Date of Award

31-8-2024

Document Type

Thesis

School

School of Arts, Sciences, Humanities & Education

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

S.Sriram

Keywords

Photocatalytic Dye Degradation, Energy Gap, Absorption Spectra, Radical Test, Stability

Abstract

In recent times, organic dyes from industrial sludge become one of the significant causes of water contamination due to their utility in textile and paper manufacturing industries. These organic dyes are highly toxic and carcinogenic. Fortunately, the photocatalytic degradation process is a practical tool for decomposing toxic organic matter in wastewater by utilizing light. The photodegradation process can be performed using semiconductor materials to purify wastewater. Thus, semiconductor photocatalysis is a desirable alternative technique for decolorizing various organic pollutants.

In this context, the present work reports the preparation and characterization of V2O5 nanocomposites by facile methods and tests them against various industrial standard dyes. V2O5 nanoparticle is prepared via soft chemical method, and its photocatalytic activity was tested against Methylene Blue (MB) and Methyl violet (MV) dyes; the degradation efficiency was observed as 92% and 85%, respectively.

Further, to enhance the photocatalytic efficiency of V2O5, a suitable dopant is chosen by employing density functional theory (DFT) simulation. Transition metals such as Cu, Co, Ni, Zn, Mn, and Fe were selected for the study. Among the different dopants, Zn was identified as a promising dopant in terms of bandgap and band edge potentials. The identified dopant is experimentally prepared (Zn- doped V2O5) by the sol-gel process with varying dopant percentages, and the photocatalytic efficiency of the prepared composite is tested against three industrial standard dyes such as Methylene Blue (MB), Methyl Violet (MV), and Malachite Green (MG). The dye degradation efficiency of the Zn-doped V2O5 nanostructures is 91 % to 99% for MB and MV dyes with maximum light exposure of 105 minutes and 96% in 30 minutes for MG dyes.

The spray pyrolysis method was employed to prepare a heterojunction between V2O5 and TiO2 thin films, and its photocatalytic activity was studied. Under the visible light illumination, the dye degradation efficiency of 99 % in 75 mins for MB, 99% in 90 mins for MV, and 95% in 30 mins for MG were obtained. From the results, it is observed that for Zn–doped V2O5 and heterostructure (V2O5/TiO2) samples, the dye degradation process is dominated by hydroxyl radicals.

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