Aggregation, reversed micelles, and microemulsions in liquid-liquid extraction: the tri-n-butyl phosphatediluent-water-electrolyte system

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The experimental evidence (e.g. distribution, viscosity, conductivity, and molecular weight measurements) suggesting the presence of aggregates in TBP extracts is assembled and critically reviewed. A variety of TBP-bascd systems are considered, such as TBP-Diluent, TBP-H2O, TBP-Diluent-H2O, TBP-H2O-Acid, TBP-Diluent-H2O-Acid, TBP- H2O-Acid-Metal Salt, TBP-Diluent-H2O-Acid-Metal Salt, TBP-H2O-Metal Salt, and TBP-Diluent-H2O-Metal Salt. It is demonstrated that aggregation is favored by high acidities and high metal concentrations. Organic extracts derived from highly acidic aqueous solutions and/or highly concentrated metal salt solutions tend to contain ion-pairs or ion-multiplets predominantly. These species possess significant amphiphilic character since they contain both hydrophobic (i.e., trialkyl radicals) and hydrophilic (i.e., P=O(H2O)xMz+ and/or P=O(H2O)xH+) groups. On the basis of current notions of aggregation and solubilization in surfactant solutions, arguments are presented for possible formation of reversed micellar structures and microemulsions in TBP solvent systems.

Original languageEnglish (US)
Pages (from-to)123-173
Number of pages51
JournalAdvances in Colloid and Interface Science
Issue number1-2
StatePublished - Jan 1 1991


All Science Journal Classification (ASJC) codes

  • Surfaces and Interfaces
  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

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