摘要:

The solvent extraction of uranium(VI) and thorium(IV) with a tetra-carboxylated calix[4]arene (LH4) in chloroform has been studied in the presence or absence of alkali ions (M+=Na+, K+). When studied alone, UO22+and Th4+were extracted into chloroform as 2:2 and 1:1 metal:ligand complexes, respectively. The efficiency of extraction increases in the presence of alkali ions, due to the formation of heteronuclear complexes. For uranium(VI), the extracted species are found to be both 2:2:2 and 1:1:1 (uoi22+:M+:LH4,) mixed complexes. For Th(IV) in the presence of Na+, the formation of a mixed complex in 1:1:1 (Th(IV):Na+:LH4,) proportions has been evidenced. However, the exact nature of this species could not be determined. In practical grounds, LH. may be useful as a selective extracting agent for Th(IV) with respect to U(VI) since separation factor Th(IV)/U(VI) close to 1000 have been measured in competitive extraction, in the presence or absence of alkali ions.

ISSN:0736-6299    

DOI:10.1080/07366299708934472

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Studies have been made on the extraction of U(VI) from nitric acid media by three n-alkylcaprolactams (hexyl-: Bg, octyl-:Bg, dodecyl-rBn) and their mixtures in toluene. The distribution ratio of U(VI) increased in the sequence of B12> B8> B6, where the extracted species have been found to be UO2(NO3)2(B)2and UO2NO3)3B12H+by slope analysis method. Moreover, the molecular structure of the extracted complex with B8was demonstrated clearly by use of a single-crystal X-ray diffractometer. The enthalpy changes in the U(VI) extraction were evaluated by.temperature variation method, indicating that the extraction process is exothermic. Stripping of U(VI) from the organic phases was also discussed. For binary mixtures of B6, a small synergistic enhancement was found, the sequence being of B6-B12> B8-B12> B6-B8

ISSN:0736-6299    

DOI:10.1080/07366299708934473

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The extraction of U(IV) by di-2-ethylhexyl phosphoric acid (HDEHP) in kerosene from phosphoric acid was measured spectrophotometrically.The effect of extractant, phosphoric acid, uranium, Fe(lI) and Fe(lll) concentrations on the extraction process were separately investigated. The effect of different reagents and temperature on the stripping of U(IV) were also tested.The results obtained showed that the extraction increases with the increase in HDEHP and Fe(lll) concentrations while it decreases with the increase in phosphoric acid, uranium and Fe(ll) concentration. The use of high phosphoric acid concentration as strip solutions at low temperature was found to give good stripping results.

ISSN:0736-6299    

DOI:10.1080/07366299708934474

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Extraction of M(ClO4)m, (Mm+= Li+, Na+, Mg2+, and Ca2+) from their aqueous solutions into hexane with trioctytphosphine oxide (TOPO) and the co-extraction of water have been measured at 298 K. The solvation number of TOPO is concluded to be 3 for Li(l) and Na(I), 4 and 7 for Mg(II), and 4 and 6 for Ca(II) from the curve-fining calculations.. The hydration number of the extracted metal salts is 2 - 3 for Li(l), Na(I), and Ca(I) but 6 - 8 for Mg(II). The hydration number seems to increase on increasing in the TOPO concentration. It is deduced that TOPO solvates both the metal ion and waters of hydration of the metal ion.

ISSN:0736-6299    

DOI:10.1080/07366299708934475

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

One new and three known derivatives of dibutylphosphonic acid, namely, the α,α′-bis(dibutylphosphonato{)-l,3-xylene and bis(dibutylphosphonato)alkanes, commonly known as the tetrabutyl 1,3-xylylenediphosphonate (TBmXDP) and tetrabutyl alkylenediphosphonates (TBADP), respectively, were synthesized for use in the solvent extraction of precious metals. From 0·1M (1M =1 mol dm−3) NaCl solution at pH 3, these bifunctional reagents substantially extract Au(III), Cu(II) and Sm(III) in 1,2-dichloroethane (DCE), where the extent of extraction as well as the extraction selectivity is governed by the length of the hydrocarbon chain joining the two P=0 groups in the diphosphonate molecule. Au(III)extraction from hydrochloric acid medium was studied in detail by using tetrabutyl 1,3-xylyienediphosphonate because of its superior extraction properties. In hydrochloric acid solutions (0·1 to 5·0 M), the extraction of Au(III) proceeds through formation of a 1:1 solvating complex, TBmXDP-HAuCl4and the equilibrium constant of the extraction reaction (Kex) varies with aqueous HCl concentration. The monofunctional P=0 containing ligand, tributyl phosphate (TBP) also follows similar stoichiometry in its extraction of Au(III); but with much lower values of Kex. On the basis of solubility and phase characteristics of TBmXDP-HAuCl4system, a mixed diluent is proposed for the recovery of gold using this reagent The selectivity of extraction, stripping and extraction kinetics were evaluated in relation to the recovery of the metal from acidic waste solutions and the data are compared with those of TBP.

