Aggregation and resuspension of graphene oxide in simulated natural surface aquatic environments

Hua, Zulin; Tang, Zhiqiang; Bai, Xue; Zhang, Jianan; Yu, Lu; Cheng, Haomiao

doi:10.1016/j.envpol.2015.05.039

Cited by 93 publications

(33 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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.…”

Section: Effect Of Ionic Strength On Go Aggregationsupporting

confidence: 84%

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

et al. 2016

View full text Add to dashboard Cite

Broad applications of graphene oxide (GO) will result in the release of GO into aquatic environments, where clay minerals and metal (hydr)oxides are commonly present. Thereby the interactions between GO and a binary system containing clay minerals and metal (hydr)oxides can occur. We investigated the aggregation of GO with kaolinite and kaolinite-goethite associations (KGAs) in aquatic systems under different pHs, ionic strengths, and GO concentrations. GO suspension was unstable at low pHs, and the aggregation of GO occurred in the presence of KGA-4% and KGA-10% until pH 5 and 6, respectively. Kaolinite decreased the critical coagulation concentration (CCC) of GO at pH 5.5 from around 50 to 20 mM NaCl due to the reduced energy barrier. Heteroaggregation of GO with KGAs was extremely sensitive to ionic strength at pH 5.5, and the CCC of GO in the presence of KGA-10% increased from less than 1 mM NaCl to 5 mM NaCl with the increase of pH from 5.5 to 9. The heteroaggregation extent of GO with KGAs was enhanced firstly, then reduced with the increase of GO concentrations at pH 5.0, which is likely because KGA plates were more efficiently wrapped by large-size GO sheets with increasing GO concentrations. These findings are useful for understanding and predicting the fate of GO in the relatively complicated aquatic and soil environments where binary minerals co-exist.

show abstract

Section: Effect Of Ionic Strength On Go Aggregationsupporting

confidence: 84%

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

et al. 2016

View full text Add to dashboard Cite

show abstract

“…21 One should consider the fact that their estimation is for a GO−water−quartz system and should not be employed for a GO−water−GO system (the mistake that has been made in recent literature on GO aggregation studies). 7,27,28 The H for GO and rGO across the different liquids is also calculated and presented in Table 1. It must be noted that eq 3 is derived for two atomically thin sheets, but the values obtained above are valid for two semiinfinite slabs.…”

Section: ■ Theoretical Basismentioning

confidence: 99%

Colloidal Stability of Graphene Oxide: Aggregation in Two Dimensions

2016

View full text Add to dashboard Cite

Colloidal stability of graphene oxide (GO) is studied in aqueous and organic media accompanied by an improved aggregation model based on Derjaguin-Landau-Verwey- Overbeek (DLVO) theory for ultrathin colloidal flakes. It is found that both magnitude and scaling laws for the van der Waals forces are affected significantly by the two-dimensional (2D) nature of GO. Experimental critical coagulation concentrations (CCC) of GO in monovalent salt solutions concur with DLVO theory prediction. The surface charge density of GO is largely affected by pH. However, theoretical calculations and experimental observations show that the colloidal stability of the 2D colloids is less sensitive to the changes in the surface charge density compared to the classical picture of 3D colloids. The DLVO theory also quantitatively predicts the colloidal stability of reduced GO (rGO). The origin of lower stability of rGO compared to GO is rooted in the higher van der Waals forces among rGO sheets, and particularly, in the removal of negatively charged groups, and possibly formation of some cationic groups during reduction. GO also exfoliates in the polar organic solvents and results in stable dispersions. However, addition of nonpolar solvents perturbs the colloidal stability at a critical volume fraction. Analyzing the aggregation of GO in mixtures of different nonpolar solvents and N-methyl-2-pyrrolidone proposed that the solvents with dielectric constants of less than 24 are not able to host stable colloids of GO. However, dispersions of GO in very polar solvents shows unexpected stability at high concentration (>1 M) of salts and acids. The origin of this stability is most probably solvation forces. A crucial parameter affecting the ability of polar solvents to impart high stability to GO is their molecular size: the bigger they are, the higher the chance for stabilization.

show abstract

“…[2][3][4][5][6][7] Graphene nanosheets may end up in the environment in various forms of particulate matter such as crumpled graphene, [8][9][10] multilayer graphene, 4,5,11 shattered nanosheets, 12 and fractal aggregates/hetero-aggregates. 13,14 Once they have entered aquatic environments, aggregation of such particles can significantly affect their functionality and transport behaviour, particularly in aqueous and porous media. 4,5,15 Despite the existence of many studies on homo-and hetero-aggregation of various nanoparticles (NP), 14,[16][17][18][19][20][21] and abundant reports on the impacts of various factors on the aggregation behaviour of these NP, [22][23][24][25][26] it still remains a problem of how system dynamics modify aggregation.…”

Section: Introductionmentioning

confidence: 99%

Aggregation and sedimentation of shattered graphene oxide nanoparticles in dynamic environments: a solid-body rotational approach

Babakhani

Bridge

Phenrat

et al. 2018

Environ. Sci.: Nano

View full text Add to dashboard Cite

Nanoparticle (NP) aggregation is typically investigated in either quiescent or turbulent mixing conditions; neither is fully representative of dynamic natural environments. In groundwater, complex interacting influences of advective-diffusive transport, pore tortuosity, and the arrival of aggregates from up-gradient pores impacts the aggregation behaviour of NPs, whereas in surface waters, continuous mixing of fresh particle and aged aggregate populations amends aggregation rates. To mimic such conditions, a cylinder reactor containing shattered graphene oxide NP (<100 nm) suspension was set to rotate with a Reynolds number (Re) close to one and with zero shear. Two main aggregation phases were then observed. Up to 250-350 min, NP remained near the rotational axis longer than in static conditions, giving rise to higher aggregation rates interpreted as an enhanced perikinetic aggregation and differential sedimentation due to mixing with resuspending aggregates. In this phase, a population-balance model estimated an attachment efficiency >5 times in the rotating system than in the static system. Later (5-13 h) aggregates collided with extensively each other, broke, and reformed on the rotating cylinder wall giving rise to larger, denser aggregates (>1 cm). These results thus shed new light on the differences in aggregation behaviour between porous media and other natural environmental systems compared to quiescent batch experiments.As production and application of graphene-based nanomaterials increase and taking into consideration their potential for environmental clean-up, concerns about their transport and fate in the environment are growing. A better understanding under realistic environmental conditions is required, in about process of aggregation which plays a fundamental role in long-term fate of nanomaterials, to help developing predictive models for managing the release of these nanomaterials. To investigate the impact of environmental dynamics on the aggregation processes of shattered graphene oxide nanoparticles, this study uses a solid-body rotational approach to mimic dynamics of interacting populations of nanoaggregate with different sizes and structures. This sheds light on the greater aggregation rates observed in the aquatic environments such as groundwater and surface water systems compared to those observed in simplifying laboratory batch experiments.

show abstract

Aggregation and resuspension of graphene oxide in simulated natural surface aquatic environments

Cited by 93 publications

References 57 publications

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

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

Colloidal Stability of Graphene Oxide: Aggregation in Two Dimensions

Aggregation and sedimentation of shattered graphene oxide nanoparticles in dynamic environments: a solid-body rotational approach

Contact Info

Product

Resources

About