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We investigated the chemical behavior of lanthanides (Ln) by multistage extraction. Using 10 aqueous phases with Ln and 3 organic phases, we drew the breakthrough curves for light and middle Ln. Our study reveals that the limit of metal extraction depends on their D values and the metal concentration employed in experiments. From the multistage extractions of 15 stage aqueous phases and 15 stage organic phases, three curves (extraction curves, back-extraction curves, and separation curves) were obtained. Setting appropriate conditions, adequate separation of light Ln from middle ones can be achieved. As an example, under the condition of the separation curve experiment (aqueous phase: 0.5 M HNO3, organic phase: 0.1 M TDDGA (N,N,N',N'-tetradecyl-diglycolamide) in n-dodecane), the recovery of more than 99% of Sm in the organic phase with less than 1% of Nd can be obtained, even in the case of two metals adjacent to each other in the Ln series.

To achieve trichotomic separation of light lanthanides (Ln), heavy Ln, and Am, batchwise multi-stage extractions using N,N,N′,N′-tetraoctyl-diglycolamide (TODGA) extractant from organic acids are studied. This technique has the advantages of both solvent extraction and chromatography, which enable successive separation and management of large volumes of aqueous solutions. Malonic acid (M-Acid) is used as the main component of the aqueous phase. It is clear that the separation factor for Nd/Am from M-Acid and that for La/Am from M-Acid + HNO3 are both around 30, thus we plan to conduct these separations.

Lanthanide (Ln) extractions from organic acids to n-dodecane by N,N,N′,N′-tetraoctyl-diglycolamide (TODGA) were conducted. Four organic acids (lactic acid, malonic acid, tartaric acid, and citric a...

The mutual separation of lanthanides has been studied by multi-stage extraction using an extractant, DGA (diglycolamide) compounds. N,N,N',N'-tetraoctyl-DGA (TODGA) has a high extractability to lanthanides and a relatively high separation factor (SF) between Dy and Nd (SF of over 20) from HNO3 media. Complete separation with such SF values can be achieved by multi-stage extraction. Less information on multi-stage extraction compared to batch extraction has been presented up to now. We thus conducted a basic study. By confirming the experimental data to be identical to calculations, the sample solution including both metals was employed for batchwise multi-stage extraction. Ninety-seven percent of Dy with under detection limit of Nd could be recovered into the organic phase from Nd with a ten-times higher concentration than Dy using the condition, 0.1 M TODGA/n-dodecane and 0.3 M HNO3 by the multi extraction of 9 × 9 stages for organic and aqueous phases.

Methylimino-di-n-octylacetamide (MIDOA) was used to extract 57 metals from HCl into n-dodecane. MIDOA is a tridentate ligand with one N donor and two carbonyl O donors and can extract soft acid met...

The simultaneous separation of Am and Cm from lanthanides is important for atomic energy fields. However, the process is difficult owing to the chemical behavior of trivalent metal ions with similar ionic radii. All lanthanides, Am, and Cm can be extracted by diglycolamide (DGA). In addition, relatively high separation factors between An and Ln were obtained by the extraction system of TODGA, DTPA (diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid) and HNO3. In this work, DTPA-BA (diethylenetriamine-N,N′,N″-triacetic-N,N″-bisamide), which is an improved version of DTPA, was employed for the separation of Ln and An. After performing a basic study on DTPA-BA, a relatively high separation factor (approximately 8) for actinides/lanthanides was obtained. Then, the multi-step extraction was performed. Thus, the recoveries of 94.7 % for Nd and 4.7 % for Am and Cm in organic phase, and 5.3 % Nd and 95.3 % for Am and Cm in aqueous phase were obtained.

The extraction behavior and complexation state of diglycolamide (DGA) and dioxaoctanediamide (DOODA) ligands were investigated for several trivalent lanthanide ions (Ln(III)). The stoichiometry of the extraction of La(III), Nd(III), and Ho(III) with the hydrophobic ligands, N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and N,N,N’,N’-tetraoctyl dioxaoctanediamide (DOODA(C8)), was determined by slope analyses in CHCl3 and CCl4 system. Ultraviolet-visible (UV-Vis) spectroscopy was employed for determination of the stability constants (β) of trivalent lanthanide ion (Ln3+) with the hydrophilic ligands, N,N,N’,N’-tetraethyl diglycolamide (TEDGA) and N,N,N’,N’-tetraethyl dioxaoctanediamide (DOODA(C2)). DGA ligands are found to have an affinity of heavier Ln(III), while DOODA ligands prefer to coordinate with lighter Ln(III). Infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic measurements reveal that the carbonyl oxygen atoms of TODGA and DOODA(C8) worked as dominant donors in complexation wit...

