Calcium-facilitated adsorption and precipitation of bacteria on the graphene oxide surface

Efficient removal of bacteria from aqueous environments is a hot research topic. Graphene oxide (GO) has been widely used due to its antimicrobial properties and high surface activity. However, GO alone could not remove bacteria from the aqueous environment through aggregation and precipitation. In this study, CaCl2 (Ca2+) was introduced into the process of bacterial removal by GO due to the negative charge on the surface of the removed bacteria (Sporosarcina pasteurii). The introduction of Ca2+ leads to the re-accumulation of GO layers, and the proportion of oxygen-containing functional groups in GO increases significantly. AFM and zeta potential results indicate a reduction in the negative charge on the GO surface in the presence of Ca2+, which reduces the electrostatic repulsion to bacteria. This leads to a gradual increase in the attractiveness of the GO surface and the adsorption of more bacteria. Ca2+ acts as a bridge, facilitating the sedimentation of GO and bacteria, resulting in the removal of bacteria from the water environment. The removal efficiency of GO against bacteria increased as the concentration of Ca2+ increased.