Selective extraction and transport of UO2 2+ with calixarene-based uranophiles

Abstract

Hexacarboxylate derivatives of p-t-butylcalix [6]arene (2b) and p-hexylcalix[6]arene (3b) extract uranyl ion (UO;+) efficiently and selectively from water into organic media. This high selectivity can be attributed to the nature of calix [6]arene; this is suitably structured for the binding of U02'+, which requires a pseudoplanar h exacoord i nation . When t r i octy I met h y I a m mo n i u m cation (T M A + ) is added to the organic phase, the stoicheiometry of the extraction species [U02'+/(2b)] changes from 1 : 3 t o 1 : 1-2. This implies that an additional 1-2 mol of UO,'+ are adsorbed to (2b) t o form 'neutral' extraction species and can be displaced by added TMA'. UO, " is transported by (2b) across a liquid membrane from a neutral IN (source) aqueous phase (pH 8.5) to an acidic OUT (receiving) aqueous phase (0.1 mol dm-3 HCI) in an active transport manner. The rate-determining step is the release of UO,*+ from the membrane to the OUT aqueous phase. On the basis of these basic data, w e have prepared polymer/liquid-crystal (N-4'-ethoxybenzylidene-4-butylaniline, EBBA/TMA+CI-) composite membranes immobilising (2b) and have found that the rate of UO, , ' transport is efficiently controlled by the changes in pH and temperature. These are novel examples for the selective transport of UO,'+.

Binding of uranyl ion by 2,2′-dihydroxyazobenzene attached to crosslinked polystyrenes covered with highly populated quaternary ammonium cations

“…2,13 In particular, efforts have been directed toward selective molecular recognition of uranyl ion with macrocyclic host molecules including crown ethers and calixarenes. [2][3][4]7,[13][14][15][16] In a previous study, 17 we found that 2,2Ј-dihydroxyazobenzene (DHAB) (1) forms a 1 : 1-type complex with uranyl ion. The pH dependence of log K f for the uranyl complex (2) of a DHAB derivative revealed that ionization of the phenol groups and the uranium-bound water molecule facilitate uranyl binding.…”

“…The design of effective host molecules for uranyl ion is connected with the economic importance of selective extraction [1][2][3][4] of uranium from seawater as well as the development of therapeutic agents 5 for removal of uranyl ion from human bodies. Uranium exists mainly as the tricarbonate complex of uranyl ion [UO 2 (CO 3 ) 3 4Ϫ ] in seawater.…”

Liquid-Liquid Extraction of Metal Ions with a Cyclic Ligand Calixarene Carboxyl Derivative

“…Izatt et al 4 first reported on the extraction of alkaline metal ions with a calixarene; then, novel calixarene ligands have been synthesized for the extraction of several metal ions. [5][6][7][8][9] In a previous paper we reported on the extraction behavior of rare-earth metals with a calixarene derivative functionalized by carboxyl groups. 10 In the present study, we investigated the extraction behavior of twelve kinds of metal ions, such as alkaline (Li, Na, K, Cs), alkaline-earth (Mg, Ca, Sr, Ba) and transition-metal ions (Cu, Zn, Co, Ni) with two cyclic compound calixarenes (o-carboxylate derivatives of p-toctylcalix[n]arene (n=4,6)) along with the monomer analog (n=1).…”

Highly Selective Transport of a Uranyl Ion through a Liquid Membrane Containing a Lipophilic Ion-Associate of Methyltrioctylammonium and Hydroxycalix[n]arene-p-sulfonates (n = 6, 8) as Metal Carriers

“…1 Shinkai et al have shown that carboxyl and hydroxamate derivatives of 16 could extract UO2 2+ with higher extractability and selectivity than those of 14 derivatives. [2][3][4][5][6] On the other hand, they first synthesized water-soluble calix[n]arenes, 2n, in 1987, and reported that 26 is a metal ligand that has a high affinity to UO2 2+ in stability and selectivity, and named it "superuranophile". 7 We studied their reaction with various metal ions, including proton in aqueous solution.…”