Synergetic effect of TiO2 and Fe3+ as co-catalysts for enhanced phenol degradation in pulsed discharge system

Abstract

In this work, the synergetic effect of TiO2 and Fe3+ in pulsed discharge plasma has systematically investigated using phenol as the probe molecule. The dominant effects of TiO2 and Fe3+ dosage were firstly studied, and then phenol degradation was investigated in four parallel experiments including plasma alone, plasma/Fe3+, plasma/TiO2 and plasma/Fe3+/TiO2. The experimental results showed that the phenol removal efficiency in plasma/Fe3+/TiO2 system increased by 25% in comparison with plasma alone, which were only 9% and 10% in plasma/TiO2 and plasma/Fe3+ system, indicating a significantly synergistic effect between Fe3+ and TiO2. To illustrate the synergetic effect of TiO2 and Fe3+ ions, the TiO2 structural characterization was analyzed by XPS, UV–vis spectra and XRD, and Fe2+ andOH concentration was also determined during discharge process. The Fe3+ ions and excited nitrogen from plasma discharge were doped on TiO2 particles, which narrowed the band gap of TiO2 from 3.0eV to 2.0eV and enlarged the absorption edge at around 600nm, and therefore enhanced the photocatalytic activity in the visible light. The co-doping of Fe3+ and nitrogen significantly increased the separation rate of photo-generated electrons and holes and prolonged their lifetime. The photoelectron-transfer pathway was blocked by Fe3+, the Fe3+ ions could be changed to Fe2+ ions using photoelectron on TiO2 surface, inducing Fenton-like reaction for the enhancement of the OH formation rate in the plasma/TiO2/Fe3+ system. The concentration of OH increased from 14.8×10−5molL−1 in the plasma/TiO2 system to 20.6×10−5molL−1 in the plasma/TiO2/Fe3+ system.