Tri-n-amyl Phosphate Research Articles

A comparison of the extraction behaviour of tris(2-methylbutyl) phosphate and tri-n-alkyl phosphates for the separation of metal ions for U–Zr and U–Pu–Zr systems by cross-current mode

Abstract Even though, pyroprocessing is considered as a suitable technique for metal fuel processing, attempts are being made in our laboratory to develop a solvent extraction based process as an interim method. Since, the metallic fuels contain considerable amount of Pu(IV) and Zr(IV), the use of conventional extractant tri-n-butyl phosphate (TBP) for reprocessing may pose problems due to third phase formation. In the exploration for the identification of an alternate extractant in the organophosphate family, tris(2-methylbutyl) phosphate (T2MBP), a branched isomer of tri-n-amyl phosphate (TAP) was found to be a potential extractant for nuclear fuel reprocessing. In this context, batch wise extraction and stripping studies with a feed solution containing U(VI) and 6 wt% Zr(IV) were carried out with unirradiated and irradiated 1.1 M solution of T2MBP in n-dodecane (n-DD) and the results were compared with corresponding solutions of TBP and TAP in n-DD. Among all these systems under identical conditions, third phase formation was observed only in the case of irradiated TBP system which makes U–Zr fuel reprocessing difficult using TBP as the extractant. Furthermore, studies have also been carried out with U–Pu–Zr feed solution to understand the extraction and stripping behaviour of these extractants. The stage wise and cumulative percentage of extraction and stripping for each metal ion of these systems were evaluated. Overall, these batch studies indicated that, T2MBP system has comparable extraction and stripping behaviour with U–Zr and U–Pu–Zr feed solutions and T2MBP exhibits better separation factor than TBP.

Hydrodynamic Properties of Tris(2-methylbutyl) Phosphate and Tri-n-alkyl Phosphates in n-Dodecane – A Comparative Investigation between Unirradiated and Gamma Irradiated Solvent Systems

ABSTRACT The physicochemical parameters of tris(2-methylbutyl) phosphate (T2MBP), a molecule possessing the essential characteristics required to be considered as a promising extractant in the solvent extraction stage of fast reactor fuel reprocessing, have been evaluated in the present study. In this context, the density, viscosity and interfacial tension (IFT), which are considered to be few among the important solvent selection criteria prior to its deployment in the plant scale have been measured for T2MBP in n-dodecane (n-DD) based systems. Similar studies have been performed with its straight chain isomer, tri-n-amyl phosphate (TAP) as well as the widely utilized commercial extractant, tri-n-butyl phosphate (TBP) so as to emphasize on the structural effects. Though the trends on the physicochemical behaviour of TBP based systems (temperature and ligand concentration effects) are well known in the literature, the data on TBP have been generated in the present work for comparison with the T2MBP results under similar experimental conditions. Solutions of trialkyl phosphates (TalP) in n-DD of different concentrations have been used to generate the data on the variation of density, IFT and viscosity with the change in the ligand concentration. In addition, the transformation in their properties has been assessed after subjecting the solvents to various levels of gamma absorbed doses. Overall, it has been observed that there was no significant variation in the density of the irradiated TalPs; however, there was a significant rise in the viscosity and reduction in the IFT of the TalP samples upon irradiation. The data on the Gibbs energy change of activation of various 1.1 M TalP/n-DD solutions have been generated by fitting their respective dynamic viscosity value as a function of temperature using Andrade’s equation. Moreover, from the IFT value, the parameters relating to the interfacial activity of TalP/n-DD solutions have been determined using the Szyszkowski adsorption isotherm.

Studies on the aggregation behavior of mineral acid and Zr(IV) loaded Tris(2-methylbutyl) phosphate and tri-n-alkyl phosphate systems using small angle neutron scattering

ABSTRACT The third-phase phenomenon has been observed during the extraction of certain metal ions and mineral acids by 30% (v/v) tri-n-butyl phosphate (TBP) in n-dodecane in the solvent extraction stage of spent nuclear fuel reprocessing. At molecular scale, it has been predicted that the self-organization of the extracted polar species to form reverse micelle-like structure is primarily responsible for third-phase formation. In this regard, the aggregation behavior of solutions of three different trialkyl phosphates in n-alkanes loaded with monoprotic mineral acids (HClO4, HCl and HNO3) as well as tetravalent Th and Zr has been evaluated using Small Angle Neutron Scattering (SANS). The aggregation of TBP has been compared with two of its five carbon analogues i.e. tri-n-amyl phosphate (TAP) and tris(2-methylbutyl) phosphate (T2MBP), which have gained its attention in the course of development of an alternate extractant for the reprocessing process. The effects of trialkyl phosphate structure, diluent chain length and extractant concentration on the aggregation have been emphasized. The contribution of the polar (anionic and cationic component) as well as the apolar part of the reverse micelle toward the phase splitting behavior has been analyzed. The SANS results are in agreement with the earlier reported solvent extraction data.

