Eudragit®-PEG Nanoparticles: Physicochemical Characterization and Interfacial Tension Measurements

The objectives of this study are to understand the mechanisms involved in the stabilization of water/oil interfaces by polymeric nanoparticles (NPs) (Eudragit®). Eudragit L100 NPs of various sizes and Zeta potentials were studied and compared at a water/cyclohexane model interface using a droplet tensiometer (Tracker Teclis, Longessaigne, France). The progressive interfacial adsorption of the NPs in the aqueous phase was monitored by tensiometry. The model interface was maintained and observed in a drop tensiometer, analyzed via axisymmetric drop shape analysis (ADSA), to determine the interfacial properties. Given the direct relationship between the stability of Pickering emulsions (emulsions stabilized by solid nanoparticles) and the interfacial properties of these layers, different nanoparticle systems were compared. Specifically, Eudragit NPs of different sizes were examined. Moreover, the reduction of the Zeta potential with PEG-6000 induces partial aggregation of the NPs (referred to as NP flocs), significantly impacting the stability of the interfacial layer. Dynamic surface tension measurements indicate a significant decrease in interfacial tension with Eudragit® nanoparticles (NPs). This reduction correlates with the size of the NPs, highlighting that this parameter does not operate in isolation. Other factors, such as the contact angle and wettability of the nanoparticles, also play a critical role. Notably, larger NPs further diminished the interfacial tension. This study enhances our understanding of the stability of Pickering emulsions stabilized by Eudragit® L100 polymeric nanoparticles.

Molecular design and applications of a nanostructure green Tripodal surface active ionic liquid in enhanced oil recovery: Interfacial tension reduction, wettability alteration, and emulsification

Surface active ionic liquids (SAILs) are considered as prominent materials in enhanced oil recovery thanks to their high interfacial activity. This study reports the preparation and applications of a nanostructure Tripodal imidazolium SAIL as an environmentally-friendly substitute to the conventional surfactants. The product has a star-like molecular structure centered by a triazine spacer, namely [(C_(4)im)_(3)TA][Cl_(3)], prepared by a one-step synthesis method and characterized with FT-IR, NMR, XRD, and SEM analysis methods. The interfacial tension of the system was decreased to about 78% at critical micelle concentration of less than 0.08 mol·dm^(−3). Increasing temperature, from 298.2 to 323.2 K, improved this capability. The solid surface wettability was changed from oil-wet to water-wet and 80% and 77% stable emulsions of crude oil–aqueous solutions were created after one day and one week, respectively. Compared to the Gemini kind homologous SAILs, the superior effects of the Tripodal SAIL were revealed and attributed to the strong hydrophobic branches in the molecule. The Frumkin adsorption isotherm precisely reproduced the generated IFT data, and accordingly, the adsorption and thermodynamic parameters were determined.

Interactions of ferro-nanoparticles(hematite and magnetite) with reservoir sandstone: implications for surface adsorption and interfacial tension reduction

There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy(strength) and adsorption of Fe2 O3 and Fe3 O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy(XPS) were used to monitor interaction of silicate species with Fe2 O3 and Fe3 O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3 O4 nanofluid,suggesting the intense adsorption of the Fe3 O4 with the crude oil.The measured IFT for brine/oil,Fe2 O3/oil and Fe3 O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3 O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2 O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3 O4 in reducing IFT.

Prediction of surface and interfacial tension based on thermodynamic data and CALPHAD approach

