Michel Burgard

Rare-earth metal-ion separation using a supported liquid membrane mediated by a narrow rim phosphorylated calix[4]arene

Abstract The transport of rare-earth metal ions through a supported liquid membrane mediated by 5,11,17,23-tetra- tert -butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy)calix[4]arene ( 1 ) (cone conformation) in o -nitrophenyl hexyl ether (NPHE) has been investigated. The effect of the initial metal concentration, salting-out agent concentration in the feed phase and temperature as well as the carrier concentration on the flux was studied. The separation ability of ligand 1 was tested for the separation of a mixture of 11 rare-earth metal ions (La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb and Y). The flux depends on the salting-out agent and varies according to the order Al(NO 3 ) 3 >NaNO 3 >HNO 3 . In each case the maximum flux was found for Pr and Nd. Calixarene 1 exhibits an improved intragroup separation efficiency with respect to the non-macrocyclic ligand tri- n -octylphosphine oxide (TOPO).

EXTRACTIVE PROPERTIES TOWARDS RARE-EARTH METAL IONS OF CALIX[ 4] ARENES SUBSTITUTED AT THE NARROW RIM BY PHOSPHORYL AND AMIDE GROUPS

ABSTRACT The extractive properties of the cone and partial-cone isomers of 5,11,17,23-tetra-?ert-butyl-25,27-bis( diethylcarbamoylmethoxy)-26,28-bisi( diphenylphospninoylmethoxy) calyx[ 4] arene ( cone-1 and partial-cone -1) in 1,2-dichloroethane towards rare-earth metal ions in nitrate media at 25 ° C were investigated. The analysis of the extraction equilibrium obtained from a mixture of four rare-earths ( La, Eu, Er and Y) revealed that the extracted species have a 1 1 metal/ ligand ratio for both ligands. The intra-group separation efficiercies of the ligandls have been evaluated in a competitive extraction process of 11 rare-earth metal ions ( La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb and Y). Significantly higher extractive properties were found for cone-1 with respect to partial-cone-1, suggesting the crucial role of the phosphoryl groups in the complexation of the rare-earth ions. These findings were

Lanthanide cation binding to a phosphoryl-calix[4]arene:the importance of solvent and counterions investigated by molecular dynamicsand quantum mechanical simulations

Molecular dynamics simulations on the 1:1 M3+ nlanthanide (La3+, Eu3+ and Yb3+) “inclusion” ncomplex of a t-butyl-calix[4]arene L nsubstituted at the narrow rim by four CH2–P(O)Ph2 narms demonstrate the role of hydration and counterions on the cation binding nmode and shielding. In dry chloroform and in the absence of counterions, nthe cation is “endo”, fully encapsulated within the pseudo-cavity ndelineated by the four phosphoryl arms and the four phenolic oxygens. This “endo” nbidentate binding mode is supported by full ab initio quantum mechanical noptimization of the calixarene M3+ complexes. In biphasic nsolution, the complexes are shown to be surface active and to adsorb at an “oil”/water ninterface with the cationic site pointing towards water and the hydrophobic t-butyl ngroups in “oil”. The cation is not encapsulated, but adopts an “exo ” nposition, coordinated to the four PO oxygens of L, to water nmolecules, and to counterions. This complex is too hydrophilic to be extracted nfrom the interface to an organic phase. The unexpected binding mode has important nimplications concerning the mechanism of liquid–liquid ion extraction n and the microscopic state of the extracted complex in the organic phase.

Non‐dispersive Solvent Extraction of Alkali Metals with the Dicyclohexano 18 Crown 6: Evaluation of Mass Transfer Coefficients

Abstract The aim of this study is both to check the feasibility of the membrane contactor for the extraction of alkali metals with the dicyclohexano 18 crown 6 as extractant and to obtain informations about the mass transfer of these metals. The influence of tube and shell side hydrodynamics on extraction rates is studied. High aqueous flow rates flowing inside the tubes increase extraction efficiency, on the other hand the organic diffusion layer seems to have a less important role on the mass transfer. Initial extraction rate order follows the order of the extraction equilibrium. The mass transfer coefficients of alkali cation are calculated by performing an unsteady state material balance and compared with values calculated by the resistance in series model and by a steady state model.

SFGP 2007 - An Analysis of the Mass Transfer in a Non-Dispersive Solvent Extraction Closed System

The experimental study that concerns the extraction of alkali picrates with the bis-crown-6-calix[4]arene in a hollow fibers membrane contactor, validates a dynamic model described in a previous paper [D. Trébouet, Sep. Pur. Tech., 50, 97-106, 2006]. The experimental data confirm the influence of parameters as the aqueous and organic phase flowrates and module capacity factor on the sensitivity of the system. It appears clearly that the closed extraction system operates in an unsteady state until equilibrium is reached and so only dynamic models can represent mass transfer within reasonable accuracy. The overall mass transfer coefficient is determined even in the case where the equilibrium is described by a non-linear distribution isotherm. The determination of an overall mass transfer coefficient shows that the diffusion of the metal complex in the microporous is the main limiting step of mass transfer.

Cation coordination by calix[4]arenes bearing amide and/or phosphine oxide pendant groups: how many arms are needed to bind Li+vs. Na+? A combined NMR and molecular dynamics study

Combined spectroscopic and theoretical studies have been performed on two recently developed calix[4]arenes in the cone conformation, L1 (bearing two –CH2C(O)NEt2 and two –CH2P(O)Ph2 substituents occupying respectively distal phenolic positions) and L2 (with four –CH2P(O)Ph2 substituents), in order to compare the Li+vs. Na+ cation binding mode. Molecular dynamics simulations indicate that coordination of the Li+ cation involves three of the four substituents (the two phosphoryl groups and one of the two amide functions of L1; three phosphoryl arms of L2). A variable temperature NMR study carried out with L1·Li+ confirms this fourfold coordination and reveals that in solution the lithium cation moves between the two adjacent OPOPOamide units. The weaker binding of the Na+ cation results in a more symmetrical coordination of the four phenolic oxygen atoms and two carbonyls of L1 or four phosphoryls of L2.

Synthèse et propriétés ionophores des phospha-calix[4]arènes

Resume La presente mise au point decrit les principales methodes de synthese de derives phosphores de calix[4]arenes, notamment de phosphates, phosphonates, oxydes de phosphine et phosphines. Les proprietes extractives des calix[4]arenes phosphorylees sont egalement exposees, laccent etant place sur leur utilisation pour lextraction et la separation des lanthanides et actinides.