Improved extraction–separation of alkaline earths and lanthanides with the aid of an ion size-selective masking reagent

Abstract

A water-solu ble macrocyclic compound, 4'-sulfobenzo-18-crown-6 (SBlSC6), was prepared and utilized as an ion size-selective masking reagent with a view to establishing a highly selective extraction-separation system. In the synergistic extraction of alkaline earths with 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone and trioctylphosphine oxide in cyclohexane or benzene, the extraction of those with larger ionic radii shifted to a higher pH region when SB18C6 was added to the aqueous phase, giving improved separations. A similar result was achieved in the extraction of lanthanides into chloroform with bis(2-ethylhexy1)phosphoric acid. The distribution of SB18C6 into cyclohexane, benzene or chloroform was so low in comparison with that of 18-crown-6 (18C6) and cryptand[2.2.2] that the synergistic extraction with 18C6, which usually reduces the selectivity, was not observed.

Facilitated alkali ion transfer at the water|1,2-dichloroethane interphase: ab initio calculations concerning alkaline metal cation–1,10-phenanthroline complexes

“…Cation transfer across liquid/liquid interphases assisted by complexing agents has been the subject of intensive research in the last years [1,2,3,4,5]. One main reason is the application of this phenomenon in cation extraction processes [6,7,8] and in the development of new ion selective electrodes. In this sense, alkaline and alkaline-earth cations transfer is mainly relevant in the field of clinical chemistry.…”

Ion-Pair Extraction System for the Mutual Separation of Lanthanides Using Divalent Quadridentate Schiff Bases

“…Mutual separation of lanthanides is very difficult due to their remarkable chemical similarities, such as their charges and radii. − The solvent extraction method − is the best choice for separation, and recently, many kinds of novel extraction systems have been investigated to improve their mutual separability. − …”

“…[1][2][3] The solvent extraction method [4][5][6] is the best choice for separation, and recently, many kinds of novel extraction systems have been investigated to improve their mutual separability. [7][8][9][10][11][12][13][14][15][16][17] Quadridentate divalent phenolic Schiff bases, such as N,N′bis(salicilidene)ethylenediamine (H 2 salen), N,N′-bis(salicilidene)o-phenylenediamine (H 2 saloph), and N,N′-bis(salicilidene)-1,3propanediamine (H 2 salpn), are well known as ligands that are easy to synthesize and have structural rigidity, and they are used also as selective extractants for several kinds of metal cations. [18][19][20][21][22][23] However, these Schiff bases have hardly been used for the extraction of trivalent lanthanide cations (Ln 3+ ).…”

Complex Formation of Metal Ions with Sulfonated Crown Ethers in Water as Ion Size Selective Masking Reagents.

“…4 and are given in Table 2. 10 The log Ii values increase in the order Mg2+ < Ca2+ < Sr2+ < Ba2+. Consequently, the extraction region for the larger metal ions shifts to higher pHs, resulting in improved separation.…”