Photocatalytic Degradation of Dichlorvos in Visible Light byMg2+-TiO2Nanocatalyst

T Siva Rao,T Susmitha,C Subrahmanyam,Teshome Abdo Segne,A Balaram Kiran

doi:10.1155/2012/168780

T Siva Rao, T Susmitha + Show 3 more

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https://doi.org/10.1155/2012/168780

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Abstract

Photocatalytic activity of TiO2was studied by doping with magnesium (Mg2+-TiO2) with varying magnesium weight percentages ranging from 0.75–1.5 wt%. The doped and undoped samples were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), N2adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), and scanning electron microscopy (SEM). The XRD data has shown that anatase crystalline phase in Mg2+-TiO2catalysts, indicating that Mg2+ions did not influence the crystal patterns of TiO2. The presence of magnesium ions in TiO2matrix has been determined by XPS spectra. DRS spectra showed that there is a significant absorption shift towards the visible region for doped TiO2. The SEM images and BET results showed that doped catalyst has smaller particle size and highest surface area than undoped TiO2. The photocatalytic efficiency of the synthesized catalysts was investigated by the photocatalytic degradation of aqueous dichlorvos (DDVP) under visible light irradiation, and it was found that the Mg2+-doped catalysts have better catalytic activity than undoped TiO2. This can be attributed that there is a more efficient electron-hole creation in Mg2+-TiO2in visible light, contrary to undoped TiO2which can be excited only in UV irradiation. The effect of dopant concentration, pH of solution, dosage of catalysts, and initial pesticide concentration has been studied.

Highlights

Advanced oxidation process (AOP) is an alternative way of treating undesirable organic pollutants, including pesticides
There are a lot of different semiconductor materials which are readily available (e.g., TiO2, ZnO, Fe2O3, CdS, and ZnS), but only a few are suitable for sensitizing the photomineralization of a wide range of organic pollutants
Previous studies have shown that the photocatalytic degradation of pesticides by irradiating with UV light source and using TiO2 or ZnO as catalyst leads to the formation of H+, Cl−, PO43−, and CO2 as final products, and their formation during the progress of the degradation of DDVP was confirmed by simple qualitative analysis tests

Summary

Introduction

Advanced oxidation process (AOP) is an alternative way of treating undesirable organic pollutants, including pesticides. There are a lot of different semiconductor materials which are readily available (e.g., TiO2, ZnO, Fe2O3, CdS, and ZnS), but only a few are suitable for sensitizing the photomineralization of a wide range of organic pollutants. Among various semiconductor photocatalysts available, TiO2 has attracted a great deal of study for its high photocatalytic activity, nontoxic property, chemical stability, and highest oxidation rate of many photoactive metal oxides investigated [11]. TiO2 has high bandgap energy (3.2 eV), which is only 4-5% of the overall solar spectrum This restricts the use of visible light. The advantage of doping the metal ions into TiO2 is the temporary trapping of the photogenerated charge carriers by the dopant and the inhibition of their recombination during migration from the inside of the material to the surface, by modifying the bandgap of the photocatalyst. The photocatalytic activities of the synthesized samples have been evaluated by the degradation of a representative model pesticide pollutant, dichlorvos

Experimental

Results and Discussions

Conclusions