Abstract
Nanocomposites (CNTi) with different mass ratios of carbon nitride (C3N4) and TiO2 nanoparticles were prepared hydrothermally. Different characterization techniques were used including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM) and Brunauer-Emmett-Teller (BET). UV-Vis DRS demonstrated that the CNTi nanocomposites exhibited absorption in the visible light range. A sun light - simulated photoexcitation source was used to study the kinetics of phenol degradation and its intermediates in presence of the as-prepared nanocomposite photocatalysts. These results were compared with studies when TiO2 nanoparticles were used in the presence and absence of H2O2 and/or O3. The photodegradation of phenol was evaluated spectrophotometrically and using the total organic carbon (TOC) measurements. It was observed that the photocatalytic activity of the CNTi nanocomposites was significantly higher than that of TiO2 nanoparticles. Additionally, spectrophotometry and TOC analyses confirmed that degraded phenol was completely mineralized to CO2 and H2O with the use of CNTi nanocomposites, which was not the case for TiO2 where several intermediates were formed. Furthermore, when H2O2 and O3 were simultaneously present, the 0.1% g-C3N4/TiO2 nanocomposite showed the highest phenol degradation rate and the degradation percentage was greater than 91.4% within 30 min.
Highlights
Semiconductor photocatalysis is considered an alternative and environmentally benign technology in the field of wastewater treatment and for renewable energy sources
For the C3N4–TiO2 nanocomposite (CNTi) nanocomposite, the weight loss increased at temperatures above 500 °C
Coupling TiO2 with C3N4 has proved to be beneficial for improving the photocatalytic performance due to a synergism that was ascribed to improved light harvesting, enhanced photostability and effective photoexcited charge separation
Summary
The deconvolution of the Ti region of the CNTi composite (Fig. 5Cd) revealed the existence of Ti-N or/and Ti-C (at 457.8 and 463.3 eV for Ti 2p3/2 and 2p1/2, respectively) with a spacing of 5.5 eV besides the TiO2 main peak. An increase in the C3N4 percentage from 0.1 to 1% in the CNTi composites decreased the photocatalytic activity, and 0.1CNTi showed the best performance in terms of the phenol degradation rate. A comparison of the phenol degradation % based on UV spectrophotometer and TOC measurements indicated similar results when the CNTi nanocomposite photocatalyst was used. Photocatalytic measurements of the 0.1CNTi nanocomposite, which yielded the best degradation rate of phenol (in this study) in the presence of both O3 and H2O2 under Xe illumination, were repeated six times after isolating the photocatalyst. The results demonstrated that the CNTi nanocomposite photocatalyst was stable under the abovementioned experimental conditions
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