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The factors affecting the photocatalytic degradation of organic pollutants under visible irradiation using TiO2/rGO nanocomposites as photocatalysts

At the beginning of the 21st century, mankind has to face the problem of availability of water as an important threat, due to the loss of the balance between the quantity and quality of available water [1]. The ubiquitous organic pollutants (drugs, pesticides, and organic dyes) have become a matter of increasing concern. They have raised considerable concerns due to their frequent detection in drinking water, groundwater, and surface water, usually in the very low concentration [2]. Organic pollutants and also their metabolites can be toxic and some of them even carcinogenic for humans. Therefore, pollutants should be removed by an appropriate purification method. It was shown how various organic pollutants can be efficiently removed by photocatalytic processes in the presence of different catalysts. Heterogeneous photocatalysis with appropriate photocatalysts is among the most promising methods for the efficient removal of pollutants. It is a clean, green, sustainable and cheap method [1, 2]. The nanocomposite photocatalyst based on titanium dioxide (TiO2) and reduced graphene oxide (rGO) was produced. The material was prepared using a direct sol- gel method followed by hydrothermal treatment at different experimental conditions (e.g., pH, time, temperature) with the aim to optimize photocatalytic degradation. Graphene oxide (GO) was produced from graphite flakes following a Hummer’s method [3]. TiO2 sol was prepared from titanium tetraisopropoxide as a precursor, i- propanol as a solvent, acetylacetone as a chelating agent and nitric acid as a catalyst [4]. TiO2 nanoparticles and TiO2/rGO nanocomposites, with different amounts of GO, were obtained by a hydrothermal method, where also time, temperature and pH of the treated suspensions were adjusted. The influence of the preparation conditions on the physico-chemical properties of synthesized powders was established by different characterization methods such as (powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy). Photocatalytic degradation of organic pollutants (caffeine, methylene blue) under visible light irradiation was used as a test reaction. The efficiency of the photocatalytic degradation was monitored by UV- Vis spectrophotometry. Obtained results show how photocatalytic properties of prepared TiO2 nanoparticles and TiO2/rGO nanocomposites depend on different experimental parameters of their synthesis.

graphene oxide, photocatalysis, reduced graphene oxide, TiO2/rGO nanocomposites, visible irradiation

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