V. Chakravortty

Separation and recovery of cobalt(II) and nickel(II) from sulphate solutions using sodium salts of D2EHPA, PC 88A and Cyanex 272

Abstract Separation and recovery of divalent cobalt and nickel ions from sulphate solutions containing 0.01 M metal ions each and 0.1 M Na 2 SO 4 have been carried out using 0.03, 0.05 and 0.06 M sodium salts of D2EHPA, PC 88A and Cyanex 272 in kerosene. The percentage extraction of metal ions increased with increasing equilibrium pH. Cobalt was preferentially extracted over nickel with the extractants; however, 0.05 M NaPC 88A and NaCyanex 272 were found to be suitable for the separation study. The highest separation factor was achieved with 0.05 M NaCyanex 272 at equilibrium pH 6.85. Recovery of cobalt from cobalt–nickel bearing solution was achieved with 0.05 M Cyanex 272 and PC 88A at equal phase ratio followed by their stripping with 0.02 M H 2 SO 4 at O:A ratio of 2:1. Nickel was extracted from the cobalt-free raffinate in two stages at equal phase ratio with PC 88A and Cyanex 272 followed by their stripping with 0.02 M H 2 SO 4 at O:A ratio of 4:3 and 2:1, respectively.

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...

Separation of divalent manganese and cobalt ions from sulphate solutions using sodium salts of D2EHPA, PC 88A and Cyanex 272

Abstract The extraction and separation of Mn(II) and Co(II) from sulphate solutions have been carried out using sodium salts of di-(2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC 88A) and bis-(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) in kerosene. The percentage extraction for the metal ions was increased with increasing equilibrium pH in the case of all the extractants. Manganese was preferentially extracted over cobalt with the extractants and NaD2EHPA was found to be the most suitable extractant for separation, the separation factor being maximum with 0.05 M NaD2EHPA at equilibrium pH 4.45. Manganese and cobalt extractions were carried out at O:A ratio of 9:8 and 1:1, respectively, followed by their strippings at O:A ratio of 2:1 and 4:3 using 0.02 M H 2 SO 4 .

Thermal studies on isolated and purified lignin

Abstract The isolation, purification and characterisation of pure lignin, extracted from black liquor obtained from a large pulp and paper mill, are reported. The ultimate analysis of the purified lignin, resulting in 0.3% ash content, confirms its quality as being comparable to any high-grade imported lignin. Thermal analysis resulted in an activation energy of 29.87 kJ mol −1 for the thermal decomposition of pure lignin; this is discussed. Detailed IR spectroscopic, XRD and DTA/DTG analyses of the lignin sample are also presented.

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.

Organophosphinic, phosphonic acids and their binary mixtures as extractants for molybdenum(VI) and uranium(VI) from aqueous HCl media

Extraction studies of uranium(VI) and molybdenum(VI) with organophosphoric, phosphinic acid and its thiosubstituted derivatives have been carried out from 0.1–1.0M HCl solutions. The extracted species are proposed to be UO2R2 and MoO2 CIR on the basis of slope analysis for uranium(VI) and molybdenum(VI), respectively. The extraction efficiencies of PC-88A, Cyanex 272, Cyanex 301 and Cyanex 302 in the extraction of molybdenum(VI) and uranium(VI) are compared. Synergistic effects have been studied with binary mixtures of extractants. Separation of molybdenum(VI) from uranium(VI) is feasible by Cyanex 301 from 1M HCl, the separation factor log βbeing 2.3.

Synergistic solvent extraction of trivalent lanthanides with mixtures of 3-phenyl-4-benzoyl-5-isoxazolone and crown ethers

ABSTRACT Synergistic solvent extraction of trivalent lanthanides such as Nd, Eu and Tm has been studied using mixtures of 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) and 18-crown-6; 15-crown-5, benzo-15-crown-5, or dibenzo-18-crown-6. The results demonstrate that these trivalent metal ions are extracted into chloroform as Ln(PBI)3 with HPBI alone and as Ln(PBI) 3. CE in the presence of crown ethers (CE). The equilibrium constants of the above species are found to increase monotonically with the decreasing ionic radii of these trivalent lanthanides. The addition of a crown ether to the metal chelate system significantly enhances the extractability of these trivalent metal ions.

Solvent extraction of uranium(VI) and molybdenium(VI) by Alamine 310 and its mixtures from aqueous H3PO4 solution

Liquid-liquid extraction of uranium (VI) from aqueous phosphoric acid solution by triisodecylamine (Alamine 310), tri-n-butyl phosphate (TBP), di-n-pentyl sulfoxide (DPSO) and their mixtures in benzene in the range 1–10M aqueous H3PO4 shows that extraction is maximum (≈80%) in the higher acidity range 6–8 M. Extraction of this metal ion by bis(2,4,4-trimethylpentyl)phosphinicacid (Cyanex 301) and its mixtures studied in the range 0.2–1.0M aqueous H3PO4 is far from being quantitative. Antagonism in extraction by mixtures of extractants is observed in most of the cases. Extraction of molybdenum(VI) under identical conditions shows that it is quantitative in the lower acidity range upto 2M H3PO4. Separation of uranium(VI) from molybdenum(VI) is feasible by Alamine 310, TBP and DPSO, the order of efficiency being TBP>DPSO>Alamine 310.

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.

Quantitative PIXE analyses of ferromanganese oxide deposits from different locations of the Indian Ocean and a deposit from the Pacific Ocean

Abstract The present studies on ferromanganese nodules and encrustations from the Indian Ocean and a sediment from the Pacific ocean, were carried out to investigate the role of Mn and Fe in the uptaking of various trace elements from seawater. The Indian Ocean samples comprised eight iron rich ferromanganese nodules and four ferromanganese encrustations, out of which two are from Mid Indian Ocean Ridge (MIOR) and one each from Afanasiy Nikitin seamount and topographically elevated region. The Pacific Ocean sample was a metalliferrous sediment from Lau Basin. The Proton Induced X-ray Emission (PIXE) measurements were carried out on all the samples using 3 MeV proton beam from a 3 MV Pelletron accelerator for quantitative multielemental analysis. The spectral data were analysed using GUPIX software. Quantitative estimate of nearly 21 elements, e.g., K, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Y, Zr, Nb, Mo, Ba, Tl, Pb, and Bi have been made. The classification of the deposits into hydrogenous and hydrothermal types was carried out on the basis of their Mn/Fe ratios and subsequently, the distribution of various minor and trace elements were studied. The growth rate of these deposits are estimated. The findings show that, the concentrations of various elements in hydrogenous deposits are higher compared to that in hydrothermal ones. The reason for this behaviour is attributed to suitable physico-chemical oceanic conditions prevailing at the depositional sites and the growth rate of these deposits. The variation in the concentrations of Co, Ni and Cu is shown to be dependent on ocean depth. It was found that the Co content is significantly high for the deposit from the Afanasiy Nikitin seamount. It has also been shown and discussed that the hydrothermal processes seem to be more controlling in the uptake of V and As than the hydrogenous processes.