Enhanced Transport of Phenanthrene and 1-Naphthol by Colloidal Graphene Oxide Nanoparticles in Saturated Soil

Abstract

With the increasing production and use of graphene oxide, the environmental implications of this new carbonaceous nanomaterial have received much attention. In this study, we found that the presence of low concentrations of graphene oxide nanoparticles (GONPs) significantly enhanced the transport of 1-naphthol in a saturated soil, but affected the transport of phenanthrene to a much smaller extent. The much stronger transport-enhancement effect on 1-naphthol was due to the significant desorption hysteresis (both thermodynamically irreversible adsorption and slow desorption kinetics) of GONP-adsorbed 1-naphthol, likely stemmed from the specific polar interactions (e.g., H-bonding) between 1-naphthol and GONPs. Increasing ionic strength or the presence of Cu(II) ion (a complexing cation) generally increased the transport-enhancement capability of GONPs, mainly by increasing the aggregation of GONPs and thus, sequestering adsorbed contaminant molecules. Interestingly, modifying GONPs with Suwannee River humic acid or sodium dodecyl sulfate had little or essentially no effect on the transport-enhancement capability of GONPs, in contrast with the previously reported profound effects of humic acids and surfactants on the transport-enhancement capability of C60 nanoparticles. Overall, the findings indicate that GONPs in the aquatic environment may serve as an effective carrier for certain organic compounds that can interact with GONPs through strong polar interactions.

Cotransport of Cu with Graphene Oxide in Saturated Porous Media with Varying Degrees of Geochemical Heterogeneity

“…This is because the presence of Cu 2+ increased the ζ-potential (less negative) and the hydrodynamic diameter (Dh) of GO (Table 1), and subsequently reduced GO transport in porous media, which is in accordance with the literature [18,21]. Likewise, Qi et al [37] demonstrated that Cu 2+ ions increased the aggregation of GO, thereby generally increasing the transport-enhancement capability of GO. In the presence of GO, the breakthrough of total ( Figure S3a), dissolved ( Figure S3b), and GO-facilitated (GO-F) Cu (Figure 4b) followed the same trend, exhibiting decreased migration and even retardant behavior as ω increased from 0 to 0.45, compared to sole Cu 2+ transport in the column ( Figure S4).…”

Environmental transformation of natural and engineered carbon nanoparticles and implications for the fate of organic contaminants

“…2). 52,106,107 CNP attachment generally decreases with increasing negative surface charge. Biochar-derived pCNPs, which contain the most O-functional groups and negative surface charge could therefore form more mobile pCNPs than less oxidized pCNPs.…”

“…For instance, oxidation of CNPs can result in negatively charged contaminants being repulsed electrostatically from the negatively charged CNP surfaces. 11,94 However, polar compounds sorbed to CNPs by hydrogen bonds will become more strongly bound with an increase in surface O-functional groups (e.g., following oxidation of the CNPs) 107 and sorption can decrease with the disappearance of these functional groups (e.g., following reduction of the CNPs). 11 Such enhanced or inhibited polar interactions between polar contaminants (e.g., 1-naphthol) and CNPs can then determine the extent of facilitated transport of contaminants by CNPs.…”

Predicting colloid transport through saturated porous media: A critical review

“…Colloids can also enhance the transport of dissolved contaminants in groundwater via their sorption onto colloid surfaces. Colloid‐facilitated transport has been studied for a wide range of contaminants including radionuclides [e.g., Kersting et al ., ; Novikov et al ., ], hydrocarbons [e.g., Qi et al ., ], and pesticides [e.g., de Jonge et al ., ; Sprague et al ., ]. Research in this area includes modeling the reduction in contaminant retardation [ Corapcioglu and Jiang , ; Johnson et al ., ; Flury and Qiu , ].…”