The removal and transformation of fipronil using a photoelectrochemical device combined with a carbonized TiO2 nanocomposite electrode

Fipronil has been a critical environmental concern due to its potential risks to aquatic environments. However, research on the effective removal of fipronil using photoelectrochemical (PEC) devices is still limited. This study represents the pioneering application of a PEC device for the efficient removal of pesticides. A carbonized titanium dioxide nanocomposite electrode was employed as the electrode in the PEC device. The extent of fipronil degradation in the PEC device was also monitored. The PEC device demonstrated higher efficiencies than the reported oxidation treatments. The applied voltage and illumination from the light source initiated the formation of various reactive species, which exhibited the ability to degrade fipronil in the PEC device. Importantly, the presence of singlet oxygen and ozone in the PEC device was demonstrated for the first time, providing new insights into the degradation mechanism in the PEC system. Furthermore, this study unveiled four byproducts that were previously unreported. The presence of fipronil chlorinated byproducts in the device resulted in the generation of reactive chlorine species, which contributed to fipronil decomposition. When the detoxification of fipronil was compared between the PEC and electrochemical devices, the PEC device demonstrated higher degradation efficiencies and more effective detoxification, providing valuable insight into removing pesticides. Novelty statement: The degradation of fipronil and the identification of its degradation byproducts, along with toxicity testing, have been extensively investigated. Previous studies have indicated that many oxidation processes for fipronil degradation lead to the formation of byproducts with higher toxicity or require extended periods to reduce toxicity. In this study, a photoelectrochemical advanced oxidation process was applied for the first time to degrade pesticides. The developed PEC degradation process demonstrated the ability to rapidly remove fipronil and effectively reduce its toxicity, showing significant potential for various applications. Furthermore, our research revealed the formation of singlet oxygen and ozone in a PEC degradation system, providing novel insights into the degradation mechanism within the PEC system. Utilizing the carbonized titanium dioxide nanocomposite electrode developed in this study, successful fipronil decomposition was achieved for the first time through a PEC device.