ISSN:0736-6299    

DOI:10.1080/07366299708934476

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In the work presented here, l,2-dihidroxy-4-oxadodecane (DHD) was synthesized and used for the solvent extraction of boron. DHD was prepared from glycidol and octanol by thermal epoxide ring opening reaction without using acid or base catalyst. The structure of this new extracting reagent was identified according to its spectroscopic data i.e.13C NMR,1H NMR and elemental analysis results. The fixed standard solution of boron (as borax) of 10−4M was extracted with different volume ratios of DHD and n-amyl alcohol (AA) at different equilibrium pH values. The best extraction result was obtained at high pH values with a mixture of equal volumes of DHD and n-amyl alcohol. The different equilibrium pH values were plotted against the extraction yields (%R) and the pH0·5value was determined by using this graph. The extraction of boron from aqueous solutions with equal volumes of DHD and various solvents were studied and it was found that petroluem ether, n-amyl alcohol and diisopropyl ether are convinient solvents for boron extraction. Stripping of boron loaded organic phase was achieved with H2SO4aqueous solutions. The effect of stripping as a function of H2SO4cocentration was also studied

ISSN:0736-6299    

DOI:10.1080/07366299708934477

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The immobilization of a strong metal chelator di(2-ethylhexyl) dithiophosphoric acid (DEHTPA) on poly(4-vinylpyridine) macroporous resin (Reillex(tm)HP and Reillex(tm)425) has been investigated. DEHTPA (ligand) adsorption mechanism was proposed on the basis of the SIR morphology and IR spectrophotometry study. Analysis of the ligand distribution between the poly(4-vinylpyridine) support and the aqueous phase was performed using curve-fitting computerized method. Equilibrium constants characterizing the DEHTPA - pyridine group interaction have been evaluated. Pore volume increase, due to this interaction, are noted. Preliminary metal extraction studies were performed.

ISSN:0736-6299    

DOI:10.1080/07366299708934478

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A novel layered sodium titanium silicate Na2TiSi2O72H2O has been synthesized by the reaction of a titanium-hydrogen peroxide complex and silicic acid in alkaline media under mild hydrothermal conditions (200°C). The product was characterized by elemental analysis. TGA, FT-IR. MAS29Si and23Na NMR and X-ray spectroscopy. The intercalation reaction of n-alkylamines from the gaseous phase and the ion exchange behavior of Na2TiSi2O72H2O towards alkali, alkaline earth and some transition metal ions in model individual and complex solutions were studied. It was found that the layered sodium titanium silicate contains acidic hydroxyl functional groups, which results in cation uptake at pH>1.5. The high affinity of the exchanger for cesium in weakly acid and neutral solutions makes it a promising material for the treatment of some types of nuclear wastes, contaminated ground water and different biological liquors.

ISSN:0736-6299    

DOI:10.1080/07366299708934479

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Several novel crystalline layered zirconium phosphates with composition Zr2O3(HPO4)-nH2O (M=Na, K) were prepared by the partial hydrolytic decomposition of amorphous or crystalline a-zirconium phosphates in alkaline media under mild hydrothermal conditions. The corresponding Li-and Cs-forms of this phosphate were obtained by successive treatment of Na- or K-forms with LiOH or CsOH solutions. Two hydrogen forms of the novel zirconium phosphate (Ψ-ZrP) - Zr2O3(HPO4)-1.5H2O and Zr2O3(HPO4)-0.5H2O were prepared by acid treatment of the salt forms. The intercalation of n-alkylamines into the Ψ-ZrP-H from the gas phase was also studied. All the synthesized materials were characterized by elemental analysis, TGA, X-ray, IR and31P MAS NMR spectroscopy. The data indicate that the novel zirconium phosphate is a monohydrogen phosphate. It was found also that Ψ-ZrP exhibits unexpectedly and extremely high hydrolytic stability in alkaline media; the phosphorus release in 1M NaOH being lower than 0.11 -0.13 mmol PO4/g in comparison with the complete hydrolytic decomposition of other known layered zirconium phosphates in this medium. The ion exchange behavior of the novel Ψ-zirconium phosphate in its H-form, theoretical ion exchange capacity (IEC) of 2.86 meq/g, as well as Na- and K-forms towards alkali, alkaline-earth, and some di- and tri-valent metal cations in different model solutions was studied over a wide pH range (2-14) by the batch technique and an explanation of the experimental facts is proposed.

ISSN:0736-6299    

DOI:10.1080/07366299708934480

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Lactic acid can be made by fermentation from inexpensive cheese whey. The acid is at present fairly costly, however, partly because of the costs of recovery and purification of the acid from the fementation broths. The present study has been undertaken to investigate a process that might reduce these costs. A number of commercial resins have been evaluated as ion exchangers for the production of lactic acid solutions. Amberlite IR-120, a gel strong cationic ion exchanger, was found to be the best resin. The loaded resin was regenerated efficiently. The results suggest that such a process is both technically and economically feasible.

ISSN:0736-6299    

DOI:10.1080/07366299708934481

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor