Abstract
Synthetic dyes are widely used in textile, paper, food, cosmetic, and pharmaceutical industries. During industrial processes, some of these dyes are released into the wastewater and their successive release into rivers and lakes produces serious environmental problems. TiO2 is one of the most widely studied and used photocatalysts for environmental remediation. However, it is mainly active under UV-light irradiation due to its band gap of 3.2 eV, while it shows low efficiency under the visible light spectrum. Regarding the exploration of TiO2 activation in the visible light region of the total solar spectrum, the incorporation of carbon nanomaterials, such as graphene, in order to form carbon-TiO2 composites is a promising area. Graphene, in fact, has a large surface area which makes it a good adsorbent for organic pollutants removal through the combination of electrostatic attraction and π-π interaction. Furthermore, it has a high electron mobility and therefore it reduces the electron-hole pair recombination, improving the photocatalytic activity of the semiconductor. In recent years, there was an increasing interest in the preparation of graphene-based TiO2 photocatalysts. The present short review describes the recent advances in TiO2 photocatalyst coupling with graphene materials with the aim of extending the light absorption of TiO2 from UV wavelengths into the visible region, focusing on recent progress in the design and applications in the photocatalytic degradation of synthetic dyes.
Highlights
The results revealed that reduced graphene oxide (rGO)/TiO2 and graphene oxide oxidereduction (GO)/TiO2 nanocomposites exhibited efficient charge separation, showing about 500%
The results showed that rGO-TiO2 presented a stratified structure composed of dispersed anatase TiO2 on the surface of rGO; the larger surface area of the composite was favorable for the Methyl orange (MO) absorption; in addition, the extension of the visible light region absorption range was observed
We have described the characteristics of both TiO2 semiconductors and graphene materials and reported several examples focusing on the recent progress in the design, synthesis, and applications of these GTiO2 Ns nanocomposites used as photocatalysts in the photocatalytic degradation of synthetic dyes
Summary
A large number of research activities have been dedicated to environmental protection and remediation as a consequence of special attention from social, political, and legislative authorities, which has led to the delivery of very stringent regulations for the environment [2]. Due to industrialization and the lack of effective treatments of the effluents at the source, a severe deterioration of freshwater resources caused by the release of a wide range of hazardous substances into water bodies has occurred. Of these substances, synthetic dyes represent a large group and deserve particular attention, due to the high quantity—more than 800,000 tons—that is produced annually worldwide [3]. About one third of these is released into receiving waters every year through industrial wastewater discharges [4], which may have a severe influence on both the environment
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