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Increasing production and application of nanomaterials lead to their environmental release possible. The nanomaterials with different properties may transport together in porous media, and consequently affect their environmental fates. In this study, column experiments were conducted to investigate the co-transport of two typical nanomaterials, graphene oxide (GO) and nano-titanium dioxide (nTiO 2), in saturated quartz sand in NaCl and CaCl 2 electrolyte solutions under both favorable and unfavorable conditions. The breakthrough curves as well as the retained profiles of single and binary nanoparticles were examined. The results indicated that nTiO 2 significantly enhanced the GO retention under all examined conditions, especially at lower pH, higher ionic strength and the presence of divalent cation Ca2+. This might be attributed to the formation of less negatively charged and larger-sized GO-nTiO 2 agglomerates as well as the increased retention sites on sand surface by preferentially deposited nTiO 2. However, GO merely slightly enhanced the transport of nTiO 2 in NaCl solutions, whereas had negligible effect on nTiO 2 transport and retention in CaCl 2 solutions. The highly hydrophilic and mobile GO served as a carrier and facilitated the transport of nTiO 2 in NaCl solutions. In CaCl 2 solutions, the strong attachment affinity between positively charged nTiO 2 and negatively charged quartz sand (at pH 4.5), and dramatical accumulation of large nTiO 2 agglomerates near the column inlets (at pH 6.5) led to significant deposition of nTiO 2 on quartz sand. The co-presence of GO failed to counteract the retention of nTiO 2 particles on sand. Image 1 • nTiO 2 inhibited GO transport, especially at lower pH, higher ionic strength and the presence of Ca2+. • The formation of GO-nTiO 2 agglomerates and increased retention sites by deposited nTiO 2 decreased GO transport. • Highly hydrophilic and mobile GO slightly enhanced the transport of nTiO 2 in NaCl solutions. • GO had negligible effects on the transport of nTiO 2 in CaCl 2 solutions. Capsule : nTiO 2 significantly inhibits the transport of GO, whereas GO has slight or negligible enhancement effects on the transport of nTiO 2 in saturated quartz sand. [ABSTRACT FROM AUTHOR]

Cobalt disulfide (CoS 2 ) has been revealed as strong adsorption and activation sites for polar polysulfides, which effectively accelerates the redox reactions of polysulfides in lithium-sulfur (Li-S) batteries. As an ideal sulfur host, a three-dimensional (3D) graphene framework is adopted for high-performance Li-S batteries. Considering the special function of the CoS 2 nanoparticles and the advantages of a 3D porous graphene framework, a porous CoS 2 /reduced graphene oxide (CoS 2 /rGO) binder-free sulfur host is prepared by a bottom-up assembly and hydrothermal treatment. The porous rGO film is stacked by interconnected graphene sheets, and the CoS 2 nanoparticles are dispersed on the graphene sheets uniformly, which effectively obstructs the stacking of graphene sheets. As a binder-free sulfur host, the porous CoS 2 /rGO sulfur host combines the sufficient electron conductivity of the porous rGO framework and the sulfur immobilization interaction of the CoS 2 nanoparticles. This host material demonstrates an initial discharge capacity of 993.5 mAh g −1 and a capacity of 806.7 mAh g −1 after 110 cycles at 0.5 C. Both the capacity and cycling stability of the CoS 2 /rGO cathode were greatly improved over that of rGO. Furthermore, the bottom-up assembly approach provides a novel opportunity for preparing self-supporting graphene-based nanocomposite electrodes. [ABSTRACT FROM AUTHOR]

The transport behaviors of nanomaterials, in especial multifunctional nanohybrids have not been well disclosed until now. In this study, environmentally relevant conditions, including cation types, ionic strength and pH, were selected to investigate the transport and retention of graphene oxide-hematite (GO-Fe 2 O 3) nanohybrids and a photoaged product in saturated sandy columns. Results show that more hybridization of hematite led to decreased negative surface charge, while increased particle size and hydrophobicity of the nanohybrids, which depressed their transport according to extented Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. However, the inhibitory transport of photoaged nanohybrids was attributed to their distinct surface roughness caused by relatively high hybridization and photoirradiation. Notably the restrained transport was alleviated in the CaCl 2 saturated media, since the less surface O-functional groups of the corresponding nanohybrids reduced the cation bridging effect caused by Ca2+. Similarly, increasing pH promoted the transport of the nanohybrids in NaCl saturated media, particularly for the nanohybrids that contained rich O-functional groups, but exerted inconspicuous effect on mobility of the nanohybrids in CaCl 2 saturated media. These observations highlight that both XDLVO interactions and surface roughness may work together to impact the transport and fate of the burgeoning, versatile nanohybrids in the environment. [Display omitted] • Nanohybrids mobility decreased in the order of NH-Low > NH-High > rNH-High. • Hybridization led to less negative charge, larger particle size and hydrophobicity of the nanohybrids. • Irradiation-induced surface roughness aggravated the inhibitory transport of rNH-High. • Depressed transport of low O-functionalized NH-High and rNH-High was alleviated in CaCl 2. • Higher pH facilitated transport of nanohybrids in NaCl, but not in CaCl 2 electrolytes. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) and polystyrene nanoplastic (PSNP) are typical carbonaceous nanomaterials which likely co-exist in soil and sediment. Here, we describe the transport of GO, irradiation reduced GO (RGO) and PSNP in saturated quartz sand both in single and binary systems. In the single transport system, the materials exhibited mobility in the order of GO > RGO > PSNP, due to increased hydrophobicity and decreased negative surface charges. Nevertheless, the co-transport of (R)GO and PSNP in the binary transport system was much more intricate. In Na+ saturated porous media, PSNP preferred to interact with (R)GO relative to the highly negatively charged quartz sand, thus (R)GO carried PSNP to break through the sand column. However, in Ca2+ saturated porous media, the transport of both (R)GO and PSNP was depressed, attributed to the particle-collector and particle-particle bridging effects between Ca2+ and the metal-complexing moieties of the nanoparticles and sand grains. Moreover, GO influenced the co-transport of PSNP to a larger extent than RGO, especially at relatively high ionic strength, because of the more abundant surface O-functional groups on GO providing more complexion sites with Ca2+. These results demonstrated that the transport of negatively charged nanomaterials was greatly related to the hydrophobicity and surface O-functional groups. ga1 • The materials mobility followed the order of GO > RGO > PSNP, which obeyed EDLVO theory. • Highly mobile (R)GO facilitated the transport of PSNP in NaCl solutions. • PSNP decreased (R)GO mobility via narrowing pore throats and providing additional retention sites. • Inhibitory transport of (R)GO and PSNP occurred in CaCl 2 solutions due to cation bridging. • GO and RGO impacted PSNP mobility to varying degrees due to different O-functional groups contents. [ABSTRACT FROM AUTHOR]