Visible light-activated N-F-codoped TiO2 nanoparticles for the photocatalytic degradation of microcystin-LR in water ☆

Abstract In this study, we developed nonmetal-doped TiO 2 nanoparticles (N-F-TiO 2 ) by a novel synthesis route employing a simple sol–gel method containing a nonionic fluorosurfactant as pore template material to tailor-design the structural properties of TiO 2 and fluorine dopant as well as ethylenediamine as nitrogen source for the photocatalytic response towards visible light. The synthesized photocatalyst was characterized by XRD, UV–vis spectroscopy, XPS, HR-TEM, ESEM and porosimetry measurements. The resulting nanoparticles exhibited enhanced structural properties such as high surface area (141 m 2 /g), high porosity (49%), mesoporous structure (2–10 nm pore size) and low degree of agglomeration (1.07). A reduction in the effective band gap (2.75 eV) was observed compared with reference TiO 2 (3.00 eV) due to the red-shift in the optical absorption spectrum of the nonmetal-doped TiO 2 photocatalyst. We also focused on the environmental application of the prepared nanoparticles for the destruction of microcystin-LR (MC-LR) under visible light irradiation ( λ  > 420 nm). Under acidic conditions (pH 3.0 ± 0.1), the highest MC-LR degradation rate was achieved with N-F-TiO 2 . The electrostatic interactions between the toxin and the N-F-codoped TiO 2 favored the photocatalytic degradation. Beneficial effects induced by codoping with nitrogen and fluorine are responsible for higher photocatalytic activity than TiO 2 nanoparticles with only fluorine or nitrogen doping. Also, commercially available visible light-activated TiO 2 showed lower degradation rate per unit surface area of the material.