiO2 core–shell under simulated solar light
2017
Mermana, J. | Sutthivaiyakit, P. | Blaise, C. | Gagné, F. | Charnsethikul, S. | Kidkhunthod, P. | Sutthivaiyakit, S.
Magnetic cerium-doped mesoporous titanium dioxide was synthesized by combining sol–gel method and calcination using tetrabutanate and ammonium cerium nitrate as precursors and Pluronic P123 as a template coating on iron oxide covered with carbon in ethanol. The magnetic Ce-doped catalyst showed only anatase structure with a slight increase in lattice parameters compared to the undoped catalyst. The Ce LIII-edge X-ray absorption near-edge spectroscopy (XANES) spectra showed Ce³⁺, and the cerium substitution doping into titanium dioxide was proposed. Degradation of S-metolachlor in aqueous magnetic photocatalyst suspension followed (pseudo) first-order kinetics in the presence of 0.5 g L⁻¹ of γ-Fe₂O₃@[email protected] mol% Ce-mTiO₂ with a half-life of 55.18 ± 1.63 min. Fifteen degradation products were identified, and their transformation routes of the photocatalytic degradation were then proposed. Complementary toxicity assessment of the treated S-metolachlor solution was undertaken with Environment Canada’s algal microplate assay measuring growth inhibition (72-h IC₅₀) in the freshwater chlorophyte Pseudokirchneriella subcapitata. This test method revealed a significant decrease in toxicity (1.7-fold reduction after 180 min of irradiation treatment), thereby confirming that the by-products formed following photocatalysis would be less harmful from an environmental point of view. Photocatalytic degradation of S-metolachlor thus appears to hold promise as a cost-effective treatment technology to diminish the presence of this herbicide in aquatic systems.
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