Showing papers in "Solvent Extraction and Ion Exchange in 1999"
TL;DR: In this article, 2.6-Di(5-alkyl-1,2,4-triazol-3-yl)-pyridine and 2,6-di(5, 6-dialkyl)-1, 2, 4, 4 triazin-3 -yl) pyridine type compounds extract Am(III) 2-bromohexanoate and nitrate from acidic solutions (≤1 M HNO3) with an appreciable efficiency and selectivity.
Abstract: 2,6-Di(5-alkyl-1,2,4-triazol-3-yl)-pyridine and 2,6-di(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine type compounds extract Am(III) 2-bromohexanoate and nitrate from acidic solutions (≤1 M HNO3) with an appreciable efficiency and selectivity, yielding Am(III)/Eu(III) separation factors of ≤150.
319 citations
TL;DR: In this paper, the authors used n-propyl (DPTP) to form dimers and trimers in mixed branched alkanes modified with 2-ethyl-1-hexanol and showed that the self-association is supported by enhancing the HNO3 concentration from 0·3 to 0·9 M.
Abstract: The extraction of Am(lll) and Eu(lll) by 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)-pyridines from mostly 1·9 M (HNO3 + NH4NO3) was studied. The compound with n-propyl (DPTP) forms dimers and trimers in mixed branched alkanes modified with 2-ethyl-1-hexanol. The self-association is supported by enhancing the HNO3 concentration from 0·3 to 0·9 M. In the above modified diluent, DPTP extracts Am(lll) and Eu(lll) nitrates as the complexes Am(NO3)3HNO3-3B and Eu(NO3)3HN033B. The Am(lll)/Eu(lll) separation factor is typically 100 -120. The extraction and separation efficiency of DPTP strongly decreases in the order of diluents (each modified with 2-ethyl-1-hexanol) branched alkanes > cyclohexane > 2-methyl-4-pentanone > 2-ethylhexyl acetate > benzene > chlorobenzene > xylene. 1-Octanol and 2-ethyl-1-hexanol modifiers support appropriately the solubility of protonated forms of DPTP in branched alkanes, and moderately enhance the extraction of Am(lll) and Eu(lll). 1-Butanol modifier allows a higher extracti...
283 citations
TL;DR: New aromatic dithiophosphinic acids (R2PSSH) were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides.
Abstract: New aromatic dithiophosphinic acids (R2PSSH) with R = C6H5−, ClC6H4−, FC6H4− and CH3C6H4− were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides. The extraction of Am(III), Eu(III) and other lanthanides was carried out from nitric acid medium with mixtures of R2PSSHS and neutral organophosphorus compounds. There was no detectable extraction when R2PSSHS were used alone as extractants for either Am(III) or Eu(III) (DAM,EU. 20) with DAM > 1 were achieved in the nitric acid range 0.1-1 mol/L by means of a synergistic mixture of bis(chloro-phenyl)dithiophosphinic acid + tributylphosphate (TBP), irioctylphosphine oxide (TOPO) or tributylphosphine oxide (TBPO). The high radiation resistance (up to 106 Gy absorbed γ-doses) of the extractants was also demonstrated.
126 citations
TL;DR: In this paper, the extraction of cesium nitrate from a mixture of alkali metal nitrates by calix7lsqb;4]arene crown-6 ethers in 1,2-dichloroethane diluent has been surveyed at 25 °C.
Abstract: The extraction of cesium nitrate from a mixture of alkali metal nitrates by calix7lsqb;4]arene crown-6 ethers in 1,2-dichloroethane diluent has been surveyed at 25 °C. The results reveal that smaller substituents (but larger than C2,) at the phenolic positions of the calixarene opposite the crown ether increase both the extraction efficiency and the cesium selectivity. Benzo substituents on the crown ether tend to decrease extraction strength while increasing cesium-to-sodium selectivity. Conversely, a cyclohexano group on the crown ether has a negative impact on both extraction strength and selectivity.
100 citations
TL;DR: In this paper, the synergistic enhancement in the extraction of trivalent actinides (Am and Cm) and some lanthanides by 2-bromodecanoic acid and different nitrogen-0-containing extractants was studied.
