Pendant Drop Method Research Articles

Interfacial tensions in the (CH4 + CO2 + H2O) system under two- and three-phase conditions

Interfacial properties of the (CH4 + CO2 + H2O) system are of great importance in many geotechnical engineering applications. In this study, we report the first experimental measurements of the interfacial tensions in the (CH4 + CO2 + H2O) system under both three-phase (VLLE) and biphasic conditions. The measurements were made by the pendant drop method. The compositions of the coexisting phases were obtained from a previous study of the phase behavior and the phase densities were then calculated from an equation of state. IFTs along five isotherms in the VLLE region and along six isotherms in biphasic region are reported. In the VLLE region, the IFT between the water-rich liquid and the gas phase varied between (33 and 39) mN·m−1, with a sharp increase as the pressure increased along an isotherm towards the upper critical end point. In the same region, the IFT between the water-rich and CO2-rich liquids varied between (30 and 33) mN·m−1. The IFT between the gas phase and the CO2-rich liquid phase was too small to measure accurately but an approximate value was obtained which is consistent with Antonov's equality. In the biphasic region, measurements were made at temperatures up to 423 K and at pressures up to 30 MPa. As observed in other water-gas systems, the IFT declines monotonically along isotherms with increasing pressure and decreases with increasing temperature at constant pressure.

Protic Imidazolium Cation-Based Ionic Liquids Show Unexpected Interfacial Properties.

Virtually, every investigation and application of ionic liquids (ILs) involves gas-liquid, liquid-liquid, and liquid-solid interactions. Therefore, understanding the behavior of ILs at those interfaces is critical. In this work, we studied the interfacial properties of protic and aprotic ILs with N-alkylimidazolium and 1-alkyl-3-methylimidazolium as cations and bis(trifluoromethylsulfonyl)imide, methanesulfonate, and trifluoromethanesulfonate as anions. The surface tension of these ILs is measured with the pendant drop method in a temperature range of 293.15-343.15 K and at atmospheric pressure. The contact angle measurements are performed at 293.15 K on three solid substrates: polytetrafluoroethylene, glassy carbon, and platinum. Dispersive and nondispersive components of the IL surface energy are determined from the experimental data using Fowkes theory. The most interesting result is that the protic ILs have lower surface tension and smaller contact angles than the equivalent aprotic ILs, despite the presence of high charge density on the proton associated with one of the nitrogens of the cation. Higher charge density on the anion results in a higher surface tension, and decreasing surface tension and contact angles are observed for increasing alkyl chain length on the cation.

Experimental study of the effects of a novel nanoparticle on enhanced oil recovery in carbonate porous media

One of the effective methods in the process of enhancing the oil recovery from oil reservoirs is the use of nanotechnology. For this purpose, a new nanofluid was used to enhance the oil recovery from the reservoir at the scale of carbonate rocks. Finally, the obtained compound, in the first stage, nano-graphene oxide (NGO) were synthesized using Hummer's method and then they were subjected to surface modifications under new compounds. Finally, the obtained compound was known as (graphene oxide (N-(1-naphthyl) ethylenediamine)) (G-NEA), where G stands for graphene oxide (GO). Also, to determine the morphological characteristics and structure of the synthesized nanoparticles, Field Emission Scanning Electron Microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and Transmission electron microscopy (TEM) were performed. In addition, zeta-potential analysis was performed to investigate the stability of nanofluids at different pHs. In order to investigate the effect of nanofluids on oil recovery, three concentrations (200, 400, and 500 ppm) of G-NEA nanofluids were prepared. Also, the interfacial-tension (IFT) measurement and rock angle measurement in the presence of nanofluid were investigated using a pendant drop and sessile drop method, respectively. The coreflood experiment was performed to evaluate the effect of G-NEA nanofluid on carbonate plugs. The results showed that when the G-NEA nanofluid concentration increased, the IFT value of 19.34 (mN/m) for deionized water to 10.8 (mN/m) for 500 ppm G-NEA and the contact angle decreased from the initial value of 166° to 40°, indicating the tendency of the wettability alteration of the rock to a water-wet conditions. The results of the coreflood experiment showed that at 400 and 500 ppm concentrations, the G-NEA nanofluid enhanced the oil recovery by 23 and 15%, respectively. Therefore, this synthesized nanofluid can have an effective approach to drive the carbonate reservoir rock into a water-wet condition and enhance oil recovery.

