Extraction Chromatography of Actinides Using Cyanex‐923 as Stationary Phase

Abstract

Cyanex‐923 has been used as the stationary phase in the extraction chromatographic separation of actinide ions from simulated high‐level waste (SHLW). Chromosorb‐W was used as the solid inert support. The uptake behaviour of U(VI), Pu(IV), and Am(III) was studied by batch studies. Breakthrough capacity of the column for Am(III) in the presence of macro amount of Eu(III) has been determined in three successive cycles of loading and elution. The influence of interfering ions like Fe(III), Cr(VI), Al(III), and Ni(II), etc. has been investigated. Effect of column parameters like diameter and height on Am(III) elution profile has also been studied.     

Third Phase Formation in the Extraction of Inorganic Acids by TBP in n‐Octane

Abstract

The extraction of HNO₃, HClO₄, H₂SO₄ and H₃PO₄ by 20% (v/v) TBP (0.73 M) in n‐octane was measured under identical conditions up to and beyond the critical point of third phase formation (Limiting Organic Concentration, or LOC condition). The data, together with those obtained previously for HCl, allowed us to establish the following lyotropic series of effectiveness with respect to third phase formation in the extraction of acids by TBP: HClO₄>H₂SO₄>HCl>H₃PO₄>HNO₃. This series correlates with the amount of water present into the organic phase at the point of phase splitting. This result reinforces the validity of the reverse micellar model developed previously for the extraction of metal salts by TBP. The measurements of LOC values as a function of temperature revealed major differences among the acid‐TBP systems investigated. For HClO₄, the strong increase of the LOC value with increasing temperatures is accompanied by a large favorable entropy change. The opposite is true for HCl, while H₂SO₄ and H₃PO₄ represent intermediate cases. Measurements of the LOC values for the extraction of HClO₄ by TBP dissolved in a series of diluents confirmed that topological parameters, such as the Connectivity Index, CI, are useful for predicting the critical condition for phase splitting in different diluents. Based on the linear correlation between LOC values for HClO₄ and CI values of diluents, the effective Connectivity Index of the French nuclear reprocessing diluent, HTP, a complex mixture of highly branched alkanes, was determined.     

Parameters Influencing Third‐Phase Formation in the Extraction of Th(NO3)4 by some Trialkyl Phosphates

Third‐phase formation in the extraction of Th(IV) by trialkyl phosphates (TalP) such as tri‐n‐butyl phosphate (TBP), tri‐iso‐butyl phosphate (TiBP), tri‐sec‐butyl phosphate (TsBP), tri‐n‐amyl phosphate (TAP), tri‐2‐methylbutyl phosphate (T2MBP), tri‐iso‐amyl phosphate (TiAP), tri‐sec‐amyl phosphate (TsAP), and tri‐cyclo‐amyl phosphate (TcyAP) has been investigated under various conditions. Formation of a third phase in the extraction of Th(IV) by TBP/n‐dodecane as a function of TBP concentration at 303 K was studied. Measurements were also carried out on the extraction of Th(IV) from its solution with near‐zero free acidity by various phosphate/diluent binary solutions (1.1 M) as a function of temperature. Third‐phase formation in the extraction of Th(IV) by 1.1 M TalP in various diluents from nitric acid media has also been studied as a function of equilibrium aqueous‐phase acidity at 303 K. Empirical equations to predict limiting organic concentration with respect to various parameters for third‐phase formation in the extraction of Th(IV) by TBP and TAP from nitric acid media have been derived. Some of the above phosphates have been investigated for the distribution of Th(NO₃)₄ between the “diluent‐rich phase” (DP) and “third‐phase” (TP) in the extraction of Th(IV) by 1.1 M TalP in various diluents from its saturated solution with near‐zero free acidity at 303 K. Results of the above studies are presented in this paper. Based on these studies, the effects of extractant concentration, the temperature, the nature of the diluent, the equilibrium aqueous‐phase acidity, and the structure of the extractant on third‐phase formation behavior of trialkyl phosphates are described in this paper.     

