Transport of graphene oxide in saturated porous media: Effect of cation composition in mixed Na–Ca electrolyte systems

Biofilms and extracellular polymeric substances mediate the transport of graphene oxide nanoparticles in saturated porous media

“…These general observations can be ascribed, in part, to the consistent increase of surface zeta potentials (less negative) and hydrodynamic diameters (Table 1), induced by ascending solution salt concentrations. The enhanced retention of GONPs by high IS coincides well with previous studies [7][8][9][10]13].…”

“…To date, several studies have been performed to investigate the influence of environmentally relevant physicochemical factors such as solution chemistry (e.g., pH, ionic strength, and ionic composition) [7][8][9], flow velocity [10], collector properties [11,12] and saturation degree [13] on the transport and deposition kinetics of graphene oxide nanoparticles (GONPs) in laboratory-scale packed column or using a quartz crystal microbalance with dissipation (QCM-D). These published studies have demonstrated that GONPs mobility is strongly influenced by the coupling of these physicochemical factors.…”

“…These published studies have demonstrated that GONPs mobility is strongly influenced by the coupling of these physicochemical factors. Specifically, the mobility of GONPs generally increased with decreasing ionic strength (IS) and increasing grain size, flow velocity, and moisture content [7][8][9][11][12][13], whereas pH changes (e.g., 5.1-9.0) showed negligible impact on the transport of GONPs [10]. Nonetheless, the roles of biofilm and extracellular polymeric substances (EPS) that occur ubiquitously in aquatic environments, on the transport of GONPs have not yet been examined.…”

Effect of co-existing kaolinite and goethite on the aggregation of graphene oxide in the aquatic environment

“…The critical coagulation concentration (CCC) of NaCl for GO aggregation in the absence of minerals was around 50 mM, being in agreement with the previous studies (Chowdhury et al, 2013;Zhao et al, 2015). According to the DLVO theory (Chowdhury et al, 2014b; Evans and Wennerstr€ om, 1999; Fan et al, 2015;Hua et al, 2015), the aggregation mechanisms are as follows: When IS below the CCC, the decrease of electrical double layer repulsion between GO sheets was improved by the increase of IS (Chen and Elimelech, 2007), which can be evidenced by the increase of EPM and the decrease of energy barrier with IS (Figs. S13 and S14A), thus, an increase of IS promoted the aggregation extent of GO (Shih et al, 2012); However, with IS above the CCC, almost all GO charges were screened and the aggregation rate of GO reached a maximum and became independent of the IS, correspondingly, the EPM showed little change with increasing IS, when IS was above 50 mM (Fig.…”

Effects of clay minerals on transport of graphene oxide in saturated porous media

“…The increasing production and use of graphene oxide make its environmental release highly probable, and the environmental fate and transport of this new material have received much attention. However, certain divalent cations (such as Ca 2 ) may significantly hinder the transport of graphene oxide by enhancing its retention via cation bridging between graphene oxide and porous media [3,4]. These studies show that graphene oxide exhibits relatively high mobility in saturated porous media, under environmentally relevant conditions.…”