Photocatalytic degradation of reactive red 3 and alachlor over uncalcined Fe–TiO₂ synthesized via hydrothermal method

Abstract

In this work, Fe³⁺ was used to modify TiO₂ to give improved performance under UV and visible light irradiation. The catalysts were prepared via a hydrothermal method without further calcination. Box–Behnken design was used to investigate the effects of hydrothermal temperature, hydrothermal time, and Fe content (wt%) on the photocatalytic performance of TiO₂. Pollutants such as reactive red 3 (RR3) dye and alachlor were examined. The synthesized catalysts have been characterized by many techniques. Photodegradation of RR3 dye was performed under UV light irradiation whereas photodegradation of alachlor was performed under both UV and visible light irradiation. In RR3 photodegradation, the effect hydrothermal settings for temperature and time were found significant and the highest removal percentages were 92 and 94% for 15 and 30 min UV irradiation, respectively. In alachlor photodegradation, the effect of Fe-doping was found significant under both UV and visible light irradiation. The highest removal percentages were 49 and 82% for 15 and 30 min of UV light irradiation, respectively, and 51% for 60 min of visible light irradiation. Only anatase crystallite was found in catalysts with and without Fe. Energy band gaps decreased with increasing Fe contents. The crystallite sizes of catalysts with 0.10 wt% Fe³⁺ content decreased with increasing hydrothermal time and temperature, while surface area increased. Energy-dispersive X-ray spectroscopy technique was able to detect nitrogen contents of about 10 wt% and X-ray absorption near edge structure was used to find the oxidation states of Fe³⁺ and Fe^3+/4+ in Fe–TiO₂ as well.

Keywords:

• Alachlor
• Box–Behnken design
• Fe–TiO₂
• Photocatalysis
• Dye

Acknowledgments

The authors would like to thank Research Center for Environmental and Hazardous Substance Management (EHSM), Khon Kaen University and the Department of Science and Technology, Philippines through the Engineering Research and Development for Technology (ERDT) for the financial support given to this research. The authors also acknowledge the Synchrotron Light Research Institute (public organization) Thailand for the courtesy on the XANES measurement (BL5.2: SUT-NANOTEC-SLRI XAS Beamline).