H. Suganuma

Solvent extraction mechanism of pertechnetate with tetraphenylarsonium chloride

A systematic study of extraction of pertechnetate with tetraphenylarsonium chloride (TPAC) in chloroform from aqueous chloride solutions has been carried out at 25°C at ionic strength of 1.0. Fundamental parameters governing the distribution equilibrium of TPAC were determined. Extraction behavior of pertechnetate was established on the basis of the distribution mechanism of TPAC.

Solvent extraction study on the hydrolysis of tracer concentration of Po(IV) in chloride solutions

Abstract The hydrolysis and chlorocomplex formation of Po(IV) was investigated through solvent extraction with dithizone-carbon tetrachloride solutions. In a 1.0 M (H,Na)Cl solution, a tracer concentration of Po(IV) (about 10 −12 M) was found to exist as; Po(OH) 2 Cl 4 2− , Po(OH) 2 Cl 3.7 1.7− , Po(OH) 2 Cl 3.5 1.5− , Po(OH) 2.1 Cl 2.0 − and Po(OH) 4 for −log[H + ] = 0, 1, 2, 3 and 6, respectively. The constants of successive hydrolysis, β 1 = [Po(OH) 3 Cl n 1− n ][Po(OH 4 ] −1 [H + ] −1 [Cl −1 ] − n and β 2 = [Po(OH) 2 Cl n 2− n ][Po(OH) 4 ] −1 [H + ] −2 [Cl − ] − n were calculated from the distribution ratios obtained, giving the results; log β 1 = 4.6 ± 0.3 and log β 2 = 8.7 ± 0.3. The chemical composition of extracted species was probably PoCl 2 (HDz) 2 , Po(OH)Cl(HDz) 2 and Po(OH) 2 (HDz) 2 .

Direct evidence for enhanced inner-sphere chloro complexation of Eu(III) and Cm(III) in anion exchange resin phase studied by time-resolved laser-induced fluorescence spectroscopy

Summary In anion exchange resin systems with LiCl-aqueous and LiCl-(H2O + CH3OH) solutions, the extent of chloro complexation of M(III) (M = Eu, Cm) was estimated from inner-sphere hydration number (NH2O), i.e., the number of water molecules in the first coordination sphere of M(III) and from peak area ratio (A2/A1) of 5D0 → 7F2 transition (A2) to 5D0 → 7F1 transition (A1) in emission spectrum of Eu(III), which reflects the ligand environment both in the inner- and outer-spheres of Eu(III). The NH2O of M(III) both in the solution and resin phases decreased with an increase of LiCl and CH3OH concentrations, indicating the formation of an inner-sphere M(III)-chloro complex. From the comparison of NH2O between the both phases, it was found that the extent of the inner-sphere chloro complexation of M(III) in the resin phase is higher than that in the solution phase. The A2/A1 ratio in the both phases increased with an increase of interaction of Eu(III) with Cl−, which are well correlated with the results of NH2O. The sorption equilibrium of M(III) was discussed by comparing the extent of the chloro complexation with the distribution coefficient.

Anion-exchange of the chemical species of tracer concentrations of polonium(IV) in chloride solutions

An anion-exchange method is used for determining the average anionic charge of polonium species in chloride solutions. This method is based on measurements of the distribution ratio of polonium at a constant internal chloride ion concentration of the anion-exchanger phase. In 1.0 mol·dm−1 (H, Na)CL solution in a vicinity of −log[H+]=1.0, tracer concentrations of polonium(IV) is found to exist in both chemical forms of [PoCl4(OH)22−] and [PoCl3(OH)2−].

Sorption behavior and coordination state of Eu(III) and Cm(III) in hydrochloric acid-methanol mixture/cation exchange resin system studied by time-resolved laser-induced fluorescence spectroscopy

A role of methanol on the enhancement of the sorption of M(III) [M=Eu, Cm] in HCl-CH3OH mixture/cation exchange resin system was investigated by comparing the distribution coefficient of M(III) with its coordination states both in the solution and the resin phases. The inner-sphere hydration number (NH2O) of M(III), i.e., the number of water molecules in the first coordination sphere, was determined by the measurement of the luminescence lifetime of M(III) using Time-Resolved Laser-induced Fluorescence Spectroscopy. From the results showing a decrease of NH2O with an increase of methanol mole fraction (XCH3OH), it was found that the inner-sphere complexations of M(III) both with Cl- in the solution phase and with exchange group, SO3-, in the resin phase were promoted with an increase of XCH3OH. The variation of the coordination environment around Eu(III) estimated from the emission spectra was correlated well with the variation of the NH2O. It was concluded that the increase of the sorption is mainly resulted from the inner-sphere complexation of M(III) with SO3- in the resin phase.

