Studies on the Extraction of Soft Acid Metal Species Using MIDOA and Analogous Compounds

Morita

Suzuki

et al. 2017

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The solvent extraction of Se(IV), Zr(IV), Pd(II), and Cs(I) from nitric acid into 1-octanol (OC), or 1-octanol and n-dodecane has been performed. These elements include long-lived radionuclides in spent nuclear fuels, so a simple separation method is indispensable for the development of the treatment of high-level liquid radioactive waste. It was found that Se can be extracted using phenylenediamine, Zr(IV) can be extracted using tetraoctyl diglycolamide and di-2-ethylhexyl phosphoric acid, and Pd can be extracted using (methylimino)bis(N,N-dioctylacetamide) and N,N,N',N',N",N"-hexaoctylnitrilotriacetamide. These elements can be recovered in over 90% yield by these extractants from nitric acid into OC. A distribution ratio of Cs(I) of greater than 1 can be obtained using di-t-butyldibenzo-18-crown-6. It is clear that 90% recovery of Cs(I) can be achieved using an extraction solvent with ten times the volume of the aqueous phase.

Section: Extraction Of Pdmentioning

confidence: 97%

Section: Extraction Of Sementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Extraction and Separation of Se, Zr, Pd, and Cs Including Long-Lived Radionuclides

Morita

Suzuki

et al. 2017

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“…According to the hard-soft acid-base (HSAB) principle [18], NTAamide has a strong bonding affinity with soft-acid metals. In this study, the masking effects on Mo, Tc, and the Pt group metals were studied in methylimino-N,N-dioctylacetamide (MIDOA) [17,[19][20] and NTAamide extraction using several water-miscible reagents. The main purpose was to establish the separation technique to strip metals from the organic phase and recover metals effectively.…”

Section: Introductionmentioning

confidence: 99%

Masking Effects for Mo, Re, Pd and Ru by S and N-Donor Reagents through MIDOA and Ntaamide Extraction

Morita

Shimazaki

et al. 2016

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In this study, we examined the masking effects of 16 water-miscible reagents, on the extraction of Mo, Re, Ru, and Pd. These reagents included soft N-and/or S-donor atoms in their structures and they function as multidentate ligands. The extractants, methylimino-N,N-dioctylacetamide (MIDOA) and N,N,N',N',N'',), show significantly high distribution ratios for these metals(D(M)), were employed in this study. Masking effects were observed as a decrease in D(M) with an increase of masking agent concentration in these extraction systems. The results showed that D(Pd) can be considerably decreased by the addition of thiourea, cysteine, cysteamine, trisaminoethylamine, and diethylenetriamine, and D(Ru) is decreased by the addition of thiourea, trisaminoethylamine, and diethylenetriamine. Pd and Ru can be masked by similar reagents including N-or S-donor atoms, which suppressed the extraction into the organic phase. In contrast, D(Mo) was only slightly masked by the above-mentioned reagents. The masking of Mo was achieved using methylimino-N,N'-diethylacetamide, hexaethyl-nitrilotriacetamide, iminodiacetic acid, and iminodimethylphosphonic acid, which have a central N(CH 2 C(P)=O) 2 framework that is important for this purpose. A masking agent for Re was not found in this study.

“…based on the HSAB principle. Some papers reported that these extractants have strong extraction abilities for Mo, Tc, Re and Pd (MIDOA), and Pd, Ag, Au and Hg (TDGA) [13][14][15][16]. These extractants have the same central frame but with different donor atoms, however less work has been reported on the investigation of the role of O, N and S donors and comparison with their extractabilities In this work, using these extractants, the feature of metal-extraction on the periodic table by different donor atoms is investigated.…”

mentioning

confidence: 99%

Extractions and Spectroscopic Studies of Various Metals with Diglycolamide-Type Tridentate Ligands

Saeki

Yoshizuka

2019

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Three tridentate extractants and three masking reagents including O, N, and S donors have been developed and their properties are compared and discussed. The extractants are N,N,N′,N′-tetraoctyl-diglycolamide (TODGA), methylimino-N,N′-dioctylacetamide (MIDOA) and N,N,N′,N′-tetraoctyl-thiodiglycolamide (TDGA(C8)) together with masking agents having the same central frame but with short alkyl chains. The results of the present study indicate that TODGA can extract mainly hard acid metals belonging to groups 2-4,13-15 in the periodic table. MIDOA can extract soft acid metals and oxyanions (groups 5-10, 16), and TDGA can extract soft acid metals (groups 10-11). Some spectrophotometric studies (UV-vis., IR, and NMR) indicate the stoichiometry and the effect of donor atoms for metal-complexation. The ΔHf values, the heat generation during complex formation, obtained by chemical calculation by DFT theory show a reverse-correlation with their extraction ability. 1. Introduction Recently, tridentate extractants and ligands have been developed and studied worldwide [1-6]. Tridentate ligands can complex effectively with metals with 6 and 9 coordination sites with 1 : 2 and 1 : 3 metal-ligand complex stochiometries, rather than monodentate and bidentate extractants. The strong extractabilities and high complexation abilities for metals by tridentate ligands have been reported in many papers[1,4,6]. One of the most important tridentate extractant is TODGA (N,N,N′,N′-tetraoctyl-diglycolamide) [5]. This compound has three oxygen donors (two carbonyl oxygen donors and an ether oxygen atom) attached with diamide groups outside of the central frame. Based on the HSAB principle [7], oxygen donors are preferred for hard acid metals, metals belonging groups 2-4 in the periodic table. TODGA can dissolve in n-dodecane and shows a very high distribution ratio (D) for actinides (An) and lanthanides (Ln) from nitric acid. Therefore, TODGA is a useful extractant for metal separation from high level radioactive liquid waste [8-12]. TODGA is composed of C, H, O, N atoms and complete gasification takes place on combustion, thus producing less secondary waste. N and S donor extractants, which are similar to TODGA, can be produced by substitution of the O atom at the ether position in TODGA. The N-compound with a methyl group attached is termed as MIDOA (methylimino-N,N′-dioctylacetamide) and the S-compound is TDGA (N,N,N′,N′-tetraoctyl-thiodiglycolamide) [6, 13-16]. These extractants can be synthesized by changing the initial materials to methylimino-diacetic acid or thiodiacetic acid from the diglycol acid of TODGA. Both N and S donors are soft donors and complexing well with soft acid metals