General patterns of the phase behavior of mixtures of water, nonpolar solvents, amphiphiles, and electrolytes. 1

Kahlweit, M.; Strey, R.; Firman, P.; Haase, D.; Jen, J.; Schomaecker, R.

doi:10.1021/la00081a002

Cited by 233 publications

(151 citation statements)

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“…To clarify this point we measured phase diagrams of systems 3 The ionic strength of the aqueous solution of an electrolyte can be calculated according to where I is the ionic strength, z Table 3 As can be seen in Fig.4, the phase diagrams are far from being equal. A more detailed analysis reveals that all but one (see Supporting Material) of the shifts follow the concept of 'hard and soft acids and bases' (HSAB concept) [48,49]. Based on this order one can argue that the harder the acid (base) for a given base (acid) the more hydrated the ions, which, in turn, shifts the wefb to lower 1-butanol and water contents.…”

Section: Discussionmentioning

confidence: 87%

Phase diagrams of microemulsions containing reducing agents and metal salts as bases for the synthesis of metallic nanoparticles

Najjar

2009

Journal of Colloid and Interface Science

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We studied the phase diagrams of microemulsions with a view to using these systems for the synthesis of metallic Pt, Pb, and Bi nanoparticles as well as of intermetallic Pt/Pb and Pt/Bi nanoparticles. The microemulsions consisted of H 2 O/salt -n-decane -SDS -1-butanol. The salt was either one metal precursor (H 2 PtCl 6 ·6H 2 O, Pb(NO 3 ) 2 , or Bi(NO 3 ) 3 ·5H 2 O), a mixture of two metal precursors (H 2 PtCl 6 ·6H 2 O + Pb(NO 3 ) 2 or H 2 PtCl 6 ·6H 2 O + Bi(NO 3 ) 3 ·5H 2 O), or the reducing agent (NaBH 4 ). In addition, other salts needed to be added in order to solubilize the metal precursors, to stabilize the reducing agent, and to adjust the ionic strength. Combining the microemulsion (µe1) that contains the metal precursor(s) with the microemulsion (µe2) that contains the reducing agent leads to metallic nanoparticles. To study systematically how the shape and size of the synthesized metallic nanoparticles depend on the size and shape of the respective microemulsion droplets, first of all one has to find those conditions under which µe1 and µe2 have the same structure. For that purpose we determined the water emulsification failure boundary (wefb) of each microemulsion as it is at the wefb where the water droplets are known to be spherical. We found that the ionic strength (I) of the aqueous phase as well as the hard acid and hard base properties of the ions are the key tuning parameters for the location of the wefb.

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Section: Discussionmentioning

confidence: 87%

Phase diagrams of microemulsions containing reducing agents and metal salts as bases for the synthesis of metallic nanoparticles

Najjar

2009

Journal of Colloid and Interface Science

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“…For electrolyte solutions, most LLLE data were determined Ž . for systems with surfactants Kahlweit et al, 1988 et al, 2002 . For these systems, the patterns of the three-liquid phase equilibria with increasing salt concentration are similar Ž .…”

