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.     

Separation of U(VI) and Th(IV) from Nd(III) by Cross-Current Solvent Extraction Mode Using Tri-iso-amyl Phosphate as the Extractant

Separation of U(VI) and Th(IV) from Nd(III) in nitric acid media with solutions of tri-iso-amyl phosphate (TiAP) in n-dodecane has been studied by batch extraction in cross-current mode to evaluate the feasibility of employing TiAP as an alternate extractant to tri-n-butyl phosphate (TBP) for monazite ore processing. The interference of U(VI), Th(IV), and Nd(III) in the presence of each other during their analyses by titrations has also been validated in the present study. The extraction studies substantiate that the high solvent loading conditions can be achieved without organic phase splitting in the extraction from concentrated feed solutions with TiAP based solvents, whereas TBP forms third phase under such conditions. The separation factor for Th(IV) with respect to Nd(III) can be improved with TiAP as the extractant and by carrying out the extraction with feed solution in 8 M HNO₃. Solvent extraction studies conducted with solutions of U(VI), Th(IV), and Nd(III) in nitric acid media by TBP and TiAP revealed the identical extraction, scrubbing, and stripping behavior of both the extractants with respect to U(VI), Th(IV), and Nd(III). The results insinuate that TiAP can be used as an alternate extractant to TBP for the separation of U(VI) and Th(IV) from monazite ores. The data generated in the present study can be exploited for the development of flow sheets using TiAP based solvents to separate U(VI) and Th(IV) from rare earths for the processing of monazite leach solutions.     

磷酸三丁酯－煤油从浓酸溶液中萃取Zr的第三相行为

本文研究了磷酸三丁酯（ＴＢＰ）在煤油中从浓硝酸和盐酸溶液中对Ｚｒ（Ⅳ）的萃取，考察了室温了初始Ｚｒ浓度、ＴＢＰ浓度以及水相酸度对萃取的影响，同时确定了体系第二相的形成条件．发现酸同Ｚｒ被—同萃取，酸度越高则萃取率越大，较高的酸度和Ｚｒ（Ⅳ）浓度易使萃取有机相分相．用红外光谱研究了第三相的组成，用Ｋａｒｌ－Ｆｉｓｃｈｅｒ滴定法和电导率仪分别测定了第三相的水含量和比电导，对可能的萃合物结构进行了推测，认为从胶体化学看第三相可能是一种具有双连续相结构的微乳液．     

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.     

Compositional Characterization of Organic Phases after the Phase Splitting in the Extraction of Th(NO3)4 by 1.1 M Tri-n-butyl phosphate/n-Alkane

Third phase formation in the extraction of Th(IV) by 1.1 M solutions of tri-n-butyl phosphate (TBP) in n-decane and n-hexadecane from Th(NO₃)₄ solution in 1 M HNO₃ has been investigated as a function of equilibrium aqueous phase Th(IV) concentration ([Th(IV)]_aq,eq) to estimate the concentrations of Th(NO₃)₄, HNO₃, and TBP in the third phase (TP) and the diluent-rich phase (DP). In this connection, new methods for the estimation of TBP in the organic phases after the phase splitting have been developed by exploiting the linear relationships of the density and refractive index of the solvent, the limiting organic concentration (LOC) for the third phase formation in the extraction of Th(IV) from solution with near-zero free acidity with TBP concentration in the solvent. TBP concentrations estimated by the above-mentioned methods have been validated by nitric acid (8 M) equilibration method. Experimental values for the concentration of TBP in the TP and DP for 1.1 M TBP/n-alkane–Th(NO₃)₄/1 M HNO₃ systems have been compared with the values computed based on a model proposed earlier. In addition, the density of organic phases and the ratio of the volume of the DP to that of the TP have been measured for the above-mentioned systems as a function of [Th(IV)]_aq,eq at 303 K.     

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.     

Palladium Extraction by a Malonamide Derivative (DMDOHEMA) from Nitrate Media: Extraction Behavior and Third Phase Characterization

Liquid-liquid extraction of palladium(II) from nitric media was carried out using, N,N’–dimethyl,N,N’-dioctylhexylethoxymalonamide (DMDOHEMA) in n-heptane. To this purpose, various experimental parameters such as reaction time, extractant concentration, pH, and nitrate concentration were investigated in detail. Efficient extraction of palladium can then be achieved, with good distribution coefficients (D up to 10) and performing kinetics (equilibration time ca. 30 min). In some cases, a solid phase appears at the interface between aqueous and organic layers. It was characterized as a palladium(II) complex with DMDOHEMA with appropriate techniques, and the conditions of its formation are discussed.     

