Effects of graphene oxides on transport and deposition behaviors of bacteria in saturated porous media

Abstract

The effects of graphene oxides on the transport and deposition behaviors of bacteria (Gram-negative Escherichia coli and Grampositive Bacillus subtilis) in quartz sand were investigated in both NaCl and CaCl2 solutions at pH 6.5. Both breakthrough curves and retained profiles of bacteria in the absence and presence of GO under all examined solution conditions were obtained. The results demonstrated that for both types of bacteria, the presence of GO increased the transport and decreased the deposition of bacteria at both low (10 mM) and high ionic strengths (50 mM) in NaCl solutions. However, opposite observations were achieved at different ionic strengths in CaCl2 solutions. Particularly, GO facilitated the transport and inhibited the deposition of bacteria in 1 mM CaCl2 solutions, while they suppressed the transport of bacteria in 2.5 mM CaCl2 solutions. Clearly, the cell transport and deposition behaviors in porous media would be greatly influenced by the GO copresent in suspensions. Furthermore, we found that with GO copresent in suspensions, the transport and deposition behaviors of bacteria were highly associated with those of GO. The heteroaggregation of bacteria and GO also contributed to the decreased cell transport in 2.5 mM CaCl2 solutions. This study showed that GO copresent in suspensions could act as mobile carriers for bacteria transport in porous media, leading to the alteration of cell transport and deposition behaviors.