Surface tension measurement of normal human blood samples by pendant drop method

The surface tension of blood plays an important role not only in the birth and decompression sickness but also in other functionality of the organism. It also provides capillary action during blood flow process. In this article, a simple and low-cost device is designed and fabricated for measuring the surface tension of blood by pendant drop method. In this device, a droplet of blood is formed in a closed chamber on tip of an 18-gauge blunt needle and it is photographed by a camera in very humid conditions (RH = 99%) to minimise the evaporation. A wetted wick is provided at the bottom of the chamber for maintaining constant relative humidity in chamber. Surface tension of blood is inferred using drop shape factor method and image analysis technique at various experimental conditions. This device is validated and calibrated with surface tension measurements of water and silicone oil. Its measurements are in good agreement against data reported in literature. Post-validation, surface tensions of blood samples with and without anticoagulant of healthy persons at various temperatures (range from 20 to 40 °C) was measured. It was found that the surface tension of normal blood samples strongly correlates with blood temperature. The surface tension of female blood was remarkably different from same of male blood. However, the effect of age (21–60 year) on the surface tension was negligible for all practical purposes. Increased percentage of anticoagulant in blood increases its surface tension. This research specifies a baseline for surface tension of normal blood samples at various conditions which in turn provides new insights to pathologists in identifying various disease conditions.

Crude oil behavior during injection of solutions containing MgSO4 in the presence and absence of CO2

ABSTRACT Pendant drop method is employed to investigate interfacial tension, bond number, and swelling behavior of crude oil in the presence of brine solutions comprised of MgSO4 and its solution saturated with carbon dioxide (CO2) (i.e. carbonated MgSO4 solution) in different temperatures and pressures, up to 80°C and 4000 psi. The results reveal that as the temperature increases, the measured dynamic IFT values getting more close to each other. In detail, the measured dynamic IFT values for the temperature of 30°C are wider than those measured for the temperature of 80°C. Besides, the results demonstrated that not only the dissolution of brine in carbonated brine can reduce the swelling factor which means a barrier against the better dissolution of carbon dioxide into the drop phase but also this salt dissolution can shift the crossover pressure toward the lower values of around 1000 psi from its original value of around 2000 psi. Moreover, examining the effect of pH reveal that at low pH value (i.e., 3.5), a reduction of about 7.6 mN/m in IFT values can be obtained. In sum up, it was deduced that the addition of CO2 which reduced the acidity of the aqueous phase due to the formation of carbonic acid caused the interruption of ionization of basic natural surfactants, consequently causing a significant diminish of IFT reduction compared to IFT of crude oil/brine solution. In addition, at a constant temperature, the presence of more CO2 to the aqueous phase at higher pressures leads to IFT reduction as a function of pressure. Moreover, the results confirm that at pressures lower than the crossover point, the effect of temperature variation on the swelling is insignificant but at pressures higher than crossover point swelling factor increases as a function of temperature. Furthermore, the results reveal that the dissolution of salt into the carbonated water reduces the crossover pressure. As the last point, the measured swelling factor revealed that the presence of CO2 combined with the effect of temperature may lead to an ultimate swelling factor of about 1.32 which means 32% enhancement in the initial volume of the drop oil as it is contacted to the carbonated brine under the temperature of 80°C.