Elucidating the extraction behaviour of tri-n-alkyl phosphates and tris(2-methylbutyl) phosphate with nitrates of uranyl and tetravalent metal ions from infrared spectroscopy and dynamic light scattering studies: A distinct correlation from conformational changes and variation in size of aggregates

Extraction of tetravalent Zr(IV), Ce(IV), Th(IV) and Pu(IV) and hexavalent U(VI) nitrates, from their aqueous solutions by tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP) and tris-2-methyl-butyl phosphate (T2MBP) diluted to 30% with n-dodecane has been studied using infrared (IR) spectroscopy and dynamic light scattering (DLS) measurements. A comprehensive interpretation of observations, from the molecular perspectives offered by IR spectroscopy and DLS techniques, allows understanding the behaviour exhibited by different extractant-metal nitrate systems. Formation of metal nitrate-ligand complex involving phosphoryl oxygen as a neutral electron donor stands affirmed by the significant red-shifting of vibrational wavenumber associated with the characteristic P=O stretching mode. Conformational interconversion (repopulation) with the enrichment of ‘trans’ cluster of conformations within the organic phase as a consequence of loading of metal nitrates has been proposed as a probable cause for, the counter-intuitive, blue-shifting of the vibrational wavenumber associated with phosphoryl stretching. This conformational interconversion could be instrumental in the onset of formation of a third phase. Conclusive evidence, for preferential stabilization of ‘trans’ cluster of conformations in a polar environment, has been obtained from the combined use of Density Functional Theory (DFT) and IR spectroscopy. Coupling the scatter profile of aggregates with the molecular information reveals, a compromise of the polar volume of an aggregate and its non-polar surface area, which in turn determine the sizes to which aggregates could grow for a given extractant-metal nitrate system.

Alpha and gamma degradation behavior of tri-n-alkyl phosphates and tris(2-methylbutyl) phosphate: A comparative study

Extensive study on a variety of symmetric trialkyl phosphates (TalP) has revealed that tris(2-methylbutyl) phosphate (T2MBP) could be considered as a promising alternate extractant to tri-n-butyl phosphate (TBP) for various solvent extraction procedures, especially in the case of fast reactor fuel reprocessing. However, the highly radioactive nature of the dissolver solution generated from spent fuel urges for understanding the radiolytic stability of T2MBP. In this context, a comparative analysis on the alpha and gamma radiation stability of TBP and T2MBP in n-dodecane (n-DD) has been determined by exposing the solvent to different levels of absorbed dose using 239Pu and 60Co sources, respectively. Similar experiments were performed with tri-n-amyl phosphate (TAP) to highlight on the effects of structure of TalP on the extent of radiation induced damage. The effects of the absorbed dose and the concentration of TalP on degree of degradation were investigated by evaluating the deviation in the extraction ability of Zr(IV) and Pu(IV) with various gamma irradiated solvent systems. In addition, the stripping studies were performed for Zr(IV) and Pu(IV) loaded organic phase (1.1 M TalP/n-DD) before and after gamma irradiation. The results have indicated that there is an increase in the metal extraction and decrease in the metal ion stripping tendency with the increment in the absorbed gamma dose. The impact of α-degradation for 1.1 M TalP/n-DD was studied by analyzing their plutonium retention behaviour as a function of time. Overall it has been observed that the stripping behaviour of alpha and gamma irradiated TBP and T2MBP solutions are better compared to TAP system. An attempt has also been made to identify the degradation products upon irradiation for TAP and T2MBP based systems using IR and GC-MS spectroscopic techniques.

