Molecular Insights in the Structure and Layered Assembly of Polyelectrolytes at the Oil/Water Interface

Robertson, Ellen J.; Richmond, Geraldine L.

doi:10.1021/jp5068022

Cited by 35 publications

(40 citation statements)

References 92 publications

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“…Khanamiri et al 24 demonstrated that Ca 2+ is conductive to lower IFT and changes the oil-water interfacial elastic modulus. Some technologies have been proposed to investigate the oil-water interface, such as surface second harmonic generation, 25 small-angle neutron scattering 26 and vibrational sum-frequency spectroscopy, 27 but the dynamics of ions or molecules near the interface are not fully addressed. The molecular dynamics (MD) method which can be used to obtain the detailed microscopic structures is a powerful tool to investigate the macroscopic properties of the oil-water interface with the applicability of the statistical mechanics.…”

Section: Introductionmentioning

confidence: 99%

Ionic hydration-induced evolution of decane–water interfacial tension

Wen

Sun

Bai

et al. 2017

Phys. Chem. Chem. Phys.

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bcBuilding a connection between the variations in interfacial tension and the microstructure of the oil-water interface is still very challenging. Here, we employ a molecular dynamics method to study the effect of monovalent ions on the decane-water interfacial tension and reveal the relationship between ionic hydration and the variation of interfacial tension. Our results indicate that interfacial tension presents a non-monotonic dependence on the ionic concentrations owing to the distinctive adsorption characteristics of ions. At low ionic concentrations, the hydration of the discrete ions at the interface causes an enhancement in the virial term of the interfacial tension, resulting in an increase of the interfacial tension with increasing ionic concentrations. At high ionic concentrations, the ion pairs at the interface weaken the ionic hydration, thus the virial term of the interfacial tension decreases and the interfacial tension decreases slightly. In addition, the kinetic energy term of interfacial tension increases only with increasing temperature, while the virial term decreases with an increase in either temperature or pressure on account of the weakening ionic hydration; therefore, the increase of temperature and pressure induces different degrees of the decrease in the interfacial tension owing to the major contribution of the virial term, particularly at high ionic concentrations.

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Section: Introductionmentioning

confidence: 99%

Ionic hydration-induced evolution of decane–water interfacial tension

Wen

Sun

Bai

et al. 2017

Phys. Chem. Chem. Phys.

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“…Previous measurements on polyacrylic acid (PAA) at water/air and water/oil interface also showed a high sensitivity of the degree of accumulation at the surface on the pH value. 25,[53][54][55] For PAA solutions, it was observed that increasing the bulk pH led to polymer depletion from the surface because of the relative increase of carboxylate anion groups with respect to the COOH. In this context, it is remarkable and surprising that in the case of hyaluronan, depletion from the surface occurs upon lowering of the pH value.…”

Section: Effect Of Ph On the Surface Accumulation Of Hyaluronanmentioning

confidence: 99%

The molecular structure and surface accumulation dynamics of hyaluronan at the water/air interface

Moll

Giubertoni

Versluis

et al. 2021

Preprint

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Hyaluronan is a biopolymer that is essential for many biological processes in the human body, like the regulation of tissue lubrication and inflammatory responses. Here we study the behavior of hyaluronan at aqueous surfaces using heterodyne-detected vibrational sum-frequency generation spectroscopy (HD-VSFG). We find that high molecular weight hyaluronan (>1 MDa) does not come to the surface, even hours after addition of the polymer to the aqueous solution. In contrast, low molecular weight hyaluronan (~150 kDa) gradually covers the water-air interface within hours, leading to a negatively charged surface and a reorientation of the interfacial water 1molecules. This strong dependence on the polymer molecular weight can be explained from entanglements of the hyaluronan polymers. We also find that the migration kinetics of hyaluronan in aqueous media shows an anomalous dependence on the pH of the solution, which can be explained from the interplay of hydrogen-bonding and electrostatic interactions of the hyaluronan polymers.

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“…It has been reported that the adsorption of HPAM on the oil-water interface increases the steric barriers of dispersed oil droplets, which leads to the enhanced stability of oil/water emulsion [16,[26][27][28]. Polymers (such as polystyrene sulfonate sodium, PSS) have the ability to form complexes with the oppositely charged molecules (such as hexadecanetrimethyl-ammonium bromide, CTAB) by electrostatic attraction or hydrophobic interaction [29,30].…”

Section: Interfacial Tension and Dilational Rheology Analysis Of The mentioning

confidence: 99%

Pilot Performance of Chemical Demulsifier on the Demulsification of Produced Water from Polymer/Surfactant Flooding in the Xinjiang Oilfield

Dong

Gao

et al. 2018

Water

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Purification of produced water (PW) from polymer/surfactant flooding is a challenge for the petroleum industry due to the high emulsion stability. Demulsification using chemical demulsifiers has been expected to be an effective way to treat PW. In this paper, five cationic (branched quaternary ammonium chloride) and four nonionic (copolymer of propylene oxide and ethylene oxide) demulsifiers with different molecular weights were employed to test their respective demulsification performance in the treatment of PW from polymer/surfactant flooding. The cationic demulsifiers, in general, exhibited better performance than the nonionic ones and one cationic demulsifier (CP-1) exhibiting the best demulsification efficiency was further employed for a pilot experiment in the Xinjiang Oilfield. The oil content of PW could be successfully reduced from 128~7364 to less than 10 mg/L with a dosage of CP-1 for 350 mg/L and polyaluminum chloride (PAC, 30% w/w Al2O3) for 500 mg/L under ambient temperature (14~22 °C). At the same time, partially hydrolyzed polyacrylamide (HPAM) was removed from 176.9~177.1 to 2.8~3.9 mg/L while petroleum sulfonate was not removed too much (from 35.5~43.8 to 25.5~26.5 mg/L). The interfacial rheology analysis on simulated PW from HPAM/petroleum sulfonate flooding revealed that the addition of CP-1 led to a significant increase of the oil-water interfacial tension (from 7 to 15~20 mN/m) and zeta potential (from −32.5 to −19.7 mV). It was, thus, assumed that the decreased net charge on the dispersed oil droplets surface and weakened oil/water film due to the formation of complex between the cationic demulsifier and HPAM may have facilitated the destabilization of the emulsion. The result of this study is useful in better understanding the demulsification processes as well as selecting suitable demulsifiers in the treatment of PW from polymer/surfactant flooding.

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Molecular Insights in the Structure and Layered Assembly of Polyelectrolytes at the Oil/Water Interface

Cited by 35 publications

References 92 publications

Ionic hydration-induced evolution of decane–water interfacial tension

Ionic hydration-induced evolution of decane–water interfacial tension

The molecular structure and surface accumulation dynamics of hyaluronan at the water/air interface

Pilot Performance of Chemical Demulsifier on the Demulsification of Produced Water from Polymer/Surfactant Flooding in the Xinjiang Oilfield

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