磷酸三丁酯和二异丙醚溶剂萃取体系脱除湿法磷酸中氟的研究

以磷酸三丁酯与二异丙醚为溶剂,采用溶剂萃取法脱除湿法磷酸中的氟。研究了萃取剂中TBP的体积分率、相比、萃取时间、搅拌转速、反萃剂加入量对氟的净化效果的影响,确定了磷酸三丁酯与二异丙醚混合溶剂体系脱氟的工艺条件。结果表明:萃取剂组成为TBP与二异丙醚体积比为1∶1;相比4∶1、萃取时间为5min、搅拌转速为300r/min、反萃剂加入量为萃取相体积的10%,在此条件下,磷酸三丁酯与二异丙醚萃取体系对氟离子有较好的分离能力。     

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.     

Chemistry of the Extraction of La(NO3)3 and Ce(NO3)3 from Nitrate Solutions with Mixtures of Tri-n-Octylmethylammonium Nitrate and Tri-n-Butyl Phosphate in Toluene

Theoretical Foundations of Chemical Engineering - The boundaries of the regions of the synergistic extraction of lanthanum nitrate and cerium(III) nitrate from low-acid nitrate solutions containing...     

Solubility in system CO(NH2)2-NH4NO3-H3PO4-H2O

Solubility data were obtained in the system CO(NH₂)₂-NH₄NO₃-H₃PO₄-H₂O at 0° and 15°C. The results show that high-analysis solution fertilizers can be produced from standard urea-ammonium nitrate (UAN) and phosphoric acid materials. These acidic solution fertilizers contain up to 35% total plant nutrient (TPN = N + P₂O₅ + K₂O), with N:P₂O₅ ratios varying from 20:1 to 1.5:1. Potential liquid products having fertilizer grades of 23-12-0, 26-9-0, 28-6-0, and 31-3-0 are feasible.     

Separation of U(VI) and Pu(IV) from Am(III) and Trivalent Lanthanides with Tri-iso-amyl Phosphate (TiAP) as the Extractant by Using an Ejector Mixer-Settler

Counter-current solvent extraction runs have been carried out to develop a suitable flow sheet for fast reactor fuel reprocessing with 1.1M Tri-iso-amyl Phosphate (TiAP)/Heavy Normal Paraffin (HNP) as the solvent by using an ejector mixer-settler facility. A spent solvent of 1.1M TiAP/HNP used for earlier runs has been employed in the present study after the regeneration. Separation of U(VI) and Pu(IV) from Am(III) and lanthanides such as La(III), Pr(III), Nd(III), Sm(III), and Eu(III) as fission product representatives with the above solvent has been investigated with an optimized flow sheet. Stage profile data generated for the extraction and strip runs for the above separation have been reported. Overall and stage-wise mass balance data for the above runs are also discussed.     

An insight into third-phase formation in the extraction of thorium nitrate by tris(2-methylbutyl) phosphate and tri-n-alkyl phosphates

Third phase (TP) formation in the extraction of Th(IV) by tris(2-methylbutyl) phosphate (T2MBP) from HNO₃ media was studied and compared with tri-n-butyl phosphate (TBP) systems. Concentrations of Th(IV) and HNO₃ and densities of organic phases were determined as a function of Th(NO₃)₄ concentration. Extractant concentrations and volume ratios in the triphasic regions were also measured. The extraction experiments show lower TP formation tendency of T2MBP. The aggregation behaviour of Th(IV) loaded solutions of tri-n-amyl phosphate (TAP), T2MBP and TBP in n-C₈D₁₈ and n-C₁₂D₂₆ were investigated using small angle neutron scattering technique and found to be in correlation with TP formation trends.     

Water Content of Organic Solvents and their Relationship to Extraction of Nitric and Acetic Acid from UREX+ Streams

This study investigates the equilibrium absorption of water in various solvents and solvent-mixtures being considered for the counter-current solvent extraction of acetic acid from improved Uranium Extraction (UREX+) process solutions. It then seeks to determine if there is any correlation between the equilibrium water content of these solvents and their equilibrium extraction of 0.25 M nitric and 0.025 M acetic acid. The UREX+ process is a proliferation resistant version of the Plutonium Uranium Extraction (PUREX) process. The solvents studied were n-Dodecane (nDD), 1,2 Dichloroethane (DCE), and Phenyltrifluoromethyl Sulfone (FS-13), and mixtures of these solvents with Tributyl Phosphate (TBP). After studying both pure water and acidified aqueous systems, it seems the water absorption mechanism is independent of the diluent used and remains constant with the addition of the 0.25 M nitric and 0.025 M acetic acid.     

