Third Phase Formation in the Extraction of Zirconium(IV) by TRPO in Kerosene

The third phase formation in the extraction of zirconium(IV) from nitric acid media by TRPO(trialkyl phosphine oxide)/kerosene was studied. The limiting organic concentrations (LOC) of Zr(IV) under various experimental conditions were determined. Low temperature and high nitric acid concentrations (> 3 M) were found to facilitate the third phase formation, while increasing the concentration of TRPO or adding phase modifier (TBP) into the organic phase resulted in increased LOC of Zr(IV). When the third phase appeared, the conductivity in the organic phase changed sharply, indicating the change of aggregating behavior in the organic phase. FT-IR spectra were used to illustrate the interaction of TRPO with HNO₃ or Zr(IV), and the composition of the two organic phases indicated by FT-IR spectra was consistent with a diluent-enriched light phase and a zirconium/TRPO-concentrated heavy phase.     

Comprehensive Studies on Third Phase Formation: Application to U(VI)/Th(IV) Mixtures Extracted by TBP in N-dodecane

ABSTRACT

Phase splitting of tributylphosphate (TBP)/n-dodecane organic phases resulting from the extraction of UO₂(NO₃)₂, Th(NO₃)₄ and mixtures of both actinides from aqueous nitrate solutions has been investigated. Limiting organic concentrations (LOC) and metals distribution beyond third phase formation have been determined, with comparison between the cases of single metal-systems and metals mixtures. Simultaneous quantification of TBP and both metals was achieved through X-ray fluorescence (XRF) analyses. LOC studies reveal that thorium (IV) drives the third phase formation as it is the most destabilizing element in the solvent. After organic phase splitting, studies of the distributions of metals between the heavy organic phase (HOP) and the diluted organic phase (DOP) in the case of U^(VI)/Th^(IV) mixtures revealed that they are similar to those observed when both metals are alone in the solvent: Thorium (IV) has a strong affinity for the HOP, whereas uranium (VI) distributes both in HOP and in DOP. A supersaturation coefficient (N_LOC) is proposed as a new tool to account for the data obtained in the present study. Furthermore, the approach was successfully applied to analyse available data in the literature regarding thorium (IV) distribution studies after phase splitting in various TBP-alkane solvents. Such a study beyond third phase formation paves the way for studying the mechanism involved in third phase formation, as the metal is clearly identified as the key parameter.     

Studies on Third Phase Formation in the Extraction of Th(NO3)4 by Tri-iso-amyl Phosphate in n-alkane Diluents

Third phase formation in the extraction of Th(NO₃)₄ from its solution with near-zero free acidity by 1.1 M solutions of tri-iso-amyl phosphate (TiAP) in n-dodecane, n-tetradecane, n-hexadecane, and n-octadecane has been investigated as a function of equilibrium aqueous phase Th(IV) concentration at 303 K. Distribution of Th(NO₃)₄ between organic and aqueous phases as well as the variation of densities of organic phases in biphasic and triphasic regions for its extraction by the above-mentioned solvents have been investigated with respect to equilibrium aqueous phase Th(IV) concentration under the above experimental conditions. Data on the ratio of volume of the diluent-rich phase to that of third phase for various TiAP/n-alkane-Th(NO₃)₄-303 K systems have also been generated in the present study. The results obtained are compared with literature data available for tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) systems which were experimented under identical conditions.     

Solvent Extraction Investigations on Pu(IV) and Th(IV) Complexes with Hydrophilic SO3-Ph-BTP and SO3-Ph-BTBP Ligands

ABSTRACT

Complexation of Pu(IV) and Th(IV) cations by the title ligands – hydrophilic sulfophenyl triazinyl derivatives of bis-triazinyl-pyridine and -bipyridine – was studied in solvent extraction systems containing a TODGA extractant and one of these hydrophilic ligands. Stoichiometries and stability constants of the complexes formed in an acidic (HNO₃) aqueous phase have been determined. The Pu(IV) complexes are significantly stronger than their Th(IV) analogues. Only two complexes of each metal with SO₃-Ph-BTP (1:1 and 1:2) have been detected, and only one (1:1) with SO₃-Ph-BTBP; both numbers being less than expected based on the coordination numbers of the metal ions and on the denticities of the ligands. Possible reasons of this discrepancy are discussed.     

