M.L.P. Reddy

Synergistic extraction of rare earths with bis(2,4,4-trimethyl pentyl) dithiophosphinic acid and trialkyl phosphine oxide

Synergistic extraction of trivalent rare earths from nitrate solutions using mixtures of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301=HX) and trialkyl phosphine oxide (Cyanex 923=TRPO) in xylene has been investigated. The results demonstrate that these trivalent metal ions are extracted into xylene as MX(3).3HX with Cyanex 301 alone. In the presence of Cyanex 923, La(III) and Nd(III) are found to be extracted as MX(2).NO(3).TRPO. On the other hand, Eu(III), Y(III) and heavier rare earths are found to be extracted as MX(3).HX.2TRPO. The addition of a trialkylphosphine oxide to the metal extraction system not only enhances the extraction efficiency of these metal ions but also improves the selectivities significantly, especially between yttrium and heavier lanthanides. The separation factors between these metal ions were calculated and compared with that of commercially important extraction systems like di-2-ethylhexyl phosphoric acid.

CYANEX 923 AS AN EXTRACTANT FOR TRIVALENT LANTHANIDES AND YTTRIUM

ABSTRACT The extraction of yttrium and some trivalent lanthanides from thiocyanate and nitrate solutions using Cyanex 923 { TRPO ) in xylene as an extractant has been investigated. It has been found that these trivalent metal ions are extracted from thiocyanate solution as M(SCN)3.n TRPO ; n in general having the values of 4 and 3 for the lighter and the heavier lanthanides respectively. On the other hand, from nitrate solutions these trivalent metal ions are extracted as M(NO3)3 3 TRPO. The equilibrium constants of the extracted complexes have been obtained by non-linear regression analysis. In both the thiocyanate and nitrate systems, the distribution ratios of trivalent lanthanides are found to increase with decreasing ionic radii and the distribution ratio of yttrium lies along with those of the middle lanthanides. The separation factors between these trivalent metal ions were evaluated and compared with those obtained using commercially important extraction reagents like tributylphosphate (TBP), trio...

The synergistic extraction of thorium(IV) and uranium(VI) with mixtures of 3-phenyl-4-benzoyl-5-isoxazolone and crown ethers.

The extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been studied using mixtures of 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) and dicyclohexano-18-crown-6, benzo-18-crown-6, dibenzo-18-crown-6 or benzo-15-crown-5. The results demonstrate that these metal ions are extracted into chloroform as Th(PBI)(4) and UO(2)(PBI)(2) with HPBI alone and as Th(PBI)(4) . CE and UO(2)(PBI)(2) . CE in the presence of crown ethers (CE). The equilibrium constants of the above species have been deduced by non-linear regression analysis. The addition of a CE to the metal chelate system enhances the extraction efficiency and also improves the selectivities between thorium and uranium. IR spectral data of the extracted complexes were used to further clarify the nature of the complexes. The binding to the CEs by Th(PBI)(4) and UO(2)(PBI)(2) follows the CE basicity sequence but with DC18C6 and DB18C6, steric effects become more important.

Application of ternary and multicomponent complexes to spectrophotometric and spectrofluorimetric analysis of inorganics.

The application of ternary and multicomponent complexes in spectrophotometric and spectrofluorimetric determination of trace elements is reviewed. Newer types of colour systems employing mixed ligand, surfactant sensitized, ion-association, flotation, derivative and FIA systems are described. Separate sections are devoted to advances in both spectrophotometric and spectrofluorimetric determination of individual elements. Future trends in spectrophotometric and spectrofluorimetric analysis are discussed.

RECENT ADVANCES IN THE SOLVENT EXTRACTION OF MERCURY(II) WITH CALIXARENES AND CROWN ETHERS

This work is focused on the recent advances, mainly achieved during the past ten years on the solvent extraction separation of mercury from aqueous solutions using macrocyclic ligands such as calix[n]arene derivatives and crown ethers.

Differential pulse anodic stripping voltammetric determination of ziram (a dithiocarbamate fungicide).

A d.c. polarographic technique has been used previously for the determination of the pesticide, ziram, in aqueous samples, this paper reports differential pulse anodic stripping voltammetric determination of ziram zinc in rice samples using a static mercury drop electrode. The procedure developed distinguishes inorganic zinc and ziram zinc in sodium acetate-sodium chloride media. The procedure developed is suitable for the determination of concentrations as low as 10 ppb of ziram with a precision of 2.1% for five successive determinations of 150 ppb of ziram.