Abstract: The synergistic enhancement in the extraction of trivalent actinides (Am and Cm) and some lanthanides by 2-bromodecanoic acid and different nitrogen-0containing extractants was studied. The extraction by mixtures of 2-bromodecanoic acid and 2,2{prime}:6{prime},2{double_prime}-terpyridine or N,N{prime}-dimethyl-N,N{prime}-dicyclohexyltetradecyl malonamide (DMDCHTDMA) respectively, in tert-butylbenzene (TBB) or hydrogenated tetrapropene (TPH), was investigated and compared with 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ) in synergy with 2-bromodecanoic acid. The synergistic enhancement and the separation factor between americium and europium was higher with the terpyridine mixture compared with the malonamide mixture. The separation factor between americium and europium from nitric acid (0.01 M) with terpyridine (0.02 M), 2-bromodecanoic acid (1 M) in TBB was determined to be 7, while the separation factor for malonamide (0.1 M), 2-bromodecanoic acid (1 M) in TBB was approximately 3. This might indicate a more covalent character in the actinide-terpyridine complex than in the actinide-malonamide complex. The terpyridine was shown to be easily transferred to the aqueous phase when protonated and thus the protonation ability for terpyridine was investigated at different concentrations of terpyridine and 2-bromodecanoic acid. Studies to determine the stoichiometry of the M(III) extracted complex with the synergistic mixtures were also performed.
81 citations
TL;DR: In this article, an ion exchange process for removal and recovery of lead present in battery manufacturing wastewaters is demonstrated, in absence of aluminium and ferric species, lead is quantitatively removed and recovered (≈90%) from the neutralised wastewater after elution on the natural zeolite clinoptilolite.
Abstract: Technical feasibility of an ion exchange process for removal and recovery of lead present in battery manufacturing wastewaters is demonstrated. In absence of aluminium and ferric species, lead is quantitatively removed and recovered (≈90%) from the neutralised wastewaters after elution on the natural zeolite clinoptilolite. Control of pH to 5.5-6 is necessary to minimise degradation of the exchanger material. Throughput volumes exceeding 2,700 bed volumes (BV) (flowrate: Fexh10 BV/h) is obtained, when the initial Pb concentration is 4 mg/L, with the metal leakage steadily below the maximum allowable concentration (MAC<0.2 mgPb/L) set by the EU for discharge in rivers, lakes, coastal seawater. Regeneration of the zeolite is carried out by controlled elution of limited amounts of IM NaCl, pH 4.5 (40BV, Freg=5 BV/h) to minimize in situ precipitation of metals and preserve the zeolite from degradation. From spent regeneration eluate lead is recovered to the battery manufacturing operations. This latt...
68 citations
TL;DR: In this paper, the effect of various parameters like concentration of acid, metal ion and extractant and nature of diluent on the extraction of Ni(II) has been studied.
Abstract: The paper embodies the details on the extraction behaviour ofNi(II) along with Cr(III), Fe(ni), Mn(II), Co(II), Cu(II) and Zn(II) from sulfuric acid media employing Cyanex 301-toluene system. The effect of various parameters like concentration of acid, metal ion and extractant and nature of diluent on the extraction of Ni(II) has been studied. On the basis of the distribution data the extracting species has been proposed. The recycling capacity of the extractant has been assessed. Some binary and ternary separations have also been achieved. The practical utility of the extractant has been demonstrated by recovering Ni(II) from spent catalyst and electroplating bath residue.
48 citations
TL;DR: The analysis of metal distribution data by numerical calculations suggested the formation of the species (R3R'N+)2PtCl6 2− in the organic phase with formation constant log β=5.26±0.02.
Abstract: The extraction of Pt(IV) by Aliquat 336 (R3R'N+Cl−) in dodecane modified with 4% dodecanol from hydrochloric acid solutions has been investigated. The analysis of metal distribution data by numerical calculations suggested the formation of the species (R3R'N+)2PtCl6 2− in the organic phase with formation constant log β=5.26±0.02. The results obtained on Pt(IV) distribution have been implemented in a solid supported liquid membrane system, being NaClO4 solutions the most effective to strip the metal from the organic solution. Influence of membrane composition and metal concentration on platinum transport have also been studied.
