Comparative performance and mechanism of bacterial inactivation induced by metal-free modified g-C3N4 under visible light: Escherichia coli versus Staphylococcus aureus

The inactivation mechanism of pathogenic microorganisms in water needs to be comprehensively explored in order to better guide the development of an effective and green disinfection method for drinking water safety. Here, metal-free modified g-C3N4 was prepared and used to inactivate two typical bacteria (namely, Gram-positive E. coli and Gram-negative S. aureus) in water under visible light from a comparative perspective. These two bacteria could be inactivated in the presence of modified g-C3N4 within 6 h of visible light, but their inactivation kinetics were quite different. E. coli were inactivated slowly in the early disinfection stage and rapidly in the later disinfection stage, whereas S. aureus were inactivated steadily during the entire disinfection process. Moreover, the impacts of important water parameters (pH, salt, temperature, and water matrix) on photocatalytic inactivation of E. coli and S. aureus were also distinct. In addition, scavenger experiments indicated that superoxide radicals played the most important role in E. coli inactivation, while both superoxide and hydroxyl radicals were important for S. aureus inactivation. Quantitative changes in fatty acids, potassium ions, proteins and DNA of the bacterial suspensions suggested that the higher resistance of E. coli in the early inactivation stage could be originated from the difference in the phospholipid repair system in cell membrane structures. This study can provide new insights into research and development of a safe and effective disinfection technology for drinking water. [Display omitted] •The inactivation performance and mechanism of E. coli and S. aureus was compared.•Photocatalytic inactivation kinetics of E. coli and S. aureus were quite distinct.•Water quality impacts on the inactivation of two kinds of bacteria were examined.•ROS played the different roles in the inactivation of E. coli and S. aureus.•Inactivation mechanisms of these two bacteria vary depending on their biomolecules.