Synthesis, characterization and evaluation of phosphoramides for actinide extraction

A new class of extractants called hexaalkylphosphoramides has been chosen for actinide separation applications in the present study. Hexaalkylphosphoramides [(NR2)3PO] are compounds which possess three nitrogen sub-units along with a strong donor oxygen atom. The studies on them provide an opportunity to synthesize a large variety of structurally diverse analogs. Thus, the desired properties of the extractant can be tuned for a specific application. We discuss the synthesis, purification, and characterization of two such hexaalkylphosphoramides (Propyl and Butyl) in this paper. Their physico-chemical properties were measured and the extraction behavior was evaluated with U(VI), Th(IV) and Pu(IV). The results were compared with trialkyl phosphates such as tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP). The results revealed that the extraction behaviors of phosphoramides are comparable to trialkyl phosphates.

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

ABSTRACTThird 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.

Thermal hazard assessment of tris(2-methyl butyl) phosphate: A comparison with tri-n-butyl phosphate and tri-n-amyl phosphate

The thermal decomposition behaviour of tris(2-methyl butyl) phosphate (T2MBP), a higher branched homologue of tri-n-butyl phosphate (TBP), which possesses the vital characteristics of a potential extractant for the processing of nuclear materials is the subject of the present work. The thermal stability of neat T2MBP and 1.1 M T2MBP/n-dodecane (in the presence and absence of HNO3) has been determined using adiabatic calorimeter. The results have been compared with the corresponding tri-n-amyl phosphate (TAP) and TBP based systems. From the calorimetric experiments, the thermo-kinetic parameters have been deduced and the resulting end products have been analysed. The data show lower magnitude of exothermicity for T2MBP compared to TAP based systems. The present work thereby highlights the influence of alkyl group chain length and branching on the thermal decomposition behaviour of trialkyl phophates, which in turn will help to identify an alternate to TBP to avoid the potential runaway explosion hazards.

Strategy for extractant residual reduction: Experimental and computational investigation of fluorinated phosphate

Extractant residual in water phase is a destined and disgusted consequence after solvent extraction operation. In order to reduce extractant residual in aqueous phase, extractants modified by fluorination were probed. In this paper, tri-n-amylphosphate (TAP) was selected as model extractant along with its fluorinated analogue, tris (2,2,3,3,4,4,5,5-octafluoropentyl) phosphate (FTAP), to extract the salicylic acid from its aqueous solution to investigate residual and extraction behaviors by both experimental and computational methods. The experimental results obtained from multiple light scattering revealed that FTAP barely interacted with water and possessed high hydrophobicity. The solubility of FTAP in aqueous phase was less than 6.0×10−5 (w/w), and declined with increase of temperature, which was similar to the nature of nonionic surfactant. In acid solution with high concentration, the solubility of FTAP remained quite low. The one-step extraction efficiency of FTAP on salicylic acid was approximately 85%. The cycling experimental results showed that the durability of FTAP was overwhelmingly excellent compared with that of TAP, especially after the cycles more than 10 times. DFT calculation demonstrated the hydrophobicity and extraction behavior at molecular level. All results implied that fluorinated modification of extractant was a possible way to reduce its loss in aqueous phase.

Comparision in the solvent extraction behavior of uranium (VI) in some trialkyl phosphates in ionic liquid

Abstract Higher homologs of trialkyl phosphates (TAlP) are proposed for reprocessing of fast reactor fuels. Solvent extraction behavior of U(VI) from nitric acid medium was studied in some TAlP present in 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C8mim][NTf2]) ionic liquid. The extractants investigated were tri-n-propylphosphate (TPP), tri-n-butylphosphate (TBP), tri-n-amylphosphate (TAP), tri-n-octylphosphate (TOP), tri-iso-amylphosphate (TIAP) and tri-iso-butylphosphate (TIBP). The extraction of uranium (VI) was investigated as a function of various parameters, such as the equilibration time, [HNO3], [TAlP], temperature and nature of ionic liquid cation. The distribution ratios of U(VI) increased with an increase in the concentration of nitric acid and decreases in the order TOP>TAP~ TIAP>TBP~TIBP>TPP. The stoichiometry of the extraction was determined by slope analysis of the extraction data. Distribution ratios of U (VI) were determined at various temperatures and the thermodynamic parameters were derived. Quantitative stripping of uranium from the loaded ionic liquid phase was achieved using dilute nitric acid.

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.

