Takuji Kanno

Transport of Uranium(VI) through a Supported Liquid Membrane Containing LIX 63

Abstract The carrier transport of U(VI) has been studied by means of the liquid membrane of LIX 63 (HR) held on a porous support. U was effectively transported from the dilute feed solution (pH = 4–5) to the product solution of 0.1 M H2SO4. Its concentration in the feed decreased according to [U]f, t = [U]f, o exp (-k obs t). The apparent rate constant (k obs) increased with an increase in carrier concentration up to 0.05 M, but it became nearly constant in the range of [HR] = 0.05–0.2 M. The rate of transport was inversely proportional to the feed volume. More than 99% of U was recovered and the final concentration ratio in the product to the feed ([U]p/[U]f) exceeded 103.

Effect of diluent on synergic extraction of europium by thenoyltrifluoroacetone and tri-n-octyl phosphine oxide

Abstract Effects of organic diluents have been studied on the adduct formation of thenoyltrifluoroacetone (TTA;HA) chelate of europium(III) with a strong neutral donor, tri- n -octyl phosphine oxide (TOPO;S). The tris-TTA chelate EuA 3 forms two types of synergic adducts EuA 3 ·S and EuA 3 ·2S. Adduct formation constants K S, m ( m = 1, 2) determined in thirteen diluents are strongly diluent-dependent, e.g. log K S,2 = 15.08 in pentane to 7.68 in chloroform. The log K S, m values are correlated to the solubility parameter δ org of the organic diluent by the linear equation, log K S, m = 2B δ org + constant, where B is a negative constant characterized by the composition of the adduct.

Regularities of extraction of uranyl thenoyltrifluoroacetonate into a number of solvents

The extraction equilibria were investigated of the thenoyltrifluoroacetone (TTA) chelate of uranyl ion between aqueous perchlorate medium and thirteen organic solvents. The extracted species was shown to be UO2A2. The solubility parameter of the chelate was estimated from the partition data and it was confirmed that the relationship lgPM=n lgPHA+const. holds for the present system. When the extraction constant (Kex) is considered in relation to the distribution coefficients, theKex values are expected to be constant under certain conditions for all of the solvents; the lgKex values were found to be constant (lgKex=−2.85±0.17).

Relation between distribution of TTA and “solubility parameter” of alcohol solvent

Abstract The distribution of thenoyltriftuoroacetone (TTA) between 11 alcohols and the aqueous perchlorate solution of ionic strength of 0·1 was studied at 25°C. Though a peculiar distribution curve of TTA was observed in the higher pH region, an equilibrium among TTA species in the organic phase is independent of hydrogen ion concentration in the aqueous phase below pH 4. There is a good correlation between the distribution coefficient of TTA and the so-called solubility parameter of alcohol solvent, and the details of this correlation are discussed.

Regularity on the distribution of scandium chelate in TTA-alcohol system

The distribution of scandium chelate with thenoyltrifluoroacetone (TTA) between 11 alcohols and the aqueous perchlorate solution of ionic strength of 0·1 was studied. After it has been confirmed that the extractable chelate is the same species shown as ScA3 in all alcohol systems, except in 1-butanol and 2-methyl-1-propanol, the distribution coefficient of scandium chelate (PM) and that of TTA (PHA) were compared, and it was found that there is an evident correlation expressed as log PM = n log PHA + const. This correlation is the same with the one obtained in the so-called inert solvent systems.

Liquid-liquid partition constants of tri-n-octyl, tris (2-ethylhexyl) and triphenyl phosphine oxides

Abstract Organic phosphine oxides (S) were determined from γ-counting of 237 U in the 1:1 adduct complex UO 2 (TTA) 2 · S (where TTA is thenoyltrifluoroacetone) extracted by synergic effect. Distribution ratios of S are independent of the aqueous pH (1–3) and the reagent concentrations. Partition constants ( P s ) were obtained between thirteen organic solvents and aqueous solutions, and they decrease in the order, tri- n -octyl > tris (2-ethylhexyl) > triphenyl phosphine oxides. The P s values much depend on the kind of solvent, and their regularity is interpreted in terms of solubility parameters.