New aminophosphonic acid extractants, α-(4- n -octylanilino)benzylphosphonic acid monobutyl ester (OABPM) and α-dodecylaminobenzylphosphonic acid monobutyl ester (DABPM) with different amino moiety basicities were synthesized to examine the effect of the basicity on their extraction selectivities for In(III), Ga(III), Zn(II), Cu(II), Se(IV) and Se(VI). The extraction order for metals using OABPM was In(III) > Ga(III) > Cu(II) > Zn(II), while Se(IV) and Se(VI) were not extracted. On the other hand, DABPM exhibited the reverse extraction order for Cu(II) and Zn(II). The mutual separation ability of DABPM for these metals was higher than that of OABPM as is determined by the basicity of the amino moiety of their extractants. The extraction equilibria for Ga(III) and Zn(II) with OABPM and DABPM were discussed using slope analysis. It was observed that only Ga(III)- and Zn(II)-DABPM complexes contained nitrate ions, because the phosphonic acid moiety of DABPM was hard to participate in the metal extraction.

In this study, the synergistic solvent extraction of lanthanide(III) with mixtures of di-(2-ethylhexyl)phosphoric acid (D2EHPA, H2A2) and monoisodecyl phosphoric acid (MIDPA, H2B2) in phosphonium-based ionic liquid was investigated from amide acid medium. The method of slope analysis was used for the determination of the extraction reaction. In the case of D2EHPA or MIDPA single extractant system, Ln(III) (Ln = Pr and Nd) was extracted as [LnA3HA] or [LnB3HB], respectively. Tb(III) or Dy(III) were extracted as [TbH2A2B2(NTf2)] or [DyH2A2B2(NTf2)] instead of [TbA3HA(NTf2)] or [DyA3HA(NTf2)] for D2EHPA and MIDPA synergistic system. According to the equilibrium constants (KA, KB and KAB) and the formation constants (β1, β1 and β3), it was found that the extracted complex [TbHA2B2] or [DyHA2B2] was more stable than [LnA3HA] or [LnB3HB] due to the synergistic effect of D2EHPA and MIDPA. The thermodynamic functions (ΔH, ΔG, and ΔS) were estimated from the temperature dependence of the synergistic extraction system. The result indicated that the synergistic extraction reaction was endothermically driven for this extraction system. Furthermore, the synergistic extraction effects were investigated to study the possibility of separating Dy(III) from Pr(III) and Nd(III) according to their separation factors.

A new extractant, [ N , N -di(2-ethylhexyl)amino]methylphenylphosphinic acid (DEAPP), was synthesized to develop the mutual separation techniques of In(III), Ga(III) and Zn(II). The extraction selectivity for In(III), Ga(III) and Zn(II) with DEAPP was higher than that of the commercial phosphorus acid extractants such as D2EHPA and PC-88A. The extraction selectivity for metal ions in 1 mol·L − 1 aqueous ammonium nitrate solution with DEAPP was in the following order: In(III) > Ga(III) > Zn(II). These selective extraction behaviors indicate that the amino moiety of DEAPP plays an important role in the mutual separation of In(III), Ga(III) and Zn(II). The extraction equilibria of In(III), Ga(III) and Zn(II) with DEAPP (= HR) were expressed by the following reactions: In 3 + + 2 H R ¯ 2 ⇋ I n R 3 H R ¯ + 3H + , Ga 3 + + 1.5 H R ¯ 2 + NO 3 − ⇋ GaR 2 H R NO 3 ¯ + 2H + , and Zn 2 + + 2 H R ¯ 2 ⇋ Z n R 2 H R ¯ 2 + 2H + . The extraction equilibrium constants of In(III), Ga(III) and Zn(II) with DEAPP were determined to be K ex,M = 1.7 × 10 4 [dm 3 ·mol − 1 ], 4.17 [(dm 3 ·mol − 1 ) 0.5 ], and 1.55 x 10 − 2 [–], respectively.

We have developed a liquid-liquid countercurrent centrifugal extractor that induces Taylor vortices in the annular fluid region. To demonstrate extraction of multiple species (Nd/Sm/Eu/Gd/Dy) with N,N,N′,N′-tetraoctyl diglycolamide (TODGA), additional chemical agents, such as a surfactant (sodium bis(2-ethylhexyl) sulfosuccinate (AOT)), a synergist (nonanoic acid) and a masking agent (N,N,N′,N′-tetraethyl-3,6-dioxaoctane-1,8-diamide (DOODA(C2))) were employed. When only TODGA was utilized, extraction performance was not effective due to the insufficient dispersion even under a high rotating speed. By combining TODGA and other chemical agents, the separation performance was improved considerably in the countercurrent flow of aqueous and organic phases due to the synergistic effect and improved dispersion.

