Yu Tachibana

Effect of alcohols on separation behavior of rare earth elements using benzimidazole-type anion-exchange resin in nitric acid solutions

The mutual separation of rare earth elements based on the ion exchange chromatography has been studied. The effect of alcohols on separation behavior of rare earth elements using the benzimidazole-type anion-exchange resin embedded in high-porous silica beads was investigated in nitric acid/alcohol mixed solvent systems. It was confirmed that the mutual separation of rare earth elements is possible by using our proposed methods. It was found that the distribution coefficients of rare earth elements depend on the corresponding alcoholic relative permittivity and on the steric hindrance due to the hydrophobic interaction among each alcoholic molecule.

Adsorptivity of various metal ions onto benzo-18-crown-6 and dibenzo-18-crown-6 resins

Adsorptivity of metal ions onto silica-supported benzo-18-crown-6 (B18C6) and dibenzo-18-crown-6 (DB18C6) resins was investigated in nitric acid and hydrochloric acid media to evaluate the applicability of these resins for selective separation of nuclides from radioactive waste solutions. Both resins adsorbed Pd(II) and Ag(I) from HNO3, and Fe(III) and Ba(II) from HCl. It was also found that the B18C6 and DB18C6 resins adsorbed Sr(II) from HCl and Ca(II) from HNO3, respectively. This indicates that the two resins adsorb metal ions with smaller cationic diameters with different selectivity. This behavior is different from other impregnated adsorbents and extractants containing the 18-crown-6 moiety.

Vaporization and deposition of cesium dimolybdate, Cs2Mo2O7

ABSTRACT Vaporization and deposition of cesium dimolybdate (Cs2Mo2O7) in argon were studied by thermogravimetry and transpiration methods. From Raman spectra and electron probe microanalysis of deposits and inductively coupled plasma mass spectroscopy of the aqueous trap of the exhaust, it was judged that the Cs2Mo2O7 vaporizes as Cs2Mo2O7 (g). The effect of water addition on Raman spectral of Cs2Mo2O7 was also investigated. Comparing the high-temperature mass losses of Cs2Mo2O7 by thermogravimetry with that of Cs2MoO4, the equilibrium vapor pressure of Cs2Mo2O7 was estimated. The vapor pressure of Cs2Mo2O7 (l) in its liquid state was calculated to be: log10P (Cs2Mo2O7)(l) = (8.95 ± 0.07) − (1.03 ± 0.01) × 104 /T (T = 1273−1573 K). The enthalpy of vaporization of Cs2Mo2O7 (l) was estimated to be 197 ± 31 kJ·mol−1.

Kinetic and Mechanistic Studies on Reactions of Pyrrolidone Derivatives with Ozone

Reactions of various pyrrolidone derivatives (NRPs = 2-pyrrolidone (2P), N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), N-iso-butyl-2-pyrrolidone (NiBP), N-n-pentyl-2-pyrrolidone (NPP), N-neopentyl-2-pyrrolidone (NNPP), N-dimethylpropyl-2-pyrrolidone (NDPP), N-cyclohexyl-2-pyrrolidone (NCP)) with O3 have been studied under pseudo–first-order conditions with excess O3 in aqueous solution of pH 2.0 at various temperatures (278–298 K). It was found that the reaction rates is expressed as –d[NRPs]/dt = k[NRP][O3], that the second-order rate constants (k) slightly increase with increasing the effective charges in order of NMP, NEP, NProP, NBP and NPP, and that the k values of NBP and NPP are larger than those of more bulky NiBP and more bulky NNPP and NDPP, respectively. In these reactions, the ΔH‡ values are consistent with each other, while the ΔS‡ values decrease with decreasing length of alkyl groups. Furthermore, it was found that reactions of NRPs (NMP, NEP, NProP, NBP, and NPP) with O3 show the linear relationship between the obtained ΔS‡ values and the softness of NRPs. From these results, it was proposed that the reactions of NRPs with O3 proceed through the interaction between O3 and N atom of NRPs. The analyses of products in the reactions of NRPs with O3 were also carried out by 13C-NMR and GC/MS measurements, and indicated that N-alkylsuccinimide and N-acyl-2-pyrrolidone are produced through intramolecular side-chain oxidations of α-carbon of NRPs. From these results, it is proposed that the reactions of NRPs with O3 proceed through the mechanism with the selective attacks of O3 to N atom of NRPs.

Effect of Pd(II) Species on Decomposition Reactions of Pyrrolidone Derivatives by Ozone

Decomposition reactions of N-dimethylpropyl-2-pyrrolidone (NDPP), which is one of pyrrolidone derivatives (NRPs), by O3 have been examined in aqueous sulfuric acid solutions containing metal ions (Fe(II), Rb(I), Sr(II), Ba(II), La(III), Ce(III), Pr(III), Nd(III), Sm(III), Y(III), Zr(IV), Ru(III), Rh(III), Pd(II), Mo(VI), Re(VII), and Te(VI)), respectively, under conditions, pH = 2.0 and Temp. = 298 K. It was found that Pd(II) ion has the highest efficacy for the decomposition of NDPP. Hence, the effect of Pd(II) ion on the decomposition reactions of NRPs (NDPP, N-neopentyl-2-pyrrolidone (NNPP), and N-n-pentyl-2-pyrrolione (NPP)) by O3 has been studied kinetically under conditions, pH = 1.0–3.5 and Temp. = 288 K. As a result, it was found that the decomposition reactions of NRPs by O3 in the system containing Pd(II) ion (abbreviated as NRPs/Pd(II)/O3 reactions) are independent on concentrations of H+ ([H+]) and proceed through two paths, one is the path depending on [Pd(II)] and the dissolved O3 concentration ([O3]D), and another is the path depending on only [O3]D. Furthermore, it was confirmed that the 1:1 complex is formed, Pd(II) + NRPs ⇌ [Pd(NRPs)]2+, under the conditions [NRPs]T/[Pd(II)]T = 1 ∼ 12 (subscript T means total concentration), and that the stability constants (K1) for [Pd(NRPs)]2+ are also evaluated as 37.8 ± 0.46, 9.33 ± 0.15, and 1.63 ± 0.11 M−1 for NPP, NDPP, and NNPP, respectively. Based on these results, it was found that the reaction rate is expressed as -d[NRPs]/dt = kaK1[O3]D[NRPs][Pd(II)]T + kb[O3]D[NRPs] (ka: rate constants for the reactions between [Pd(NRPs)]2+ and O3, kb: rate constants for the reactions between NRPs and O3, K1: stability constants for [Pd(NRPs)]2+), and that the ka values are (6.03 ± 0.69) × 103, (4.33 ± 0.21) × 103, and (7.61 ± 0.23) × 103 M−1s−1 for NPP, NDPP, and NNPP, respectively. From these results, it was proposed that the path depending on [Pd(II)] in the NRPs/Pd(II)/O3 reactions proceeds through the attack of O3 to [Pd(NRPs)]2+.