Decolourisation of Metanil Yellow by visible-light photocatalysis with N-doped TiO₂ nanoparticles: influence of system parameters and kinetic study

Abstract

A nitrogen-doped photocatalyst (N-TiO₂) is prepared from 15% TiCl₃ and 25% aqueous NH₃ solution as precursor. The synthesised material is characterised by XRD, BET, TEM, DRS and XPS and is used for photocatalytic decolourisation of Metanil Yellow under visible-light illumination. The experimental parameters, viz, photocatalyst dose, initial dye concentration and solution pH influence the decolourisation process. At pH 3.5, N-TiO₂ can decolourise almost 89% of the dye at equilibrium within 240 min. COD study reveals ∼92% mineralisation of the dye in 360 min of irradiation. The photocatalytic reaction is allowed to proceed only after the attainment of adsorption equilibrium between N-TiO₂-Metanil Yellow. The adsorption is carried out by batch process under different experimental conditions, namely, N-TiO₂ dose, initial dye concentration and solution pH. The adsorption process attains equilibrium within 60 min and follows Lagergren first-order kinetics. On the other hand, the photocatalytic decolourisation of Metanil Yellow is suitably fitted with the modified Langmuir–Hinselwood model. Modification of TiO₂ improved the decolourisation of the dye by ∼8 times compared to TiO₂ P25.

Keywords:

• Decolourisation
• Kinetics
• Metanil Yellow
• Nitrogen-doped Titania
• Photocatalysis

Acknowledgements

The authors are thankful to Dr. C.V.V. Satyanarayana, Scientist, Heterogeneous Catalysis Division, NCL, Pune for his support in various stages of this work. We gratefully acknowledge the use of CAMCOR facilities of University of Oregon, USA, which have been purchased with combination of federal and state funding. The authors are also thankful to U.G.C, New Delhi for financial assistance through a Major Research Project grant.