α-Radiation effect on the solvent extraction of 241Am using the solution of N,N,N′,N′-tetraoctyldiglycolamide was investigated by means of the external and internal irradiation systems. In contrast to the internal irradiation system using an actinide radionuclide as an α-particles emitter, the external irradiation with 4He2+ ions provided by an accelerator can be carried out in a reasonable timescale and without contamination with radionuclides. No significant decrease in distribution ratio was observed even after irradiation over 200 kGy in both systems. It was also confirmed that the external irradiation system could be a useful alternative to the internal irradiation.

Extraction chromatographic separation of trivalent minor actinides (MA: Am and Cm) was investigated by using solid adsorbents impregnating the lipophilic diamide-type ligands, TODGA (N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide) and DOODA(C8) (N,N,N′,N′-tetraoctyl-3,6-dioxaoctane-1,8-diamide). In nitric acid eluents, hydrophilic diamide-type ligands, DOODA(C2) (N,N,N′,N′-tetraethyl-3,6-dioxaoctanediamide) and TEDGA (N,N,N’,N’-tetraethyl-diglycolamide) were included for the respective adsorbents as masking agents in order to produce a synergistic effect in mutual separation of Am and Cm. The adsorption tendency of Am and Cm for the adsorbents was opposite each other, that was similar to the case of lanthanides.

The novel tridentate extractant including a soft donor group or atom has developed and was examined. The extractant, N , N , N ′, N ′-tetraoctyl-thiodiglycolamide (TOTDGA), is analogous structure to N , N , N ′, N ′ - tetraoctyl-diglycolamide (TODGA), but with sulfur donor instead of ether oxygen of TODGA. TOTDGA has a unique property to extract silver from acidic solutions to n -dodecane with relatively high D values. We investigated the extraction behavior of Ag in various acids, HNO 3 , H 2 SO 4 , and HClO 4 . The results suggest that TOTDGA can extract Ag from these acids.

A novel extractant, N,N,N′,N′,N′′,N′′-hexaalkyl-nitrilotriacetamide (NTAamide), was developed for the extraction and separation of actinides (An) and lanthanide (Ln). NTAamide has a nitrogen atom in the center of a backbone and is bonded to three acetamide groups; the nitrogen and three amide oxygen atoms can work as the donor atoms. NTAamide extracted Am and Cm with a low distribution ratio of Ln in diluted HNO3, and the separation factor (SF) for An/Ln was equal to or higher than 23.6 using 0.5 M NTAamaide/n-dodecane and 0.2 M HNO3. The addition of N,N,N′,N′-tetraethyldiglycolamide as a masking agent to the NTAamide extraction system was effective for separating Am from Cm; the maximum SF was 6.5, one of the highest SF values obtained using the HNO3 and n-dodecane system.

Four novel diamide and triamide extractants developed in our group, TODGA, DOODA, MIDOA, and NTAamide, were examined to see the extractability trends of up to 74 metal ions from nitric acid into n-dodecane. TODGA and DOODA have one or two etheric and two amidic oxygen donor atoms, and MIDOA and NTAamide have a nitrogen donor atom centered in the backbones and two or three diamidic O atoms. The former two extractants are expected to have high extractability for metal ions classified as hard acids and the latter ones have higher extractability for soft acids. TODGA and DOODA have high distribution ratios, D, for metal ions in the 2A-4A groups. On the other hand, MIDOA and NTAamide have high D values for group 5A-7A and 8 metal ions, which follows HSAB theory. The positive relation between the slope values of the extractant dependence and the extraction constant, α, is found, which suggests that a high order of successive formation of metal complexes with extractants gives high extractability.