In this article, following a brief introduction concerning experimental measurements of surface and interfacial tensions, methods for calculating surface tension and surface segregation for binary, ternary, and multicomponent high-temperature melts based on Bulter＇s original treatment [ 1] and on available physical properties and thermodynamic data, especially excess Gibbs free energies of bulk phase and surface phase versus temperature obtained from thermodynamic databases using the calculation of phase diagram （CALPHAD） approach, with special attention to the model parameter β, have been described. In addition, the geometric models can be extended to predict surface tensions of multicom- ponent systems from those of sub-binary systems. For illustration, some calculated examples, including Pb-free soldering systems and phase-diagram evaluation of binary alloys in nanoparticle systems are given. On the basis of surface tensions of high-temperature melts, interracial tensions between liquid alloy and molten slag as well as molten slag and molten matter can be calculated using the Girifalco-Good equation [2]. Modifications are suggested in the Nishizawa＇s model [3] for estimation of interracial tension in liquid metal （A）/ceramics （MX） systems so that the calculations can be carried out based on the sublattice model and thermodynamic data, without deliberately differentiating the phase of MX at high temperature. Finally, the derivation of an approximate expression for predicting interfacial tension between the high-temperature multicomponent melts, employing Becker＇s model [4] in conjunction with Bulter＇s equation and inteffacial tension data of the simple systems is described, and some examples concerning pyrometallurgical systems are given for better understanding.

Effect of active species in crude oil on the interfacial tension behavior of alkali/synthetic surfactants/crude oil systems

The effect of active species present in crude oil on the interfacial tension （IFT） behavior of alkali/synthetic surfactants/crude oil systems was studied. The system consisted of heavy alkyl benzene sulfonate, sodium chloride, sodium hydrate and Daqing crude oil. Experimental results indicated that active species would diffuse from oil/aqueous interface to aqueous phase and finally an equilibrium could be reached in the system with increasing contact time. Moreover, the minimum IFT and equilibrium IFT values increased with increasing contact time and a linear relationship existed between dynamic IFT and f^-1/2 when IFT value approaching the minimum and after the minimum IFT was reached. This indicated that the dynamic IFT-time behavior was diffusion controlled. The oil and aqueous phases were analyzed by infrared （IR） spectroscopy. IR spectra of oil and aqueous phases illustrated that the content of active species in the oil phase decreased, but the content of active species in the aqueous phase increased after alkali reacted with crude oil. This indicated that the active species present in oil played an important role in reducing IFT.

Study of Oil/Water Interfacial Tension of Vacuum Residual Fractions from Iranian Light Crude Oil

The vacuum residual from Iranian Light crude oil are separated into a series of 16 narrow fractions according to the molecular weight by the supercritical fluid extraction and fractional (SFEF) technology. The chemical element and the UV spectrum of each fraction are analyzed. The effects of several factors on the interfacial tension are investigated, which are the fraction concentration in oil phase, the ratio of oil component, the salts dissolved in the water phase and the pH value. The interfacial tension decreases rapidly as the concentration of the residual fraction in the oil increases, showing a higher interfacial activity of the fraction. The interfacial tension changes, as the amount of absorption or the state of the fractions in the interface changes resulting from different ratios of oil, different kinds or concentrations of salts in water, and different pH values. It is concluded that the interfacial tension changes regularly, corresponding to the regular molecular parameters of the vacuum residual fractions.

INTERFACIAL TENSION BETWEEN SLAG AND COPPER MATTE

The interfacial tension between FeO-CaO-SiO_2-MgO system slag and Cu-Fe-S system matte was determinated by the X-ray radiograph sessile drop method.The effects of FeO/SiO_2 ratio in the slag,contents of CaO,FeO,ZnO and CaF_2 in the slag on interracial tension and the relation of inter facial tension with the grade of matte and temperature have been studied.The floatation coefficient and film coefficient of slag-matte system has been calculated and the mechanism of the transition of iron and oxygen from slag to matte has also been discussed.

Substrate elastic deformation due to vertical component of liquid-vapor interfacial tension

Young＇s equation is a fundamental equation in capillarity and wetting, which reflects the balance of the horizontal components of the three interracial tensions with the contact angle （CA）. However, it does not consider the vertical component of the liquid-vapor interracial tension （VCLVIT）. It is now well understood that the VCLVIT causes the elastic deformation of the solid substrate, which plays a significant role in the fabrication of the microfluidic devices because of the wide use of the soft materials. In this paper, the theoretical, experimental, and numerical aspects of the problem are reviewed. The effects of the VCLVIT-induced surface deformation on the wetting and spreading, the deflection of the microcantilever, and the elasto.capillarity and electro- elasto.capillarity are discussed. Besides a brief review on the historical development and the recent advances, some suggestions on the future research are also provided. Key words

