Graphene oxide-facilitated transport of Pb 2+ and Cd 2+ in saturated porous media.

This paper provides an overview of the effect of graphene oxide (GO) on sorption, transport, and remobilization of Pb2+ and Cd2+ ions in saturated porous media. The affinity of GO to Pb2+ and Cd2+ ions was investigated via kinetic and isothermal sorption experiments. Laboratory packed-column experiments were also conducted to investigate the cotransport of Pb2+ and Cd2+ ions with GO across a quartz sand matrix. In addition, the Pb2+ - and Cd2+ -preequilibrated sand column was sequentially flushed with GO to test its remobilization effect on these ions. GO exhibited a high affinity toward both Pb2+ and Cd2+ ions with maximum sorption capacities of 1428.57 and 911.43mgg-1 , respectively. On the other hand, while GO improved the transport ability of Pb2+ and Cd2+ , both ions reduced the mobility of GO in saturated porous media. Data from the elution experiment revealed that the high affinity of GO toward the metal ions led to the remobilization of the presorbed Pb2+ and Cd2+ ions onto the quartz sand surfaces and their concurrent migration across the sand column. XDLVO (Extended Derjaguin-Landau-Verwey-Overbeek) calculations were employed to interpret the GO transport behavior in the column wells. The cotransport of Pb2+ and Cd2+ ions with GO in the saturated quartz sand was successfully simulated by the advection-dispersion-reaction equation. Findings from this study provide an insight on the potential implications of remobilization and spread of pollutants by nanomaterials existing in vulnerable ecosystems.