Note: Effect of Temperature in the Extraction of Uranium and Plutonium by Triisoamyl Phosphate

The extraction of uranium(VI) by triisoamyl phosphate (TiAP) has been studied to derive the thermodynamic parameters such as entropy change and the free-energy change. The extraction of U(VI) and Pu(IV) has also been studied with 1.1 M solutions of tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP), and TiAP as a function of temperature. While the enthalpy of U(VI) extraction was found to be exothermic, the enthalpy for the extraction of Pu(IV) was always found to be endothermic. The temperature at which the distribution ratios of U(VI) and Pu(IV) cross each other (the temperature of inversion) has been derived for TBP, TAP, and TiAP, and the results reveal the lowest temperature of inversion occurs for TiAP. The results indicate the advantage of TiAP as an extractant in avoiding plutonium reflux during the PUREX process involving high plutonium feed solutions, in addition to lower aqueous solubility, freedom from the third-phase formation problem, lower degradation, and better economics.

Comparative Studies on Third-Phase Formation in the Extraction of Thorium Nitrate by Tri-n-Butyl Phosphate and Tri-n-Amyl Phosphate in Straight Chain Alkane Diluents

This paper reports the results of the studies on third-phase formation during the extraction of thorium nitrate from solutions with near-zero free acidity by 1.1 M solutions of tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) in n-octane, n-decane, n-dodecane, n-tetradecane, and n-hexadecane. The concentration of Th(NO3)4 in the organic phase in biphasic regions and the distribution of Th(NO3)4 between the diluent-rich phase (DP) and the third phase (TP) in triphasic regions for the extraction from its solution with near-zero free acidity by the aforesaid solvents has been investigated as a function of equilibrium aqueous-phase thorium nitrate concentration at 303 K. Densities of organic phases in the biphasic and triphasic regions have been measured as a function of equilibrium aqueous-phase thorium nitrate concentration at 303 K. Also discussed are the variations of the ratios of the volume of the diluent-rich phase to that of the third phase as a function of the equilibrium aqueous-phase Th(NO3)4 concentration and chain length of the diluent in the extraction of Th(IV) from its solutions with near-zero free acidity by the above solvents at 303 K.

Extraction of U(VI) by Tri-n-Amyl Phosphate Under High Solvent Loading Conditions

Tri-n-butyl phosphate (TBP) is being employed as the extractant for the processing of nuclear materials all over the world. However, some of its limitations such as third-phase formation, aqueous solubility, chemical and radiation degradation, etc., affect the performance of TBP-based extraction processes. Hence, there is a need to identify alternative extractants that do not possess the disadvantages of TBP but retain the desirable properties of TBP. In this connection, higher homologues of TBP such as tri-n-amyl phosphate (TAP) and some of its isomers are considered to be important for various solvent extraction processes. Batch extraction studies have been carried out on the extraction of U(VI) by 1.1 M solutions of TBP and TAP in n-dodecane as well as heavy normal paraffin (HNP), and the results are reported in this paper. Extraction of U(VI) by 1.1 M TAP/HNP under high solvent loading conditions and subsequent stripping of U(VI) by 0.01 M HNO3 from loaded 1.1 M TAP/HNP in a countercurrent mode were also carried out with an ejector mixer-settler. This paper describes the results of these mixer-settler runs. Results revealed the suitability of higher homologues of TBP for reprocessing applications.

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.

The Effect of the Structure of Trialkyl Phosphates on their Physicochemical Properties and Extraction Behavior

The density of various 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 (tri‐3‐methylbutyl phosphate, TiAP), tri‐sec‐amyl phosphate (tri‐2‐amyl phosphate, TsAP), tri‐cyclo‐amyl phosphate (TcyAP), tri‐n‐hexyl phosphate (THP), and 1.1 M solutions of some of these phosphates in various diluents, solubility of water in trialkyl phosphates, and the aqueous solubility of trialkyl phosphates have been measured. Extraction of nitric acid, Th(IV), and U(VI) by trialkyl phosphates has also been studied by the batch extraction method. Metal‐solvate stoichiometry in the extraction of Th(IV) and U(VI) by some of the phosphates has been evaluated. Data on the extraction of U(VI) by various trialkyl phosphates as a function of equilibrium aqueous‐phase nitric acid concentration at 303 K are presented in this paper. Data on the extraction of Th(IV) and U(VI) from 1 M and 5 M HNO3 by trialkyl phosphates as a function of equilibrium aqueous‐phase metal concentration at 303 K are also presented in this paper. The effects of the structure of trialkyl phosphates on their physicochemical properties and extraction behavior are described in this paper.