An experimental investigation on the use of saponin as a non-ionic surfactant for chemical enhanced oil recovery (EOR) in sandstone and carbonate oil reservoirs: IFT, wettability alteration, and oil recovery

Surfactant flooding, a chemical enhanced oil recovery (EOR) technique, boosts oil production mainly through lowering oil–water interfacial tension (IFT) and altering reservoir rock wettability. In the current study, the performance of pure saponin, a non-ionic surfactant, was evaluated for EOR in sandstone and carbonate reservoirs. The performance evaluation experiments were IFT by pendant drop method, wettability through the use of sessile drop technique, and core flood to discover the oil recovery improvement. According to IFT experiments, the surfactant had a critical micelle concentration (CMC) of 5g/L, and which it decreased the oil–water IFT by 66.98% at CMC, for the system free from salt. Moreover, after increasing the salinity by sodium chloride up to 100g/L, it not only was salt-tolerant but also lowered oil–water IFT up to 77.31%. Depending on salt concentration, the surfactant decreased the sessile drop contact angle by 4.49–27.84° and 5.62–16.98° for the sandstone and carbonate slices, respectively. From the core flood experiments, the oil recovery was improved by 8.4% and 6.23% for the surfactant flooding in the sandstone and carbonate cores, respectively. All in all, the non-ionic surfactant saponin performed best in improving oil recovery from both sandstone and carbonate reservoirs.

Experimental Investigation of Asphaltene Content Effect on Crude Oil/CO2 Minimum Miscibility Pressure

Minimum Miscibility Pressure (MMP) is regarded as one of the foremost parameters required to be measured in a CO2 injection process. Therefore, a reasonable approximation of the MMP can be useful for better development of injection conditions as well as planning surface facilities. In this study, the impact of asphaltene content ranging from 3.84 % to 16 % on CO2/heavy oil MMP is evaluated. In this respect, slim tube miscibility and Vanishing Interfacial Tension (VIT) tests are used. Regarding the VIT test, the Interfacial Tension (IFT) is measured by means of two methods including pendant drop and capillary apparatuses, and thereafter the MMP measurement error between slim tube and VIT methods are calculated. Based on the results, by increasing the asphaltene content, the measured MMP by slim tube method increases linearly while that by VIT follows no clear trend. The results also indicate that there is an asphaltene content range within which the MMP error between slim tube and VIT tests is minimized. IFT measurement by pendant drop and Capillary Glass Tube (CGT) methods show that by increasing asphaltene content up to 10.15 %, IFT declines, whereas for further increase in content, IFT increases because of the irregular dispersion of asphaltene in oil droplets.

Interfacial Phenomena on the Phase Boundary Between Hydrocarbon Systems and Acids

A study was carried out on aspects of phenomena on the interfacial boundary of acids and hydrocarbon systems of different complexity. These phenomena were evaluated relative to the interfacial tension measured by the pendant drop method. We discovered peculiarities of the interaction of hydrochloric and sulfamic acids with individual hydrocarbons as well as complex hydrocarbon systems. The complex dependence of the interfacial tension on the composition and properties of the hydrocarbon phase, type and concentration of the acid, and the chemical composition of asphaltenes was elucidated.

On the effective surface tension of powder-derived liquid marbles

Effective surface tension (γeff) is a fundamental property of liquid marbles, i.e., particle-covered drops in an air environment. Recently, studies of monolayer nanoparticle-covered (mNPc) liquid marbles produced with a sol-gel film have significantly updated previous understandings regarding γeff. Examining the derived explanations with the most common powder-derived liquid marbles should be meaningful. Here, the maximum height and pendant drop methods were employed for γeff measurements of liquid marbles produced with a polytetrafluoroethylene powder. Following the methodology proposed in mNPc liquid marble studies, the measurement processes were addressed in detail with the uncertainties in parameter identification as the main concerns, and the results were analyzed by highlighting the effective surface tension's equivalence nature and liquid marbles' surface solidity. By combining the present findings and conclusions related to both mNPc and powder liquid marbles, the key issues in measuring and understanding liquid marble γeff were summarized.