Determination of interfacial tension and viscosity under dripping flow in a step T-junction microdevice

Microfluidic approaches for the determination of interfacial tension and viscosity of liquid-liquid systems still face some challenges.One of them is liquid-liquid systems with low interfacial and high viscosity,because dripping flow in normal microdevices can’t be easily realized for the systems.In this work,we designed a capillary embedded step T-junction microdevice to develop a modified microfluidic approach to determine the interfacial tension of several systems,specially,for the systems with low interfacial tension and high viscosity.This method combines a classical T-junction geometry with a step to strengthen the shear force further to form monodispersed water/oil(w/o)or aqueous two-phase(ATP)droplet under dripping flow.For systems with low interfacial tension and high viscosity,the operating range for dripping flow is relative narrow whereas a wider dripping flow operating range can be realized in this step Tjunction microdevice when the capillary number of the continuous phase is in the range of 0.01 to 0.7.Additionally,the viscosity of the continuous phase was also measured in the same microdevice.Several different systems with an interfacial tension from 1.0 to 8.0 m N·m^(-1) and a viscosity from 0.9 to 10 m Pa·s were measured accurately.The experimental results are in good agreement with the data obtained from a commercial interfacial tensiometer and a spinning digital viscometer.This work could extend the application of microfluidic flows.

Toward accurate density and interfacial tension modeling for carbon dioxide/water mixtures

Phase behavior of carbon dioxide/water binary mixtures plays an important role in various CO2-based industry processes. This work aims to screen a thermodynamic model out of a number of promising candidate models to capture the vapor–liquid equilibria, liquid–liquid equilibria, and phase densities of CO2/H2O mixtures. A comprehensive analysis reveals that Peng–Robinson equation of state (PR EOS) (Peng and Robinson 1976), Twu α function (Twu et al. 1991), Huron–Vidal mixing rule (Huron and Vidal 1979), and Abudour et al. (2013) volume translation model (Abudour et al. 2013) is the best model among the ones examined;it yields average absolute percentage errors of 5.49% and 2.90% in reproducing the experimental phase composition data and density data collected in the literature. After achieving the reliable modeling of phase compositions and densities, a new IFT correlation based on the aforementioned PR EOS model is proposed through a nonlinear regression of the measured IFT data collected from the literature over 278.15–477.59 K and 1.00–1200.96 bar. Although the newly proposed IFT correlation only slightly improves the prediction accuracy yielded by the refitted Chen and Yang (2019)’s correlation (Chen and Yang 2019), the proposed correlation avoids the inconsistent predictions present in Chen and Yang (2019)’s correlation and yields smooth IFT predictions.

White-box machine-learning models for accurate interfacial tension prediction in hydrogen-brine mixtures

The severity of climate change and global warming necessitates the need for a transition from traditional hydrocarbon-based energy sources to renewable energy sources.One intrinsic challenge with renewable energy sources is their intermittent nature,which can be addressed by transforming excess energy into hydrogen and storing it safely for future use.To securely store hydrogen underground,a comprehensive knowledge of the interactions between hydrogen and residing fluids is required.Interfacial tension is an important variable influenced by cushion gases such as CO_(2) and CH4.This research developed explicit correlations for approximating the interfacial tension of a hydrogen–brine mixture using two advanced machine-learning techniques:gene expression programming and the group method of data handling.The interfacial tension of a hydrogen–brine mixture was considered to be heavily influenced by temperature,pressure,water salinity,and the average critical temperature of the gas mixture.The results indicated a higher performance of the group method of data handling-based correlation,showing an average absolute relative error of 4.53%.Subsequently,Pearson,Spearman,and Kendall methods were used to assess the influence of individual input variables on the outputs of the correlations.Analysis showed that the temperature and the average critical temperature of the gas mixture had considerable inverse impacts on the estimated interfacial tension values.Finally,the reliability of the gathered databank and the scope of application for the proposed correlations were verified using the leverage approach by illustrating 97.6%of the gathered data within the valid range of the Williams plot.

