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A magnetic demulsifier, denoted M-Gn-PAMAM (n = 1, 2, 3), was synthesized by reacting polyamidoamine (PAMAM) dendrimers with Fe3O4@SiO2. The characteristics of magnetic nano-polymer were investigated via using XRD analysis, FT-IR, TEM, and VSM methods. The as-prepared M-Gn-PAMAM was highly effective at removing oil from wastewater produced from ASP flooding, with a maximum oil removal rate of 94% at 60 °C. Furthermore, the regeneration experiments illustrated that M-Gn-PAMAM could be readily recovered by an external magnetic field and it could be recycled up to 9 times without a significant loss in demulsification efficiency. In conclusion, the magnetic demulsifier synthesized in this study could be a promising nanomaterial for use in emulsified oil-water separation. [ABSTRACT FROM AUTHOR]

The in situ activation of silica nanoparticles (NPs) by adsorption of an anionic surfactant, nonylphenol-substituted decylsulfonate (C10-NPAS), has been studied. The mechanism whereby such NPs stabilize foams has been elucidated. Traditional static foam tests were carried out, focusing on the influence of stirring intensity on the stability characteristics of the foams. A freezing method has been applied for the first time to fix aqueous foams, and an anticipated mechanism has been verified. It was found that higher stirring intensity results in a finer foam and thinner foam lamellae, and the distribution of NPs is inhomogeneous therein. The foam stabilizing effect of NPs is more noticeable for thinner foam films. The anticipated mechanism, whereby partial aggregation of nano-SiO2 is beneficial to foam stability, has been verified by observing SEM images. Due to the strong hydrogen bonds interactions, C10-NPAS has the ability to activate NPs in situ and to stabilize negative charge thereon, making it potentially applicable in oilfields. The obtained results may expedite the development of super-long-term stable foams and potential application of NPs in enhanced oil recovery technology. [ABSTRACT FROM AUTHOR]

In this paper, molecular dynamics simulation methods were used to investigate salt effects on micellization of N-Dodecyl-N,N-Dimethyl-3-Ammonio-1-Propane-sulfonate (SB12-3) in aqueous solution. It is proved that micelle shapes transform from spherical to prolate spherical shape after 30.0 ns simulation with different NaCl and CaCl2 concentration. By comparison with the eccentricity value without salt addition, SB12-3 shows salt tolerance behaviors due to its unique “inner salt” structure of amphiphilic surfactant. Radial distribution function (RDF), hydrophobic groups solvent accessible surface area (SASA), hydrogen bond, and the deuterium order parameter (SCD) are to elucidate salt effects on SB12-3 micelle formation. The radius of micelle is achieved by the related RDF value and in accordance with other researches. The addition of NaCl and CaCl2 didn’t change the structure of micelle significantly and have little effects on the interactions between SB12-3 and water molecule. By comparison with the results without salt system, SASA of hydrophobic groups is almost the same, and SASA of hydrophilic groups and total molecule fluctuates only slightly. This further indicates that the surface of micelles is more hydrophilic due to the strong interactions between SB12-3 and water molecules. The existence of NaCl and CaCl2 will enhance the hydrophilic interactions. [ABSTRACT FROM AUTHOR]

The dentritic quaternary ammonium salt-type tetrameric surfactant (4C12tetraQ) was synthesized, and the molecular structure was confirmed by 1H NMR and FTIR. The surface activity of 4C12tetraQ was investigated by surface tension, and surface chemical parameters, such as critical micelle concentration (cmc), efficiency (pC20), effectiveness (πcmc), the surface tension value at cmc (γcmc), minimum surface area (Amin), maximum surface excess (Γmax), and cmc/C20 were obtained from the measurement results. The results show that the 4C12tetraQ surfactant has higher surface activity than the traditional monomeric surfactants (dodecyl trimethyl ammonium bromide, DTAB). The Krafft points were taken as <0°C, indicating that the synthesized tetrameric surfactants had good water solubility. Free energies of micellization and adsorption show that 4C12tetraQ display greater propensity to absorb at the interface than form micelle in the bulk of the aqueous solution, and that the two processes are spontaneous. The measurement results show that 4C12tetraQ has good emulsification power and foam performance. The corrosion efficiency was evaluated with the loss weight method in 1 mol/L HCl solution, and the results show that the 4C12tetraQ surfactant has good corrosion inhibition, and can be considered as a corrosion inhibitor. [ABSTRACT FROM AUTHOR]

First-principle calculations based on the density functional theory (DFT) are implemented to study the structural and electronic properties of the SiS2/WSe2 hetero-bilayers. It is found that the AB-2 stacking model is most stable among all the six SiS2/WSe2 heterostructures considered in this work. The AB-2 stacking SiS2/WSe2 hetero-bilayer possesses a type-II band alignment with a narrow indirect band gap (0.154 eV and 0.738 eV obtained by GGA-PBE and HSE06, respectively), which can effectively separate the photogenerated electron–hole pairs and prevent the recombination of the electron–hole pairs. Our results revealed that the band gap can be tuned effectively within the range of elastic deformation (biaxial strain range from −7% to 7%) while maintaining the type-II band alignment. Furthermore, due to the effective regulation of interlayer charge transfer, the band gap along with the band offset of the SiS2/WSe2 heterostructure can also be modulated effectively by applying a vertical external electric field. Our results offer interesting alternatives for the engineering of two-dimensional material-based optoelectronic nanodevices. [ABSTRACT FROM AUTHOR]