47 citations
TL;DR: N-dodecyl- and N,N-dihexylpyridinecarboxamides with amide group at 2, 3 or 4 position were synthesized and individual amides were used to recover copper(II) from chloride solutions at constant water activity and constant total concentration of dissolved species in aqueous solution as mentioned in this paper.
Abstract: N-dodecyl- and N,N-dihexylpyridinecarboxamides with amide group at 2, 3 or 4 position were synthesized Model individual amides were used to recover copper(II) from chloride solutions at constant water activity and constant total concentration of dissolved species in aqueous solution It was found, that pyridine-2-carboxamide forms with copper complexes (CuCl2)x (Ext)2 Remaining amides form with copper complexes CuCl2(Ext)2 Monoalkylamides are not suitable for extraction because they and their complexes are slightly soluble in the hydrocarbon diluents N,N-dialkylpyridinecarboxamides and their copper complexes are sufficiently soluble in the hydrocarbon phase to carry out extraction However, they are strong extractants and extract efficiently copper already from dilute chloride solutions ([Cl] = 01 M) They extract also significant amounts of copper from concentrated (3-4M) nitrate solutions
39 citations
TL;DR: In this paper, it has been found that the maximum extraction of rare earth elements is exhibited by reagents containing one ether oxygen atom in the molecule, bound to diphenylphosphoryl or ditolylphosphoricl containing podands towards REE.
Abstract: The extraction of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO3 solutions by phosphoryl-containing podands of various structures has been studied. It has been found that the maximum extraction of rare earth elements is exhibited by reagents containing one ether oxygen atom in the molecule, bound to diphenylphosphoryl or ditolylphosphoryl containing podands towards REE varies in a wide range, depending on the number of oxygen atoms in the polyether chain and the structure of the fragment connecting the ether oxygen atom with the terminal PO group. The podand structure which ensures a polydentate coordination of the reagent molecule to yield chelate complexes is favourable for REE extraction. The replacement of phenyl radicals in the podand VII molecule for butyl ones (compound IX) drastically reduces REE extraction. REE extraction by podands VII and VII increase from La to Lu with a decrease in the radii of extracted ions
38 citations
TL;DR: In this paper, Potassium nickel hexacyanoferrate(II) (KNiFC)-loaded silica gels were prepared by successive impregnation of macro pores with Ni(NO3)2, and K4Fe(CN)6 solutions.
Abstract: Potassium nickel hexacyanoferrate(II) (KNiFC)-loaded silica gels were prepared by successive impregnation of macro pores with Ni(NO3)2, and K4Fe(CN)6 solutions. The KNiFC precipitates uniformly dispersed in the matrix of silica gel, and the loading percentage of KNiFC increased with the number impregnation cycles. The uptake of Cs+ on KNiFC-loaded silica gels (SLFC) attained equilibrium within 2 d, and relatively large distribution coefficients of Cs+, Kd,cs, above 104 cm3/g, were obtained even in the presence of 5 M NaNO3. The ion exchange of K+ Cs+ in SLFC followed a Langmuir-type isotherm and the maximum uptake amount of Cs+ was estimated to be 0.305 mmol/g. The breakthrough curve of Cs+ through a column packed with SLFC exhibited a favorable S-shaped profile. This exchanger proved to be effective for the selective removal of radioactive cesium from neutral waste solutions containing highly concentrated NaNO3.
TL;DR: In this paper, the distribution of neodymium(III) between acidic aqueous nitrate solutions and organic solutions of di(2-ethyl-hexyl)phosphoric acid (D2EHPA) in hexane has been studied for different extractant and metal ratios at constant ionic strength 0.1
Abstract: The distribution of neodymium(III) between acidic aqueous nitrate solutions and organic solutions of di(2-ethyl-hexyl)phosphoric acid (D2EHPA) in hexane has been studied for different extractant and metal ratios at constant aqueous ionic strength 0.1 M (Na+,H+-NO3). The distribution data have been evaluated by both graphical and numerical analysis, in order to determine the speciation in the organic phase. The results obtained suggest the formation of two complexes in the organic phase: NdA3-3HA, which is predominant when the extractant/metal ratio is higher than one, and NdA3, which is the main species when the ratio is equal to one. For lower concentrations of extractant it has been found that the possible formation of species at the interface creates difficulties in the modelling of the extraction process.
