Photocatalytic Degradation of Mixed Dyes in Aqueous Phase by MgAlTi and ZnAlTi Mixed Oxides

Abstract

This study reported the synthesis and evaluation of mixed metal oxides MgO/Al 2 O 3 -TiO 2 and ZnO/Al 2 O 3 -TiO 2 as heterogeneous photocatalysts for the potential degradation of a mixture of organic dyes such as methylene blue and methyl orange. First, hydrotalcites were synthesized by two different methods (conventional and microwave); then they were treated at 500 °C to obtain the corresponding Mg/Al-Ti and Zn/Al-Ti mixed metal oxides. The Layered Double Hydroxide (LDH) and the Mixed Metal Oxides were characterized by N 2 adsorption-desorption, X-ray Diffraction, Fourier transform infrared, X-Ray photoelectron Spectrometry and Scanning Electron Microscopy. The degradation processes of the dyes were carried out under ultraviolet light irradiation and absorbance readings were compared using a UV-vis spectrometer. The ensuing degradation of products was corroborated through a mass spectrometry analysis. According to the photodegradation efficiency of dyes under UV irradiation, the activity of the samples showed the following order: ZnAlTiM > ZnAlTiC > MgAlTiC > MgAlTiM. The improvement in the activity of ZnAlTiM may be attributed to its lowest reflectance and highest degree of UV light absorbance, its smallest valence band and its ZnO-support interaction. Degradations of 25% and 68% were achieved for methyl orange and methylene blue, respectively, after 120 min of reaction. The degradation process conforms to the Langmuir-Hinshelwood type kinetic model.

Photodegradation and Mineralization of Phenol Using TiO2Coated γ-Al2O3: Effect of Thermic Treatment

“…Furthermore, the apparent kinetics (Kapp) for the photodegradation of phenol were obtained by the Langmuir-Hinshelwood formalism, which applies for pseudo-first-order in the photodegradation of phenol. As shown in the graph of ln C/Co versus time (Figure 9) [54,55], the kapp values and half-life time for the reactions were also obtained, as reported in Table 2.…”

“…Furthermore, the apparent kinetics (K app ) for the photodegradation of phenol were obtained by the Langmuir-Hinshelwood formalism, which applies for pseudo-first-order in the photodegradation of phenol. As shown in the graph of ln C/Co versus time (Figure 9) [54,55], the k app values and half-life time for the reactions were also obtained, as reported in Table 2. When following the photodegradation of phenol with a UV-vis spectrophotometer, the following behavior was observed: the most active photocatalyst was the one that was treated at 600 °C, followed by the catalysts treated at 500 > 700 > 400 > 800 °C.…”

Photocatalytic Degradation and Kinetics of Dyes in Textile Effluent Using UV – ZnO-Al System

“…"In this same vein, a study has reported the synthesis and evaluation of the mixed metal oxides MgO/Al 2 O 3 -TiO 2 and ZnO/Al 2 O 3 -TiO 2 as heterogeneous photocatalysts for the photo degradation of a mixture of organic dyes such as methylene blue and methyl orange" [12]. Similar works but with different types of photocatalyst, mostly in the form of nanoparticles or composites have been reported in literature [13,14,15].…”