Sorption Behavior of Carrier-Free Technetium-95m on Minerals, Rocks and Backfill Materials under both Oxidizing and Reducing Conditions

The sorption behavior of 95mTc on various sorbents, including minerals, rocks and backfill materials was studied in both oxidizing (0.16 M-mol·dm−3-NO− 3), reducing (0.1 M and NaBH4) solutions. Under oxidizing condition, distribution coefficient K d ranged from 0 to 4.5cm3·g−1 for minerals and rocks. Under reducing condition, the values exceeded 140 cm3·g−1 for active carbon, and ranged from 13 to 70 cm3·g−1 for minerals and rocks, and in both cases showing a tendency to decrease with increase of coexisting salt concentration and of sorbent particle size. Similarly under reducing condition, the Freundlich sorption isotherms of Tc on active carbon and on bentonite presented a break in slope when the concentration of unsorbed Tc remaining in solution lowered to a certain level. The slopes before and after the break were more moderate on active carbon and on bentonite than on other minerals and rocks, in which case no break in slope took place on the isotherms within the range covered in the present experiment.

Extraction of uranyl 2-thenoyltrifluoroacetone complexes into alcohol, ketone, ether and ester solvents

Summary The extraction of the 2-thenoyltrifluoroacetone (TTA) complex of uranyl ion into four types of solvents containing donor solvents has been investigated. The species extracted was found to be UO2A2 · S (S=alcohol, ketone, ether and ester). The extraction was much enhanced with donor solvents. The distribution ratios (DM) were estimated by means of the equations, log DM = a log PHA + b, and log DM = log DZn + c (where a, b and c is constant). The estimated values were in good agreement with the observed values in a number of oxygen-containing solvents. The regularities in extraction are discussed in terms of the two main roles of donor solvents, as medium and as coordinating reagent.

Effect of Denitration with Formic Acid on Precipitation and Volatilization of Ruthenium and Technetium

It is necessary to investigate the effect of the denitration with formic acid on the precipitation behaviors of Ru and Tc from a simulated high-level liquid wastes, and the effect of the heat-treatments on the volatility behaviors of them from the sludges. The experiments were carried out using radiotracer techniques. Nitrosylruthenium ion was quantitatively converted into RuNO(OH)3 by the denitration at the initial molar ratio of [HCOOH]/[NO− 3] from 1.2 to 1.3, and the precipitation rate decreased drastically at the molar ratio over 1.5. Ferric ion was reduced to Fe2+ ion by the denitration. Pertechnetate ion was reduced to TcO2 by Fe2+ ion, and the quantitative yield of coprecipitation was achieved at the [HCOOH]/[NO− 3] ratio above 1.8. The volatilities of Ru and Tc from the sludges in- creased with heating times and temperatures, however, decreased with an increase in the [HCOOH]/[NO− 3] ratios. The denitration lowered the volatilization rate of Ru less than 4% at 1,000°C for 3 h in an air flow. The ...

EQUILIBRIA AND KINETICS OF URANIUM EXTRACTION WITH 5,8-DIETHYL-7-HYDROXYDODECAN-6-ONE OXIME IN VARIOUS SOLVENTS

ABSTRACT The extraction of uranium(VI) with 5,8-diethyl-7-hydroxydodecan-6-one oxime (LIX 63; HR) has been studied from the viewpoint of solvent effects. The distribution constant of LIX 63 (KDR) determined between organic solvents and the aqueous phase In creased In the order: n-heptane < n-hexane < kerosene < carbon tetrachloride < chlorobenzene < toluene < chloroform. The extracted species was found to be UO2R2, whose extraction equilibrium constant was evaluated as log Kex= −2.11±0.14 independent of solvent types. This reaction was first-order in metal and second-order in extractant and inverse first-order in hydrogen ion. The apparent rate constant has been found to vary inversely with the square of the KDR value in accordance with the view that the rate-determining step is ascribed to the reaction of UO2R+with the second ligand in the aqueous phase.