Oil-water Interfacial Properties Research Articles

Interfacial and Oil/Water Emulsions Characterization of Potato Protein Isolates

Interfacial and emulsifying properties of potato protein isolate (PPI) have been studied to evaluate its potential application to stabilize oil/water emulsions at two pH values (2 and 8). The amount, type, and solubility of proteins and the size of aggregates have been determined in aqueous dispersion. Air-water and oil-water interfacial properties (adsorption, spreading, and viscoelastic properties) have been determined as a function of concentration and pH using soluble phases of PPI. The behavior of PPI stabilized oil/water emulsions has been then analyzed by droplet size distribution measurements and interfacial concentration. PPI exhibits low solubility over a wide range of pH values, with the presence of submicrometer aggregates. The pH value exerts a negligible effect on interfacial tension (oil-water) or surface pressure (air-water) but displays very important differences in viscoelastic properties of the interfacial films formed between oil and water. In this sense, pH 8 provides a major elastic response at oil-water interfaces as compared to pH 2. In relation with this result, a much higher ability to produce fine and stable emulsions is noticed at pH 8 as compared to pH 2. Consequently, there is an evident relationship between the rheological properties of the oil-water interfacial films and the macroscopic emulsion behavior.

The effects of oil displacement agents on the stability of water produced from ASP (alkaline/surfactant/polymer) flooding

Alkaline/surfactant/polymer (ASP) flooding technology has been successfully used in Chinese oil fields, such as Daqing and Shengli. However, water produced from ASP flooding contains large quantities of residual chemicals (alkali, surfactant and polymer) making it a complex and stable emulsion system which is difficult to treat. The emulsion stability of water produced from ASP flooding was investigated by conducting settling experiments and measuring the oil–water interfacial properties. The experimental results showed that the addition of polymer (HPAM, hydrolyzed polyacrylamide) degrades the emulsion stability when its concentration is below 300 mg/L for the 1.2 × 10 7 MW polymer, and 800 mg/L for the 3.0 × 10 6 MW polymer. But it enhances the emulsion stability when polymer concentrations are above those levels. At low polymer concentrations, flocculation induced by the polymer on oil droplets in the produced water is the dominant factor, while at high polymer concentrations the produced water viscosity plays an important role in the emulsion stability. The adsorption of surfactant on the oil–water interface increases the zeta potentials and decreases interfacial tension, and thus remarkably enhances the emulsion stability. Furthermore, the emulsion stability is enhanced gradually with the increase of NaOH concentration up to 300 mg/L due to the increase of zeta potentials and decrease of interfacial tension, and then weakened with the further increase of NaOH concentration, which is attributed to the decreased strength of the interfacial film. A pilot experiment for the treatment of simulated water was done, and the result showed that the simulated produced water from ASP can be successfully treated by using a leaching solution of alkaline white mud.

Analysis of biological demulsification process of water-in-oil emulsion by Alcaligenes sp. S-XJ-1

A demulsifying strain (S-XJ-1) was isolated from petroleum-polluted soil and identified as Alcaligenes sp. It showed emulsion breaking ratio of 81.3% for W/O emulsion within 24 h when the cell concentration was 500 mg/L. Evolution of water droplets during the biological demulsification process was investigated using a Turbiscan stability analyzer and microphotography. Further investigation focused on cell surface hydrophobicity and oil–water interfacial properties. The biological demulsification process began with rapid dispersal of the cells into the oil phase and adsorption onto the oil–water interface. This occurred due to high cell surface hydrophobicity and the presence of amphiphilic compounds in the cell walls. The cells had higher interfacial activity than the emulsifier molecules, and they displaced some of the emulsifier molecules, which effectively reduced the interfacial tension gradient. As a result, the interfacial film strength decreased, the water droplets coalesced and eventually phase separation occurred.

Effects of short chain alcohols on the styrene emulsion polymerization

AbstractThe effects of a series of short chain alcohols, 1‐butanol (C4OH), 1‐pentanol (C5OH), and 1‐hexanol (C6OH), on the styrene (ST) emulsion polymerization mechanisms and kinetics were investigated. The CMC of the ST emulsions stabilized by sodium dodecyl sulfate (SDS) first decreases rapidly and then levels off when the CiOH (i = 4, 5, or 6) concentration ([CiOH]) increases from 0 to 72 mM. Furthermore, at constant [CiOH], the CMC data in decreasing order is CMC (C4OH) > CMC (C5OH) > CMC (C6OH). The effects of CiOH (i = 4, 5, and 6) on the ST emulsion polymerization stabilized by 6 mM SDS are significant. This is attributed to the reduction in CMC by CiOH, the different oil–water interfacial properties, the different concentrations of monomer within latex particles, and the different effectiveness of SDS/CiOH in stabilizing latex particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4406–4411, 2006

Effect of Acidification and Heating on the Rheological Properties of Oil-Water Interfaces with Adsorbed Milk Proteins

The behavior of casein and whey proteins at the oil-water interface was studied using a dynamic drop tensiometer (DDT). The dilational modulus of the interface was measured for aqueous solutions of skim milk powder (SMP) and whey protein concentrate (WPC) with various additions (salt, calcium, lactose) and (order of) various processing steps. Acidification or heating was performed before or after creation of the interface. The elastic properties of oil-water interfaces with adsorbed milk proteins could partly determine the rate of partial coalescence and resulting product instability.For WPC, preacidification slows down the adsorption, but the modulus is not affected. This is probably because, although the whey proteins change conformation more slowly at the interface, still a homogeneous film is formed. If postacidification is applied, coarsening of the protein film leads to loss of interfacial rigidity. Preheating of the aqueous phase with WPC leads to denaturation and aggregation, but the aggregates formed are still surface active and give high moduli. If preheating of a WPC solution is followed by postacidification, the resulting modulus is high (∼60 mN/m).The oil-water interfacial properties of SMP are only minimally affected by preheating or by choice of powder (low, medium, or high heat). At low pH, however, aggregates are formed that are less surface active, and interfacial moduli are lower.If measurements are performed at high temperature (i.e., if postheating is applied), for both SMP and WPC systems, moduli became much lower (∼10 mN/m). This is probably because of accelerated rearrangements, leading to the formation of inhomogeneous film structures.