Interaction of graphene oxide nanoparticles with quartz sand and montmorillonite colloids.

Graphene oxide (GO) nanomaterials are used extensively in a wide range of commercial applications. With GO production growing rapidly, it is expected that GO eventually could reach sensitive environmental systems, including subsurface formations, where montmorillonite, one of the most common minerals, is in abundance. This study examines the interaction of GO with quartz sand and montmorillonite (MMT) colloids at pH = 7, ionic strength IS  = 2 mM, and 25°C, under dynamic conditions. Moreover, the effect of pH on MMT kinetic attachment onto quartz sand was investigated. The experimental data suggested that pH affected slightly the attachment of MMT colloids onto quartz sand. GO was attached in greater amounts onto MMT than quartz sand. Also, the attachment of GO onto quartz sand was shown to increase slightly in the presence of MMT colloids. However, when GO and MMT coexisted, the total GO mass attached onto quartz sand, suspended MMT, and attached MMT was increased. Furthermore, the equilibrium attachment experimental data were fitted nicely with a Freundlich isotherm, and the attachment kinetics were satisfactorily described with a pseudo-second-order model. Finally, the extended DLVO (XDLVO) theory was used to quantify the various interaction energy profiles based on electrokinetic and hydrodynamic measurements.