Surfactant-influenced transport of graphene and graphene oxide in saturated porous media

Graphene is a single-layer carbon nanomaterial that has drawn significant attention for a variety of applications. The industrial production of graphene is projected to increase greatly in the coming years. However, little is known about its transport and fate in the environment. In this study, miscible-displacement experiments were conducted to investigate the transport and retention of graphene and graphene oxide in sand and/or Vinton soil. Graphene was dispersed into a surfactant solution, producing a final graphene concentration of 2 mg/L. The breakthrough curves for surfactant-dispersed graphene and graphene oxide transport exhibited typical colloid transport behavior, with breakthrough at 1 pore volume (PV) and steady-state plateaus at relative concentrations less than 1. The effluent relative-concentration plateau increased slowly towards 1, indicating the existence of a colloid blocking phenomenon. Greater retention was observed in Vinton soil compared to the sand. In addition, retention was greater at lower pore-water velocity and in the presence of SDBS versus Tween. Graphene oxide displayed a higher mobility compared to graphene. The study presents to our knowledge the first attachment efficiency coefficients for surfactant-dispersed graphene transport.