There has been an increasing demand for scandium (Sc). However the supply is insufficient because the separation and recovery of Sc as a byproduct from ores is difficult. In this study, extraction and separation of Sc³⁺ from a sulfuric acid solution containing transition metals such as Al³⁺, Fe³⁺, Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ was investigated using a β-diketone, HTTA and a neutral extractant, TOPO. Due to the synergistic effect with the two extractants, Sc³⁺ was effectively and selectively separated even from Fe³⁺, the separation of which is difficult with HTTA alone. The extraction mechanism was examined and it was revealed that Sc³⁺ is extracted with three HTTA and one TOPO molecules. Scandium was readily stripped from the extracting phase by 1 M sulfuric acid. The potential use of the combination of the β-diketone with TOPO for the recovery of Sc³⁺ in a refining process was demonstrated.

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The possible use of 2-Mercaptopyridine N-oxide (HSPyO) as an extractant in ionic liquid chelate extraction was investigated with using several divalent metals (M²⁺, M = Cu, Ni, Zn, Cd and Mn). The extraction performance of HSPyO in the 1-buthyl-3-methyimidazolium bis(trifluoromethanesulfonyl)imide (C₄mimTf₂N) system was very similar to that in the chloroform system, except for Cd²⁺. Over wide pH range, Cu²⁺, Ni²⁺ and Zn²⁺ were extracted quantitatively into C₄mimTf₂N as neutral 1:2 complexes M(SPyO)₂. Furthermore, the strange extraction behavior for Cd²⁺ into C₄mimTf₂N was found to originate in the competitive extraction of neutral Cd(SPyO)₂ and anionic Cd(SPyO)₃^–.

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Liquid–liquid extraction of rare-earth (RE) cations has been investigated using N-dodecyldiglycolamic acid (C₁₂DGAA) with a secondary amide group, and compared with that using N,N-dioctyldiglycolamic acid (DODGAA) with a tertiary amide group. C₁₂DGAA enables quantitative transfer of all RE cations from moderately acidic solution, while being selective toward the heavier RE cations, and performs better than typical carboxylic-acid-type extractants. However, C₁₂DGAA provides low extraction performance and separation ability for RE cations compared with DODGAA because of the weaker basicity of the amide oxygen. Slope analysis demonstrated that RE³⁺ transfer with C₁₂DGAA proceeded through a proton-exchange reaction, forming a 1:3 complex, RE(C₁₂DGAA)₃. Structural characterization by X-ray diffraction revealed that three N-butyldiglycolamic acid (C₄DGAA) molecules coordinated to the La³⁺ central ion in a tridentate fashion and the La³⁺ primary coordination sphere consisted of three oxygen atoms from the amide group, three oxygen atoms from the ether group, and three oxygen atoms from the carboxy group.

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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'',N''-hexaoctyl-nitrilotriacetamide (NTAamide(C8)), 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(CH₂C(P)=O)₂ framework that is important for this purpose. A masking agent for Re was not found in this study.

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The microbial production of 1,3-propanediol from renewable resources is of great interest. However, its strong hydrophilic property makes the separation of 1,3-propanediol from the fermentation broth difficult. In this study, reactive extraction using boronate esterification, and anion exchange with a quaternary ammonium salt were utilized to extract 1,3-propanediol from an aqueous solution. For this process, the effects of the quaternary ammonium cation and the counter anion on the extraction were examined. Symmetrical quaternary cations were found to provide higher distribution ratios than their unsymmetrical counterparts. Following this, quaternary ammonium fluoride and hydroxide (which have smaller association constants than commercially available quaternary ammonium salts) were prepared. It was found that the distribution ratio of symmetrical quaternary ammonium hydroxide such as [N_8,8,8,8][OH] increased by roughly double that for Aliquat 336.

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Solid phase extractive removal of harmful formaldehyde with an imination reaction on a resin impregnated with a trident amine derivative has been investigated to compare the removal behavior with extractive removal with the trident amine derivative reported in the previous work. The impregnated resin also effectively removed formaldehyde while maintaining the extractive removal performance of the impregnated triamine. In particular, the leakage of the impregnated amine was significantly suppressed in the solid phase extraction with the impregnated resin compared with that in the extraction system.

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We report here the effect of a hydrophobic ionic liquid (IL), 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]), for in situ extraction of hydrophobic taxanes such as 10-deacetyl baccatin III, baccatin III, cepharomannine and paclitaxel from an aqueous medium, on the production of the taxanes by Taxus cuspidata callus in the IL-medium two phase culture system. The effect of an additional elicitor, methyl jasmonate (MJ), on the production of the taxanes was also examined. The callus growth in the culture with the IL decreased compared to that without the IL. The production amount of 10-deacetyl baccatin III in the culture with the IL was enhanced significantly, which might cause the callus growth to decrease. Addition of MJ in the culture with the IL promoted the amount of cepharomannine produced. It was clear that [C₆MIM][PF₆] was an effective solvent for extraction and production of the taxanes in the callus culture.

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