Extractants chelating

FIGURE 2.1 Structural representation of some chelating extractants. 

FIGURE 2.2 Structural representation of the (a) keto-form, (b) enol-form, and (c) metal complex. 

FIGURE 2.3 Structures of some beta-diketones used for the extraction of actinides. 

Two-phase Extraction Constants for Actinides with Several Beta-Diketones 

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From these results, one can understand that the liquid-liquid interface can assist effectively in the interfacial reaction through the adsorption of extractants like a solid catalyst. The whole extraction scheme of the chelate extraction system is represented in Scheme 1. 

When an auxiliary ligand is added to a chelate extraction system and it enhances the extractability and extraction rates, such a phenomenon is termed synergism. A typical... 

From the fundamental knowledge concerning the interfacial complexation mechanism obtained from the kinetic studies on chelate extraction, ion-association extraction, and synergistic extraction, one can design the interfacial catalysis. The main strategy is to raise the concentration of the reactant or intermediate at the interface. 

The given structure shows two molecules of TTA to have reacted with a cobalt ion to form the cobalt-TTA complex, in which the cobalt atom forms a valence bond solid lines) with one, and a coordinate bond (broken lines) with the other, oxygen atom of each TTA molecule. Thus, in the cobalt-TTA complex there is a six-membered ring formed by each TTA molecule with the cobalt atom. Metal chelate complexes of this type have good stability, they are nonpolar and soluble in the organic phase. The usefulness of the chelating extractants in solvent extraction is therefore obvious. 

When a 350 ml seawater sample was spiked with 54Mn and taken through the chelation, extraction, and back-extraction procedures, the observed recovery of the radio-tracer was 100.6%. Estimates of detection limits for manganese based on sets of both shipboard and shore laboratory separations are of the order of 0.1 nmol/1. The accuracy of the technique is demonstrated by data from the ICES fifth-round intercalibration exercise for trace metals in seawater [449 ]. 

Rodionova and Ivanov [667] used chelate extraction in the determination of copper, bismuth, lead, cadmium, and zinc in seawater. The metal complexes of diethyl and dithiophosphates are extracted in carbon tetrachloride prior to determination by atomic absorption spectrometry. 

Element Direct Chelation- extraction Ion exchange Ion exchange... 

Determination of the ionic forms of alkyllead compounds is difficult because of the incomplete extraction of the dimethyl and trimethyl species from sample matrices. Recently a chelation extraction method followed by derivatization to their butyl homologues has overcome all the previous difficulties to achieve quantitative extraction of the dialkyl- and trialkyllead (R=Me, Et) from water samples at nanogram levels [f 8]. 

Stary, J. Freiser, H., Compilers, Part IV "Chelating Extractants" in "Equilibrium Constants of Liquid-Liquid Distribution Reactions" IUPAC Chemical Data Series No. 

The process of transferring a metal ion M" from an aqueous solution to a water-immiscible organic solvent by an acidic chelating extractant HL that forms a lipophilic neutral complex ML with the ion can be represented as ... 

The control system is largely situated in a series of 19" rack-mounted units. As far as possible, each of these units is self-contained with one controlhng the sample introduction unit, one the neutralization unit, one the chelation—extraction and extract collection units and another being used as the source of the various power supphes. The neutralization controller and phase boundary sensor are situated in small separate units and the digestion unit controller is incorporated into the digester module. 

The system control is based on a series of six cam timers, which control the following sample introduction unit, sampling phase sample introduction unit, refilling phase neutralization unit, neutralization phase neutralization unit, wash phase chelation— extraction unit, extraction phase and chelation—extraction unit, collection and wash phase. 

Chelating extractants owe effectiveness to the attraction of adjacent groups on the molecule for the metal. Anionic extractants are commonly based tin high molecular weight amines. Solvating extractants contain one or more electron donor atoms, usually oxygen, which can supplant or partially supplant the water W hich is altached to the metal ions. 

The complex species is more soluble in organic solvents than in water. Many examples are quoted in the literature, with special emphasis on metal chelates extraction. 

In the case of anionic chelating extractants such as HDEHP, HDBP, HTTA or generally HA, the reaction stoichiometry with respect to the metal, Mz+, and extractant, HA, is given by equation (134). In this case, DM is given by equation (135),90 where [MAJ is the neutral extracted species and [MA ] represents all the aqueous phase species for n = 0-N of which MAX is one. A plot... 

Kakitani, T., Hata, T., Katsumata, N. (2007) Chelating extraction for removal of chromium, copper, and arsenic from treated wood with bioxalate. Environmental Engineering Science, 24(8), 1026-37. 

The organic extractants used for the separation of metal ions broadly fall into three classes, chelating extractants, solvating extractants, and ion-pair extractants. For the first two classes, usually nonpolar organic diluent is preferred. On the other hand, polar diluents are preferred in the case of ion-pair extraction. 

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