Deposition and remobilization of graphene oxide within saturated sand packs.

In this research, we examined the deposition kinetics of graphene oxide (GO) particles within saturated sand packs as a function of ionic strength as well as the remobilization of previously retained GO particles due to chemical perturbation. The retention of GO particles within saturated quartz sand was found to be strongly dependent on ionic strength. At low ionic strength (e.g., 1 mM of NaCl), little retention of GO particles occurred. When the ionic strength was increased to 100 mM of NaCl, the retention of GO particles increased significantly but would be limited by its retention capacity. The reduction of ionic strength from 100 mM (NaCl) to 1 mM (NaCl) released ~100% of previously retained GO particles. The transport behavior of GO particles within saturated sand packs could be described by the Langmuir-type of transport model. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, which considers Lifshitz-van der Waals (LW) interaction, the electrostatic double layer (EDL) interaction as well as the Lewis acid-base (AB) (i.e., hydrophobic) interaction between GO plates and the surface of quartz sand, could explain the observed trend of GO retention under various ionic strength conditions.