TL;DR: In this article, the extraction behavior of technetium, thorium, uranium, neptunium, plutonium, americium and curium in the Aliquat-336 -nitric acid system have been studied.
Abstract: The extraction behaviour of technetium, thorium, uranium, neptunium, plutonium, americium and curium in the Aliquat-336 (diluted with 1,3-diisopropyl benzene) - nitric acid system have been studied. Aliquat-336 (tricapryl-methyl ammonium nitrate) is a quaternary ammonium salt extracting different species with an anion exchange mechanism. Distribution data obtained are modeled by anion exchange (technetium) and ion-pair formation mechanisms (actinides) with the extraction of nitric acid included to account for the lowering of the free extractant concentration. Reasonably high distribution ratios were obtained for technetium and the tetravalent elements (Th, Np and Pu) and Aliquat-336 can therefore be useful for partitioning of these elements.
TL;DR: In this paper, the aggregation of several metal complexes formed during solvent extraction with P,P'-di(2-ethylhexyl) methanediphosphonic acid, H2DEH[MDP], in deuterated toluene, has been investigated by small angle neutron scattering (SANS).
Abstract: The aggregation of several metal complexes formed during solvent extraction with P,P'-di(2-ethylhexyl) methanediphosphonic acid, H2DEH[MDP], in deuterated toluene, has been investigated by small angle neutron scattering (SANS). The SANS results show that the Ca(II)-, Al(ni)-, La(III)- and Nd(III)-H2DEH[MDP] compounds exhibit little or no tendency to aggregate. Uranyl complexes of H2DEH[MDP] at high metal loading form small aggregates with an aggregation number of approximately 14. This behavior is in sharp contrast with the Th(IV)-H2DEH[MDP] system which forms large aggregates in the organic phase under high metal loading conditions. The aggregation behavior of the various metal-H2DEH[MDP] compounds is discussed in light of the information obtained from earlier solvent extraction, vapor pressure osmometry, and infrared spectroscopy studies.
TL;DR: In this article, the extraction of europium(III) nitrate from sodium nitrate with a series of tetrahexylmalonamides has been investigated, and it was shown that the malonamide/Eu ratio in the extracted complexes is 3.
Abstract: The extraction of europium(III) nitrate from sodium nitrate with a series of tetrahexylmalonamides has been investigated. The tetrahexylmalonamides considered were N.N.N’N’-tetrahexylmalonamide (THMA), N,N,N’N’-tetra-hexyl-2-methylmalonamide (MeTHMA), and N,N,N’N’-tetrahexyl-2,2-dimethy-lmalonamide (DiMeTHMA). This series allowed for a systematic determination of the effects of alkyl substitution of the methylene carbon. Equilibrium modeling of the extraction data indicates that the malonamide/Eu ratio in the extracted complexes is 3 for all three malonamides investigated. This stoichiometry is different than that determined for isolated complexes. This can be rationalized by the formation of complexes with monodentate-bound diamide ligands in the extracts. The extraction constant for Eu decreases by seven-fold in going from THMA to MeTHMA, and a precipitous drop in the extraction constant occurs upon substitution of a second methyl group on the methylene carbon (i.e., for DiMeTHMA).
TL;DR: In this article, the effect of increasing 1-decanol concentration in the solvent has been investigated for dialkyl-substituted diphosphonic acids in nonpolar (toluene and CCl{sub 4}) and alcohol (1decanol) solutions.
