Electroactive Bacteria Accelerate the Degradation of Gallic Acid by Nano Iron Minerals and Its Mechanism
Iron-based catalysts are widely used in water pollution treatment due to their high stability and redox capabilities. However, conventional single-component iron-based catalytic systems face challenges such as slow reaction kinetics and low efficiency in generating reactive oxygen species (ROS) during organic pollutant degradation. In this study, three electroactive bacteria (Bacillus megaterium, Lactococcus lactis, and Shewanella putrefaciens) were selected to interact with nano-Fe3O4 to construct bacterial/Fe3O4 hybrid materials, accelerating the degradation of gallic acid. The results showed that bacterial interaction with Fe3O4 facilitated rapid electron transfer, enhancing gallic acid degradation. The bacterial/Fe3O4 hybrid materials exhibited significantly higher gallic acid degradation rates compared to Fe3O4 alone. This improvement was mainly attributed to the ability of electroactive bacteria to promote the formation of oxygen vacancies (OVs) on the Fe3O4 surface, accelerating electron transfer and subsequently enhancing the generation of ROS, including hydroxyl radicals, superoxide radicals, and singlet oxygen. Correlation analysis demonstrated a significant positive relationship between OVs and ROS generation, with hydroxyl radicals showing the highest correlation with the gallic acid degradation rate constant (r = 0.98), indicating its dominant role in gallic acid degradation; the hydroxyl radicals quenching experiment also verified its dominant role. Additionally, due to the temperature sensitivity of bacteria, the degradation rate of gallic acid reached its peak in the temperature range of 30–40 °C. This study reveals the mechanism by which electroactive bacteria enhance the catalytic activity of Fe3O4, providing a new strategy for its application in advanced oxidation technology for water pollution treatment.