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confidence: 99%

Three‐liquid phase equilibria in water+benzene+caprolactam+(NH₄)₂SO₄ mixtures

2003

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IntroductionIn 1975, Lang and Widom published their well-known arti-Ž . cle on liquid᎐liquid᎐liquid equilibria LLLE in systems of waterq benzene q ethanolq ammonium sulfate at atmo-Ž . spheric pressure Lang and Widom, 1975 . In that publication, equilibrium data are presented at different temperatures up to very close to the tricritical point, the temperature at which the three phases become identical. During experiments to determine the liquid᎐liquid phase behavior of water qbenzeneqcaprolactamqammonium sulfate systems, phase behavior similar to that for water qbenzene qethanolq ammonium sulfate systems was encountered.The practical importance of LLLE is, for example, for the waterqoilqsurfactant systems in enhanced oil-recovery processes, where capillary forces in reservoir pores are reduced by surfactant flooding. Also, for improving the performance of an extraction process, understanding of the phase behavior of systems exhibiting three liquid phases can be essential Ž . Garcia-Sanchez et al., 1996 . Equilibria of three liquid phases can occur when two-liquid phase regions overlap. LLLE received considerable interest, mainly inspired by the possibility of a tricritical point, as a test for theories of critical phenomena. Despite this degree of interest, the amount of Ž . three-liquid phase equilibrium data is limited Bocko, 1980 . For electrolyte solutions, most LLLE data were determined Ž . for systems with surfactants Kahlweit et al., 1988 et al., 2002 . For these systems, the patterns of the three-liquid phase equilibria with increasing salt concentration are similar Ž . to those investigated by Knickerbocker et al. 1979Knickerbocker et al. , 1982 for a variety of waterqhydrocarbonqalcoholqsalt systems.The phase-behavior pattern observed for LLLE in quaternary electrolyte solutions is a progression with increasing salt concentration from two liquid phases at low salt concentrations, a three-liquid phase region at higher salt concentrations, and again a two-liquid phase region at still higher salt concentrations. The three-phase region is limited by two critical tie-lines, where two of the three phases become identical. Ž In this pattern, temperature or pressure Sassen et al., 1989; . Andersen et al., 1999 can play a role similar to that of the salt concentration. With increasing temperature, the size of the LLLE-region decreases. At a given pressure in a quaternary system, a point with a certain temperature and composition exists, where the three coexisting phases become identi-Ž . cal. This is the tricritical point. Lang and Widom 1975 attempted to locate this tricritical point for the system waterq benzeneqethanolqammonium sulfate.The amount of literature on the modeling of LLLE using an excess Gibbs energy model is quite limited. Negahban et Ž . al. 1986Negahban et Ž . al. , 1988 In this article, LLLE are reported and modeled for the system waterqbenzeneqcaprolactamqammonium sulfate in a temperature range of 293 K to 330 K. The system waterq benzeneqcaprolactamqammonium sulfate is of imp...

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“…1 (top). The phase behavior follows the general pattern of systems with nonionic surfactants as described in [6]. A partial replacement of 1-bromooctane by toluene causes a shift of the one-phase region towards lower temperatures.…”

Section: Phase Diagrammentioning

confidence: 69%

The Kinetics of an Interfacial Reaction in a Microemulsion

Tjandra¹,

Lade

Wagner³

et al. 1998

Chem. Eng. Technol.

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We propose an interfacial reaction model describing the kinetics of the synthesis of 1-phenoxyoctane from 1-bromooctane and sodium phenoxide in a nonionic microemulsion. In this model the microemulsion is divided into the aqueous and the organic subvolume. The interface is covered by a monolayer of surfactant molecules. The interfacial area is determined by the concentration of surfactant in the microemulsion. The reaction is assumed to take place only at the internal interface of the microemulsion. Due to the nanometer dimensions of the microemulsion droplets it is also assumed that there is no concentration gradient between the core of the droplets and the internal interface. Therefore, bulk concentrations of the reactants within the subvolumes are used for the kinetic evaluation of the obtained data. The model proves to be valid for the complete range of variations of the microemulsion composition studied here.

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General patterns of the phase behavior of mixtures of water, nonpolar solvents, amphiphiles, and electrolytes. 1

Cited by 233 publications

References 0 publications

Phase diagrams of microemulsions containing reducing agents and metal salts as bases for the synthesis of metallic nanoparticles

Phase diagrams of microemulsions containing reducing agents and metal salts as bases for the synthesis of metallic nanoparticles

Three‐liquid phase equilibria in water+benzene+caprolactam+(NH₄)₂SO₄ mixtures

The Kinetics of an Interfacial Reaction in a Microemulsion

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General patterns of the phase behavior of mixtures of water, nonpolar solvents, amphiphiles, and electrolytes. 1

Cited by 233 publications

References 0 publications

Phase diagrams of microemulsions containing reducing agents and metal salts as bases for the synthesis of metallic nanoparticles

Phase diagrams of microemulsions containing reducing agents and metal salts as bases for the synthesis of metallic nanoparticles

Three‐liquid phase equilibria in water+benzene+caprolactam+(NH4)2SO4 mixtures

The Kinetics of an Interfacial Reaction in a Microemulsion

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Three‐liquid phase equilibria in water+benzene+caprolactam+(NH₄)₂SO₄ mixtures