Variation of meniscus shape and initial steel solidification under different steel-slag interfacial tension in continuous casting mold of slab

A two-dimensional model was applied to investigate the influence of the interfacial tension between the steel and the slag on the behavior of the meniscus in continuous casting mold of slab.The shape of the meniscus and phenomena near the meniscus were revealed,and the profile of the slag rim and the depth of the solidified meniscus and oscillation marks with different interfacial tension of the steel and slag were compared.With the increase in the interfacial tension,the size of the curved meniscus increased,while the curvature and the height of the local meniscus close to the mold decreased.Besides,the thickness of the slag rim,solid slag and total slag near the meniscus had the tendency to increase,and the bottom of the slag rim became lower and thicker.With the increase in the interfacial tension from 0.1 to 2.5 N/m,the location of the largest heat flux near the meniscus decreased from 10.0 to 2.5 mm above the initial level of the steel,and the largest heat flux was within 3.52-4.58 MW/m^(2).Meanwhile,the largest depth of the solidified meniscus decreased from 3.3 to 2.3 mm,and the depth of oscillation marks decreased,which was conducive to the shallow hook at the subsurface of the slab,and the improvement of surface cleanliness of the slab.

Renewable non-edible oils derived long chain (C24.1) bio-based zwitterionic surfactant with ultralow interfacial tension between crude oil and formation brine

A new ultra-long chain monounsaturated 4-(N-nervonicamidopropyl-N,N-dimethylammonium)butane sulfonate(NDAS)zwitterionic surfactant with ultralow interfacial tensions was developed through the modification of nervonic acid derived from renewable non-edible seed oils by a simple and effective method.Its structure was characterized by ESI-HRMS,1 H NMR,and 13 C NMR.NDAS surfactant exhibited a strong interfacial activity(~10^(-4) mN/m)between the crude oil and the formation brine at a very low surfactant dosage(0.05 g/L)and at high salinity conditions,which is equivalent to 2%(w/w)of dosage of the most traditional surfactants used in the enhanced oil recovery field.Meanwhile,at a very low concentration(0.05 g/L),NDAS demonstrated strong NaCl compatibility up to 100 g/L,Ca^(2+)ions compatibility up to 200 mg/L,and temperature stability up to 90℃.The surface tension,emulsification,and biodegradability parameters were also evaluated.This work consolidates our hypothesis that increasing the hydrophobic chain length of a surfactant certainly contributes to the high interfacial activity and good compatibility of salts and temperatures.Hence,it will facilitate the design of a sustainable alternative to petroleum-based chemicals to develop bio-based surfactants and extend the domain of bio-based surfactants to new applications such as in enhanced oil recovery(EOR).

Study on the Mechanism of Asphaltenes Reducing Oil-Water Interfacial Tension

As high polar components of crude oil, asphaltenes play a significant role in reducing oil-water interfacial tension(IFT). In this paper, the effects of asphaltenes on reducing IFT in the presence of surfactant were compared, and the mechanism of asphaltenes reducing the IFT was studied by the dynamic interfacial tension(DIFT) equation. Whether asphaltenes were added to the oil or 2,5-dimethyl-4-(4-dodecyl) benzene sodium sulfonate(p-S14-4) was added to the water phase, either of all results in the IFT reducing and the IFT is related to the coverage and the mass of asphaltenes adsorption at the interface. In the presence of asphaltenes, the adsorption of the active substances to the interface is not entirely dependent on diffusion, and the process can be divided into three regions. Region I: the IFT rapidly reducing, this process is controlled by diffusion of surfactant;Region II: the IFT reducing slowly, resulted from the lower diffusion rate that is limited due to the aggregates formed by the interaction of asphaltene-asphaltene;Region III: the interaction of asphaltene-asphaltene is broken by the interaction of surfactant-asphaltene. The asphaltene aggregates are reduced and adsorbed rapidly at the interface. Furthermore, the results reveal that the asphaltenes concentration affects the coverage rate and adsorption at the interface.