Abstract: Hydrogen bonding of dialkyl-substituted diphosphonic acids in nonpolar (toluene and CCl{sub 4}) and alcohol (1-decanol) solutions is examined. The compounds are monomeric in 1-decanol and dimeric or higher in nonpolar organic diluents. Infrared spectroscopy and molecular mechanics calculations suggest that the dimers of P,P{prime}-di(2-ethylhexyl) methanediphosphonic acid (H{sub 2}DEH[MDP]) and its straight-chain isomer, P,P{prime}-dioctyl methanediphosphonic acid (H{sub 2}DO[MDP]), adopt rigid highly hydrogen-bonded structures such as C or D. The homologous P,P{prime}-di(2-ethylhexyl) ethane- and butanediphosphonic acids, H{sub 2}DEH[EDP] and H{sub 2}DEH[BuDP], respectively adopt structures that are also intermolecularly hydrogen-bonded but more flexible. The effect on the P+O stretching vibration of increasing 1-decanol concentration in the solvent differs for these compounds. In the case of H{sub 2}DEH[MDP] and H{sub 2}DO[MDP], the frequency remains constant until all CCl{sub 4} has been replaced by the alcohol, then the P=O stretching frequency shifts to a lower energy. In the case of H{sub 2}DEH[edp] and H{sub 2}DEH[BuDP], a gradual shift to higher energy occurs as the alcohol concentration increases. The magnitude of the difference in the P=O stretching frequencies between CCL{sub 4} and 1-decanol solution is greatest for organophosphonic acids, less for organodiphosphonic acids, and least for organophosphoric acids.
TL;DR: In this paper, the aggregation of several metal complexes formed during solvent extraction with P,P'-di(2-ethylhexyl) ethanediphosphonic acid, H2DEH[EDP], and by P, P'-di, 2-hexyl methanediphosphorac acid in deuterated toluene, was investigated by small angle neutron scattering (SANS).
Abstract: The aggregation of several metal complexes formed during solvent extraction with P,P'-di(2-ethylhexyl) ethanediphosphonic acid, H2DEH[EDP], and by P,P'-di(2-ethylhexyl) butanediphosphorac acid, H2DEH[BuDP], in deuterated toluene, has been investigated by small angle neutron scattering (SANS). With H2DEH[EDP], the extraction of Ca(II), La(IH) and U(VT) does not disrupt the cyclic hexameric structure of the ligand in solution. Fe(III) and Th(IV) complexes of H2DEH[EDP], on the other hand, exhibit a very modest tendency to aggregate but only at very high metal loading in the organic phase. With H2DEH[BuDP], the extraction of Ca(H), La(III), U(VI) and Th(IV) is not accompanied by significant aggregation of the metal complexes The Fe(HI)-H2DEH[BuDP] complexes, however, form long cylindrical aggregates similar to those previously observed with P,P'di(2-ethylhexyl) methanediphosphonic acid, H2DEH[MDP]. The aggregation behavior of the various metal-extractant species is discussed in light of the informat...
TL;DR: In this article, the second part of a theoretical approach aimed at establishing structure-activity relationships in a data base made of twenty-two monoamides (A) used as uranium (VI) nitrate extractants was described.
Abstract: This report describes the second part of a theoretical approach aimed at establishing structure-activity relationships in a data base made of twenty-two monoamides (A) used as uranium (VI) nitrate extractants. It was found that predominant factors determining the extracting ability of a monoamide are of three kinds : i) electron density of the coordinating atoms or groups, which should be as high as possible ; ii) steric effects, which should be as low as possible ; and Hi) lipophilicity of the ligands, which should be above a minimum threshold value. In the first paper of this series[1], quantum chemistry calculations were reported to account for electronic properties of the ligands. This second paper reports molecular mechanics calculations made on UO2(NO3)2A2 complexes in order to determine the influence of steric effects on the formation of these compounds. Calculations of monoamide lipophilicity using Rekker's method showed that all the molecules of the data base were lipophilic enough and, ...
TL;DR: In this paper, two types of alkylcalix[4]arene carboxylates with different alkyls chains, together with three types with the same Alkyl chains were synthesized to investigate their solubility in four different organic diluents.
