Photocatalytic conversion of gaseous ethylbenzene on lanthanum-doped titanium dioxide nanotubes

•1.2%-La3+-TNTs was synthesized via sol–gel method combined with nanotube-formation.•1.2%-La3+-TNTs had a higher photocatalytic activity for EB conversion than pure TiO2.•Rate controlling steps were different under various RHs of reaction media.•Active radicals by photocatalysis played dominant roles during the conversion of EB.•A detailed pathway was proposed for the photocatalytic conversion of EB. The photocatalytic properties of titanium dioxide (TiO2) make it an attractive material for environmental remediation. In the present study, lanthanum (La3+)-doped TiO2 nanotubes with excellent photocatalytic activity were fabricated by a combination of sol–gel method and hydrothermal technique. The optimal preparation parameters were determined by the structural characterization using a range of methods and the photocatalytic degradation of gaseous ethylbenzene (EB). Compared with pure TiO2 nanoparticles, 1.2%-La3+-doped – titania nanotubes (1.2%-La3+-TNTs) exhibited higher activity under 254nm UV for conversion of EB. The initial EB concentrations and relative humidity (RH) obviously influenced the photocatalytic activity of 1.2%-La3+-TNTs. Kinetic analysis showed that surface adsorption and surface reaction controlled the rate-determining step for RH of 40–50% and >80%, respectively. Gas chromatography and mass spectrometry were used to analyze the intermediates generated in the conversion of EB, allowing a tentative decomposition pathway to be proposed. The prepared photocatalyst exhibited enhanced EB conversion compared with undoped TiO2, and showed a promise for the decomposition of recalcitrant compounds before subsequent biopurification.