A. D. Damodaran

Liquid-liquid extraction of yttrium (III) with mixtures of organophosphorus extractants: theoretical analysis of extraction behaviour

Abstract The extraction of yttrium (III) from chloride solutions with mixtures of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) and di-2-ethylhexylphosphoric acid (DEHPA) or tri-n-octyl phosphine oxide (TOPO) in kerosene has been studied systematically over a wide range of conditions. A relatively small synergistic enhancement has been observed with mixtures of acidic organophosphorus extractants (EHEHPA+DEHPA). On the other hand, antagonistic effects have been observed with mixtures of acidic and neutral organophosphorus compounds (EHEHPA+TOPO). These extraction data have been analysed theoretically taking into account complexation of the metal in the aqueous phase by inorganic ligands and plausible complexation in the organic phase.

Energy dispersive X-ray fluorescence (EDXRF) determination of lanthanides after preconcentration on 1-(2-pyridylazo)-2-naphthol modified naphthalene

A method is described for the simultaneous multielement determination of yttrium and lanthanides at microgram level. This is based on the preconcentration of these lanthanides on to 1-(2-pyridylazo)-2-naphthol (PAN) modified naphthalene. The optimal conditions for quantitative preconcentration viz., pH, amount of PAN modified naphthalene, time of stirring and aqueous phase volume were systematically evaluated. The quantitation of lanthanides was carried out by energy dispersive X-ray fluorescence analyzer, employing241Am annular source, via their characteristic K X-rays. The developed procedure gave reliable results in the analysis of xenotime samples.

Synergistic solvent extraction of Eu(III) and Tb(III) with mixtures of various organophosphorus extractants

Synergistic solvent extraction of Eu(III) and Tb(III) from thiocyanate solutions with mixtures of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) and di-2-ethylhexylphosphoric acid (DEHPA) or tributyl phosphate (TBP) or trioctylphosphine oxide (TOPO) or triphenylphosphine oxide (TPhPO) in benzene has been studied. The mechanism of extraction can be explained by a simple chemically based model presented in this paper. The equilibrium constants of the mixed-ligand species of the various neutral donors have been determined by non-linear regression analysis.

Solvent extraction of zinc/II/ with sulphoxides: Theoretical analysis of extraction behaviour

AbstractThis paper describes a theoretical method for analyzing the behaviour of65Zn during solvent extraction from ammonium thiocyanate solutions with dialkyl sulphoxides. The mechanism of extraction of Zn/II/ from thiocyanate medium by sulphoxides may be represented by the following general equation:n

Extraction equilibrium of ytterbium(III) with sulfoxides and their mixtures

xM_{aq}^{m + } + ySCN_{aq}^ - + zS_{org} rightleftharpoons [M_x /SCN/_y ]^{mx - y} .zS_{org}

Synergic liquid-liquid extraction studies of neodymium and praseodymium with mixtures of tributyl phosphate and Aliquat-336 in nitrate media

n where Mm+ is the metal ion and S is the extractant. Expressions for the distribution coefficients were derived taking into account complexation of the metal in the aqueous phase by inorganic ligands and also the dissociation of the extracted ion-pairs in the organic phase. Using these expressions, the values of the extraction constants were determined by a least-squares fit with the experimental extraction data. From these extraction constants, the various species extracted into the organic phase were resolved. The influence of the metal concentration, temperature and the diluent on the extraction of Zn/II/ has been investigated.

Synergistic solvent extraction of cerium(III) with mixtures of thenoyltrifluoroacetone and dialkyl sulfoxides

The extraction of Er(III) and Lu(III) from thiocyanate media with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) and also with mixtures of EHEHPA and thenoltrifluoroacetone (HTTA) or tri-n-octylphosphine oxide (TOPO) or bis 2-ethylhexyl sulfoxide (B2EHSO) in benzene has been studied systematically. Synergistic effects have been observed with mixtures of EHEHPA+HTTA or TOPO. On the other hand, antagonistic effects have been observed with mixtures of EHEHPA+B2EHSO. These extraction data have been analyzed theoretically with the aid of a computer by taking into account complexation of the metal in the aqueous phase by SCN− and plausible complexation in the organic phase. The extraction constants of the various product species have been deduced by non-linear regression analysis. The stability constants for the thiocyanate complexes of the metal ions have also been determined.

Synergistic solvent extraction of lutetium(III). Computer aided analysis

The extraction equilibria of175Yb from thiocyanate solutions with di-n-pentyl sulfoxide (DPSO), di-n-octyl sulfoxide (DOSO), tri-n-octylphosphine oxide (TOPO) and their mixtures in carbon tetrachloride has been investigated. A relatively small synergistic enhancement has been observed with mixtures of dialkyl sulfoxides (DPSO+DOSO) and also with mixtures of DPSO+TOPO. These extraction data have been analyzed with the aid of a computer by taking into account complexation of the metal in the aqueous phase by inorganic ligands and assuming a set of product species in the organic phase and adjusting their formation constants through an iterative non-linear least-squares procedure to obtain the best fit to the data. The extraction of the metal is inversely and linearly dependent upon the dielectric constant of the solvent and temperature of the system.