Abstract: Two types of alkylcalix[4]arene carboxylates with different alkyl chains, together with three types with the same alkyl chains were synthesized to investigate their solubility in four different organic diluents. The solubility was found to be enhanced by using the calixarene compounds with longer alkyl chains and by using mixtures of compounds with different alkyl chains. The order of solubility in the different organic diluents was found to be: chloroform > toluene ≫ EXXSOL D80 ≈ hexane. The stoichiometry of the copper complex with the compounds having the same alkyl chains was also determined and the maximum loading capacity of copper with each extractant was estimated.
TL;DR: In this paper, the influence of di-n-butyl phosphoric acid (HDBP) upon extraction of uranium(VI) by tri-nbutyl phosphate (TBP) from 0.5-3.0 M nitric acid solutions has been studied.
Abstract: The influence of di-n-butyl phosphoric acid (HDBP) upon extraction of uranium(VI) by tri-n-butyl phosphate (TBP) from 0.5--3.0 M nitric acid solutions has been studied. It has been shown that the uranium(VI) distribution coefficient D{sub U} for extraction by 1.1 M TBP in tri-decane or xylene is increased when HDBP is present in the organic phase. For iso-molar solutions of (TBP + HDBP) with a total concentration of 0.36 M, and Uranium(VI) aqueous concentration up to 10--20 g/l, a maximum value of D{sub U} is observed when TBP/HDBP = 1; for higher U(VI) concentration the maximum gradually disappears, with D{sub U} growing monotonically with the HDBP content in the organic phase. Uranium(VI) absorption spectra for 1.1 M TBP in tri-decane or xylene, containing HDBP, provide evidence for the formation of compounds, of which composition is intermediate between uranyl nitrate--TBP disolvate and the U(VI)--HDBP complex. It is proposed that these intermediate compounds are UO{sub 2}(NO{sub 3}){sub 2}HDBP.TBP and UO{sub 2}(NO{sub 3}){sub 2}(HDBP){sub 2}.
TL;DR: In this paper, the third phase formation in the extraction of Nd(III) by 0.2 M Octyl(Phenyl)-N,N,Diisobutyl Carbamoyl methyl phosphine oxide (OΦCMPO) in n-dodecane has been studied with tri-n-butyl phosphate (TBP) and trin-amyl phosphate(TAP) as modifiers to provide a comparison between these two modifier systems.
Abstract: Third phase formation in the extraction of Nd(III) by 0.2 M Octyl(Phenyl)-N,N-Diisobutyl Carbamoyl methyl phosphine oxide (OΦCMPO) in n-dodecane has been studied with tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) as modifiers to provide a comparison between these two modifier systems. The effect of concentration of TAP as modifier for the extraction of Nd(III) by 0.2 M OΦCMPO has been studied. The extraction of Nd(III) by TAP/n-dodecane in the absence of OΦCMPO has also been studied and the results are reported here.
TL;DR: In this article, the influence of the podand molecule structure on the process of extraction is considered and the stoichiometry of the complexes extracted into the organic phase has been established.
Abstract: Extraction of microquantities of Sc, Mn(II), Ni, Co, Cu, Zn, Ga, Y, Pd, Cd, In, La, Eu, Tl(III). Pb, Bi, Th, and U(VI) from aqueous solutions of HNO3 by solutions of phosphoryl-containing podands in dichloroethane has been studied. The influence of the podand molecule structure on the process of extraction is considered. The stoichiometry of the complexes extracted into the organic phase has been established.
TL;DR: In this article, the influence of operating variables such as initial pH, Cd(H) concentration, time and temperature on the equilibrium parameters of resins was measured, i.e., binding constant (b) and saturation capacity (xm) depend on the functional group structure.
Abstract: Cadmium sorption from aqueous solutions on sulfonic (C-150) and iminodiacetic (S-930) Purolite macroporous resins was investigated. The influence of operating variables such as initial pH, Cd(H) concentration, time and temperature on the equilibrium parameters was measured. The ion preference and sorption ability of resins, i.e. binding constant (b) and saturation capacity {xm), derived from sorption isotherm, depend on the functional group structure. The Cd(II) uptake is only particle diffusion controlled. The kinetic parameters, i.e. t1/2 values for 50 % attainment of equilibrium sorption, rate constant (K¯ ) and diffusion coefficient (D¯) are higher on the sulfonic resin. The “moving boundary” particle diffusion model fits the entire ion sorption process on chelating resin, but only the initial sorption on the sulfonic resin, confirming the difference in chemistry between chelation and ion exchange.