Extraction Behavior of Ln(III) Ions by T2EHDGA/n-Dodecane from Nitric Acid and Sodium Nitrate Solutions

The diglycolamide extractant T2EHDGA has proven to be promising for the separation of lanthanides and minor actinides in high-level nuclear waste reprocessing. This neutral extractant has shown significant extraction capacity for HNO₃ into the nonpolar organic phase, along with hyper-stoichiometric nitrate dependence on extraction of trivalent f-elements. The transport behavior of T2EHDGA/n-dodecane toward trivalent lanthanides is not well understood. This work found a significant increase in distribution ratios for Eu(III) extracted from aqueous HNO₃ media compared with that from NaNO₃. The extraction of Eu(III) from HNO₃ results in a different thermodynamic product than predicted by classic solvent extraction of 3:1 ligand–metal complex as observed with NaNO₃ in FTIR and UV-vis spectroscopy. Experimental distribution measurements in conjunction with mass-action modeling using the solvent extraction modeling program SXLSQI suggest participation of 1 to 2 HNO₃ molecules in the Eu(III)/T2EHDGA complex upon extraction from HNO₃ media, indicative of a mechanism change responsible for the enhanced extraction behavior toward lanthanides in the presence of HNO₃.     

超声辅助提取-固相萃取净化-高效液相色谱法测定沉积物中的2甲4氯残留

[目的]2甲4氯(MCPA)是农业生产和市政管理中一种广泛使用的除草剂,具有使用量大、生物毒性强、易迁移累积于水体沉积物等特点。针对其在沉积物中潜在环境风险大的现状,一种简单、有效的残留测定方法迫切需要建立。[方法]建立了一种C18为分离色谱柱,甲醇-水(体积比80:20)为流动相,PDA为检测器,检测波长为280 nm的MCPA高效液相检测法,并比较了不同提取方法和净化方法对检测的影响。[结果]对于提取方法,回收率:超声萃取2次>超声萃取1次>涡旋振荡萃取;对于净化方法,回收率:固相萃取净化法>QuEChERS法>未净化法。因此,应采用2次超声辅助提取-固相萃取净化作为前处理方法。所建立的方法在0.5~40 mg/L范围内线性良好,检出限为0.02 mg/kg,定量限为0.06 mg/kg;在0.08~0.8 mg/kg的添加水平范围内,回收率为85.12%~98.66%,相对标准偏差为2.86%~4.24%。[结论]该方法准确性高、稳定性好,适用于沉积物中MCPA的测定。     

Role of Phase Modifiers in Controlling the Third-phase Formation During the Solvent Extraction of Trivalent Actinides

ABSTRACT

Diglycolamides have been proposed for partitioning of trivalent actinides from high-level liquid waste (HLLW). Third-phase formation is an undesirable event during the course of solvent extraction of trivalent actinides from HLLW into the solution of N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in n-dodecane (n-DD). Polar reagents such as tri-n-butyl phosphate (TBP), and N,N-dihexyloctanamide (DHOA) have been added to the TEHDGA phase, as phase modifiers in significant concentration, to overcome the third-phase formation. To understand the role of these phase modifiers in controlling the third-phase formation, the extraction behaviour of nitric acid and the trivalent representative metal ion Nd(III) was studied in a binary solution containing TEHDGA and phase modifier in n-dodecane. The organic phase obtained after extraction was subjected to dynamic light-scattering studies to examine the aggregation behaviour of the reverse micelles formed upon extraction and to unravel the unique role of TBP and DHOA in controlling the third-phase formation. The study revealed that the addition of these modifiers brought down the average size of aggregates and their distribution in organic phase below the limiting aggregate size for third-phase formation and increased the dispersion of aggregates in the n-dodecane phase. Among the two phase modifiers proposed for trivalent actinide separation from HLLW, TBP has been identified as a promising reagent for minimizing the third-phase formation.     

吡啶从硝酸介质中萃取铀(VI)的研究

研究了新萃取剂吡啶从硝酸介质中萃取铀的机理。考察水相硝酸浓度、萃取剂浓度、盐析剂硝酸钠以及振荡时间和温度对萃取分配比的影响 ,确定了萃合物的组成。求得萃取硝酸铀酰过程的平衡常数及反应的热力学函数。同时研究了相比的影响 ,以及稀释剂的影响。发现吡啶萃取能力在不同稀释剂中由弱到强的顺序为 :四氯化碳、氯仿、苯、甲苯、环己烷、煤油。