Liquid-liquid interfacial tension of equilibrated mixtures of ionic liquids and hydrocarbons

Ionic liquids are possible alternative solvents for the separation of aromatic and aliphatic hydrocarbons by liquid-liquid extrac- tion. Interfacial tension is an important property to consider in the design of liquid-liquid extraction processes. In this work, the liquid-liquid interfacial tension and the mutual solubility at 25 ℃ have been measured for a series of biphasic, equilibrated mixtures of an ionic liquid and a hydrocarbon. In particular, the ionic liquids 1-alkyl-3-methylimidazolium bis（trifluorome- thanesulfonyl）imide （with the alkyl substituent being ethyl, hexyl or decyl）, 1-ethyl-3-methylimidazolium ethylsulfate, and 1-ethyl-3-methylimidazolium methanesulfonate have been selected, as well as the hydrocarbons benzene, hexane, ethylben- zene, and octane. The selected sets of ionic liquids and hydrocarbons allow the analysis of the influence of a series of effects on the interfacial tension. For example, the interfacial tension decreases with an increase in the length of the alkyl substituent chain of the cation or with an increase of the degree of charge delocalisation in the anion of the ionic liquid. Also, the interfa- cial tension with the aromatic hydrocarbons is markedly lower than that with the aliphatic hydrocarbons. A smaller effect is caused by variation of the size of the hydrocarbon. Some of the observed trends can be explained from the mutual solubility of the hydrocarbon and the ionic liquid.

Oil-water interfacial tension, wettability alteration and foaming studies of natural surfactant extracted from Vernonia Amygdalina

Surfactant flooding is an enhanced oil recovery(EOR)method for recovering residual oil in the reservoir through mechanism of interfacial tension(IFT)reduction and wettability alteration.Due to toxicity and high cost associated with conventional surfactants,recent research has focussed on developing low-cost and environmentally benign surfactants.Herein,a low-cost green surfactant is extracted from Vernonia Amygdalina(VA)and appraised for EOR applications.The extracted surfactant was characterized using Fourier Transform Infrared(FTIR)and High-Pressure Liquid Chromatography(HPLC).The IFT of the synthesized surfactant at the oil-water interface was determined using Kruss tensiometer.Additionally,the foam stability of the synthesized surfactant was examined.Moreover,the wettability of the saponin based natural surfactant(SBNS)at the rock-fluid interface was analysed using Dataphysics drop shape analyser.Experimental result revealed that SBNS(1 wt%concentration)stabilized foam for longer periods with half-life of 1100 min.Furthermore,the synthesized surfactant was effective in lowering the IFT of oil-water interface from 18 mN/m to 0.97 mN/m.Finally,SBNS altered the wettability of sandstone cores to water-wetting condition by reducing the contact angle from 118.5° to 45.7°.Overall,SBNS exhibit excellent properties desirable for EOR and thereby recommended as supplementary alternative to conventional surfactants.

Effects of synthesized nanoparticles and Henna-Tragacanth solutions on oil/water interfacial tension:Nanofluids stability considerations

Rising global energy demand has encouraged engineers to create and design new methods to improve oil recovery from reservoirs.In this study,feasibility of using Henna extract as a natural surfactant and synthesized nanoparticles(Titanium dioxide(TiO2),Silicon dioxide(SiO2),Graphene and composite of TiO2-Graphene)for reduction of oil-water interfacial tension has been experimentally investigated.Nanoparticles were synthesized via sol-gel method and XRD,FESEM,EDAX and FTIR tests were conducted to confirm the authenticity of this synthesizing materials.Nano-surfactants were stabled with a natural water-based suspending surfactant called Tragacanth extract,which could be introduced as a practical substitute for industrial nanoparticles'stabilizers in oil industry.After CMC determination of Henna extract surfactant,the optimal concentration of Tragacanth extract surfactant,with the purpose of nano-surfactants’stabilization,was determined through particle size and zeta potential tests.Results of interfacial tension(IFT)measurements showed that the increase of Henna extract concentration from 0 wt%to 10 wt%reduced IFT between kerosene and water from 37.23 to 15.24 mN/m.Furthermore,adding 1 wt%of synthesized TiO2 nanoparticle to the Henna extract surfactant at its CMC value reduced IFT from 18.43 to 14.57 mN/m.As an impact of this significant reduction in IFT value,oil recovery factor could be improved drastically during EOR operations.Results proved that TiO2 nano-surfactant was as effective as industrial surfactants,which put human's and environment's health at risk and impose heavy economic strain on governments.