In order to examine extraction behavior of ReO 4 - from HNO 3 aqueous solution to dodecane containing 2,2′-(imino)bis( N , N ′-dioctylacetamide) (IDOA) as an extractant, we have measured distribution ratios ( D ) by changing [HNO 3 ] under constant [IDOA] (5.00 × 10 −2 M, M = mol dm −3 ) in dodecane and also by changing [IDOA] in dodecane under constant [HNO 3 ] 0.1, 1.0, and 2.0 M. It was found that the D values decrease with an increase in [HNO 3 ] and increase with increasing [IDOA]. The decrease in D values with increasing [HNO 3 ] is considered to be due to effect of the protonation of IDOA in aqueous phase and also competitive extraction of NO 3 - with ReO 4 - from aqueous to organic phase. A plot of log D values against log [IDOA] gave the linear relationship with slope of ca. 1.03 ± 0.01 ([HNO 3 ] = 0.1 M), 1.02 ± 0.01 ([HNO 3 ] = 1.0 M) and 0.94 ± 0.01 ([HNO 3 ] = 2.0 M). These results suggest that one IDOA molecule contributes to the extraction of ReO 4 - . Effects of diluents (dodecane, toluene, dichloromethane) on the extraction of ReO 4 - with IDOA showed that IDOA exhibits higher extraction efficiencies into dodecane than toluene and dichloromethane. Furthermore, the influences of HNO 3 , H 2 SO 4 and HCl on the extraction of ReO 4 - into dodecane were examined by changing their concentrations from 0.1 to 2.0 M at [IDOA] = (5.00 × 10 −2 M). The results showed that the highest D values of ReO 4 - were observed in the H 2 SO 4 system. The effects of the concentrations of the various salts ((NH 4 ) 2 SO 4 , NH 4 Cl, and NH 4 NO 3 ) on the extraction of ReO 4 - into dodecane were also examined under constant [IDOA] (3.00 × 10 −2 M) and [acid] (0.1 M). It was found that the D values of ReO 4 - decrease with an increase in the concentrations of salts in the aqueous phase. These results suggest that anionic species ( SO 4 2 - , Cl − , NO 3 - ) are extracted with ReO 4 - from aqueous to organic phase. This is confirmed by the extraction experiments of (NH 4 ) 2 SO 4 , NH 4 Cl, and NH 4 NO 3 in the absence of ReO 4 - using IDOA into dodecane. Hence, it was proposed that the decrease of D values with an increase in acid concentrations is due to the competitive extraction of anionic species ( SO 4 2 - , Cl − , NO 3 - ).

Mutual separation of trivalent lanthanides (Ln) and actinides (An) is a challenging study in order to dispose effectively these metals in high-level radioactive liquid waste. Both extractant and masking agent are used simultaneously in an extraction system. The strong extractants, diglycolamide (DGA) and dioxaoctane-diamide (DOODA), and several kinds of the masking agents, were employed. The four novel-synthesized aminopolyacetamide compounds, namely, nitrilotriacetamide (NTAamide), hydroxypropane-triacetamide (Citricamide), ethylenediamine-tetracetamide (EDTAamide), and diethylenetriamine-pentacetamide (DTPAamide), were also examined. It can be seen that these compounds has more affirmative to heavy Ln than light ones and mutual separation factors by addition of these compounds are slightly high.

In order to examine extraction behavior of ReO 4 − from HNO3 aqueous solution to dichloromethane containing 2,2′-(methylimino)bis(N,N-diethylacetamide) (MIDEA) as an extractant, we have measured distribution ratios (D) by changing [HNO3] under constant [MIDEA] (1.064 × 10−1 M, M = mol dm−3) in CH2Cl2 and also by changing [MIDEA] in CH2Cl2 under constant [HNO3] (0.1 M) and (0.2 M). As a result, it was found that the D values decrease with an increase in [HNO3] and increase with increasing [MIDEA]. The decrease in D values with increasing [HNO3] is considered to be due to the effect of acid extraction with MIDEA. A plot of log D values against log [MIDEA] was found to show the linear relationship with slope of ca. 1.1. This result suggests that one MIDEA molecule contributes to the extraction of ReO 4 − , i.e., 1:1 complex. This is supported by the fact that the ReO 4 − species extracted from HNO3 solution to CH2Cl2 phase containing MIDEA is assigned as [C13H28O2N3+] [ ReO 4 − ] by the single crystal x-ray analysis.

The mutual separation of Am, Cm and lanthanides (Ln) by the hydrophilic and lipophilic ligands present in both aqueous and organic phases was studied. The hydrophilic ligands used here are DTPA(diethylene-triamine-N,N,N’,N’’,N’’-pentaacetic acid), malonamide, amic acid, TEDGA(N,N,N’,N’-tetraethyl-diglycolamide) and DOODA(C2) (N,N,N’,N’-tetraethyl-3, 6-dioxaoctanediamide) and four types of extractants, TODGA (N,N,N’,N’-tetraoctyl-diglycolamide), TDdDGA (N,N,N’,N’-tetradodecyl-diglycolamide), DOODA(C8) (N,N,N’,N’-tetraoctyl-3, 6-dioxaoctanediamide) and DOODA(C12) (N,N,N’,N’-tetradodecyl-3, 6-dioxaoctanediamide). DOODA(C8, 12) can extract light lanthanides with high D values into the organic phase. On the other hand (TO, TDd)DGA shows the opposite trend for Ln extraction. The high separation factor, over 1000, between D for La and that for Gd can be seen in the extraction using the extractant, TDdDGA, and DOODA(C2) as the masking agent in the aqueous phase. The separation factors for Am/Cm by DOODA(C8, C12) and (TO, TDd)DGA are 1.51-1.94, while values over 3 can be obtained by the conditions introduced in this work.

