Alachlor photocatalytic degradation over uncalcined Fe–TiO₂ loaded on granular activated carbon under UV and visible light irradiation

Abstract

Alachlor is a recalcitrant carcinogenic contaminant that may easily spread in water sources due to its wide usage as an herbicide. The aim of this study is to synthesize Fe–TiO₂ on granular activated carbon (GAC) support via hydrothermal method for the photocatalytic degradation of alachlor under ultraviolet and visible light irradiation. The effects of Fe–TiO₂ loading, initial alachlor concentration, and initial solution pH were determined using Box–Behnken design (BBD). X-ray diffraction (XRD) analysis of Fe–TiO₂-GAC samples showed anatase TiO₂ peaks as well as the graphite peak from carbon. Scanning electron microscope (SEM) images verified that Fe–TiO₂ was immobilized onto the GAC. In UV photocatalysis, the interaction between Fe and TiO₂ loading and initial alachlor concentration is significant wherein low Fe–TiO₂ loading and 50 ppm initial alachlor concentration increased the removal efficiency. In visible light photocatalysis, low Fe–TiO₂ loading and initial alachlor concentrations of 30 and 70 ppm are significant. The interactions of the initial solution pH with Fe–TiO₂ loading and initial alachlor concentration are also significant in which low solution pH increased alachlor removal for low Fe–TiO₂ loading and low initial concentration. The highest alachlor removal percentages obtained were 99.74 and 99.96% under UV and visible light irradiation, respectively. Total organic carbon analysis confirmed the mineralization of alachlor with 92.44 and 66.49% removal by UV and visible light photocatalysis, respectively.

Keywords:

• Alachlor
• Box–Behnken design
• Fe–TiO₂
• Granular activated carbon support
• Photocatalysis

Acknowledgments

The authors would like to thank the National Research Council of Thailand (NRCT) Fund 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.