Phosphate modified zerovalent iron enhances the interfacial hydrogen bond mediated adhesion and inactivation of Escherichia coli.

The microbe-surface interaction plays essential roles in various natural and anthropogenic water processes, and it is of great benefit to tailor their interfacial contact. For instance, zero-valent iron (ZVI) holds great promise as an emerging disinfection agent, but its efficiency remains limited due to the insufficient ZVI-bacteria contact. Herein we modified the surface of ZVI with potassium dihydrogen phosphate (KHPO) by ball milling (P-ZVI) to facilitate the close adhesion and inactivation of Escherichia coli (E. coli). ExDLVO simulation indicated the significantly alleviated Lewis acid-base repulsion between P-ZVI and E. coli due to the enhanced hydrogen bonding. ATR-FTIR spectra and DFT calculation suggested that the surface phosphate moiety could form dual hydrogen bonds with the amide domain of bacterial proteins (e.g., membrane proteins, pili, flagella, etc.), significantly shortening the length of hydrogen bonds from 1.784 to 1.781 and 1.646 Å. The enhanced adhesion of E. coli on P-ZVI lead to more pronounced oxidative stress and inactivation of the cells. Impressively, P-ZVI exhibited superior bactericidal efficiency of 99.2% in batch experiments, far surpassing that of ZVI (33.9%, p < 0.001). As a prototype of application, the sand column packed with P-ZVI continuously removed E. coli to below 100 CFU/mL from simulated groundwater. This study provided an effective and facile strategy of phosphorylation to modulate the ZVI-bacterium adhesion for contact sterilization, and may shed light on the development of novel disinfection techniques, and the design of biofilm carriers for wastewater treatment, etc.