TL;DR: In this paper, the extraction of Pd(II) from HC1 solutions by impregnated resins containing di-(2-ethylhexyl) thiophosphoric acid (DEHTPA or HL) on the Amberlite XAD2 polymeric support has been studied.
Abstract: The extraction of Pd(II) from HC1 solutions by impregnated resins containing di-(2-ethylhexyl) thiophosphoric acid (DEHTPA or HL) on the Amberlite XAD2 polymeric support has been studied. Graphical and computer analysis with the program LETAGROP-DISTR demonstrated that the Pd(II) extraction can be explained by the formation of metal complexes in the resin phase having the composition PdL2(HL)2. DEHTPA/XAD2 resins extracted Pd(II) in the presence of other metals: Pt(IV), Rh(III), Cu(II), Fe(III) as well as Zn(II). The stripping of Pd(II) loaded on the organic phase and the lifetime of the resins were also investigated.
TL;DR: In this article, the isotope enrichment factors showed breakdowns of the conventional Bigeleisen-Mayer approximation for every condition of the initial phases; the concentrations of gadolinium and hydrochloric acid and the type of organic solvents.
Abstract: Gadolinium isotopes were fractionated in a liquid-liquid extraction system using dicyclohexano-18-crown-6. The isotope enrichment factors showed breakdowns of the conventional Bigeleisen-Mayer approximation for every condition of the initial phases; the concentrations of gadolinium and hydrochloric acid and the type of organic solvents. The nuclear mass effect and the field shift effect were estimated by use of the isotope pairs 152Gd-160Gd and 154Gd-160Gd. Since both isotopes, 152Gd and 154Gd, have the unique characteristics of the nuclear charge radii, 's, the unusual isotope effects due to the field shifts took place, while the mass effects of the other isotopes canceled the field shift effects. The maximum isotope effect was observed to be e160,152 =0·0252 ± 0·0024 whose initial aqueous phase was 0·023 M GdCl3 in 12 M HC1, and its organic phase was 0·2 M DC18C6 in chloroform: this was 0·00315 ± 0·00030 in terms of the enrichment factor for unit mass.
TL;DR: In this paper, the distribution equilibrium of DEHTPA between the aqueous phase and the organic phase was investigated by treating the data with the computer program LETAGROP-DISTR.
Abstract: Liquid-liquid extraction of Pd(II) from hydrochloric acid solutions using di-(2-ethylhexyl) thiophosphoric acid (DEHTPA or HL) dissolved in kerosene has been studied. The distribution equilibrium of DEHTPA between the aqueous phase and the organic phase was investigated by treating the data with the computer program LETAGROP-DISTR. The extraction of Pd(II) from HC1 solutions by DEHTPA was studied as a function of several variables: equilibration time, organic phase diluent, HC1 and DEHTPA concentrations as well as temperature. Experimental equilibrium data were analyzed numerically using the program LETAGROP-DISTR and the results showed that Pd(II) extraction can be explained assuming the formation of PdL2 complexes in the organic phase. DEHTPA was found to be selective for Pd(II) against Pt(IV), Rh(HI), Cu(II), Fe(III) and Zn(II). The back-extraction of Pd(II) loaded in the organic phase using different stripping reagents is also reported.
TL;DR: In this paper, the authors studied the thermodynamics of extraction of metal picrates from water to a chloroform or to a dichloromethane solution using UV spectroscopy.
