Graphene oxide-facilitated transport of Pb2+ and Cd2+ in saturated porous media

This paper provides an overview of the effect of graphene oxide (GO) on sorption , transport, and remobilization of Pb 2+ and Cd 2+ ions in saturated porous media. The affinity of GO to Pb 2+ and Cd 2+ ions was investigated via kinetic and isothermal sorption experiments. Laboratory packed-column experiments were also conducted to investigate the cotransport of Pb 2+ and Cd 2+ ions with GO across a quartz sand matrix. In addition, the Pb 2+ - and Cd 2+ -preequilibrated sand column was sequentially flushed with GO to test its remobilization effect on these ions. GO exhibited a high affinity toward both Pb 2+ and Cd 2+ ions with maximum sorption capacities of 1428.57 and 911.43   mg   g −1 , respectively. On the other hand, while GO improved the transport ability of Pb 2+ and Cd 2+ , 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 Pb 2+ and Cd 2+ 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 Pb 2+ and Cd 2+ 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.