The extraction of actinides, fission products, some non-nuclear elements, and nitric acid by N,N,N′,N′-tetraoctyl-3,6-dioxaoctanediamide (DOODA-C8) in dodecane was extensively studied. Also studied was the extraction of HNO3 and Nd(III) by the tetradodecyl analog of DOODA-C8 in dodecane. Both extractants contain two ether oxygen atoms in the backbone chain carrying the two amide groups and can thus act as tetradentate ligands. The extractability of actinides decreases in the order Pu(IV) > U(VI), Am(III) > Np(V) in the extraction from nitric acid and Pu(IV) > Am(III) >> U(VI) in the extraction from perchloric acid. Ions of di-, tri-, tetra-, hexa-, and heptavalent metals strongly differ in the extractability by DOODA-C8 but, except for lanthanides(III), there is no visible correlation of their distribution ratios with ionic radii. Due to the efficient extraction of actinides, weak extraction of fission products, and sufficient extraction capacity, DOODA-C8 is a promising extractant for the recove...

2,2′‐(Methylimino)bis(N,N‐dioctylacetamide) (MIDOA) was developed as a new extractant for technetium. MIDOA has a similar backbone to TODGA, N,N,N′,N′‐tetraoctyldiglycolamide, where the nitrogen atom bearing a methyl group replaces the ether oxygen in TODGA. MIDOA is highly lipophilic and ready to use in the HNO3–n‐dodecane extraction system. The distribution ratio (D) for Tc(VII) is extremely high. In addition, Cr(VI), Re(VII), Mo(VI), W(VI), Pd(II), and Pu(IV) are well extracted by MIDOA. MIDOA has high selectivity toward certain oxometallates. The D(Tc) values decrease gradually with HNO3, H+, and NO3 − concentrations, and the log D vs log [MIDOA] dependence indicates the species extracted to be the 1:1 metal‐ligand complex. It is clear that MIDDA [2,2′‐(methylimino)bis(N,N‐didodecylacetamide)] and IDDA [2,2′‐(imino)bis(N,N‐didodecylacetamide)], which have structures analogous to MIDOA, have similar extraction behavior to that of MIDOA.

The extraction of various metals by N,N,N',N'-tetraoctyldiglycolamide (TODGA) from nitric acid to ndodecane was investigated. It was obvious that divalent Ca (ionic radius: 100 pm), trivalent and tetravalent ions with ionic radii of 87–113 and 83–94 pm are highly extractable by TODGA. The limits of metal concentration (LOC) for Ca(II), Nd(III) and Zr(IV) in the extraction solvents, TODGA/n-dodecanen, TODGADHOA(N,N-dihexyloctamide)/n-dodecanen, TDDGA (N,N,N',N'-tetradecyldiglycolamide) and TDdDGA(N,N,N',N'-tetradodecyldiglycolamide) were determined. It is evident that LOC is influenced strongly by and increases with DHOA concentration and the length of alkyl chain attached to N atom of DGA.

Many diamide-type extractants were synthesized and tested for the extraction of actinides (III), (IV), (V) and (VI) . The diglycolamides (DGA) with two amidic oxygen and one ether oxygen, which show the tridentate feature, have the high extractability of actinides (An) . In order to increase the lipophilic property, the diglycolamides with the different functional groups attached to N atoms were synthesized and examined for their extractability. It was found that N, N, N', N'- tetraoctyl-diglycolamide (TODGA) and N, N, N', N'- tetradecyl-diglycolamide (TDDGA) exhibit the satisfactory dissolution into n-dodecane with less solubility in H2O. The results of various metal extractions using TODGA revealed that the divalent, trivalent and tetravalent metals with ionic radius of 90-120 pm gave notably high D values. After elucidation of the effect on substitution of the functional group, the chemical form of DGA to have high performance on An extraction was proposed.

