Macrocyclic extractants separation

Composition of Macrocyclic Extractables. The quantitative procedure used in this work to separate and determine the level of the low molecular weight oily fraction is based on using a solvent mixture (hex-... 

Kumar, A., Singh, R.K., Bajpai, D.D., and Shukla, J.P., Some aspects of the extraction-separation of actinides hy macrocyclic crown compounds, BARC/1994/E/006. 

Macrocyclic compounds have been proposed for selective extractive separation of metals, mostly alkali and alkaline earth metals [44-51]. An exhaustive review of applications of these compounds is given in articles [44,49]. Macrocyclic compounds form cationic... 

An example of crown ether applied in selective separation of alkali metals is dibenzo-18-crown-6 (formula 1.15). Extractive separations of metal ions are also performed with macrocyclic ligands containing nitrogen or oxygen atoms, as well as macrocycles with combinations of oxygen, nitrogen, and sulphur atoms (N-0, S-0, N-S) [45,48]. A macrocyclic compound with only nitrogen hetero-atoms (formula 1.16) is selective for copper. 

Macrocycllc compounds (some crown ethers and cryptands) are selective reagents for extractive separation of alkali metals [22-27]. These ligands form cationic complexes with alkali metal ions, and these can be extracted as ion-pairs with suitable counter-ions e.g., picrate) [28], most often into chloroform. For potassium, p-nitrophenoxide was used as counter-ion [29]. In cases, where a coloured anionic complex is a counter-ion [30], the extract may serve as a basis for determining the alkali metal. The effect of the structure of the dibenzo-crown ether rings upon the selectivity and effectiveness of isolation of alkali metals has been studied in detail [31]. Chromogenic macrocyclic reagents applied for the isolation and separation of alkali metals have been discussed [32]. 

Cyclodextrins can solubilize hydrophobic molecules in aqueous media through complex formation (5-8). A nonpolar species prefers the protective environment of the CDx cavity to the hulk aqueous solvent. In addition, cyclodextrins create a degree of structural rigidity and molecular organization for the included species. As a result of these characteristics, these macrocycles are used in studies of fluorescence and phosphorescence enhancement (9-11), stereoselective catalysis (.12,13), and reverse-phase chromatographic separations of structurally similar molecules (14,15). These same complexing abilities make cyclodextrins useful in solvent extraction. 

Dozol, J. F. Scwing-Weill, M. J. Arnaud-Neu, F. Bohmer, V. Ungaro, R. van Veggel, F. C. J. M. Wipff, G. Costero, A. Desreux, J. F. de Mendoza, J. Extraction and Selective Separation of Long-Lived Nuclides by Functionalized Macrocycles, European Commission, Nuclear Science and Technology series, EUR19605 EN 2000 p. 198. 

Mixed donor macrocycles have been employed in a number of applications involving the separation or analysis of manganesetll). These include examples of use of such a ligand as the extractant in solvent extraction processes " and as the ionophore in membrane transport studies. 

A series of N-alkyl aza-18-crown-6 efhers were synfhesized and characterized. These monoaza-substituted crown ethers in ILs were investigated as recyclable extractants for separation of Sr " and Cs from aqueous solutions. The pH-sensitive complexation capability of these ligands allows for a facile stripping process to be developed so that both macrocyclic ligands and ILs can be reused. 

Dozol, J.E., Schwing-Weill, M.J., Amaud-Neu, F. et al. 2000. Extraction and selective separation of long-lived nuclides by functionalized macrocycles European Commission, Nuclear Science and Technology Report. EUR 19605. 

In 2001, the SRS announced its choice of CSSX as the baseline cesium-removal technology over small-tank precipitation (a small-scale version of the ITP process) and ion exchange with CST for its Salt Waste Processing Facility (SWPF) to go into operation in 2010 [22], An optimized solvent system, model, and flowsheet were developed and demonstrated in 2001 and 2002 [37,49], and a modular concept was developed by ORNL in 2003 [68], Thus, the past decade has seen the emergence and maturation of a powerful new technology based on a macrocyclic cation receptor designed to function in solvent extraction to meet the critical need of the USDOE for a means of cleanly separating Cs from alkaline tank waste. 

Crown ether complexes of the -block metals number in the many hundreds, " and reviews focused on them, including their use in separation chemistry and selective ion extractions, are extensive. Growing interest has been expressed in the use of macrocyclic ethers in the design of electroactive polymers. ... 

Macrocyclic reagents, such as chromogenic crown ethers of the type 14-crown-4 (extraction to 1,2-dichloroethane in the presence of picrate) were used for determination of Li [53]. The 14-crown-4 type derivatives have been applied for determination of Li in blood by a continuous FIA method [54,55]. The use of chromogenic reagents aza-12 (-13 or -14)-crown-4 has also been proposed [56,57]. The effect of substituents on the selectivity of separation of Li (and Na) by means of benzo-14-crown-4 and 13-crown-4 ethers was studied [58]. A review of chromogenic macrocyclic reagents used for determination of lithium (and other alkali metals) has been published [32]. 

Scandium can also be separated from rare-earth and other metals by extraction as a complex of HTTA [8,9], or salicylate [10]. Xylene [8], CHCI3 [9], and mesityl oxide [10] have also been used for extraction of Sc. Scandium has been extracted from ascorbic acid medium with Aliquat 336S [11], or with acetylacetone in the presence of 3,5-dichlorophenol [12]. Macrocyclic ethers have also been used for extraction of Sc [13]. 

Initial attempts to perform LLE in flow analysis without phase separation were carried out by Kina et al. [160] who designed a flow injection system for the fluorimetric determination of potassium involving extraction into 1,2-dichloroethane containing a macrocyclic compound. The aqueous sample was injected into an unsegmented organic flowing... 

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