Graphene oxide nanoparticles and hematite colloids behave oppositely in their co-transport in saturated porous media

• Published in: Chemosphere (Oxford) 2021-02, Vol.265, p.129081, Article 129081
• Main Authors: Wang, Mengjie, Zhang, Haojing, Chen, Weifeng, Lu, Taotao, Yang, Huihui, Wang, Xinhai, Lu, Minghua, Qi, Zhichong, Li, Deliang
• Format: Article
• Language: English
• Subjects: Colloids; Ecosystem; Ferric Compounds; Graphene oxide; Graphite; Hematite; Nanoparticles; Osmolar Concentration; Porosity; Sand; Silicon Dioxide; Solution chemistry; Transport
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.129081

Since iron oxide minerals are ubiquitous in natural environments, the release of graphene oxide (GO) into environmental ecosystems can potentially interact with iron oxide particles and thus alter their surface properties, resulting in the change of their transport behaviors in subsurface systems. Column experiments were performed in this study to investigate the co-transport of GO nanoparticles and hematite colloids (a model representative of iron oxides) in saturated sand. The results demonstrated that the presence of hematite inhibited GO transport in quartz sand columns due to the formation of less negatively charged GO-hematite heteroaggregates and additional deposition sites provided by the adsorbed hematite on sand surfaces. Contrarily, GO co-present in suspensions significantly enhanced the transport of hematite colloids through different mechanisms such as the increase of electrostatic repulsion, decreased physical straining, GO-facilitated transport of hematite (i.e., highly mobile GO nanoparticles served as a mobile carrier for hematite). We also found that the co-transport behaviors of GO and hematite depended on solution chemistry (e.g., pH, ionic strength, and divalent cation (i.e., Ca2+)), which affected the electrostatic interaction as well as heteroaggregation behaviors between GO nanoparticles and hematite colloids. The findings provide an insight into the potential fate of carbon nanomaterials affected by mineral colloids existing in natural waters and soils. [Display omitted] •Hematite inhibited GO mobility by heteroaggregation and providing retention sites.•GO significantly enhanced hematite transport through multi-mechanisms.•Highly mobile GO acted as a carrier of hematite colloids.•Low pH or high ionic strength decreased the mobility of both particles.•Ca2+ magnified transport-enhancement effect of GO on hematite transport.