In order to evaluate the extraction property of new extractants, diglycolamide (DGA) compounds, we investigated the maximum extraction of di-, tri-, and tetravalent metal ions using nitric acid and n-dodecane. The limits of metal concentration (LOC) for Ca(II), Nd(III) and Zr(IV) in the organic phase are strongly influenced by HNO3 and the extractant concentration. For the purpose of enhancing the LOC value, we employed a modifier of the solvent, N,N-dihexyl-octanamide (DHOA) and DGA with a long alkyl chain, and examined the results. It was evident that LOC increased with the DHOA concentration and the length of the alkyl chain attached to the N atom of DGA. The stoichiometric values of LOC(Zr) estimated from the extraction reaction were confirmed by using the extraction condition: tetraoctyl-DGA/1 M DHOA + n-dodecane and 3 M HNO3.

The detailed study on the extraction capacity of N , N , N ′, N ′-tetraalkylderivatives of diglycolamide (DGA) was performed by using the novel analytical method, which determines the limit of metal concentration in the organic phase (LOC). The analytical results suggest that LOC of Nd(III) by N , N , N ′, N ′-tetraoctyl-diglycolamide (TODGA) depends on HNO 3 concentration and temperature. In order to increase LOC and suppress the third liquid phase, the modifier, N , N -dihexyl-octanamide (DHOA) of the aliphatic diluent was employed and its effect was investigated. The modifier can raise the LOC value, and it is noteworthy that LOC corresponds to the stoichiometric value, which is obtained by the extraction reaction, by using the extraction solvent of 0.1 M TODGA—(0.5–1 M) DHOA in n-dodecane. This condition suppresses the third liquid phase. In the absence of modifier, the relation of several DGA based compounds with LOC was investigated. It is confirmed that LOC using N , N , N ′, N ′-tetradodecyl-diglycolamide (TDdDGA), whose extractant has the longest alkyl chain in this work and forms hardly the third liquid phase, reaches to the stoichiometric value.

For the separation of trivalent lanthanides [Ln(III)] and actinides[An(III)], the chelating agent, diethylenetriamine‐N,N,N′,N″,N″‐pentaacetic acid (DTPA), was used to decrease selectively the distribution ratios (D) of An(III) between TODGA/n‐dodecane and nitrate solution. The D values of An(III) and Ln(III) decrease with an increase of the pH of the aqueous phase. Their dependencies for light Ln(III) are different from those for medium and heavy Ln(III), which implies that the complexing ability of DTPA5− with Ln(III) is different from each other. The calculation of D values was performed using dissociation constants of H5DTPA and the formation constants of Ln–DTPA. Their results suggested the existence of Ln(III) ions without any complexation at the intermediate stage of the extraction reactions and demonstrated the curvilineal relation of D with pH in Ln–TODGA–DTPA extraction system. Americium(III) and Cm(III) form more stable 1:1 complex with DTPA5− and show lower D values than light Ln(III)...

N,N,N′,N′‐Tetraoctyl‐3‐oxapentane diamide (TODGA) and its homologues were shown to be usefully applied to the extraction of divalent alkaline earth metal: M(II) ions from aqueous solutions of high nitric acid concentration, specifically around 3 M. The stoichiometry of the extracted Sr(II)‐DGA species was found to depend mainly on the concentration of nitric acid and molecular structure of DGA. The degree of extraction of M(II) by TODGA decreases in the order of Ca(II) > Sr(II) > Ba(II).

The effect of the alkyl substituents on amidic N atoms in diglycolamide (DGA) compounds on solvent extraction has been investigated. The solubility in water and n-dodecane, lanthanide loading capacity, and distribution ratios (D) of lanthanides and actinides for various DGA compounds are reported. DGA derivatives with short alkyl chains, for example methyl and ethyl groups, are very water soluble, while DGA derivatives with long alkyl chains, for example octyl (TODGA), decyl (TDDGA), dodecyl (TDdDGA), and 2-ethylhexyl (TEHDGA) group are moderately soluble in n-dodecane. DGA derivatives with phenyl substituents have very low solubility in both aqueous and organic solvents, which suggests that these compounds will not be suitable for solvent extraction applications in the HNO3/n-dodecane systems. The lanthanide loading capacities of DGA extractants correlate with their alkyl chain lengths according to the following order: TDdDGA > TDDGA > TODGA > TEHDGA. The branched-alkyl-chain DGA derivative (TEHDGA) exhibits both lower D and loading capacity than TODGA. The results of masking-effect and solubility tests indicate that TEDGA is the best actinide masking agent among the water-soluble DGA derivatives tested. Actinide and lanthanide extractions using ten DGA compounds in six diluents (nitrobenzene, 1,2-dichloroethane, 1-octanol, chloroform, toluene, and n-dodecane) are also reported; it was observed that lipophilic DGA derivatives with shorter alkyl chains show higher D values.