Study of Asphaltene Precipitation during CO2 Injection into Oil Reservoirs in the Presence of Iron Oxide Nanoparticles by Interfacial Tension and Bond Number Measurements

CO2 injection is one of the most frequently used enhanced oil recovery methods; however, it causes asphaltene precipitation in porous media and wellbore and wellhead facilities. Carbon dioxide saturated with nanoparticles can be used to enhance oil recovery with lower asphaltene precipitation issues. In this study, the vanishing interfacial tension technique was used to investigate the possibility of diminishing asphaltene precipitation by nanoparticles. The interfacial tension (IFT) of synthetic oil/carbon dioxide was measured using the pendant drop method. The results illustrated that, for synthetic oil samples containing asphaltene, the IFT data versus pressure decrease linearly with two different slopes at low- and high-pressure ranges. At high pressures, the slope of the plot is lower than the one in the low-pressure range. The addition of iron oxide nanoparticles to the oil solution reduces the interfacial tension at higher pressures with a steeper slope, showing that nanoparticles can decrease asphaltene precipitation. The plot of Bond number versus pressure also confirmed the impact of nanoparticles on reducing asphaltene precipitation. In terms of the temperature effect, the presence of nanoparticles at 50 °C resulted in a 16.34% reduction in asphaltene precipitation and a 19.65% reduction at 70 °C. The minimum miscibility pressure changed from 10.17 to 30.96 MPa at 70 °C; however, in the presence of nanoparticles, it reduced from 10.06 to 16.56. Therefore, the technique introduced in this study could be applied to avoid the problems associated with altering the gas injection mode from miscible to immiscible.

Effect of CO2 injection on interfacial tension of oil-formation water system under high temperature and pressure

The interfacial interaction between CO2 and oil and water is one of the important factors affecting the effect of CO2 enhanced oil recovery. Taking dead oil in Zhoucheng Oilfield as an example, the variation of interfacial tension between crude oil-carbonated water two-phase system and oil-formation water two-phase system was studied by pendant drop method. The influence of different CO2 saturation on the equilibrium interfacial tension of oil-formation water system and changes of equilibrium interfacial tension between crude oil-carbonated water system and crude oil-formation water system were analyzed. Moreover, previous studies did not reflect the experimental phenomena of extracting light hydrocarbons from oil droplets by CO2 through gas-water interface. This paper provides experimental research and analysis for this experimental phenomenon. The results show that the equilibrium interfacial tension of crude oil-carbonated water system decreases with the increase of pressure, and the dissolution and diffusion of the system becomes more and more obvious with the increase of pressure. The medium exchange occurs between oil and carbonated water, and the phenomenon of partial miscibility occurs. There is a threshold pressure value between crude oil and formation water with different CO2 saturation. Each group of samples has its threshold pressure and optimum CO2 injection rate. It’s not that the more CO2 injection, the better oil displacement effect. This research provides a reference for us to save the cost of CO2 flooding.

Dispersion stability and surface tension of SDS-Stabilized saline nanofluids with graphene nanoplatelets

The dispersions of engineered nanomaterials in fluids have envisioned numerous industrial applications. Despite less experimental data available on the surface tension of nanofluids, it is one of the critical parameters to define thermal configurations and two-phase transport properties. This study focuses on the benchmark experimental investigation of the surface tension behavior in graphene nanoplatelets-based saline nanofluids in ambient air using the pendant drop method. Graphene nanoplatelets are dispersed in saline fluid (30PPT) using optimum anionic SDS stabilizer and ultrasonication, exhibiting excellent stability for minimum 72 h. Different characterizations are performed for nanoplatelets and nanofluid stability such as electron microscopy, FTIR, XRD, DLS and sedimentation analysis. Surface tension measurements are taken at varying concentrations of graphene nanoplatelets range of 0-0.25 wt% and temperature range of 25−65 °C. The obtained results from this research exhibit that the addition of nanoplatelets drops the surface tension of saline fluid by 21 %. However, the increase in concentration from 0.05 wt% to 0.25 wt% does not have a considerable implication on the overall surface tension behavior. It is observed that the surface tension of the saline fluid and the nanofluid decrease with the elevation in temperature.

