Abstract
In industrial pollutants, phenol is a kind of degradation-resistant hazardous compound. It is generated during industrial processes in factories and treatment at sewage plants. In this study, we analyse the photocatalytic activity of TiO2 and rGO as a composite for the degradation of phenol. Hybridised titanium dioxide/reduced graphene oxide (TiO2/rGO) nanocomposites were synthesised by a simple hydrothermal method using flake graphite and tetrabutyl titanate as raw materials. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET) specific area analysis, Fourier transform infrared spectroscopy (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), photoelectrochemical analysis, and UV–vis diffuse reflectance spectra (DRS) were employed to characterise the physicochemical properties of the as-prepared nanocomposites. The results showed the TiO2/rGO nanocomposites’ significant anatase phase and a small fraction of the rutile phase the same as that of the as-prepared TiO2 nanoparticles. The spherical TiO2 nanoparticles (diameter 20–50 nm) were agglomerated slightly and the agglomerates were anchored on the rGO sheets and dispersed symmetrically. The specific surface area of TiO2/rGO-4% nanocomposites was 156.4 m2/g, revealing a high specific surface area. Oxygen-containing functional groups that existed in TiO2/rGO-4% nanocomposites were almost removed during hydrothermal processing. The photocurrent response of TiO2/rGO-4% was strongest among the TiO2/rGO nanocomposites, and the bandgap of TiO2/rGO-4% was 2.91 eV, showing a redshift of absorption into the visible region, which was in favour of the high photocatalytic activity of TiO2/rGO nanocomposites under visible light (λ > 420 nm). Moreover, the samples were employed to photodegrade phenol solution under visible light irradiation. TiO2/rGO-4% nanocomposite degraded the phenol solution up to 97.9%, and its degradation rate constant was 0.0190 h−1, which had higher degradation activity than that of other TiO2/rGO nanocomposites. This is a promising candidate catalyst material for organic wastewater treatment.
Highlights
In recent years, wastewater treatment has attracted attention with the continuous deterioration of the global environment
TiO2/reduced graphene oxide (rGO) nanocomposites were successfully synthesised by hydrothermal methods and investigated as a new catalyst to degrade the phenol solution
The addition of rGO resulted in a reduction in the energy bandgap and enhanced absorption in the visible light region
Summary
Wastewater treatment has attracted attention with the continuous deterioration of the global environment. The removal of toxic and refractory pollutant in coal-chemical wastewater has become a huge challenge [1,2,3]. Coal-chemical wastewater, produced from gasification and coking, possesses high concentrations of contaminants, such as phenolic compounds, benzene, cyanide, aromatic organic, (oxygen, sulphur, and nitrogen)-heterocyclic compounds, and other harmful substances, which are posing a great threat to human health and sustainable development [4,5]. Symmetry 2020, 12, 1420 techniques for the removal of phenol and phenolic derivatives include adsorption, coagulation, electrochemical, extraction, biological treatment, enzyme oxidation, and supercritical water oxidation. These methods cannot degrade them completely and even generate secondary pollution [8,9,10,11]
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