Abstract
Layered Double Hydroxide (LDH)/TiO2 nanocomposites with photocatalytic properties were synthesized by both impregnation and the direct coprecipitation of LDH matrices using a colloidal suspension of TiO2 nanoparticles. While the two methods led to an efficient TiO2 nanoparticle immobilization, the direct coprecipitation allowed us to tune the amount of immobilized TiO2 within the materials. The LDH/TiO2 nanocomposites obtained were deeply characterized by chemical analysis (ICP-AES), Powder X-ray diffraction (XRD), Fourier Transformed Infra-Red (FTIR), Thermogravimetric analysis (TGA), and High-Resolution Transmission Electron Microscopy (HRTEM). Clearly, the immobilization of TiO2 by direct coprecipitation promoted a modification of the textural properties and a net increase in the surface area. The crystallized TiO2 nanoparticles can be distinctly visualized by HRTEM at the surface of the layered material. Several parameters, such as the nature of the chemical composition of LDH (ZnAl and MgAl), the method of immobilization and the amount of TiO2, were shown to play a crucial role in the physicochemical and photocatalytic properties of the nanocomposites. The photocatalytic efficiency of the different LDH/TiO2 nanocomposites was investigated using the photodegradation of a model pollutant, the Orange II (OII), and was compared to a pure TiO2 colloidal solution. The degradation tests revealed that the nanocomposite obtained from MgAl LDH at a low MgAl LDH/TiO2 ratio was the most efficient for the photodegradation of OII leading to complete mineralization in 48 h.
Highlights
Dyes, as all other organic compounds, are introduced into water bodies through waste from industrial processes such as pharmaceutical, dyes and textiles, petrochemicals, and pesticide factories [1,2]
Titanium oxides are known to be amphoteric in aqueous suspensions
In the following parts, the TiO2 dispersion at pH 9.30 was used for the synthesis of Layered Double Hydroxide (LDH)/TiO2 assemblies
Summary
As all other organic compounds, are introduced into water bodies through waste from industrial processes such as pharmaceutical, dyes and textiles, petrochemicals, and pesticide factories [1,2]. The positive charge generated at the layer surface is balanced by the presence of intercalated anions in between the layers [34,35] These matrices are known for their adsorbent properties, allowing for the adsorption of organic compounds causing pollution [36]. LDH/TiO2 assemblies have been investigated for their efficiency toward pollutant photodegradation [49,50,51] In this approach, LDH is mainly expected to: (1) enhance the vicinity of the organic pollutant with the TiO2 surface, thanks to the LDH adsorption properties; (2) facilitate the photocatalyst’s recovery by filtration; (3) limit the TiO2 nanoparticle aggregation through a homogeneous distribution on the two-dimensional materials. The solid was collected by centrifugation and subjected to three washing cycles and dried at room temperature
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