SANS Study of Third Phase Formation in the Extraction of HCl by TBP Isomers in n‐Octane

Abstract

Third phase formation in the extraction of HCl by triisobutyl phosphate (T‐iso‐BP) and tri‐sec‐butyl phosphate (T‐sec‐BP) has been investigated and compared with the tri‐n‐butyl phosphate (T‐n‐BP) system. The three TBP isomers exhibit comparable affinities for HCl, but the branched isomers extract much more water than the linear one. For T‐sec‐BP, the LOC (limiting HCl organic concentration) is characterized by much lower HCl concentrations both in the organic and aqueous phase than for the other isomers. SANS data for T‐iso‐BP and T‐sec‐BP organic phases loaded with progressive amounts of HCl have been interpreted using the Baxter model for hard spheres with surface adhesion. The critical values of the stickiness parameter, τ^?1, and the interaction potential energy, U(r), are slightly different and characteristic for each of the extractants. Their values are consistent with the expectation derived from the micellar interaction model.     

Interpretation of Third Phase Formation in the Th(IV)–HNO3, TBP–n‐Octane System with Baxter's “Sticky Spheres” Model

Abstract

Small‐angle neutron scattering (SANS) data for the tri‐n‐butylphosphate (TBP)–n‐octane, HNO₃–Th(NO₃)₄ solvent extraction system, obtained under a variety of experimental conditions, have been interpreted using two different models. The particle growth model led to unrealistic results. The Baxter model for hard‐spheres with surface adhesion, on the other hand, was more successful. According to this model, the increase in scattering intensity in the low Q range observed when increasing amounts of Th(NO₃)₄ are extracted into the organic phase, has been interpreted as arising from interactions between small reverse micelles containing three TBP molecules. Upon extraction of Th(NO₃)₄, the micelles interact through attractive forces between their polar cores with a potential energy of up to about 2 k_BT. The intermicellar attraction, under suitable conditions, leads to third phase formation. Upon phase splitting, most of the solutes of the original organic phase separate in a continuous phase containing interspersed layers of n‐octane.     

Salt Effects on the Recovery of Phenol by Liquid‐Liquid Extraction with Cyanex 923

Abstract

In this work, the effect of salt addition on the recovery of phenol from a 46 g/L aqueous solution simulating a phenolic resin plant effluent by liquid‐liquid extraction at 298 K has been studied by using an organic phase containing 0.6 M Cyanex 923 extractant in ShellSol T. Addition of sodium sulfate, potassium nitrate, and sodium chloride to the aqueous phase was tested and sodium chloride was selected. Based on the obtained results, a study of phenol recovery process was undergone by taking advantage of the salting‐out effect. Equilibrium curves are presented for liquid‐liquid extraction with and without salt addition to the aqueous phase. An integrated process involving salting‐out and liquid‐liquid extraction was proposed. The stripping concentrates can be reused for phenolic resin production.     

硝酸体系中Cyanex923萃取La(Ⅲ)性能研究

研究了硝酸体系中中性萃取剂Cyanex923(三烷基氧膦混合物)对轻稀土元素La(Ⅲ)的萃取性能.考察了金属离子、Cyanex923及硝酸根的浓度对La(Ⅲ)萃取的影响,由斜率分析法确定了反应机理,得出萃取平衡方程.探讨了温度对Cyanex923萃取La(Ⅲ)的影响,由Van't Hoff方程计算出温度范围在298～3...     

Reagent Degradation in the Synergistic Solvent Extraction System LIX®63/Versatic™10/Nonyl-4PC

Direct solvent extraction of nickel and cobalt from nitrate-based leach liquors has become of interest due to the successful piloting of nitric acid processes for treating nickel laterite ores. The current study investigated the stability of both hydroxyoxime and nonyl-4PC (nonyl-4-pyridine carboxylate) in LIX 63/Versatic 10/nonyl-4PC under conditions relevant to the recovery of nickel and cobalt from a nitrate-based leach liquor with stripping into sulfuric acid. Nonyl-4PC increased both the rate of hydroxyoxime degradation under the pH 1.5 extract conditions required for a potential nickel–cobalt separation process and the rate of cobalt poisoning of LIX 63. Under strip conditions and the pH 4 extract conditions required for co-extraction of nickel and cobalt, nonyl-4PC did not otherwise affect the rate of hydroxyoxime loss. Additionally, the presence of nitrate anions did not increase the loss of either hydroxyoxime or nonyl-4PC. The combination LIX 63/Versatic 10/nonyl-4PC therefore appears prospective for the co-extraction of nickel and cobalt at pH 4 from nitrate-based leach liquors.     