Measurement of enthalpies of vaporization of trialkyl phosphates using correlation gas chromatography

The enthalpies of vaporization of several trialkyl phosphates such as, tri- n-butyl phosphate (TBP), triisobutyl phosphate (TiBP), tri-secondary butyl phosphate (TsBP), tri- n-amyl phosphate (TAP), triisoamyl phosphate (TiAP), Tri-2-methyl butyl phosphate (T2MBP), tri-secondary amyl phosphate (TsAP), and trihexyl phosphate (THP) have been measured for the first time using correlation gas-chromatographic technique. Normal paraffin hydrocarbons have been used as references after demonstrating the suitability of them by determining the enthalpies of vaporization of trimethyl phosphate (TMP) and triethyl phosphate (TEP) for which data is available in the literature. The vaporization enthalpies were correlated to structural parameters characterizing the compounds studied. Solvent accessible surface area (SAS), among the parameters, was found to exhibit excellent correlation to the enthalpies of vaporization of trialkyl phosphates as well as the normal paraffin hydrocarbons used as the reference. The Hildebrand's solubility parameters for the trialkyl phosphates were derived from the values of enthalpy of vaporization at 298.15 K.

Physiochemical and Plutonium Retention Properties of Hydrolytic and Radiolytically Degraded Tri‐n‐Amylphosphate

Hydrolytic and radiolytic degradation of tri‐n‐amylphosphate (TAP) diluted in normal paraffin hydrocarbon (NPH) in the presence of nitric acid has been investigated. Physicochemical properties such as density, viscosity, and phase disengagement time (PDT) were measured for undegraded and degraded solutions. The extent of damage caused by chemical and radiation induced reactions in TAP‐NPH‐HNO3 system has been assessed by the measurement of plutonium retention in the organic phase. The results are compared with those obtained using undegraded TAP as well as tri‐n‐butylphosphate (TBP) in NPH. The effectiveness of sodium carbonate washing of the degraded organic phase for restoring the original quality of the solvent has been detailed. The study indicates that plutonium retention exhibited by TAP/NPH is insignificant at dose levels typically encountered in the first extraction cycle (∼0.2 kGy), and the marginal increase of plutonium retention at higher dose levels is not, however, undesirable for the employment of TAP in an actual process.

Calorimetric Measurement of the Enthalpy of Extraction of Uranyl Nitrate by Tri-n-Amyl Phosphate

Enthalpy of extraction of uranyl nitrate by tri n-amyl phosphate (TAP) and its solutions in n-dodecane has been directly measured by solution calorimetry for the first time. Measurements have been made at 303+1 K, in both forward as well as the reverse extraction modes. The enthalpies of the accompanying reactions such as the dilution of the uranyl nitrate in the aqueous phase, the hydration of TAP, the mixing of TAP and n-dodecane, the mixing of the metal-solvate (U02(NO3)2.2TAP) and n-dodecane and mixing of the metal-solvate and TAP have also been independently measured and used to derive both the equilibrium state enthalpies and the standard state enthalpies for the extraction reaction. Two distinct standard states have been used for the organic phase, viz.,1) all solutes infinitely diluted in diluent (AH*) and 2) all solutes infinitely diluted in the water saturated extractant (ΔH°). The results have been compared with the enthalpies of extraction measured by employing the temperature dependence of the distribution ratio as well as calorimetry reported in the literature for extraction of uranyl nitrate by TAP and TBP.

THIRD PHASE FORMATION IN THE EXTRACTION OF Nd(III) BY OCTYL(PHENYL)-N,N-DHSOBUTYL CARBAMOYL METHYL PHOSPHINE OXIDE (OΦCMPO)

ABSTRACT Third phase formation in the extraction of Nd(III) by 0.2 M Octyl(Phenyl)-N,N-Diisobutyl Carbamoyl methyl phosphine oxide (OΦCMPO) in n-dodecane has been studied with tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) as modifiers to provide a comparison between these two modifier systems. The effect of concentration of TAP as modifier for the extraction of Nd(III) by 0.2 M OΦCMPO has been studied. The extraction of Nd(III) by TAP/n-dodecane in the absence of OΦCMPO has also been studied and the results are reported here.