LIQUID-LIQUID EXTRACTION OF TETRAVALENT TITANIUM FROM ACIDIC CHLORIDE SOLUTIONS BY BIS(2,4,4-TRIMETHYLPENTYL)PHOSPHINICACID

ABSTRACT The extraction of titanium(IV) from hydrochloric acid solutions has been investigated using bis(2,4,4-trimemylpentyl)phosphinic acid (Cyanex 272 = HX) in xylene as an extractant. The results demonstrate that the extraction of titanium occurs via the following reaction where (HX)2 refers to the dimeric form of Cyanex 272. For comparison, extraction studies also have been carried out with bis(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302). The equilibrium constant of the extracted complex has been deduced by non-linear regression analysis taking into account the aqueous phase complexation of the metal ion with inorganic ligands and plausible complexes extracted into the organic phase. The effect of the nature of diluent on the extraction of titanium(IV) with Cyanex 272 has been studied and correlated with the dielectric constant. IR spectral studies of the extracted complex were used to further clarify the nature of the extracted complex. The separation possibilities of titanium(IV) from other associated multivalent metal ions viz. magnesium(II), vanadiwn(V), manganese(II), iron(HI) and zinc(II), which are present in the leach liquors of titanium minerals processing industry has also been discussed.

Solvent Extraction and Separation of Vanadium (V) from Multivalent Metal Chloride Solutions by Cyanex 923

Abstract The solvent extraction behavior of vanadium (V) has been investigated using Cyanex 923 [trialkylphosphine oxide (TRPO)] in kerosene as an extractant. For comparison, extraction studies have also been carried out with vanadium (IV). The results demonstrate that vanadium (V) is extracted into the organic phase as VO2Cl·TRPO. On the other hand, vanadium (IV) is extracted into the organic phase as VOCl2·TRPO. The equilibrium constants of the extracted complexes have been calculated and found to be K ex,V(V) = 3.13 and K ex,V(IV) = 0.14 for vanadium (V) and vanadium (IV), respectively. IR spectral studies of the extracted complex were used to further clarify the nature of the extracted complex. The separation and recovery possibilities of vanadium (V) from other associated metal ions viz, magnesium (II), aluminum (III), titanium (IV), chromium (III), manganese (II), and iron (III), which are present in the waste chloride liquors of titanium minerals processing industry has also been discussed.

4-ACYLBIS(1-PHENYL-3-METHYL-5-PYRAZOLONES) AS EXTRACTANTS FOR f-ELEMENTS

ABSTRACT The liquid-liquid extraction of early actinides such as thorium(IV) and uranium(VI) and trivalent lanthanoids such as neodymium(lll), europium(lll) and lutetium(lll) from nitrate solutions was studied using 4-sebacoylbis(1-phenyl-3-methyl-5-pyrazolone) (H2SP) and 4-dodecandioyl-bis(1-phenyl-3-methyl-5-pyrazolone) (H2DdP) in chloroform as extractants. The results demonstrate that these metal ions are extracted into chloroform as Th(SP)2, Th(DdP)2, UO2(HSP)2, UO2(HDdP)2, Ln(SP)(HSP) and Ln(DdP)(HDdP) with H2SP or H2DdP. The equilibrium constants of the above species were deduced by non-linear regression analysis. The results clearly highlight that thorium(IV) can be selectively separated from uranium(Vl) and trivalent lanthanoids when extracted from 0.2 mol/dm3 nitric acid solutions using 4-acylbis(1-phenyl-3-methyl- 5-pyrazolones). Thorium(IV), uranium(VI) and lutetium(lll) complexes of H2SP were synthesised and characterised by IR and 1H NMR spectral data to further clarify the nature of the complexes.

Studies on the liquid-liquid extraction of iron(III) and titanium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone

The extraction behaviour of iron(III) and titanium(IV) from acidic chloride solutions has been investigated using 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in xylene as an extractant. The results demonstrate that these metal ions are extracted into xylene as Fe(PBI)(3) and TiO(PBI)(2). The equilibrium constants of the extracted complexes have been deduced by non-linear regression analysis by taking into account complexation of metal ion with inorganic ligands in the aqueous phase and all plausible complexes extracted into the organic phase. IR and proton NMR ((1)H NMR) spectra were used to further clarify the nature of complexes extracted into organic phase. The effect of the nature of the diluent on the extraction of iron(III) and titanium(IV) has been studied and correlated with dielectric constants. The extraction behaviour of titanium(IV) has also been compared with that of other metal ions, viz. magnesium(II), vanadium(V), chromium(VI), iron(III), manganese(II), zinc(II) and zirconium(IV), which are associated with the titanium in waste chloride liquors of the titanium-mineral-processing industry.