Photocatalytic removal of 2-nitrophenol using silver and sulfur co-doped TiO2 under natural solar light

Abstract

To overcome the drawback of poor solar light utilization brought about by the narrow photoresponse range of TiO₂, a silver and sulfur co-doped TiO₂was synthesized. Using the prepared catalyst, solar photocatalytic degradation of 2-nitrophenol (2-NP) by a TiO₂-based catalyst was studied for the first time. Effects of the co-doping on the structural, optical and morphological properties of the synthesized nanoparticles were investigated by different characterization methods: X-ray diffraction, N2 adsorption-desorption measurements, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy. Solar experiments showed that the co-doping with silver and sulfur significantly increased the photocatalytic activity. In various initial concentrations of 2-NP more than 99% of the contaminant was decomposed by Ag-S/TiO₂in less than 150 minutes, while the degradation efficiency was much less in the presence of bare TiO₂. Kinetic studies suggested that solar photocatalytic degradation of 2-NP is consistent with the Langmuir-Hinshelwood model. The rate constant of the reaction and adsorption constant of the modified photocatalyst were found to be 2.4 and 4.1 times larger than that of bare TiO₂, respectively.

Individual and interaction effects of operating parameters on the photocatalytic degradation under visible light illumination: Response surface methodological approach

“…Several scientific studies on the modification and development of TiO 2 catalyst in order to increase its visible light sensitivity have been reported over the past decades . Doping TiO 2 with metals and non‐metals (such as silver and sulphur respectively) has been known as an efficient strategy to extend its optical response from UV to visible light range . Doping these impurities into the TiO 2 matrix can decrease the band gap of the semiconductor and increase the photocatalytic activity of TiO 2 under the visible light significantly without modifying its surface properties .…”

An intrinsic kinetic model for liquid‐phase photocatalytic hydrogen production

“…6. The photo-generated electron competes with the substrate to react with the adsorbed hydroxyl radical according to Equation (10). As no oxygen exists to react with the formed hydroxide, it can transfer the electron back to the photocatalyst and convert to hydroxyl radical.…”

“…8 Photocatalytic reactions have been considered as a promising alternative for future chemical conversion, since the discovery of water photolysis on a TiO 2 electrode by Fujishima and Honda. 9 Titanium-based photocatalysts are the most recognized [10][11][12][13] and alternative photocatalysts are not still reliable due to issues such as their stability, cost, toxicity, availability, and activity under full solar spectrum. 14…”

Hydrogen peroxide‐assisted photocatalysis under solar light irradiation: Interpretation of interaction effects between an active photocatalyst and H2O2

“…Among various transition metal and non‐metal doping agents, silver and sulphur have been recognized as promising candidates . Thereby, the co‐doping of TiO 2 with Ag and S can exhibit the significant enhancement of the photocatalytic activity under visible light due to their synergistic effect . In addition, it has been reported that by incorporating polyethylene glycol (PEG) as the chelating agent in the synthesis process of a titanium dioxide‐based photocatalyst, macroporous powders with large surface areas can be obtained .…”

“…Therefore, to achieve a comprehensive understanding of the H 2 O 2 ‐assisted photocatalytic process, investigating the interaction effects is as substantial as the individual effects. For this purpose, the response surface methodology (RSM) based on a statistical design of experiments (DOE) can be used . Therefore, this technique can be utilized to find the interaction effects between the parameters (i.e., photocatalyst and H 2 O 2 ) and obtain optimum conditions.…”