Experimental Study of the Effect of Strong Alkali on Lowering the Interfacial Tension of Oil/Heavy Alkylbenzene Sulfonates System

Experimental studies were conducted to explore the fundamental mechanisms of alkali to lower the interfacial tension of oil/heavy alkylbenzene sulfonates （HABS） system. Sodium hydroxide was used as the strong alkali chemical to investigate the interracial tension （IFT） of oil/HABS system. The influences of salt and alkali on the interracial activity were studied by the measurement of interfacial tension and partition coefficient. Moreover, the al- kali/surfactant solutions were measured by dynamic laser scattering. The results showed that compared with the salt, the function of alkali to lower the interfacial tension and improve partition coefficient is more significant. The mi- celles formed by surfactants could be disaggregated because of adding alkali, so the size of micelles decreases and the number of mono-surfactants increases, then more surfactant molecules move to the interface of oil/surfactant system and the adsorption of surfactants at oil-water interfaces increases, which can lead to the decrease of IFT.

Eco-friendly calcium alginate microspheres enable enhanced profile control and oil displacement

Polymer microspheres(PMs),such as polyacrylamide,have been widely applied for enhanced oil recovery(EOR),yet with environmental concerns.Here,we report a microfluid displacement technology containing a bio-based eco-friendly material,i.e.,calcium alginate(CaAlg)microspheres for EOR.Two dominant mechanisms responsible for EOR over Ca Alg fluid have been verified,including the microscopic oil displacement efficacy augmented by regulating capillary force(determined by the joint action of interfacial tension and wettability between different phases)and macroscopic sweep volume increment through profile control and mobility ratio reduction.This comprehensive effectiveness can be further impacted when the CaAlg microsphere is embellished ulteriorly by using appropriate amount of sodium dodecyl sulfonate(SDS).The core flooding and nuclear magnetic resonance(NMR)tests demonstrate that CaAlg-SDS microsphere can balance the interphase property regulation(wettability alteration and IFT reduction)and rheology properties,enabling simultaneous profile control and oil displacement.Excessive introduction of SDS will have a negative impact on rheological properties,which is not favored for EOR.Our results show that the involvement of 4-m M SDS will provide the best behavior,with an EOR rate of 34.38%.This cost-effective and environmentally-friendly bio-microspherebased microfluidic displacement technology is expected to achieve“green”oil recovery in future oilfield exploitation.

Interfacial assembly of two-dimensional MXenes

Two-dimensional(2D) transition metal carbides, carbonitrides and nitrides, known as MXenes, are emerging quickly at the frontiers of 2D materials world. Their exotic properties such as the highest electrical conductivity among all solution-processed 2 D materials, the best electromagnetic interference shielding performance outperforming that of copper or aluminum at a nanoscale thickness, as well as the highest volumetric capacitance for pseudocapacitors, have been attracting extensive fundamental research and applications. Their unique surface chemistries, that is, hydrophilic groups terminated on the surface of MXenes after etching and delamination, enable plenty of opportunities for assembling into MXene building blocks. Particularly, assembling at liquid–liquid, liquid–solid, liquid–air, and solid–solid interfaces allows the efficient fabrication of various structures, including MXene surfactants, MXene heterostructures, MXene transparent films. Interfacial assembly of MXenes is of significance in unveiling more versatilities of MXenes as well as impacts on novel MXene-based architectures, based on which enhanced performance of devices is achieved. As such, this review focuses on the interfacial assembly of MXenes, explaining mechanisms behind various assembling and providing classical examples for corresponding interfacial assembling techniques. Applications of these as-assembled architectures are also discussed in brief. We believe this review may shed light on the interfacial chemistry of MXenes, thus guiding more efficient fabrication of MXene-based functional films/coatings/electrodes/devices.