Abstract
Photocatalysis using semiconductor oxides was being investigated extensively for the degradation of dyes in effluent water. This paper reports our findings on visible light induced photocatalytic degradation of azo dye, methyl red mediated nitrogen and manganese codoped nano-titanium dioxide (N/Mn-TiO2). The codoped samples with varying weight percentages were synthesized by sol-gel method and characterized by various analytical techniques. The X-ray diffraction data showed that the synthesized samples were in anatase phase with 2θ at 25.3°. UV-visible diffuse reflectance spectral analysis revealed that the presence of dopants in TiO2 caused a significant absorption shift towards visible region and their presence was confirmed by X-ray photoelectron spectral data. The release of hydroxyl radical (major active species in photocatalytic degradation) by the photocatalyst in aqueous solution under visible light irradiation was quantitatively investigated by the photoluminiscent technique (PL). The effect of various experimental parameters like dopant concentration, pH, catalyst dosage, and initial dye concentrations was investigated and optimum conditions were established. The extent of mineralization of methyl red was studied by chemical oxygen demand (COD) assays and the results showed complete mineralization of the dye.
Highlights
Dyes are the resistant compounds that are found in industrial waste water causing adverse environmental problems
Nitrogen and manganese were successfully doped into TiO2 matrix and its photocatalytic activity was studied for the degradation of methyl red under visible light
All the synthesized samples were in anatase phase and band-gap has been reduced
Summary
Dyes are the resistant compounds that are found in industrial waste water causing adverse environmental problems. 15% of these are lost with waste water during synthesis and processing [1] This represents a great hazard to human and environmental health due to the toxicity of azo dyes [2]. A number of studies have been reported on the modification of TiO2 in order to extend the absorption of light to the visible region These include dye sensitization, semiconductor coupling, impurity doping, use of coordination metal complexes, and metal deposition [5]. In our research work we have selected nitrogen (N) and manganese (Mn) as nonmetal and metal dopants to be codoped in TiO2 and study its photocatalytic activity by degrading a model azo dye pollutant, methyl red. Sol-gel method has been followed for the synthesis of nitrogen and manganese codoped TiO2 (N/MnTiO2) photocatalysts. Where Ao is initial absorbance of dye solution before degradation and At is absorbance of dye solution at time t
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