Adsorption Kinetics of Asphaltenes at the Heptol–Water Interface

The dynamic pendant drop method was employed to better understand the adsorption kinetics at the oil/water interface. Various volume ratios of n-heptane/toluene (heptol) have been chosen as solvent...

Surface characterization of amphiphilic block copolymers possessing polyisoprene and poly[tri(ethylene glycol) methacrylate] segments and the effect of side chain ω-function on surface energy

A series of amphiphilic polyisoprene-b-poly[oligo(ethylene glycol) methyl (and tert-butyldimethylsilyl) ether methacrylate] (PIsp-b-PR3, R = methyl (M), tert-butyldimethylsilyl (Si)) diblock copolymers were prepared with varying PR3 compositions. The PIsp-b-PR3s were synthesized by the sequential anionic copolymerization of isoprene and corresponding methacrylate monomer (M3 or Si3). The obtained polymers had narrow molecular weight distributions (Mw/Mn ≤ 1.04) and predictable molecular weights. The bulk-state self-assembled nanostructure was studied by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). We also evaluated the surface energy of PR3s having an inherent amphiphilic character by pendant drop method along with PIsp. In addition, the surface structure of the block copolymer thin films was investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurement. It was concluded that the estimated surface energy values (PM3 (37.3 ± 0.3 (mJ/m2)) and PSi3 (32.4 ± 1.4 (mJ/m2))) were authentic by comparison with the observation result of surface structure and depended on side chain ω-function.

Zein for hydrocarbon remediation: Emulsifier, trapping agent, or both?

Pump and treat of hydrocarbons from the subsurface is largely ineffective because capillary forces impede hydrocarbon mobility. This study uses zein (corn protein) dissolved in water at pH = 13 at low concentrations (4 and 8 g of zein/L) as a natural surfactant to emulsify hydrocarbons, facilitating their recovery from the subsurface (biosurfactant flushing). The effectiveness of zein in emulsifying a model hydrocarbon (toluene) was verified with bottle tests, optical microscopy and confocal microscopy. Interfacial tension measurements conducted with an optical tensiometer and the pendant drop method demonstrated that zein adsorbed onto hydrocarbon-water interfaces. Langmuir-Blodgett interfacial zein films deposited onto glass slides were smooth, as demonstrated using a scanning electron microscope (SEM). Langmuir trough experiments indicate that interfacial zein films either rapidly re-adsorbed or did not desorb from oil-water interfaces upon compression, followed by rapid expansion and recompression. Uncontrolled hydrocarbon migration through the aquifer is a risk associated with surfactant flushing. Therefore, this study also uses zein at high concentrations (33 g of zein/L) to form barriers around the areas where hydrocarbons are emulsified, preventing their migration. Barriers were formed by gelling zein dissolved at pH = 13 with either glacial acetic acid or salts (CaCl2, KCl, and NaCl). Zein gelation was confirmed with compression tests, tensile tests, and shear rheology. Zein gels formed with CaCl2 and glacial acetic acid had the highest shear viscoelastic moduli and tensile strength. The effectiveness of zein gels in impeding contaminant migration was demonstrated in flow experiments conducted using sand columns. This study is a proof of concept that zein can be simultaneously injected in the polluted zones to emulsify hydrocarbons to enhance their recovery, and around the polluted areas to ensure that they are safely contained.

