Photocatalytic Degradation of Toluene, Butyl Acetate and Limonene under UV and Visible Light with Titanium Dioxide-Graphene Oxide as Photocatalyst

Birte Mull,Olaf Wilke,Lennart Möhlmann

doi:10.3390/environments4010009

Birte Mull, Olaf Wilke + Show 1 more

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https://doi.org/10.3390/environments4010009

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Abstract

Photocatalysis is a promising technique to reduce volatile organic compounds indoors. Titanium dioxide (TiO2) is a frequently-used UV active photocatalyst. Because of the lack of UV light indoors, TiO2 has to be modified to get its working range shifted into the visible light spectrum. In this study, the photocatalytic degradation of toluene, butyl acetate and limonene was investigated under UV LED light and blue LED light in emission test chambers with catalysts either made of pure TiO2 or TiO2 modified with graphene oxide (GO). TiO2 coated with different GO amounts (0.75%–14%) were investigated to find an optimum ratio for the photocatalytic degradation of VOC in real indoor air concentrations. Most experiments were performed at a relative humidity of 0% in 20 L emission test chambers. Experiments at 40% relative humidity were done in a 1 m³ emission test chamber to determine potential byproducts. Degradation under UV LED light could be achieved for all three compounds with almost all tested catalyst samples up to more than 95%. Limonene had the highest degradation of the three selected volatile organic compounds under blue LED light with all investigated catalyst samples.

Highlights

People from the Western world spend most of their time indoors, either in houses or in transportation, the indoor air quality is of particular importance [1]
Under blue LED light limonene was degraded in most cases but butyl acetate could only be degraded by six samples, whereas toluene could not be degraded at all
Limonene has the highest degradation rate of the three volatile organic compounds (VOC), which becomes most obvious by comparing the results obtained under blue LED light (Table 3)

Summary

Introduction

People from the Western world spend most of their time indoors, either in houses or in transportation, the indoor air quality is of particular importance [1]. Volatile organic compounds (VOC) are ubiquitous in the indoor air, emitting, e.g., from building materials, wall and floor coverings and interior equipment. Those emissions can have a negative impact on the indoor air quality, health and wellbeing of occupants. This effect is described as sick-building-syndrome [2]. Photocatalytic active coatings, mostly made of the semiconductor titanium dioxide (TiO2 ) [3], have been developed and tested for indoor air use. TiO2 in its anatase modification has a band gap of 3.2 eV and can be activated under UV-light (λ = 387 nm). By light irradiation with a corresponding wavelength, electrons from the valence band are transferred to the conduction band and as a result electron-hole pairs are formed (Figure 1)

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