EXTRACTION OF U(VI), Pu(IV) AND Th(IV) BY SOME TRIALKYL PHOSPHATES

ABSTRACT

This paper reports the data on the extraction of U(VI), Pu(IV) and Th(IV) from nitric acid by tri-isobutyl phosphate, tri-n-amyl phosphate, tri-isoamyl phosphate and tri-n-hexyl phosphate and provides a comparison of their extract ion behaviour with that of tri-n-butyl phosphate. Data on the third phase formation in the system Th(NO₃) ₄ ^?HNO₃ ^?1.1 M trialkyl phosphate/n-dodecane are also presented.     

Extraction of Uranium(VI) and Plutonium(IV) with Tetra-Alkylcarbamides

ABSTRACT

The use of tetra-alkylcarbamides as novel extractants for the separation of uranium(VI) and plutonium(IV) by solvent extraction from spent nuclear fuels is investigated in this study. Batch extraction experiments show that tetra-alkylcarbamides strongly extract U(VI) with high distribution ratios. Plutonium(IV) can be co-extracted with U(VI) at high nitric acid concentration, while high U(VI)/Pu(IV) selectivities can be reached at lower acidity. Loading capacity experiments with high uranium concentrations show that alkyl chains longer than butyl are necessary to avoid third phase formation. Nevertheless, the viscosity of uranium-loaded solvents gets too high with alkyl chains longer than pentyl. Overall, this study shows that with TPU extractant (with four pentyl chains), an efficient co-extraction of uranium and plutonium can be reached (D_U,Pu > 1) for a concentration of nitric acid higher than 4 mol?L^?1, while the partition between uranium(VI) and plutonium(IV) could be operated even at 2 mol?L^?1 nitric acid without redox chemistry.     

腐植酸对高岭土吸附四价铀的影响

在土壤中,对放射性废物处理的安全性评估,要求评价放射性核素的迁移.PH值从4到8,腐植酸浓度从15 mg/kg到200 mg/kg条件下,腐植酸对高岭土吸附四价铀的影响试验表明,没有腐植酸的情况下,20%～40%的四价铀存在于溶液中,pH值越高,吸附作用越强.在腐植酸的存在下,随着腐植酸浓度和PH值的升高,四价铀的溶解...     

硝酸-硝酸铜电解精炼高杂阳极铜的生产实践

从铅锑复合矿中综合回收产出的粗铜阳极含铜低,含铅银锑铋等杂质很高,无法采用常规电解方法电解。采用硝酸-硝酸铜体系电解这类高杂粗铜,可以有效实现银铜的分离,并提高铜的纯度。但也存在槽压高、电流效率低等问题。     

Ion Exchange of Th(IV), U(VI), and Pu(IV) on Macroreticular Resins in TBP-Shell Sol-T Solutions

Abstract

Absorption of thorium, uranium, and plutonium by macroreticular cation and anion exchange resins from solutions of TBP in Shell Sol-T as a function of TBP and HNO₃ concentrations in the organic phase has been investigated. The absoiption behavior is compared with that on conventional gel-type resins from TBP medium on the one hand and on macroreticular resins from aqueous nitric acid on the other.     

Adsorption of Uranium(VI) and Zirconium(IV) from Acid Solutions on Silica Gel

Abstract

Adsorption of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel was investigated by the batch equilibration method. The influence of shaking time and concentrations of nitric acid (i.e., pH of solution) and metal ions in solution were studied. Adsorption of uranium(VI) and zirconium(IV) increases with an increase of pH (decrease of nitric acid concentration) and ion concentrations. The adsorption mechanism of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel is proposed. It is shown that zirconium(IV) and uranium(VI) can be separated if the concentration of nitric acid in solution is higher than 0.01 mol/dm³.     

Plutonium Third Phase Formation in the 30% TBP/Nitric Acid/Hydrogenated Polypropylene Tetramer System

Abstract

A study on plutonium third phase formation in 30% TBP/nitric acid/hydrogenated polypropylene tetramer (HPT) was performed. Characterization studies of HPT indicate its composition to be a mixture of many highly branched alkanes with a volatility close to n‐undecane. This composition results in about a factor of two better resistance to Pu(IV) third phase formation than dodecane. At 7 M nitric acid in the aqueous phase, the presence of Pu(VI) was observed to substantially reduce the organic phase metal concentration necessary to induce phase splitting in both diluents. Spectroscopic investigation of mixed valence systems also suggest a prominent role for Pu(VI) in the formation of the dense organic phase. Accumulation of Pu(VI) in the heavy phase, as well as certain spectral features, suggest that Pu(VI) is forming a different species, possibly a plutonyl trinitrato, with a strong tendency to form third phase.     