Impacts of motileEscherichia colion air-water surface tension

Immiscible multiphase flow in porous media is largely affected by interfacial properties, manifested in contact angle and surface tension. The gas-liquid surface tension can be significantly altered by suspended particles at the interface. Particle-laden interfaces have unique properties, for example, a lower surface tension of interfaces laden with surfactants or nanoparticles. This study investigates the impacts of a motile bacteriumEscherichia coli(E. coli, strain ATCC 9637) on the air-water surface tension. Methods of the maximum bubble pressure, thedu Noüyring, and the pendant droplet are used to measure the surface tension of the motile-bacteria-laden interfaces. Measured surface tension remains independent to theE. coliconcentration when using the maximum bubble pressure method, decreases with increasedE. coliconcentration in thedu Noüyring method, and presents time-dependent changes by the pendant drop method. The analyses show that the discrepancies may come from the different convection-diffusion processes ofE. coliin the flow among various testing methods.

Surface Tension and Dilatational Rheology of Blood in Patients Subjected to Cardiological Operations under Conditions of Artificial Circulation

Pendant drop and bubble shape methods are employed to study the tensiometric and rheological parameters of blood serum and plasma in 45 patients 49–70 years old subjected to surgical operations under the conditions of artificial circulation because of ischemic heart disease (first group) and heart valve pathology (second group). Blood sampling is performed 1 h before and 12 h after (the first day) the operation, as well as on the 7th postoperative day. Statistically significant changes in the surface tension and viscoelasticity modulus are observed on the 1st day after the operation in both groups, thereby indicating a substantial increase in the content of surfactants in the blood serum. On the seventh day of the postoperative period, a positive dynamics is observed; however, the studied rheological parameters—in particular, viscoelasticity modulus E—at frequencies of 0.1 and 0.01 Hz statistically reliably exceed their preoperative level and do not reach the values characteristic of healthy people. Thus, the pathological deviations of biochemical parameters (contents of glucose, urea, creatinine, albumin, and lipoproteins) that affect blood viscosity are accompanied by substantial changes in the surface tension and dilatational viscoelasticity of blood serum. However, the examined biochemical markers are not dominating predictors for changes in the rheological and tensiometric properties of blood.

A laminar-jet-discharging method for measuring the interfacial tension of deformable surfaces

We propose a laminar-jet-discharging method to measure the interfacial tension of deformable surfaces such as soap bubbles. This method avoids the need to measure the small pressure difference inside and outside a soap bubble in a static state. By allowing the air in a soap bubble to discharge in a laminar flow state through a long tube, we show that the surface tension of the soap bubble is proportional to the rate of change of the fourth power of the bubble radius. Experimentally, we verify that this linear relationship is valid over a long period and thus can be measured with cameras at slow recording rates. Our method offers a straightforward and accurate way to measure the surface tension of soap bubbles using easy-to-obtain devices. In addition, we propose a new development of the pendant drop method based on the silhouette of the drop, which does not require any pressure transducer or computation of the second-order derivatives of the drop profile and hence is easier to implement and less sensitive to the accuracy of the drop profile determination. For pure liquids, results from the new pendant drop method compare well with standard values. This method is thus used to verify the laminar-jet-discharging measurements.

Tensiometric and Rheological Characteristics of Fractions of Humic and Hymatomelanic Acids

The Du Nouy ring detachment and pendant drop methods have been employed to study the tensiometric (dynamic and equilibrium surface tensions) and surface rheological (viscoelasticity modulus and phase angle) characteristics of aqueous solutions of fractions of humic and hymatomelanic acids at a solution–air interface. It has been found that the fraction of low-molecular-weight hymatomelanic acids has high surface activity, while its surface layers are characterized by high viscoelasticity and storage elastisity moduli. The experimental dependences of the equilibrium surface tension and viscoelasticity modulus on the concentration of hymatomelanic acid salt solutions are adequately described in terms of the model of real two-dimensional solutions for polymolecular adsorption of polyelectrolytes.

Interfacial tension measurements of n-dodecane/CO2 from (298.15 to 573.15) K at pressures up to 10 MPa by pendant drop method

Interfacial tension measurements of n-dodecane/CO2 from (298.15 to 573.15) K at pressures up to 10 MPa by pendant drop method