Mechanism of the solvent extraction of pertechnetate with tetraphenylarsonium chloride

Based on the fundamental parameters governing the distribution equilibrium of tetraphenylarsonium chloride (TPAC) between then-hexane-chloroform and aqueous solutions, the extraction mechanism of pertechnetate with TPAC has been systematically investigated. By the analysis of a relation of the distribution ratio of pertechnetate and the hydrogen ion concentration, the dissociation constant of pertechnetic acid was determined to beKa=2.09±0.18 at 25 °C.

Solvent extraction of pertechnetate with TBP from perchloric acid solution

Solvent extraction mechanism of pertechnetic acid with TBP from perchloric acid solutions is discussed. When cyclohexane is used as a diluent of TBP, perchloric acid can be extracted in the form of HClO4(TBP)2 into the organic phase. The TBP extraction of pertechnetic acid competes with perchloric acid and its equilibria are expressed as follows: HTcO4+3TBP⇄HTcO4(TBP)3 and HTcO4(TBP)3+TBP⇄HTcO4(TBP)4.

Separation of Americium(III) from Europium(III) by Extraction Based on in situ Formation of Dioctylammonium Dioctyldithiocarbamate Extractant

In this study an efficient method is developed for removal of minor actinoids (MA) from trivalent rare earth element (RE(III)) ions. An extraction technique is employed that is based on the in situ formation of dioctylammonium dioctyldithiocarbamate (DOA+DODTC−) as an extractant. This technique has an advantage in that the chemical stability of the extractant need not be taken into consideration. The extraction of Am(III) and Eu(III) from a nitric medium with DOA+.DODTC− resulting from carbon disulfide and dioctyl amine in nitrobenzene is studied. The separation factor of Am(III)/Eu(III) is a higher value than that obtained by a cyanex301/kerosene extraction and a similar value with that obtained by a normal extraction of synthesized DOA+DODTC−/nitrobenzene. The high selectivity for the separation of Am(III) from RE(III) arises from the difference in the reactivity of their metal ions to two sulfur atoms in the functional group of dithiocarbamate.

On the size variation of the primary solvation sphere of Nd3+ and Tm3+ in mixed system of methanol and water

The stability constants, α1, of each monochloride complex of Nd(III) and Tm(III) have been determined in the mixed system of methanol and water with 1.0 mol·dm−1 ionic strength using a solvent extraction technique. The values of α1 of Nd(III) and Tm(III) increase as the mole fraction of methanol in the mixed solvent system (Xs) increases. However, the variation mode of α1 againstXs in the region of 0.00≤Xs≤0.40 differs from each other, a concave curve for the Nd(III) and a convex curve for the Tm(III). The LnCl2+ formed is present as a solvent-shared ion-pair. Since Cl− is a structure breaking ion, it was assumed that the primary solvation sphere of Ln3+ directly contacted with Cl−. Calculation of Ln3+−Cl− distance using Bom-type equation revealed the followings: (1) for Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl− increases linearly withXs in 0.00≤Xs≤0.40. The results mean an increase of the primary solvation sphere size of Tm3+ withXs. (2) For Nd3+, the distance between Nd3+ and Cl− decreases linearly withXs in 0.00≤Xs<0.13, where both coordination numbers of 9 and 8 coexist, while it increases withXs in 0.13<Xs≤0.40. The results mean a decrease of the primary solvation-sphere size of Nd3+ withXs in 0.00≤Xs<0.13 and an increase of that withXs in 0.13<Xs≤0.40.

SEPARATION OF POLONIUM SPECIES IN NITRATE SOLUTIONS BY PAPER CHROMATOGRAPHY

Ascending paper chromatography using Toyo No. 50 paper and n-BuOH saturated with 1.0M HNO3 as a developing solvent, was useful to examine the separation of polonium species in (H,NH4)NO3 solutions. A neutral mononuclear species (Po(OH)4) appeared in the vicinity of Rf=0.6. The Rf values of each species decreased depending on the increasing cationic tendency and polymerization of the polonium species.