Abstract
The present research reports the synthesis of ZrO2-doped TiO2 photocatalysts at different ZrO2 contents (1, 3 and 5% wt.) synthesized by the sol–gel method. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, attenuated total reflectance-Fourier transform infrared, ultraviolet–visible, X-ray photoelectron spectroscopy and N2 adsorption–desorption analysis. The photocatalytic activity of the ZrO2-doped TiO2 was investigated against the dyes methyl orange and rhodamine B through mineralization studies. The ZrO2-doped TiO2 samples presented a semiglobular-ovoid agglomerate shape around 500–800 nm. The samples presented high crystallinity of the TiO2 anatase phase, XPS suggested the formation of Zr–O–Ti bonds and the samples were classified as mesoporous materials with slight changes in the optical features in comparison with pure TiO2. Our study shows that the ZrO2-doped TiO2 composites exhibited a higher photocatalytic activity than just utilizing the synthetized TiO2 and a commercial P25. The different degradation behaviors are attributed to differences in the textural properties, and to the different optical absorptions of the samples due to structural defects created by the level of doping of Zr4+ ions into the TiO2 lattice. Reaction kinetics parameters were calculated by the Langmuir–Hinshelwood model, and a third run cycle of the ZrO2-doped TiO2 at 1% wt. achieved a photocatalytic degradation of 78.1 and 75.5% for RhB and MO, respectively.
Highlights
There is a special interest in the elimination of synthetic dyes from fabric effluents that, in most of cases, have azo compounds [1,2]
The materials synthesized in this study presented the anatase phase of TiO2, the crystalline arrangement with more photoactivity of TiO2
This anatase phase of TiO2 was slightly modified by the insertion of Zr4+ ions in its structure according to XRD and XPS analysis
Summary
There is a special interest in the elimination of synthetic dyes from fabric effluents that, in most of cases, have azo compounds [1,2]. The photoactivity of TiO2 is strongly delimited by factors such as the interaction between the active surface and the chemical nature of the pollutants, efficiency to prevent the charge transfer recombination and the type of reactive oxygen species created by the e-/h+ pairs in the aqueous medium [8,9]. A diversity of surface modification approaches have been applied to improve the photocatalytic activity of TiO2 These chemical modifications include hybridization with other semiconductors through metal deposition, carbon material coating, non-metal doping and anion absorption [11]. The modifications are aimed to modify the band gap and/or extend the excitation wavelength, reduce the rate of charge carrier recombination, increase the stability of the photoactive crystalline phase and increase the quality and quantity of the surface-active sites [6]
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