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ETUDE THERMODYNAMIQUE ET CINETIQUE DE L'EXTRACTION LIQUIDE-LIQUIDE DU NICKEL(II) PAR LA 2-ETHYLHEXANAL OXIME ET UN MELANGE DE 2-ETHYLHEXANAL OXIME ET D'ACIDE DI-2-(ETHYLHEXYL) PHOSPHORIQUE

Abstract : Both thermodynamics and kinetics studies were systematically investigated on the liquid-liquid extraction of the nickel(II) by 2-ethylhexanal oxime (EHO) and its mixture with di-(2-ethylhexyl) phosphoric acid (D2EHPA) in dodecane.
Various aggregations of the EHO and D2EHPA were characterized by vapour pressure osmometry technique VPO. While EHO and D2EHPA multimers were shown to be monomers (namely HOx and HA), dimers and trimers, no mixed complex between EHO and D2EHPA is evidenced.
The study of the extraction of the nickel by the oxime was carried out in various aqueous media. If kinetics was relatively slow, only chloride favoured the extraction from acidic media. The organic extracted complexes were identified by means of the slope method. In the presence of NH4NO3 or without any salt, the complexes were Ni(Ox)2(HOx)n. In chloride medium, the organic complex were NiCl2(HOx)n for quite acidic media (pH<4) or NiCl(Ox)(HOx)n for less acidic pH; n being equal to 3 or 4 for higher oxime concentrations.
The kinetic study, conducted in a highly stirred homothetic cell of Rushton type, showed that the extraction process undergone interfacial limitations. For the chloride media, the limiting step is the solvation reaction of the neutral complex NiCl2(H2O) for pH<4, or the adsorbed NiCl(Ox)(H2O) for higher pH, by a molecule of oxime. Otherwise, the process is kinetically controlled by the cationic exchange reaction between Ni(Ox)(H2O)5+ and HOx.
The addition of D2EHPA co-extractant led to a significant kinetics enhancement. The organic extracted complex was identified as NiA2(Hox) through slope method and iso-molecular study. The limiting step was an interfacial reaction of cationic exchange type between the adsorbed Ni(A)(H2O)5+ and the HA monomer. For comparison, kinetic study was equally achieved in a constant interfacial area cell of Armollex type. Chemical results were exhaustively confirmed and the interfacial specific area value deduced for the Rushton cell.
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https://tel.archives-ouvertes.fr/tel-00011562
Contributor : Arnaud Buch <>
Submitted on : Wednesday, February 8, 2006 - 12:30:34 PM
Last modification on : Wednesday, December 9, 2020 - 3:11:14 PM
Long-term archiving on: : Tuesday, June 15, 2010 - 4:30:28 PM

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  • HAL Id : tel-00011562, version 1

Citation

Arnaud Buch. ETUDE THERMODYNAMIQUE ET CINETIQUE DE L'EXTRACTION LIQUIDE-LIQUIDE DU NICKEL(II) PAR LA 2-ETHYLHEXANAL OXIME ET UN MELANGE DE 2-ETHYLHEXANAL OXIME ET D'ACIDE DI-2-(ETHYLHEXYL) PHOSPHORIQUE. Autre. Université Pierre et Marie Curie - Paris VI, 2001. Français. ⟨tel-00011562⟩

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