Spinning drop tensiometer

Tests were performed at 75°C using a University of Texas Model 500 spinning drop tensiometer. Active surfactant concentration in the aqueous phase prior to oil addition was 0.50% wt. The Kem River crude oil was from the Patricia Lease. The pH of the deionized water surfactant solutions was 8. The pH of the aqueous NaCl surfactant solutions was 9.5 unless otherwise noted. values represent the average deviation of two or three measurements at different times (0.75-1 h apart). D.I., deionized. 

Tests were performed at 75°C using a University of Texas Model 500 spinning drop tensiometer. Active surfactant concentration in the aqueous phase prior to addition of the oil phase was 0.5% wt. Interfacial tension values are the average of duplicate or triplicate determinations. 

The dynamic interfacial tension behavior of reacting acidic oil-alkaline solutions has been studied for both an artificially acidified synthetic oil and a real crude oil at various concentrations [131,132] with either a drop volume tensiometer or a spinning drop tensiometer. 

S. D. Ball. Comparison of transient interfacial tension behaviours of oiUalkaline systems as measured by the drop volume and spinning drop tensiometers. PhD thesis, Ottawa Univ, 1995. 

Equipaent and Procedures. Crude o iI/aqueous i nterfac ia I tens i ons were measured using a spinning drop tensiometer built at the Alberta Research Council and designed for operation at elevated temperatures [211. The main difficulty in operating at elevated temperatures was the wear on the bearing improved operation was... 

Modifications of the conventional spinning drop tensiometer were required for operating at temperatures up to 200°C. Measurements carried out with heavy oil samples required the use of D20 instead of H20 to maintain a sufficient density difference between oil and water. For accurate measurements, considerable care must be used to ensure that heavy oil drops do not lag behind the rotation of the capillary tube in the tensiometer. Also, repeatability of measurements conducted with chemically ill-defined substances may be hampered by the inhomogeneity of the oil drops. 

Surface and interfacial tension measurements were made at 40° C with a Model 300 Spinning Drop Tensiometer obtained from the University of Texas at Austin, Chemistry Department. 

Figure 11. Photograph of bitumen drop in aqueous NaOH showing low- and high-tension sites due to periodic diffusion of natural surf actants from the oil-water interface to the aqueous phase in a spinning drop tensiometer.

Dynamic Interfacial Tension. Crude-oil-alkali systems are unusual in that they exhibit dynamic interfacial tension (Figure 11). A solution of 0.05 wt% sodium hydroxide in contact with David Lloydminster crude oil initially produces ultralow values of IFT. A minimum value is reached, after which IFT increases with time by nearly 3 orders of magnitude, measured in the spinning drop tensiometer. Taylor et al. (57) showed that dynamic inter-facial tension can also occur in crude-oil-alkali-surfactant systems. Figure 11 shows interfacial tension versus time for a solution containing 1 wt% sodium carbonate, and the same solution containing 0.02 wt% of Neodol 25-... 

The results of spinning drop experiments with the equilibrated oil (styrene) and aqueous (1 1 SLS/LA) phases are shown in Figure 5. No "tails" were formed on droplets of the pre-equilibrated styrene when injected into the capillary tube containing the pre-equilibrated aqueous phase. Thus, the formation of an interfacial layer in the spinning drop tensiometer is a non-equilibrium affect. 

Figure 6.7 Liquid surface tension determination by the spinning drop tensiometer method. A liquid drop (7) is suspended in an immiscible denser liquid (2) in a horizontal transparent tube which can be spun about its longitudinal axis, and the drop (7) elongates from a spherical shape to a prolate ellipsoid with increasing speed of revolution. Later, the drop becomes approximately cylindrical, at very high rotational velocities. A camera with a frame grabber captures the images of the drop inside the transparent tube.

Equation (515) is known as Vonnegut s equation and it is valid on the assumption that the drop is in equilibrium and its length is larger than four times its diameter (/ > 4r ). The spinning drop tensiometer method is widely used for measuring liquid-liquid interfacial tension, and is especially successful for examination of ultra-low interfacial tensions down to l(T6mNnr1. In addition, it can also be used to measure interfacial tensions of high viscosity liquids when precise temperature control is maintained. 

The spinning drop tensiometer method is particularly suitable for measuring the interfacial tension of melted polymers and is generally used in polymer compatibility, blend and composites research. In this case, a spinning polymer drop (smaller density) is rotated inside another immiscible polymer (higher density). Measurement of drop diameter versus time allows the determination of relaxational and extensional properties of polymeric systems. 

