| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1992: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1991: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Salicylaldehyde n-alkanohydrazones (SAAH or H_2L)having 1 to 13 carbon atoms in their alkyl chains and 5-bromo,3,5-dibromo-and 5-nitrosalicyladehyde acetohydrazones (BSAH,DBSAH and NSAH, respectively, SSAH or H_2L) were synthesized. The extraction of lanthanoid ions (Ln^<3+>) including praseodymium(III), europium(III) and ytterbium(III) into 1,2-dichloroethane with the synthesized hydrazones in the presence of both tri-n-butylphosphate (TBP) and perchlorate has been investigated. The extracted species were (Ln^<3+>)(HL^-)_2(TBP)_3(ClO_4^-) for all the hydrazones. The acid dissociation constants, Ka, and the partition coefficients, K_D, of the hydrazones and the extraction constants, K_<ex>, of the lanthanoid complexes were determind. The K_D values of SAAH increased with an increase in the carbon number of the alkyl chain, the increment of log K_D being 0.64 per a carbon atom. The K_D values also increased slightly with an increase in the carbon number, but the K_<ex> values of their l
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anthanoid complexes were almost independent of the length of the alkyl chain, On the other hand, the introduction of electron-withdrawing bromo or nitro groups to the 3-and/or 5-position of the benzene ring in salicylaldehyde acetohydrazone (SAH) was very effective for increasing not only the K_a value of SAH but also its K_D value and the K_<ex> values of its lanthanoid complexes. The kinetics of the solvent extraction of ytterbium(III) from aqueous media with a 1,2-dichloroethane solution of salicyladehyde n-octanohydrazone(SOH or H_2L) in the presence of both tributylphosphate (TBP) and perchlorate have been studied at 25*0.1ﾟC and an ionic strength of 0.2. The rate of extraction was first-order with respect to the concentrations of ytterbium(III) in the aqueous phase and SOH in the organic phase, inversely first-order with respect to the hydrogen-ion concentration and zero- and first-order with respect to the TBP concentration in the organic phase. Two mechanisms operate for this extraction, depending on the TBP concentration in the organic phase. One is a mechanism in which the formation of the first complex, [Yb(HL)]^<2+>, between Yb^<3+> and HL^- in the region of log[TBP]_<org>< -0.95 becomes the rate-determining step, and the other is that in which the formation of the first complex, [Yb(HL)(TBP)]^<2+>, between [Yb(TBP)]^<3+> and HL^- in the region of log [YBP]_<org>>-0.85 is the rate-determining step. The rate constant and activation parameters for the former reaction were calculated, but those for the latter one could not be determined. Taking into consideration the above-mentioned three constants, of the synthesized hydrazones DBSAH was the most balanced and recommendable extractant for the lanthanoids. Less
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