Molecular Dynamics Study on the Mechanism of Graphene Oxide to Destabilize Oil/Water Emulsion

Lan, Tu; Zeng, Hongbo; Tang, Tian

doi:10.1021/acs.jpcc.9b05906

Cited by 36 publications

(20 citation statements)

References 62 publications

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“…Another nonionic surfactant simulated was polyethylene glycol oleyl ether Brij-93 (C 22 H 44 O 3 , MW: 357 g/mol), as shown in Figure c where the hydrophilic group is highlighted. Force field parameters of the three molecules were validated in our previous works and directly adopted. − Briefly, chemical structures for the nonionic surfactants were drawn in ChemDraw Prime 16.0. The geometry and force field parameters were optimized using Gaussian 16 at the B3LYP/6-31G + (d,p) level, with partial charge calculated with CHELPG (CHarges from ELectrostatic Potentials using a Grid based method) .…”

Section: Methodsmentioning

confidence: 99%

Unraveling the Interaction of Water-in-Oil Emulsion Droplets via Molecular Simulations and Surface Force Measurements

et al. 2021

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Water-in-oil emulsions widely exist in various chemical and petroleum engineering processes, and their stabilization and destabilization behaviors have attracted much attention. In this work, molecular dynamic (MD) simulations were conducted on the water-in-oil emulsion droplets with the presence of surface-active components, including a polycyclic aromatic compound (VO-79) and two nonionic surfactants: the PEO 5 PPO 10 PEO 5 triblock copolymer and Brij-93. At the surface of water droplets, films were formed by the adsorbate molecules that redistributed during the approaching of the droplets. The redistribution of PEO 5 PPO 10 PEO 5 was more pronounced than that of Brij-93 and VO-79, which contributed to lower repulsion during coalescence. The interaction forces during droplet coalescence were also measured using atomic force microscopy. Jump-in phenomenon and coalescence were observed for systems with VO-79, Brij-93, and a low concentration of Pluronic P123. The critical force before jump-in was lowest for the low concentration of Pluronic P123, consistent with the MD results. Adhesion was measured when separating water droplets with a high concentration of Pluronic P123. By correlating theoretical simulations and experimental force measurements, this work improves the fundamental understanding on the interaction behaviors of water droplets in an oil medium in the presence of interface-active species and provides atomic-level insights into the stabilization and destabilization mechanisms of water-in-oil emulsion.

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Section: Methodsmentioning

confidence: 99%

Unraveling the Interaction of Water-in-Oil Emulsion Droplets via Molecular Simulations and Surface Force Measurements

et al. 2021

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“…The organic solvents were represented by heptane and toluene. The topologies for VO-79, quartz surface, heptane, and toluene were generated and validated in our previous work ,,− and directly adopted here.…”

Section: Methodsmentioning

confidence: 99%

Temperature-Induced Transition from Indirect to Direct Adsorption of Polycyclic Aromatic Hydrocarbons on Quartz: A Combined Theoretical and Experimental Study

Lan

Liu

Zeng

et al. 2020

Ind. Eng. Chem. Res.

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Adsorption of polycyclic aromatic hydrocarbons (PAHs) on mineral surfaces plays an important role in many engineering fields, such as oil recovery and oil sand production. In this work, the adsorption behaviors of a PAH compound, violanthrone-79 (VO-79), on quartz surface were investigated at different temperatures by molecular dynamics (MD) simulation and atomic force microscopy (AFM). Our simulations demonstrated that with increasing temperature, the rate of adsorption increased, whereas the total amount of stably adsorbed VO-79 molecules hardly changed. On the other hand, the adsorption mode had a strong dependence on the temperature. At 323 K, approximately half of the adsorbed VO-79 formed a monolayer with their polyaromatic cores directly contacting and parallel to the quartz surface. The other half were in an aggregated form and adsorbed indirectly, via interaction with directly adsorbed molecules. The polyaromatic cores of VO-79 in the aggregates tend to be oriented slant to the surface. A transition from indirect to direct adsorption was observed as temperature increased, and nearly 90% of VO-79 molecules were adsorbed in direct form at 523 K. AFM imaging confirmed the observations in the MD simulations, showing that smaller and more uniformly distributed VO-79 aggregates adsorbed on the surface with increasing temperature. This work provides valuable insights, at the molecular level, into the effect of temperature on the adsorption of PAHs on mineral surfaces.

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“…Currently, it is relatively difficult to investigate the properties of GO nanoparticles at liquid–liquid interfaces solely through experiments. As an alternative to experimental methods, molecular simulation has become a powerful tool for studying the interfacial behavior at molecular level. − …”

Section: Introductionmentioning

confidence: 99%

Molecular Insight into the Adsorption Thermodynamics and Interfacial Behavior of GOs at the Liquid–Liquid Interface

Yang

2021

J. Phys. Chem. B

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The adsorption of two-dimensional (2-D) graphene oxide (GO) nanosheets at liquid−liquid interfaces has broad technological implications from functional material preparations to oil−water emulsification. Molecular-level understanding of the adsorption thermodynamics and the interfacial behavior is of great significance. Here, the adsorption free energy of GO nanosheets at the water−cyclohexane system was simulated, in which the effect of oxygencontaining groups and deprotonation has been investigated. It was observed that the neutral GO (GO−COOH) has obvious interfacial activity with a reduction of interfacial tension, while the deprotonated GO (GO−COO − ) shows a weak interface affinity. There exists an optimal oxidization degree that could cause the best interfacial stability, which is attributed to the balance of interfacial hydrophilic−hydrophobic interactions. The interaction arising from water is the main factor determining interfacial activity. The interfacial morphology and dynamics of GO nanosheets have also been simulated, in which an anisotropic 2-D translation and rotation along the interface were revealed. Our simulation results provide new insight into the adsorption mechanism and dynamics behavior of GO at the oil−water interface.

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Molecular Dynamics Study on the Mechanism of Graphene Oxide to Destabilize Oil/Water Emulsion

Cited by 36 publications

References 62 publications

Unraveling the Interaction of Water-in-Oil Emulsion Droplets via Molecular Simulations and Surface Force Measurements

Unraveling the Interaction of Water-in-Oil Emulsion Droplets via Molecular Simulations and Surface Force Measurements

Temperature-Induced Transition from Indirect to Direct Adsorption of Polycyclic Aromatic Hydrocarbons on Quartz: A Combined Theoretical and Experimental Study

Molecular Insight into the Adsorption Thermodynamics and Interfacial Behavior of GOs at the Liquid–Liquid Interface

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