Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO2Nanotubes

Claudio W Backes,Francine R Scheffer,Daniel E Weibel,Sérgio R Teixeira,Marcelo B Pereira

doi:10.5935/0103-5053.20140268

Claudio W Backes, Francine R Scheffer + Show 3 more

Open Access

https://doi.org/10.5935/0103-5053.20140268

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Abstract

Visible light-assisted degradation of indigo carmine (IC), methylene blue (MB) and methyl orange (MO) aqueous solutions has been achieved on the surface of TiO2 nanotube (NT) arrays impregnated with riboflavin (RF). Diluted RF water solutions in the presence of RF-TiO2 NTs irradiated with UV light produced O2, CO and CO2 as main gas products. On the contrary, the same solutions irradiated with visible light evolved O2 as a main product. This in situ O2 generation under visible light absorption allows the degradation of the dyes without the necessity to bubble air or oxygen in the reaction system The photocatalytic degradation of MO, MB and IC can be described by a pseudo-first-order kinetic model obtaining ca. 100% degradation of MB, MO and IC in less than 3 h of visible light illumination. The results provided here are highly promising in view of various photocatalytic applications of the prepared RF-TiO2 NTs catalysts by two environmentally friendly compounds in the degradation of pollutants using solar radiation.

Highlights

Organic pollutants are a particular type of mankind compound whose concentrations continue to increase each year
The results indicate that the photocatalytic degradation of methyl orange (MO), methylene blue (MB) and indigo carmine (IC) can be described by the first-order kinetic model
RF water solutions irradiated in the presence of RF-TiO2 NTs with UV or visible light led to different gaseous products

Summary

Introduction

Organic pollutants are a particular type of mankind compound whose concentrations continue to increase each year. The bio-degradation of pollutants emitted from various sources is often very slow and conventional treatment is mostly ineffective and not environmentally compatible In this sense, the application of photocatalysis using semiconductor nanostructured systems appears to Titanium dioxide nanoparticles (TiO2 NPs), in their usual commercial form known as P25, have been extensively used to oxidise organic pollutants of water using ultraviolet (UV) light.[2,4,5,6,7,8] Despite TiO2 presenting high photocatalytic activity in its anatase form, the charge separation of this semiconductor is only possible by absorption of UV solar photons which represent less than 5% of the solar energy that reaches the Earth’s surface.

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