Eleven diamide extractants having the different backbones were synthesized and their extractability for lanthanides(III) and actinides(III), (IV), (V) and (VI) were measured and compared. The diamides investigated include (CH2) n ─(CONR1,R2)2, (n = 0, 1, 2, 3), O─((CH2) n′─CONR1,R2)2, S─((CH2) n″─CONR1,R2)2, and SS─((CH2)n′″─CONR1,R2)2, (n′, n″, n′″ = 1, 2). The diglycolamide introducing an ether oxygen into the main frame, O─(CH2─CONR1,R2)2, exhibited the highest extractability for An(III), (IV) and (VI), as compared with the other bidentate diamides. It is clear from the present results that the thiadiglycolamide, TDGA, which substitutes ether sulfur atom for oxygen in DGA molecule, also enhances the extraction of actinides. The lanthanide pattern, the distribution ratios versus the atomic number, by diglycolamide in HNO3-n-dodecane system exhibited a gradual increase of distribution ratio with increase in the atomic number, the opposite trend to that obtained by the other diamides.

N,N,N ′,N ′-Tetraoctyl-3-oxapentanediamide (TODGA) in n-dodecane solvent was studied to clarify the characteristics of third phase formation in extraction of lanthanides(III) and to modify the solvent. The loading capacity of the solvent was found to be dependent not only on the aqueous acidity and the temperature but also on molecular size of alkane solvent and kinds of aqueous anions. The loading capacity of 0.1 M TODGA-n-dodecane was 0.008 M Nd(III) with an aqueous phase of 3 M HNO3. Addition of N,N,-dihexyloctanamide (DHOA) of more than 0.5 M to the solvent eliminated the third phase in the extraction of Nd(III). The modified solvent of 0.1 M or 0.2 M TODGA with 1 M DHOA exhibited a satisfactorily high metal loading and slightly lower extractability for Nd(III) and moderately higher extraction of HNO3 than neat TODGA.

The novel extractants, six diglycolamides synthesized in our laboratory, were investigated for actinide extraction from nitric acid into n-dodecane. The dependence of the distribution coefficients of Eu(III) and Am(III) on the length of alkyl chain in the extractants was examined. Among the diglycolamides studied, N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TOOPDA) and N,N,N′,N′-tetradecyl-3-oxapentanediamide (TDOPDA) showed a sufficient solubility in n-dodecane, due to their appropriate lipophilicity modified by increasing the length of the alkyl chain attached to amidic N atoms. The distribution coefficients, D M, of actinides obtained by TOOPDA increased with an increase in HNO3 concentration. The number of diglycolamide molecules coordinated to the actinide ions was estimated to be three for Th(IV), U(VI), Pu(IV), and four for Am(III) and Cm(III) by slope analysis. The order of D M for the actinides at high nitric acid concentrations is An(III), An(IV) > An(VI) > An(V) and that for lanthanides, heavier ...

Actinide(III), (IV), (V) and (VI) ions were extracted by N,N′-dimethyl-N,N′-dihexyl-3-oxapentanediamide (DMDHOPDA) and thenoyltrifluoroacetone (HTTA). The extraction behaviors suggested the possibility of the mutual separation, and the convenient separation method of actinide ions (III), (IV), (V) and (VI) without reducing and oxidizing agents was studied. Th(IV) was extracted from the aqueous phase by HTTA (5 mM in toluene) in the first step. The Am(III) and U(VI) ions can be extracted by 1 and 20 mM DMDHOPDA in toluene, and the Np(V) ion can be extracted into nitrobenzene with 100 mM DMDHOPDA in the last step. The residual activities in the aqueous phase were much lower than the initial activities. These activities in the fractions were confirmed by the gamma- and the alpha-spectrometry. The one-through and rough separation is advanced, and in case of the fine isolation of actinide elements, each fraction should be purified in more detail.

N,N′-ジメチル-N,N′-ジヘキシル-3-オキサペンタンジアミド(DMDHOPDA)又はN,N′-ジメチル-N,N′-ジヘキシル-3-チアペンタンジアミド(DMDHTPDA)と2-テノイルトリフルオロアセトン(Htta)を用いてY,Eu及びアクチノイドの協同抽出を行い,抽出錯体の化学形を調べた。試薬濃度が一定の条件下で(すなわちY,Cm,Cfについては0.748mM[DMDHOPDA]及び5mM[Htta],Uについては2.8mM[DMDHOPDA]及び0.5mM[Htta],溶媒はトルエンを使用した)log DとpHのプロットが曲線関係を示した。更にlog Httaとlog D及びlog DMDHOPDAとlog D関係の結果を併せて解析して,M(DA)2(tta)(X)2やM(DA)(tta)2(X)(ここでM:Cm,Cf;DA:DMDHOPDA;X-:ClO4-)など2種以上の抽出錯体を見いだした。更に,DMDHTPDAとHttaの協同抽出において,Eu,Am,Th,及びUをニトロベンゼンに抽出する際にも,複数の錯体が生成することを確認した。

