Effect of modification degrees on the interfacial properties and EOR efficiency of amphiphilic Janus graphene oxide

Asymmetrically modified Janus graphene oxide(JGO)has attracted great attention due to its unique physical chemistry properties and wide applications.The modification degree of Janus nanosheets inevitably affects their interfacial activity,which is essential for their performances in enhanced oil recovery(EOR).In this study,the interfacial properties of Janus graphene oxide(JGO)with various modification degrees at liquid-liquid and liquid-solid interfaces were systematically evaluated via the measurements of interfacial tension(IFT),dilatational modulus,contact angle,and EOR efficiency was further assessed by core flooding tests.It is found that JGO-5 with higher modification degree exhibits the greater ability to reduce IFT(15.16 mN/m)and dilatational modulus(26 mN/m).Furthermore,JGO can construct interfacial and climbing film with the assistance of hydrodynamic power to effectively detach the oil from the rock surface and greatly enhance oil recovery.Moderately modified JGO-2 can highly improve recovery of residual crude oil(11.53%),which is regarded as the promising EOR agent in practical application.The present study firstly focuses on the effects of modification degrees on the JGO interfacial properties and proposes diverse EOR mechanisms for JGO with different modification degrees.

Spatially resolved micron-scale wrinkle structures at asphaltene films induced by mild thermal treatment and its impact on emulsion stability

Mild thermal treatment is an important partial upgrading technique to enable bitumen pipeline transportation,but no attention has been paid to the impact of mild thermal treatment on the emulsification behavior of emerging partially upgraded bitumen.Asphaltene compounds are active emulsion stabilizers in bitumen oil.The emulsion stabilizing capacity of bitumen asphaltenes was investigated,before and after a mild thermal treatment at 400℃.The structural morphology and mechanical property of the asphaltene interfacial films were analyzed by using a combination of cryo-SEM,Langmuir trough,and Brewster angle microscopy.The thermal treatment significantly enhanced the emulsion stabilizing capacity of bitumen asphaltenes;the interfacial films formed by the thermally treated asphaltene samples appeared to be rougher and thicker with more abundant micron-scale wrinkle structures.The interfacial corrugation may intensify the mechanical stability/flexibility of the asphaltene films and consequently strengthen the stability of emulsion droplet.

Studies on Middle-Phase Microemulsions of Green Surfactant n-Dodecyl Polyglucoside C_(12)G_(1.46)

The three-phase behavior in the quaternary system of n-dodecyl polyglucosideC_(12)G_(1.46)/1-butanol/cyclohexane/water has been studied at 40℃ in terms of the variables γ andδ. Increasing δ at constant γ causes a phase inversion from an oil-in-water microemulsion incontact with excess oil (winsor Ⅰ or 2) to a water-in-oil microemulsion in contact with excesswater (winsor Ⅱ or 2) via a middle-phase microemulsion in contact with excess oil and water (winsorⅢ or 3). By taking into account the different solubilities of alkyl pdyglucoside and 1-butanol inthe oil phase, the composition of the hydrophile-lipophile balanced interfacial film in the middleof the three-phase body can be calculated. The effects of different oils and aqueous media on thephase behavior and on the composition of the interfacial film and the efficiency for alkyipolyglucoside to make equal weights of water and oil to a single phase were investigated. It wasfound that the oil molecules with small molecular volumes can improve the solubilizing efficiency ofthe surfactant to form single-phase microemulsion. In inorganic salt (NaCl) and acid (HCl)solutions, less 1-butanol is needed than that in alkali (NaOH) solution to form middle-phasemicroemulsion.

Destructing surfactant network in nanoemulsions by positively charged magnetic nanorods to enhance oil-water separation

The separation of ultrafine oil droplets from wasted nanoemulsions stabilized with high concentration of surfactants is precondition for oil reuse and the safe discharge of effluent.However, the double barriers of the interfacial film and network structures formed by surfactants in nanoemulsions significantly impede the oil-water separation. To destroy these surfactant protective layers, we proposed a newly-developed polyethyleneimine micelle template approach to achieve simultaneous surface charge manipulation and morphology transformation of magnetic nanospheres to magnetic nanorods. The results revealed that positively charged magnetic nanospheres exhibited limited separation performance of nanoemulsions, with a maximum chemical oxygen demand(COD) removal of 50%, whereas magnetic nanorods achieved more than 95% COD removal in less than 30 s. The magnetic nanorods were also applicable to wasted nanoemulsions from different sources and exhibited excellent resistance to wide pH changes. Owing to their unique one-dimensional structure, the interfacial dispersion of magnetic nanorods was significantly promoted, leading to the efficient capture of surfactants and widespread destruction of both the interfacial film and network structure, which facilitated droplet merging into the oil phase. The easy-toprepare and easy-to-tune strategy in this study paves a feasible avenue to simultaneously tailor surface charge and morphology of magnetic nanoparticles, and reveals the huge potential of morphology manipulation for producing high-performance nanomaterials to be applied in complex interfacial interaction process. We believe that the newly-developed magnetic-nanorods significantly contribute to hazardous oily waste remediation and advances technology evolution toward problematic oil-pollution control.

Improvement in the Adhesion Between Electrode of a SOFC and Ag Paste as a Current Collector by Au Deposition

This paper reports the use of Au films to improve the performance of the stacked solid oxide fuel cell(SOFC) based on the characterization of the interface and the adhesion between the electrodes of the SOFCs and the Ag paste. The specimens were manufactured to perform the experiment as follows. A Si O2 wafer with a 300 mm notch was attached to the electrodes of a SOFC by a Ag paste and Au film, which were deposited on the electrodes by sputtering for 1 min or 5 min deposition time and annealed at300 C for 1 h. The four-point bending test was performed, which resulted in the formation of an extended crack at the tip on the wafer notch, and the crack propagation was observed using a stereo microscope equipped with a charge-coupled device(CCD). Consequently, the interfacial adhesion energy and the effect of the Au film between the each electrode and the Ag paste can be evaluated. On the cathode, the interfacial adhesion energy without Au film was 2.59 J/m2(upper value) and the adhesion energy increased to 11.59 J/m2(upper value) and 15.89 J/m2(lower value) with the Au film. On the anode,the interfacial adhesion energy without Au film was 1.74 J/m2(upper value), which increased to 11.07 J/m2(upper value) and 14.74 J/m2(lower value) with the Au film. In addition, the interface areas were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) to estimate the interface delamination.