The Formation of Clusters with Reactive Species Precursors to Aerosol Formation in the Ammonia—Sulfur Dioxide System

Reactions between ammonia and sulfur dioxide are known to form aerosols, but no information on the precursors to particle formation are available in the literature. Herein, the first results on the formation of clusters containing both ammonia and sulfur dioxide are presented. Clusters produced by expansion through a dual nozzle into vacuum have been investigated using a molecular beam mass spectrometer technique. Interestingly, under similar expansion conditions, NH₃ incorporation into SO₂ clusters is more extensive than SO₂ into NH₃ clusters. In contrast to findings from the stoichiometry of the solid precipitate of the aerosol, the cluster distributions fail to reveal clusters of any stoichiometry as particularly abundant or stable, except for NH⁺ ₄·NH₃·SO₂.     

Actinide Third Phase Formation in 1.1 M TBP/Nitric Acid/Alkane Diluent Systems

Abstract

Additional information on the organic phase speciation of Np and Pu was obtained in order to further understand the impact on third phase formation. In the Np(VI) extraction system, indications of the presence of a species associated with the absorbance at 1210 nm appears to be consistent with an increased tendency for third phase formation. Attempts to couple this absorption peak to a higher order nitrate species were inconclusive, and further study is required. For Pu(VI), continued evidence has emerged suggesting a role of higher order nitrate species in third phase formation.     

Interphase Distribution of V(IV) in the Polyethylene Glycol 1500–Sodium Nitrate–Water System

Theoretical Foundations of Chemical Engineering - A study has been made of the interphase distribution of V(IV) ions in a nitrate system with polyethylene glycol 1500. The dependences of the...     

Combined Ion Exchange—Solvent Extraction (CIESE): A Novel Separation Technique for Inorganic Ions

Abstract

In the present paper a novel separation technique for inorganic ions is described. This has been termed combined ion exchange—solvent extraction (CIESE), because it is assumed that both ion exchange and solvent extraction are operative simultaneously to effect the separations. This concept is illustrated with two examples: the separation of iron(III), Co(II), and Ni(II) on the ion-exchange resins Dowex 50 and Dowex 1 using acetone or tetrahydrofuran—hydrochloric acid mixtures, and the separation of uranium from numerous metal ions on Dowex 50, employing as eluent a medium consisting of tetrahydrofuran—nitric acid. Because this separation principle is superior to methods employing the conventional separation techniques of ion exchange in pure aqueous solutions and of common liquid-liquid extraction, it is expected that it will also find application for the solution of other problems encountered in inorganic analytical chemistry.     

Specific Features of the Formation of Crystalline Phases of the W—C—N System in a Cumulative Process

Results of x–ray diffractometric studies of coatings and powders of the W—C, W—N, and W—C—N systems that were obtained under conditions of a shaped–charge explosion are reported. The dependence of the phase composition on the experimental conditions is investigated. Diffusion of nitrogen to the initial polycrystalline tungsten is shown.     

The Formation of γ—AlON Spinel in the Reaction of Al2O3—AlN—MgO System

The stabilization of γ-aluminium oxyni-tride spinel(γ-AlON) has been investigated by addition of MgO,MgAl2O4,etc.,in reaction process.The results indicated that there are wider solid solution areas near ,Al2O3-rich side in AlN-Al2O3-MgO ternary systems,The content of stabilized AlON phase in samples is related to heating temperatures,additives,etc.The lattice parameters of their AlON phases could be well describedby the equation: a0=0.7900 0.0375[MgO] 0.015[AlN](nm)     

Determination of N,N’, N’’-tris(3,7-dimethyloctyl)guanidine (TiDG) in Cesium Extraction Solvent

Several analytical methods were evaluated for determining the concentration of N,N’,N”-tris(3,7-dimethyloctyl)guanidine (TiDG) in a cesium extraction solvent. Of the methods evaluated, non-aqueous titration and ¹H NMR were shown to be successful at quantifying the amount of TiDG present in both a pure solvent extraction system, and a blended system containing an additional base, trioctylamine.