When the value of the interfacial tension is significantly less than 1 mN m 1, then we consider the measurement of ultra-low interfacial tension, which is common in liquid-liquid emulsification processes when effective surfactant solutions are used. The dynamic spinning drop tensiometer method is especially suitable for this purpose. Ultra-low interfacial tension measurement is important in the chemical industry because the cleaning of solid surfaces of dirt, grease, and oil the formulation of stable emulsions the recovery of petroleum, and other applications often rely on lowering the interfacial tension between immiscible liquids to ultra-low values by the use of surfactants. 

Overbeek and coworkers [41] studied oil-water-alcohol-surfactant mixtures close to the cmc and showed that ultralow interfaciai tensions could be obtained as well in their systems. They determined the monolayer composition from the 7(c) curve below the cmc. Similar work on ternary oil-water-surfactant mixtures was reported by Aveyard et al. [42]. In these studies, ) was measured by using a spinning drop tensiometer. 

To quantify the effects of mixed waste con sition on wettability and interfacial tension equilibrium, aqueous phase receding contact angle and interfacial tension were measured. Inter cial tension was measured ida a spinning drop tensiometer Model 500 (University of Texas, Austin, TX) and contact angles were obtained using axisymmetric drop shape analysis (17) on quartz slides. Contact angles are reported through the aqueous phase. 

The interfacial tension measurements were carried out using the spinning drop tensiometer using methodology described in previous work. The main advantage of using this technique was the ease and convenience of operation and its amenability for further studies planned at elevated temperatures. The major limitation of this technique is that adsorption phenomena below about 60 sec are not captured because of the... 

The interfacial tensions (IFT) between the crude oil and eleven caustic, NaOH, solution samples of different concentrations were measured by a Spinning Drop Tensiometer. The lowest IFT recorded was 0.08-mN/m at a caustic concentration of 0.5-g/kg. 

Interfacial tensions between the equilibrated oil and aqueous phases were measured by a spinning drop tensiometer using the method described by Schechter and co-workers (2,3,5). Each drop of oil was spun until a constant interfacial tension was reached. 

Studies on displacement dynamics and interfacial tensions were carried out to establish and improve recovery efficiencies of acidic crudes by alkaline agents. Displacement tests were carried out on restored state oil-field cores and on synthetic Ottawa sand-packs with permeabilities ranging from 100 to 3,500 millidarcies. Concomitant experiments were carried out with a spinning-drop tensiometer and a contact angle goniometer capillary pressure-determined wettability indices were measured and the type and stability of emulsions were characterized. These experiments indicate that the recovery mechanisms cited in the literature are valid under specific conditions of pH, electrolyte type and con-... 

Minimum values which are measured in a spinning-drop tensiometer. Parentheses indicate best estimate from same or similar condition. NA—Not available. 

Interfacial tension measurements Interfacial tension between various oleic and aqueous phases was measured using the Spinning Drop Tensiometer at 25 C. The spinning time and rate were kept constant so that comparative results could be obtained. 

The sulfonate concentration in the microemulsion was determined from the equilibrated microemulsion phase volume and the known weight of sulfonate in the system the assumption that the microemulsion phase contained all of the sulfonate was justified for all microemulsions. The volume fractions of oil and brine in the microemulsion were determined from the excess volumes of oil and brine, respectively. The microemulsion density and index of refraction needed to calculate the specific refraction (Eq. (1)) were measured on a Mettler-Paar DMA 40 digital density meter with accuracy of 0.0001 g/cm and a Zeiss Abbe refractometer ( 0.0001), respectively the temperature was controlled with an Exacal 100 and Endocal 150 constant temperature circulator-baths connected in series. Interfacial tensions between the microemulsion and equilibrated excess phases were measured on a University of Texas Spinning Drop Tensiometer or a Spinning Drop Tensiometer from S S Instrument Mfg. measurements were carried out until equilibrium values were obtained as indicated by constant readings over a period of at least 1 hour. 

The interfacial tension measurements were carried out with a Kruss spinning drop tensiometer. To simulate practical conditions, the measurements were performed in hard water (270 ppm Ca Mg = 5 1) at a surfactant concentration of 0.15 g/L and at 50 °C. Figure 46 shows a comparison of the interfacial tension of C12 alkyl polyglycoside derivatives against octyl dodecanol. The C12 monobutyl ether has the highest interfacial tension and hence... 

Figure 23 Schematic cross section of a spinning-drop tensiometer. (From Ref. 66.)...

For lower viscosity fluids, an alternate to rod pulling is to use a buoyancy fluid to squeeze the sample radially. Hsu and Flummer-felt (1975) have adapted the spinning drop tensiometer (Joseph et al., 1992) shown in Figure 7.2.9 to extensional measurements. If the surrounding fluid is more dense, P2 > Pi > then the test fluid will move to the center when rotation starts. It will elongate until interfacial tension balances the inertial forces. 

The experiments were performed in the spinning-drop tensiometer. In a series of experiments, we systematically investigated the Dodecane/water and the Isooctane/water interface... 

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