Third Phase Formation in the Extraction of Th(NO3)4 by Tri-n-Butyl Phosphate and Tri-iso-Amyl Phosphate in n-Dodecane and n-Tetradecane from Nitric Acid Media

Binary solutions of tri-n-butyl phosphate (TBP) or tri-iso-amyl phosphate (TiAP) in n-dodecane or n-tetradecane (1.1 M) as diluents have been investigated for third phase formation in the extraction of Th(NO₃)₄ from its solutions with 1 M or 5 M HNO₃ as a function of equilibrium aqueous phase Th(IV) concentration ([Th(IV)]_aq,eq) at 303 K. Extraction isotherms for the extraction of Th(IV) and HNO₃ have been generated with respect to [Th(IV)]_aq,eq. The difference in density between the third phase and the diluent-rich phase as well as the diluent-rich phase and the pure diluent, ratio of volume of the diluent-rich phase to that of the third phase have also been determined over a wide range of [Th(IV)]_aq,eq in the triphasic region. An attempt has also been made to determine the extractant concentrations in the third phase and the diluent-rich phase in the extraction of Th(NO₃)₄ by the above solvents from its saturated solutions with 1 M and 5 M HNO₃.     

第三相的加入对气液传质过程的影响

系统地介绍了气液传质过程中,固体小颗粒或第二分散液相(有机相)所形成的第三相的加入对传质过程的影响.分别论述了在不同的气-液接触器(搅拌釜、鼓泡塔)中,固体小颗粒和第二分散液相的加入对体系的传质系数、传质速率及界面面积等的影响,叙述并讨论了传质机理及模型的最新进展.     

Formation of a Third Liquid Phase and Its Reuse for Dibenzyl Ether Synthesis in a Tetraalkylammonium Salt Phase Transfer Catalytic System

This paper describes the formation of a third liquid phase in a phase transfer catalytic system in the presence of benzyl alcohol and potassium hydroxide, where dodecane and tetraalkylammonium bromide serve as organic solvent and catalyst, respectively. In this kind of system, a symmetrical ether (dibenzyl ether) was synthesized from benzyl chloride and benzyl alcohol at 323 K. In particular, the investigation demonstrates that the observed reaction rate constant depends on the length of the alkyl group of the catalyst. Tetrabutylammonium bromide exhibits the highest catalytic activity among the catalysts explored. With respect to the reuse of the third liquid phase, the results confirm that there is no decrease in phase transfer catalytic activity in three consecutive runs.     

Investigation of the Phase Formation in the Na3NbO4–La3NbO7 System

The optimum conditions for synthesis of samples in the Na₃NbO₄–La₃NbO₇ system are determined with due regard for the volatility of Na₂O at high temperatures. The phase diagram of the system in the temperature range from 600°C to the liquidus point is constructed. It is shown that a phase of variable composition is formed in this system in the concentration range 13–60 mol % Na₃NbO₄ (at 1000°C).     

Formation of the Liquid Phase in the System Bi-Pb-Sr-Ca-Cu-O

Differential thermal analysis (DTA), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) were carried out to investigate the origin of the partial melting which is closely related to the formation of the 110 K superconducting phase in the Bi-Pb-Sr-Ca-Cu-O system. The occurrence of a liquid phase in the presence of the Bi₂Sr₂Ca-Cu₂O _y , Ca₂PbO₄, and CuO phases was demonstrated. Large grain growth and promotion of the 223 phase formation resulting from the reactive liquid-phase-aided sintering were also observed.     

Effect of Cobalt(II) Oxide and Manganese(IV) Oxide on Sintering of Tin(IV) Oxide

Additions of 0. 5 to 2. 0 mol% of CoO or MnO₂ onto SnO₂ promote densification of this oxide up to 99% of theoretical density. The temperature of the maximum shrinkage rate ( T_M ) and the relative density in the maximum densification rate (p*) during constant sintering heating rate depend on the dopant concentration. Thus, dopant concentration controls the densifying and nondensifying mechanisms during sintering. The densification of SnO₂ witih addition of CoO or MnO₂ is explained in terms of the creation of oxygen vacancies.