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Titolo:
Thermodynamic modeling of precipitation behavior in mixed micellar systems
Autore:
Smirnova, NA;
Indirizzi:
St Petersburg State Univ, Dept Chem, St Petersburg 198504, Russia St Petersburg State Univ St Petersburg Russia 198504 burg 198504, Russia
Titolo Testata:
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
, volume: 183, anno: 2001,
pagine: 635 - 649
SICI:
0927-7757(20010715)183:<635:TMOPBI>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
CALCIUM DODECYL-SULFATE; DODECYLDIMETHYLAMINE OXIDE; CATIONIC SURFACTANTS; NONIONIC SURFACTANTS; ANIONIC SURFACTANTS; AQUEOUS-SOLUTIONS; PHASE-EQUILIBRIA; SOLID-PHASE; MIXTURES; SODIUM;
Keywords:
mixed micellar solutions; phase diagrams; precipitation; thermodynamic models;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Smirnova, NA St Petersburg State Univ, Dept Chem, Universitetsky Prosp 2, St Petersburg198504, Russia St Petersburg State Univ Universitetsky Prosp 2St Petersburg Russia 198504
Citazione:
N.A. Smirnova, "Thermodynamic modeling of precipitation behavior in mixed micellar systems", COLL SURF A, 183, 2001, pp. 635-649

Abstract

Results of thermodynamic modeling of solubility diagrams for various typesof mixed micellar systems (nonionic surfactants with added alkanols, mixtures of two nonionics, two anionics, anionic plus semipolar surfactants) aresummarized. Phase behavior over a wide range of surfactant concentrations is under study and the model description is aimed at prediction of the solubility diagrams in ternary systems on the basis of data for aqueous solutions of the pure surfactants. In this case the pseudo-phase separation approach is quite efficient. When the total surfactant concentration in mixed solutions far exceeds the CMC it is expedient to describe the dependence of the dissolution (precipitation) temperature on the relative content of two surfactants using the concentration variables of the micellar pseudo phase. It follows from thermodynamic equations that a substantial decrease of the precipitation temperature can be produced by additives forming mixed micelles with the basic surfactant, and the distribution coefficient between micelles and the aqueous surroundings is an important characteristics of the additive. In some cases (mixtures of nonionic surfactants, solutions of ionic surfactants without a salt background at concentrations substantially abovethe CMC) the composition of mixed micelles is very close to the overall surfactant based composition of the solution. That is why in the both cases the eutectic type curves 'dissolution temperature versus surfactant-based mole fraction' can be modeled in a similar manner which is simpler than calculations for ionic systems based on the solubility product approach. For mixtures with added salts the ion exchange between micelles and the aqueous surroundings should be taken into account. The specificity of systems whose phase behavior is affected by chemical reactions (protonation, complex formation) is discussed and a version of the pseudo-phase model is proposed for description of the solubility diagrams in aqueous sodium dodecylsulfate-alkyl amine oxide mixtures. Experimental results obtained by the author and collegues and data from literature serve to illustrate the model performance. (C) 2001 Elsevier Science B.V. All rights reserved.

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Documento generato il 09/08/20 alle ore 23:34:35