Abstract: Using UV spectroscopy, we have studied the thermodynamics of extraction of metal picrates M+Pic− (M+ = Li+, Na+ K+, Rb+, Cs+ Tl+ and Ag+) and M2+(Pic−)2 (M2+ = Ca+, Sr+,Ba+, Pb+, and UO2 2+) from water to a chloroform or to a dichloromethane solution. The extractant molecules are mono-podands R-O-(CH2-O-CH2-)n-O-R containing an ether chain and terminal phosphoryl groups: R = (Ph)2P(O)-C6H4 -; n = 3,4 (I - H) and R = (Ph)2P(O)-CH2-C6H4 -, n = 1, 3, 4 (III - V). We found that podand displays a remarkable Ba2+/Ca2+ extraction selectivity. All podands extract alkali and alkaline earth picrates in dichloromethane (as dissociated ion pairs) better than in chloroform (as non-dissociated ion pairs). Based on Molecular Dynamics simulations of the complexes IM2+ and IM2+(Pic−)2 in the gas phase and in chloroform we suggest that the high selectivity of I for Ba2+ is due to (i) the formation of the complex with an “optimal” pseudocavity for Ba2+, in which six donor atoms of the ligand and four oxygens of the...
TL;DR: In this article, the volumes and compositions of the equilibrium phases for three-phase extraction systems have been determined at 298K at a phase ratio of one, and the solubilization capacities are within the saturation value of TOAHCl:H20:n-heptane=l:2:3 (molar ratio).
Abstract: The three-phase extraction systems TOA-n-heptane / HC1, TOA-kerosene / HC1, TOA-kerosene / HCl-ZnCl2 and TOA-kerosene / HCl-FeCl3 have been investigated. The volumes and compositions of the equilibrium phases for these systems have been determined at 298K at a phase ratio of one. In the HC1 extraction system, amphiphilic molecules TOA-HC1 in heavy organic phase (i.e. the third phase or the middle phase) self-assemble into a lamellar structure, and water and alkane are solubilized in polar layers and nonpolar layers respectively. The solubilization capacities are within the saturation value of TOAHCl:H20:n-heptane=l:2:3 (molar ratio). The solubiiizition decreases when the ratio of initial HC1 concentration to initial TOA concentration is less than one and excess acid and water are extracted into the middle phase if initial concentration of HC1 is higher than that of TOA. Zinc and iron are mainly extracted into the middle phase. The metal extraction systems have different phase behavior than the ac...
TL;DR: In this paper, the solvent extraction process of yttrium(III) from nitrate media by di(2-ethylhexyl) phosphoric acid (D2EHPA), represented as HA, has been studied as a first step to accomplish the homogeneous precipitation of YA{sub 3{center_dot}}2HA.
Abstract: The solvent extraction process of yttrium(III) from nitrate media by di(2-ethylhexyl) phosphoric acid (D2EHPA, represented as HA) has been studied as a first step to accomplish the homogeneous precipitation of yttrium oxalate from an organic metal loaded D2EHPA solution. The analysis of liquid-liquid distribution data at low metal concentrations determined YA{sub 3{center_dot}}2HA as the only metal organic species formed during the extraction, with a formation constant of log{beta} = 16.410 {+-} 0.055. A polymerization of such organic metal species was observed at high metal loading of the organic phase. A comparison of these results with previous studies carried out in chloride or perchlorate media reveals a strong influence of the aqueous medium on the metal species formed in the organic phase, affecting mostly the stoichiometry of such species. The homogeneous precipitation of yttrium as yttrium oxalate using oxalic acid has been carried out as direct recovery of the metal from the organic solution. The observed precipitation-stripping kinetics has been related to the formation of organic yttrium species. The acidity of the stripping solution and the oxalic acid concentration also affects the kinetics and the precipitation yield. The morphology and particle size distribution of the powders obtained support the mentioned influencemore » of the precipitation-stripping kinetics.« less
TL;DR: The feasibility of using trialkylphosphine oxides to remove cadmium from mixed, acidic chloride-phosphate systems was investigated in this paper, and the results indicated that raffinates containing very low levels of Cadmium (approximately 0.5 mg/L) could be produced readily.
Abstract: The feasibility of using trialkylphosphine oxides to remove cadmium from mixed, acidic chloride-phosphate systems was investigated. Interpolations from extraction isotherms indicated that raffinates containing very low levels of cadmium (approximately 0.5 mg/L) could be produced readily. Stripping was accomplished with water. The co-extraction of acids was minimal.