Reverse micelles and microemulsions in near-critical and supercritical fluids

Journal Article · Thu Jan 25 00:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100365a050· OSTI ID:6656528

Smith, R D; Fulton, J L; Blitz, J P; Tingey, J M ^[1]

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1. Pacific Northwest Lab., Richland, WA (USA)

Reverse micelle and water-in-oil (w/o) microemulsion phases can be formed in near-critical and supercritical fluids, giving rise to uniquely pressure dependent phase behavior. The solvating power of reverse micelles formed from the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in fluids with moderate critical temperatures (e.g., ethane, propane, or xenon) depends largely upon the water-to-surfactant ratio of the micelle phase (W{sub m}), which at large W{sub m} can approach that of bulk water. The maximum water-to-surfactant ratio (W{sub 0}), which defines the boundary between a one-phase and a two-phase fluid system (where a second, predominantly aqueous phase exists), is strongly pressure dependent. The physical size of a reverse micelle in one-phase AOT/H{sub 2}O systems at constant W{sub m} has been shown to be nearly independent of the continuous-phase identity and pressure. In contrast, the apparent hydrodynamic size increases dramatically as W{sub 0} is approached due to increased micelle-micelle attractive interactions (e.g., clustering). The maximum reverse micelle size (W{sub m} {proportional to} diameter) increases with pressure for fluids such as ethane and propane, approaching W{sub m} = 40, corresponding to a droplet size of {approximately} 17 nm. Significant micelle densities are obtained for two phase systems, even at relatively low pressure (< 100 bar). These systems can be used to efficiently extract hydrophilic substances, including proteins, from dilute aqueous solution with substantial selectivity without the need for any chemical change to the system.

• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6656528
• Journal Information: Journal of Physical Chemistry; (USA), Vol. 94:2; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
MICELLAR SYSTEMS
SYNTHESIS
DATA ANALYSIS
ETHANE
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
MICROEMULSIONS
PRESSURE EFFECTS
PROPANE
PROTEINS
SUPERCRITICAL STATE
SURFACTANTS
ALKANES
COLLOIDS
DATA
DISPERSIONS
EMULSIONS
HYDROCARBONS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
360603* - Materials- Properties
400201 - Chemical &amp; Physicochemical Properties
550000 - Biomedical Sciences
Basic Studies