We have studied the extraction of Eu(III), Am(III), Th(IV), U(VI) and Np(V) by 4 diamides (DMDHOPDA, N , N ′-dimethyl- N , N ′-dihexyl-3-oxapentanediamide; DHOPDA, N , N ′-dihexyl-3-oxapentanediamide; DMDHTPDA, N , N ′-dimethyl- N , N ′-dihexyl-3-thiopentanediamide; DHTPDA, N , N ′-dihexyl-3-thiopentanediamide) from perchlorate solutions. Synergistic extraction was observed with these diamides and thenoyltrifluoroacetone (TTA) in which the main extraction species determined are M(TTA) 3 (DA) (M=Eu, Am), Th(TTA) 3 (DA)(X), UO 2 (TTA) 2 (DA) (DA: diamide, X − : ClO 4 − or CH 2 ClCOO − ). The species, M(DA) 3 (X) 3 , M(DA) 3 (TTA)(X) 2 , M(DA) 2 (TTA) 2 (X) and M(DA)(TTA) 3 are observed in the synergistic extraction of DMDHOPDA+TTA.

The diamide, N,N′-dimethyl-N,N′-dihexyl-3-thiopentanediamide (DMDHTPDA) was synthesized and thested for extraction of Eu(III), Am(III), Th(IV) and U(VI). DMDHTPDA shows a very weak complexation with these metal ions, which can be attributed to the soft base nature of the sulfur atom. None of the cations were extracted into the organic phase when DMDHTPDA alone was present. Synergistic extraction was measured for DMDHTPDA plus thenoyltrifluoroacetone. From the extraction dependencies on pH and extractant concentration, formation of mixed TTA+DMDHTPDA complexes were indicated. Except for the Th(IV) system, the separation and synergistic factors were smaller for the TTA+DMDHTPDA extractant than for the system of TTA+DMDHOPDA (the oxo ether analog of DMDHTPDA).

The diamide type extractants (N, N′-dimethyl-N, N′-dihexyl-3-oxapentanediamide, DMDHOPDA, N, N′-dihexyl-3-thiopentanediamide, DHTPDA, and N, N′-dihexyl-3-oxapentanediamide, DHOPDA) were synthesized and tested for the extraction of the lanthanide and actinide elements. The elements, Eu3+, Am3+, Th4+, NpO2+ and UO22+, when extracted by DMDHOPDA, showed no pH-dependence. The relationships between log[DMDHOPDA] and log D under different ionic strengths were investigated in order to clarify the extraction reactions. The separation factor for Eu3+/Am3+ is 8.64.

Several complexing agents with a soft donor incomporated into their structures are examined for the masking effects of Mo and Re through solvent extraction. The available extractants are N,N,N′,N′,...

International audience; Extraction of Eu(III) and Am(III) from HNO3 into the organic solvents using N,N,N-,N--tetraoctyl-diglycolamide (TODGA) was investigated in order to study the detailed extraction reaction. The chemical species 12 for metalTODGA complex is present in polar diluents. On the other hand, the metal complexes need three or more TODGA molecules to remain stable in non-polar diluents. The HNO3 concentration dependence on the distribution ratio suggests that HNO3 participates in the metal extraction. Infrared spectra indicate that the carbonyl oxygen coordinates with Eu(III), and luminescence lifetimes suggest that there are no water molecules in the inner coordination sphere of the extracted Eu-complex.

A new concept of the electrochemical process for the reprocessing of nuclear spent fuel, SREEP, has been developed on the basis of fundamental studies of the electrochemical reactions of actinide elements and fission products. SREEP consists of unit processes for (1) spent fuel dissolution by electrolytic oxidation, (2) recovery of platinum group metals by electrodeposition, (3) TBP extraction of U, Pu and Np after the successive electrolytic preparation of U(VI), Pu(IV) and Np(VI), (4) recovery of Cs and Sr by electrolytic ion transfer extraction and (5) separation of transplutonium and lanthanide elements by electrodeposition in the molten salt.

New reagent, N,N,N′,N′-tetraoctyl-3,6-dioxaoctanediamide (DOODA-C8), was synthesized and examined for the actinide and fission product extractions. Extraction from nitric acid to n-dodecane was stu...

A new technique for the back-extraction using photoreduction by the fourth harmonic of Nd:YAG laser has been successfully demonstrated in a liquid–liquid extraction system composed of a 1-octanol s...