The role of the interface in the kinetics and mechanism of liquid-liquid extraction.

Persistent Link:
http://hdl.handle.net/10150/184800
Title:
The role of the interface in the kinetics and mechanism of liquid-liquid extraction.
Author:
Dietz, Mark L.
Issue Date:
1989
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
When solutions of various metal 8-quinolinolates or beta-diketonates in an organic solvent were contacted with an aqueous phase and vigorously stirred to generate a large interfacial area, a reversible decrease in the organic phase concentration of the complex was observed. The magnitude of this decrease varied with interfacial area, solvent, temperature, and the nature and concentration of the complex. Analysis of the phenomenon using the Langmuir isotherm showed that the concentration change may be explained by adsorption of significant quantities of the complexes at the increased liquid-liquid interface generated by stirring. Such adsorption was found to complicate extraction kinetics measurements using the high-speed stirring technique when the product chelate is interfacially active, distorting the absorbance/time profile from which rate constants are derived, altering the interfacial area in the reaction vessel, and displacing reactant molecules from the interface. Neutral surfactants were observed to have similar effects. Chelate adsorption was also demonstrated to affect metal ion extraction equilibria, shifting the pH 1/2 value associated with a given metal ion. The magnitude of this shift was found to depend on the concentration of the chelate, its interfacial adsorption constant, and interfacial area. Differences in the pH 1/2 shift were shown to serve as a means of separating metal ions. Studies of the rate of nickel extraction by 8-quinolinols showed that the distribution constant and interfacial activity of the ligand are important factors governing the balance between bulk and interfacial pathways in the extraction. The interfacial rate constant for a given ligand was independent of organic solvent and was typically 10 times larger than the corresponding bulk value, indicating that the interface, although essentially aqueous in character, is a more conducive medium for the reaction of the metal ion and ligand.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Solvent extraction.; Chemical kinetics.; Surface chemistry.; Liquid metals.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Freiser, Henry

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleThe role of the interface in the kinetics and mechanism of liquid-liquid extraction.en_US
dc.creatorDietz, Mark L.en_US
dc.contributor.authorDietz, Mark L.en_US
dc.date.issued1989en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractWhen solutions of various metal 8-quinolinolates or beta-diketonates in an organic solvent were contacted with an aqueous phase and vigorously stirred to generate a large interfacial area, a reversible decrease in the organic phase concentration of the complex was observed. The magnitude of this decrease varied with interfacial area, solvent, temperature, and the nature and concentration of the complex. Analysis of the phenomenon using the Langmuir isotherm showed that the concentration change may be explained by adsorption of significant quantities of the complexes at the increased liquid-liquid interface generated by stirring. Such adsorption was found to complicate extraction kinetics measurements using the high-speed stirring technique when the product chelate is interfacially active, distorting the absorbance/time profile from which rate constants are derived, altering the interfacial area in the reaction vessel, and displacing reactant molecules from the interface. Neutral surfactants were observed to have similar effects. Chelate adsorption was also demonstrated to affect metal ion extraction equilibria, shifting the pH 1/2 value associated with a given metal ion. The magnitude of this shift was found to depend on the concentration of the chelate, its interfacial adsorption constant, and interfacial area. Differences in the pH 1/2 shift were shown to serve as a means of separating metal ions. Studies of the rate of nickel extraction by 8-quinolinols showed that the distribution constant and interfacial activity of the ligand are important factors governing the balance between bulk and interfacial pathways in the extraction. The interfacial rate constant for a given ligand was independent of organic solvent and was typically 10 times larger than the corresponding bulk value, indicating that the interface, although essentially aqueous in character, is a more conducive medium for the reaction of the metal ion and ligand.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectSolvent extraction.en_US
dc.subjectChemical kinetics.en_US
dc.subjectSurface chemistry.en_US
dc.subjectLiquid metals.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorFreiser, Henryen_US
dc.contributor.committeememberSalzman, W. R.en_US
dc.contributor.committeememberBurke, M. F.en_US
dc.contributor.committeememberFernando, Quintusen_US
dc.contributor.committeememberMiller, Walter B.en_US
dc.identifier.proquest9003482en_US
dc.identifier.oclc703255644en_US
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