Synthesis of the ZnTiO3/TiO2 Nanocomposite Supported in Ecuadorian Clays for the Adsorption and Photocatalytic Removal of Methylene Blue Dye

Abstract

Currently, the study of semiconductor materials is very promising for the photocatalytic remediation of hazardous organic substances present in the air and water. Various semiconductors have been investigated in this interesting photo-assisted methodology, among them metal oxides such as ZnO, TiO2 and their derivatives. In this study, ZnTiO3/TiO2 was synthesized by the sol-gel method using Ti(OC3H7)4 and Zn(CH3COO)2 · 2H2O as reagents. The role of several conditions such as synthesis temperature and TiO2:ZnO proportion on the morphology and purity of compounds obtained was studied, and the suitable conditions for the synthesis of photocatalysts were determined. Various techniques were used to conduct a systematic investigation on the structural, morphological, and photocatalytic properties of ZnTiO3/TiO2. Scanning Electron Microscopy (SEM) images show that ZnTiO3/TiO2 have a typical particle size of approximately 100 nm with a quasi-spherical shape. The adsorption and photocatalytic activity were investigated by the decolorization of Methylene Blue (MB) as an organic contaminant under UV irradiation both in TiO2 and ZnTiO3/TiO2 supported over some Ecuadorian clays. The materials evaluated were prepared in the shape of 0.2 cm (diameter) and 1.0 cm (length) cylindrical extrudates. The degradation percentage of MB obtained was 85% approximately after 150 min of irradiation. The results obtained allow us to conclude that these synthesized materials can be used as adsorbents and photocatalysts.

Structuring of ZnTiO3/TiO2 Adsorbents for the Removal of Methylene Blue, Using Zeolite Precursor Clays as Natural Additives

“…Regarding the results, the diffraction pattern showed that R-Clay was formed from kaolinite (K), quartz (Q), and hematite (H), while G-Clay consisted mainly of metahalloysite (M) and quartz (Q). Furthermore, Figure 1 shows the diffraction pattern of the ZnTiO 3 /TiO 2 heterostructure, which was obtained without impurities, as we reported in previous works [ 26 ].…”

“…Table 6 shows that the presence of the mixed oxide ZnTiO 3 /TiO 2 did not significantly improve the MB adsorption capacity of the extrudates compared to the extrudates free of ZnTiO 3 /TiO 2 . However, this mixed oxide can act as a photocatalyst to improve MB removal in aqueous systems when the process is carried out under UV or solar light, as we reported in a previous study [ 26 ]. The efficiency of ZnTiO 3 /TiO 2 in the photocatalytic removal of MB in aqueous systems depends on the appropriate contact between the photocatalyst and the dye.…”

“…When comparing the diffraction patterns of the extruded composites with their respective constituent compounds ( Figures S1 and S2 ), no alteration of the diffraction peaks of the zeolites or the mixed oxide ZnTiO 3 /TiO 2 was observed, probably due to the calcination temperature of the extruded composites being lower than the thermal stability of the zeolites [ 60 ] and mixed oxide [ 26 ] used. Therefore, the calcination temperature of 500 °C made it possible to achieve a mechanically strong adsorbent while keeping the crystalline structure of the zeolites and the photocatalyst intact.…”

“…This mixed oxide is interesting for its technological applications as an adsorbent and photocatalyst; it is also a low-cost and environmentally friendly material [ 24 , 25 ]. Previous studies show that ZnTiO 3 /TiO 2 can eliminate methylene blue dye from aqueous systems, being of interest for effluent treatment [ 26 ].…”

“…In addition, we previously reported the use of ZnTiO 3 /TiO 2 to remove methylene blue. The results of this study showed that this mixed oxide can degrade the dye, especially by photocatalysis, although it also showed slight adsorbent activity [ 26 ]. However, no studies have been found in the literature in which ZnTiO 3 /TiO 2 , zeolites, and clays are combined to prepare composites that serve to adsorb colorants in general, and methylene blue in particular, from aqueous systems.…”